How do starfishes eat?
Common starfish
The common starfish feeds on a variety of benthic organisms. These include bivalve molluscs, polychaete worms, barnacles, gastropod molluscs, other echinoderms and carrion. When feeding on a mollusc such as a mussel, it attaches its tube feet to each shell valve and exerts force to separate them slightly. Even a gap of only is sufficient for the starfish to insert a fold of its stomach, secrete enzymes and start digesting the mollusc body. When the contents is sufficiently liquid, it brings its stomach back to its rightful position with the food inside. The common starfish has a well-developed sense of smell and can detect the odour of prey species such as the common mussel ("Mytilus edulis") and crawl towards it. It can also detect the odour of the predatory common sunstar ("Crossaster papposus"), which eats other starfish, and take evasive action.
The common starfish is dioecious, which means that each individual is either male or female. In the spring, the females release their eggs into the sea. A moderate sized starfish is estimated to be able to produce 2.5 million eggs. The males shed their sperm and fertilisation takes place in the water column. The larvae are planktonic and drift for about 87 days before settling on the seabed and undergoing metamorphosis into juveniles. Common starfish are believed to live for about seven to eight years. When well fed, the juveniles can increase their radius at the rate of slightly more than per month during the summer and autumn and slightly less than per month in the winter. An adult common starfish can survive starvation for several months although it loses weight in the process. One specimen shrank from a radius of to a radius of after starvation for five months.
Starfish
Most starfish embryos hatch at the blastula stage. The original ball of cells develops a lateral pouch, the archenteron. The entrance to this is known as the blastopore and it will later develop into the anus. Another invagination of the surface will fuse with the tip of the archenteron as the mouth while the interior section will become the gut. At the same time, a band of cilia develops on the exterior. This enlarges and extends around the surface and eventually onto two developing arm-like outgrowths. At this stage the larva is known as a bipinnaria. The cilia are used for locomotion and feeding, their rhythmic beat wafting phytoplankton towards the mouth.
Starfish
Each starfish arm contains two gonads that release gametes through openings called gonoducts, located on the central disc between the arms. Fertilization is generally external but in a few species, internal fertilization takes place. In most species, the buoyant eggs and sperm are simply released into the water (free spawning) and the resulting embryos and larvae live as part of the plankton. In others, the eggs may be stuck to the undersides of rocks. In certain species of starfish, the females brood their eggs – either by simply enveloping them or by holding them in specialised structures. Brooding may be done in pockets on the starfish's aboral surface, inside the pyloric stomach ("Leptasterias tenera") or even in the interior of the gonads themselves. Those starfish that brood their eggs by "sitting" on them usually assume a humped posture with their discs raised off the substrate. "Pteraster militaris" broods a few of its young and disperses the remaining eggs, that are too numerous to fit into its pouch. In these brooding species, the eggs are relatively large, and supplied with yolk, and they generally develop directly into miniature starfish without an intervening larval stage. The developing young are called lecithotrophic because they obtain their nutrition from the yolk as opposed to "planktotrophic" larvae that feed in the water column. In "Parvulastra parvivipara", an intragonadal brooder, the young starfish obtain nutrients by eating other eggs and embryos in the brood pouch. Brooding is especially common in polar and deep-sea species that live in environments unfavourable for larval development and in smaller species that produce just a few eggs.
Longfin inshore squid
"The diet of the longfin inshore squid changes with size; small immature individuals feed on planktonic organisms while larger individuals feed on crustaceans and small fish. Studies showed that juveniles fed on euphausiids and arrow worms, while older individuals fed mostly on small crabs, but also on polychaetes and shrimp. Adults fed on fish (clupeids, myctophids) and squid larvae/juveniles, and those larger than 16 cm fed on fish and squid. Fish species preyed on by longfin inshore squid include silver hake, mackerel, herring, menhaden, sand lance, bay anchovy, weakfish, and silversides. Maurer and Bowman (1985) discovered a difference in inshore/offshore diet: in offshore waters in the spring, the diet is composed of crustaceans (mainly euphausiids) and fish; in inshore waters in the fall, the diet is composed almost exclusively of fish; and in offshore waters in the fall, the diet is composed of fish and squid. Cannibalism is observed in individuals larger than 5 cm."
Bat star
Bat stars can be many different types of colors.The bat star breathes through gill-like structures on its back that perform as respirators. It lacks the pincers or pedicellariae that most starfish use to clean the skin surface of debris, but its small, moving hairs or cilia may create enough of a water current to keep the surface of its skin clean. It has visual sensors at the end of each ray that can detect light and note prey. To eat its prey, it covers the prey with its stomach and oozes digestive juices over it; this liquefies the food, enabling the bat star to ingest it. It is omnivorous, eating both plants and animals alive or dead.
Starfish
The gut of a starfish occupies most of the disc and extends into the arms. The mouth is located in the centre of the oral surface, where it is surrounded by a tough peristomial membrane and closed with a sphincter. The mouth opens through a short oesophagus into a stomach divided by a constriction into a larger, eversible cardiac portion and a smaller pyloric portion. The cardiac stomach is glandular and pouched, and is supported by ligaments attached to ossicles in the arms so it can be pulled back into position after it has been everted. The pyloric stomach has two extensions into each arm: the pyloric caeca. These are elongated, branched hollow tubes that are lined by a series of glands, which secrete digestive enzymes and absorb nutrients from the food. A short intestine and rectum run from the pyloric stomach to open at a small anus at the apex of the aboral surface of the disc.
Metridium farcimen
"Metridium farcimen" is found on the western seaboard of the United States and Canada. Its range extends from Alaska southwards to California. It is at its most common in Puget Sound and around Vancouver Island. It is found in the sublittoral zone on rocks, mollusc shells, pilings, docks and other man-made structures and even in polluted waters. It is also found at great depths, near hydrothermal vents, cold water seeps and decomposing whale carcases on the seabed.
"Metridium farcimen" is a carnivore. It captures small invertebrates, zooplankton and other food particles with the nematocysts on its tentacles and thrusts them into the mouth in the centre of its oral disc. Large anemones have few predators but smaller specimens are eaten by the starfish, "Pisaster spp.", and by various nudibranchs. The starfish, "Dermasterias imbricata", has been observed feeding on larger anemones in Puget Sound.
Crown-of-thorns starfish
Many of the reports of fish preying on "Acanthaster" are single observations or presumed predation from the nature of the fish. For example, the humphead wrasse may prey on the starfish amongst its more usual diet. Individual puffer fish and trigger-fish have been observed to feed crown-of-thorns starfish in the Red Sea, but there is no evidence that they are a significant factor in population control. A study, however, based on the stomach contents of large carnivorous fish that are potential predators of the starfish found no evidence of the starfish in the fish's guts. These carnivorous fish were caught commercially on the coral reefs on the Gulf of Oman and examined at local fish markets.
Crown-of-thorns starfish
In reef areas of low densities of hard coral, reflecting the nature of the reef community or due to feeding by high density crown-of-thorns, the starfish may be found feeding on soft corals (Alcyonacea).
Starfish
Most species of starfish are gonochorous, there being separate male and female individuals. These are usually not distinguishable externally as the gonads cannot be seen, but their sex is apparent when they spawn. Some species are simultaneous hermaphrodites, producing eggs and sperm at the same time and in a few of these, the same gonad, called an ovotestis, produces both eggs and sperm. Other starfish are sequential hermaphrodites. Protandrous individuals of species like "Asterina gibbosa" start life as males before changing sex into females as they grow older. In some species such as "Nepanthia belcheri", a large female can split in half and the resulting offspring are males. When these grow large enough they change back into females.
Striped dolphin
The adult striped dolphin eats fish, squid, octopus, krill, and other crustaceans. Mediterranean striped dolphins seem to prey primarily on cephalopods (50-100% of stomach contents), while northeastern Atlantic striped dolphins most often prey on fish, frequently cod. They mainly feed on cephalopods, crustaceans, and bony fishes. They feed anywhere within the water column where prey is concentrated, and they can dive to depths of 700 m to hunt deeper-dwelling species.
California moray
California morays mainly eat fish, although they are opportunistic predators whose diet also consists of invertebrate prey such as octopuses, lobsters, and shrimp. Interestingly, it appears that California morays will share habitat space in the with potential prey species, including both shrimp and lobsters. Like other morays, California morays have a special set of pharyngeal jaws that allows prey to be transported from their mouths into their throats. As an additional aid to prey transport, they have a set of depressible teeth in the roof of their mouths that fold upward as prey is swallowed.
Pteraster militaris
"Pteraster militaris" is unusual among starfishes in that it broods some of its young. About forty fertilised eggs are retained in the water-filled chamber below its papery outer skin and these develop into juveniles that may reach across before they make their way out through the central pore. Eggs that are too numerous to be brooded are released direct into the sea where they become planktonic larvae. The brooded juveniles seem to behave as ectoparasites of the female, feeding on maternal tissues in the brood chamber. They may also eat dead embryos, faecal material and mucus.
Stingray
The flattened bodies of stingrays allow them to effectively conceal themselves in their environments. Stingrays do this by agitating the sand and hiding beneath it. Because their eyes are on top of their bodies and their mouths on the undersides, stingrays cannot see their prey after capture; instead, they use smell and electroreceptors (ampullae of Lorenzini) similar to those of sharks. Stingrays settle on the bottom while feeding, often leaving only their eyes and tails visible. Coral reefs are favorite feeding grounds and are usually shared with sharks during high tide.
Whale
All whales are carnivorous and predatory. Odontocetes, as a whole, mostly feed on fish and cephalopods, and then followed by crustaceans and bivalves. All species are generalist and opportunistic feeders. Mysticetes, as a whole, mostly feed on krill and plankton, followed by crustaceans and other invertebrates. A few are specialists. Examples include the blue whale, which eats almost exclusively krill, the minke whale, which eats mainly schooling fish, the sperm whale, which specialize on squid, and the grey whale which feed on bottom-dwelling invertebrates. The elaborate baleen "teeth" of filter-feeding species, mysticetes, allow them to remove water before they swallow their planktonic food by using the teeth as a sieve. Usually whales hunt solitarily, but they do sometimes hunt cooperatively in small groups. The former behaviour is typical when hunting non-schooling fish, slow-moving or immobile invertebrates or endothermic prey. When large amounts of prey are available, whales such as certain mysticetes hunt cooperatively in small groups. Some cetaceans may forage with other kinds of animals, such as other species of whales or certain species of pinnipeds.
Pacific spiny dogfish
The Pacific dogfish is an elasmobranchs or cartilaginous fish which includes sharks, skates and rays. Dogfish are carnivorous or meat eaters. Their teeth are sharp and are inclined laterally in order to cut through their prey. The Pacific dogfish usually eat on mollusks or crustaceans such as squid, krill, and shrimp. They also eat other small sharks and fish. According to Jennifer Bigman, a marine scientist, there is no difference between what male dogfish eat versus what female dogfish eat. Their prey are usually found on the sea floor, so the Pacific spiny dogfish has to scan the bottom in order to invest in their prey. Elasmobranchs consume very little carbohydrates and glucose. During times of starvation, they rely on ketone bodies to give them enough energy to survive. Cartilaginous fish are able to endure severe hypoglycemia due to their ketone oxidation. "Squalus suckleyi" are able to eat more carbohydrates compared to other elasmobranchs. The rectal gland is activated when a dogfish consumes food. This gland helps the Pacific dogfish become glucose dependent. This means that they have the ability to break down a small amount of glucose.
Marthasterias
Like other starfish in the family Asteriidae, "Marthasterias glacialis" is a predator and feeds mostly on bivalve molluscs and other invertebrates. It has been found that secondary metabolites known as saponins, found within the starfish's tissues, have a dramatic effect on the whelk "Buccinum undatum". At low concentrations they cause the mollusc to withdraw from the vicinity of the starfish and at higher concentrations they cause convulsions in the mollusc's musculature. The sea urchins "Strongylocentrotus droebachiensis" and "Psammechinus miliaris" are also affected by the chemicals. "S. droebachiensis" flees but "P. miliaris" has toxic pedicellariae and is able to defend itself.
Oyster
Oysters are filter feeders, drawing water in over their gills through the beating of cilia. Suspended plankton and particles are trapped in the mucus of a gill, and from there are transported to the mouth, where they are eaten, digested, and expelled as feces or pseudofeces. Oysters feed most actively at temperatures above . An oyster can filter up to of water per hour. The Chesapeake Bay's once-flourishing oyster population historically filtered excess nutrients from the estuary's entire water volume every three to four days. Today, that would take nearly a year. Excess sediment, nutrients, and algae can result in the eutrophication of a body of water. Oyster filtration can mitigate these pollutants.
Coscinasterias calamaria
"Coscinasterias calamaria" mostly feeds on the blue mussel ("Mytilus edulis") and other benthic invertebrates. It has been found that it seldom feeds on the blacklip abalone ("Haliotis rubra") unless there is a scarcity of mussels. When this happens, aggregations of starfish do feed on it. This is despite laboratory feeding tests demonstrating that it prefers abalone. It seems that the abalone has some behavioural responses to attack that make it more likely to escape, one of which seems to be the production of a chemical deterrent by the mollusc. There are smell chemoreceptors on the tips of the arms, and the starfish can navigate accurately by smell towards a source of food. It then extends its stomach over its prey, secretes enzymes onto it and liquefies before returning the stomach to its normal position. When food is scarce, this starfish can exist for many weeks without food.
Anasterias rupicola
On the sub-Arctic Marion Island, "Nacella delesserti" and "Anasterias rupicola" are the two dominant members of the inshore community. When it reaches a size of about long, the limpet is too large for even the largest individual starfish to tackle. Under these circumstances, the starfish adopt a co-operative strategy. If a limpet fleeing from an attacker finds its path blocked by other starfish and has nowhere to which to retreat, it may be overwhelmed. Groups of up to fourteen starfish have been observed feeding on a single large limpet, each with part of their everted stomach inserted under its rim. Some feeding groups of smaller starfish act co-operatively to attack a limpet even though individually they are incapable of preying on limpets of this size. This is advantageous for these small starfish because the limpet is much the commonest available prey species in terms of biomass.
Spiny lobster
Spiny lobsters tend to live in crevices of rocks and coral reefs, only occasionally venturing out at night to seek snails, clams, sea-hares, crabs, or sea urchins to eat. Sometimes, they migrate in very large groups in long files of lobsters across the sea floor. These lines may be more than 50 lobsters long. Spiny lobsters navigate using the smell and taste of natural substances in the water that change in different parts of the ocean. It was recently discovered that spiny lobsters can also navigate by detecting the Earth's magnetic field. They keep together by contact, using their long antennae. Potential predators may be deterred from eating spiny lobsters by a loud screech made by the antennae of the spiny lobsters rubbing against a smooth part of the exoskeleton. Spiny lobsters usually exhibit the social habit of being together. However recent studies indicate that healthy lobsters move away from infected ones, leaving the diseased lobsters to fend for themselves.
Dichotomyctere ocellatus
Pufferfish are classed as molluscivores and feed mainly on benthic organisms which may include mussels, cockles, oysters and krill, though some puffers will take other foods, such as flake, it is not recommended that their primary food is flake. Their teeth, a beak formed from two plates, are capable of crushing shells in order to feed on prey. In captivity many fishkeepers feed snails as a substitute for the aforementioned foods as snails help keep the beak trim; it would otherwise be susceptible to overgrowth.
Coral reef fish
Some fishes associated with reefs are generalized carnivores that feed on a variety of animal prey. These typically have large mouths that can be rapidly expanded, thereby drawing in nearby water and any unfortunate animals contained within the inhaled water mass. The water is then expelled through the gills with the mouth closed, thereby trapping the helpless prey For example, the bluestripe snapper has a varied diet, feeding on fishes, shrimps, crabs, stomatopods, cephalopods and planktonic crustaceans, as well as plant and algae material. Diet varies with age, location and the prevalent prey items locally.
Swordfish
Swordfish prefer water temperatures between , but have the widest tolerance among billfish, and can be found from . This highly migratory species typically moves towards colder regions to feed during the summer. Swordfish feed daily, most often at night, when they rise to surface and near-surface waters in search of smaller fish. During the day, they commonly occur to depths of and have exceptionally been recorded as deep as . Adults feed on a wide range of pelagic fish, such as mackerel, barracudinas, silver hake, rockfish, herring, and lanternfishes, but they also take demersal fish, squid, and crustaceans. In the northwestern Atlantic, a survey based on the stomach content of 168 individuals found 82% had eaten squid and 53% had eaten fish, including gadids, scombrids, butterfish, bluefish, and sand lance. Large prey are typically slashed with the sword, while small are swallowed whole.
Swordfish are not schooling fish. They swim alone or in very loose aggregations, separated by as much as from a neighboring swordfish. They are frequently found basking at the surface, airing their first dorsal fin. Boaters report this to be a beautiful sight, as is the powerful jumping for which the species is known. This jumping, also called breaching, may be an effort to dislodge pests, such as remoras or lampreys.
Almost 50 species of parasites have been documented in swordfish. In addition to remoras, lampreys, and cookiecutter sharks, this includes a wide range of invertebrates, such as tapeworms, roundworms, and copepods. A comparison of the parasites of swordfish in the Atlantic and in the Mediterranean indicated that some parasites, particularly Anisakis spp. larvae identified by genetic markers, could be used as biological tags and support the existence of a Mediterranean swordfish stock.
Starfish
Starfish sometimes have negative effects on ecosystems. Outbreaks of crown-of-thorns starfish have caused damage to coral reefs in Northeast Australia and French Polynesia. A study in Polynesia found that coral cover declined drastically with the arrival of migratory starfish in 2006, dropping from 50% to under 5% in three years. This had an unintended effect on reef-feeding fish and the whole benthic community. "Asterias amurensis" is one of a few echinoderm invasive species. Its larvae likely arrived in Tasmania from central Japan via water discharged from ships in the 1980s. The species has since grown in numbers to the point where they threaten commercially important bivalve populations. As such, they are considered pests, and are on the Invasive Species Specialist Group's list of the world's 100 worst invasive species.
Vegetarian finch
As its name suggests, the vegetarian finch is largely a plant-eater. It feeds primarily on buds, leaves, flowers and fruit, and will strip the bark off twigs to get to the cambium and phloem which lies underneath. Although it forages mainly in trees, it will descend to the ground to search for fallen fruits and young plant shoots. It also occasionally eats caterpillars. It feeds primarily at mid-levels, in what has been described as a "rather leisurely" manner. Because its principal food items are soft, the vegetarian finch has a beak morphology unlike those of Darwin's finches which specialize on hard seeds. Described as "parrot-like", the beak is small and stout, with a steep profile and a strong curve in the upper mandible. Its primary function is food manipulation at the tip, rather than seed crushing at the base. The vegetarian finch has a disproportionately large gizzard, as well as a long intestine and a disproportionately small heart. These allow it to process the "relatively indigestible" leaves and buds that make up a large proportion of its diet.
Echinoderm
Echinoderms form part of the diet of many organisms such as bony fish, sharks, eider ducks, gulls, crabs, gastropod molluscs, sea otters, Arctic foxes and humans. Larger starfish prey on smaller ones and the great quantity of eggs and larvae produced form part of the zooplankton, consumed by many marine creatures. Crinoids are relatively free from predation. The body cavities of many sea cucumbers and some starfish provide a habitat for parasitic or symbiotic organisms including fish, crabs, worms and snails.
Thresher shark
Thresher sharks are solitary creatures which keep to themselves. It is known that thresher populations of the Indian Ocean are separated by depth and space according to sex. Some species however do occasionally hunt in a group of two or three contrary to their solitary nature. All species are noted for their highly migratory or oceanodromous habits. When hunting schooling fish, thresher sharks are known to "slap" the water, herding and stunning prey. The elongated tail is used to swat smaller fish, stunning them before feeding. Thresher sharks are one of the few shark species known to jump fully out of the water, making turns like dolphins; this behavior is called breaching.
Two species of the thresher have been identified as having a modified circulatory system that acts as a counter-current heat exchanger, which allows them to retain metabolic heat. Mackerel sharks (family Lamnidae) have a similar homologous structure to this which is more extensively developed. This structure is a strip of red muscle along each of its flanks, which has a tight network of blood vessels that transfer metabolic heat inward towards the core of the shark, allowing it to maintain and regulate its body heat.
Bottlenose dolphin
Fish is one of the main items in the dolphin diet. They also eat shrimps, squid, mollusks, and cuttlefish, and only swallows the soft parts. They eat 22 pounds of fish a day. When they encounter a shoal of fish, they work as a team to herd them towards the shore to maximize the harvest. They also hunt alone, often targeting bottom-dwelling species. The bottlenose dolphin sometimes hits a fish with its fluke, sometimes knocking it out of the water, using a strategy called "fish whacking". "Strand feeding", is an inherited feeding technique used by bottlenose dolphins near and around coastal regions of Georgia and South Carolina. When a pod finds a school of fish, they will circle the school and trap the fish in a mini whirlpool. Then, the dolphins will charge at the school and push their bodies up onto a mud-flat, forcing the fish on the mud-flat, as well. The dolphins then crawl around on their sides, consuming the fish they washed up on shore.
Sand star
The sand star is well-camouflaged on the sandy and muddy seabeds where it is found, and is often half-covered with sediment. It can create a shallow depression and work its way under the bivalve molluscs, polychaete worms, brittle stars, and sea cucumbers on which it feeds. Unlike some other starfish, it cannot evert its stomach, so is limited to smaller-sized prey. It is agile, and can right itself rapidly if turned upside down. The long, pointed tube feet are specially adapted for movement over soft sediments, but lose traction if the sand star tries to scale steeply sloping rocks. It is a fast traveller, and can move across the seabed at the rate of per minute, many times faster than slow species such as the leather star ("Dermasterias imbricata"), which can only traverse in a minute.
Northern wolffish
This fish feeds in open water on comb jellies and jellyfish, and on bottom-living crustaceans and invertebrates, such as crabs, sea urchins, brittle stars, and starfish.
Crown-of-thorns starfish
The starfish show preferences between the hard corals on which they feed. They tend to feed on branching corals and table-like corals, such as "Acropora" species, rather than on more rounded corals with less exposed surface area, such as "Porites" species. Avoidance of "Porites" and some other corals may also be due to resident bivalve molluscs and polychaete worms in the surface of the coral which discourage the starfish. Similarly, some symbionts, such as small crabs, living within the complex structures of branching corals, may ward off the starfish as it seeks to spread its stomach over the coral surface.
Crown-of-thorns starfish
The adult crown-of-thorns is a corallivorous predator that usually preys on reef coral polyps. It climbs onto a section of living coral colony using the large number of tube feet on its oral surface and flexible body. It fits closely to the surface of the coral, even the complex surfaces of branching corals. It then extrudes its stomach out through its mouth over the surface to virtually its own diameter. The stomach surface secretes digestive enzymes that allow the starfish to absorb nutrients from the liquefied coral tissue. This leaves a white scar of coral skeleton which is rapidly infested with filamentous algae. An individual starfish can consume up to of living coral reef per year. In a study of feeding rates on two coral reefs in the central Great Barrier Reef region, large starfish (40 cm and greater diameter) killed about 61 cm²/day in winter and 357–478 cm²/day in summer. Smaller starfish, 20–39 cm, killed 155 and 234 cm²/day in the equivalent seasons. The area killed by the large starfish is equivalent to about from these observations. Differences in feeding and locomotion rates between summer and winter reflect the fact that the crown-of-thorns, like all marine invertebrates, is a poikilotherm whose body temperature and metabolic rate are directly affected by the temperature of the surrounding water. In tropical coral reefs, crown-of-thorns specimens reach mean locomotion rates of 35 cm/min, which explains how outbreaks can damage large reef areas in relatively short periods.
Starry sturgeon
The starry sturgeon is a harmless species that feeds on fish, worms, crustaceans and mollusks. It lies on the bottom during the day and feeds mostly at night. This fish is anadromous and moves upriver into shallow waters to spawn.
Orthasterias
The rainbow star is a predator and feeds on a range of invertebrates including gastropod molluscs, limpets, bivalves, brachiopods, chitons, barnacles and tunicates. In Alaska, it especially favours the ribbed clam "Humilaria kennerleyi". It can dig up clams buried in the substrate and force the valves apart with the suction provided by its tube feet. It then everts part of its stomach, thrusting a fold inside the bivalve and excreting digestive enzymes onto the tissues. When these have liquefied sufficiently, the stomach engulfs them and is returned to its normal position inside the starfish.
Charonia
Adult tritons are active predators and feed on other molluscs and starfish. The giant triton has gained fame for its ability to capture and eat crown-of-thorns starfish, a large species (up to 1 m in diameter) covered in venomous spikes an inch long. The crown-of-thorns starfish has few other natural predators and has earned the enmity of humans in recent decades by proliferating and destroying large sections of coral reef, turning them into coral skeletons, empty husks of calcium carbonate.
Tritons can be observed to turn and give chase when the scent of prey is detected. Some starfish (including the crown-of-thorns starfish) appear to be able to detect the approach of the mollusc by means which are not clearly understood, and they will attempt flight before any physical contact has taken place. Tritons, however, are faster than starfish, and only large starfish have a reasonable hope of escape, and then only by abandoning whichever limb the snail seizes first.
List of Star Wars creatures
Space slugs, also called exogorths or giant asteroid worms, are silicon-based gastropods capable of surviving in near-vacuum conditions. Space slugs generally make their habitats in asteroids, where they spend the majority of their lives. Many space slugs have been found in Hoth's asteroid field, some reaching thousands of meters (feet) in length, up to a recorded maximum around , although most are much smaller at around . They feed by absorbing an asteroid's minerals through their roots. Smaller space slugs also devour mynocks (in large space slugs, consumed mynocks are not digested and instead become parasites within the space slug). Large space slugs may also consume starships and have been known to eat sections of Imperial Star Destroyers that flew too close. The burrow of a space slug is called a "caysh". They first appeared in "The Empire Strikes Back" (1980).
Spinner shark
Spinner sharks feed primarily on small bony fish, including tenpounders, sardines, herring, anchovies, sea catfish, lizardfish, mullets, bluefish, tunas, bonito, croakers, jacks, mojarras, and tongue-soles. They have also been known to eat stingrays, cuttlefish, squid, and octopus. Groups of spinner sharks are often found pursuing schools of prey at high speed. Individual prey are seized and swallowed whole, as this shark lacks cutting dentition. This species employs an unusual tactic when feeding on schools of small fish; the shark charges vertically through the school, spinning on its axis with its mouth open and snapping all around it. The shark's momentum at the end of these spiraling runs often carries it into the air, giving it its common name. The blacktip shark also performs this behavior, though not as often. Off Madagascar, spinner sharks follow migrating schools of mackerel, tunas, and jacks. Like blacktip sharks, they congregate around shrimp trawlers to feed on the discarded bycatch, and may be incited into feeding frenzies.
Scorpaenidae
Most species are bottom-dwellers that feed on crustaceans and smaller fish. Many inhabit shallow waters, but a few live as deep as . Most scorpionfish, such as the stonefish, wait in disguise for prey to pass them by before swallowing, while lionfish often ambush their prey. When not ambushing, lionfish may herd the fish, shrimp, or crab into a corner before swallowing. Like many perciform fishes, scorpionfish are suction feeders that capture prey by rapidly projecting a suction field generated by expansion of the fish's buccal cavity.
Starfish
The starfish are a large and diverse class with about 1,500 living species. There are seven extant orders, Brisingida, Forcipulatida, Notomyotida, Paxillosida, Spinulosida, Valvatida and Velatida and two extinct ones, Calliasterellidae and Trichasteropsida. Living asteroids, the Neoasteroidea, are morphologically distinct from their forerunners in the Paleozoic. The taxonomy of the group is relatively stable but there is ongoing debate about the status of the Paxillosida, and the deep-water sea daisies, though clearly Asteroidea and currently included in Velatida, do not fit easily in any accepted lineage. Phylogenetic data suggests that they may be a sister group, the Concentricycloidea, to the Neoasteroidea, or that the Velatida themselves may be a sister group.Extinct groups within the Asteroidea include:
Starfish
There may also be papulae, thin-walled protrusions of the body cavity that reach through the body wall and extend into the surrounding water. These serve a respiratory function. The structures are supported by collagen fibres set at right angles to each other and arranged in a three-dimensional web with the ossicles and papulae in the interstices. This arrangement enables both easy flexion of the arms by the starfish and the rapid onset of stiffness and rigidity required for actions performed under stress.
Crab
Crabs are omnivores, feeding primarily on algae, and taking any other food, including molluscs, worms, other crustaceans, fungi, bacteria and detritus, depending on their availability and the crab species. For many crabs, a mixed diet of plant and animal matter results in the fastest growth and greatest fitness. However, some species are more specialised in their diets. Some eat plankton, some eat primarily shellfish like clams, and some even catch fish.
Neoferdina cumingi
Although the feeding habits of this starfish have not been studied, it is part of the order Valvatida, and starfish in this order typically evert their stomach to engulf and digest their food before retracting the stomach back into the disc, bringing the partially digested prey with it.
Crown-of-thorns starfish
Popular anxiety to news of high densities of "A. planci" on the Great Barrier Reef was reflected in many newspaper reports and publications such as 'Requiem for the Reef', which also suggested that there was a cover-up of the extent of damage. There was a popular idea that the coral and with it whole reefs were being destroyed by the starfish. In fact, as described above, the starfish preys on coral by digesting the surface of living tissue from the coral skeletons. These skeletons persist, together with the mass of coralline algae that is essential for reef integrity. The initial change (first order effect) is loss of the veneer of living coral tissue.
Spotted sunfish
Spotted sunfish are largely insectivores throughout their entire lives, feeding on midge larvae and other immature insects. Most prey is benthic in origin, but insects at the surface are also preyed upon. Bream anglers have caught spotted sunfish using crickets or worms. They are also known to feed on microcrustaceans such as amphipods (Hyalella) and cladocerans. Spotted sunfish capture individual prey by suction feeding. Competition among various centrarchids is limited by physical difference in jaw mechanisms. For example, spotted sunfish and bluegill feed on similar prey items. Design of the lower jaw and therefore speed of capture varies between these two fishes; what one can easily capture the other cannot.
Asterias forbesi
Asterias forbesi, commonly known as Forbes sea star, is a species of starfish in the family Asteriidae. It is found in shallow waters in the northwest Atlantic Ocean and the Caribbean Sea.
Coral Sea
Crown-of-thorns starfish ("Acanthaster planci") is the major predator of the reefs, as it preys upon coral polyps by climbing onto them, extruding its stomach over them, and releasing digestive enzymes to absorb the liquefied tissue. An individual adult can eat up to 6 m of reef per year. In 2000, an outbreak of crown-of-thorns starfish contributed to a loss of 66% of live coral cover on sampled reefs. Changes in water quality and overfishing of natural predators, such as the Giant Triton, may have contributed to an increase in the number of crown-of-thorns starfish.
Archaster typicus
"Archaster typicus" is a detritivore and eats detritus and anything else edible it comes across. To feed, it everts its stomach through its mouth which is situated centrally on its underside. The food item is engulfed and brought inside the starfish when its stomach is returned to its normal position.
Starfish
Another area of research is the ability of starfish to regenerate lost body parts. The stem cells of adult humans are incapable of much differentiation and understanding the regrowth, repair and cloning processes in starfish may have implications for human medicine.
Coscinasterias tenuispina
"Coscinasterias tenuispina" is a predator and an omnivore. The starfish is found on hard bottoms and under stones and seaweed where it mainly feeds on other echinoderms and on bivalve molluscs. In most of its range, it undergoes sexual reproduction in the winter, while in the summer, it proliferates by asexual reproduction. To begin the process of asexual reproduction, or "fission", the disc tears itself into two sections, with each part eventually growing extra arms and developing into a new individual. In Brazil, all individuals seem to be male and fission occurs throughout the year.
School shark
The school shark feeds primarily on fish. Examination of stomach contents of fish caught off California showed that they were not fussy eaters and consumed whatever fish were plentiful at the time. Their diet was predominantly sardines, midshipmen, flatfish, rockfish, and squid. Feeding is done both in open water and near the seabed as sardines and squid are pelagic animals, while the remainder are benthic species.
Starfish
The feeding activity of the omnivorous starfish "Oreaster reticulatus" on sandy and seagrass bottoms in the Virgin Islands appears to regulate the diversity, distribution and abundance of microorganisms. These starfish engulf piles of sediment removing the surface films and algae adhering to the particles. Organisms that dislike this disturbance are replaced by others better able to rapidly recolonise "clean" sediment. In addition, foraging by these migratory starfish creates diverse patches of organic matter, which may play a role in the distribution and abundance of organisms such as fish, crabs and sea urchins that feed on the sediment.
Starfish
Starfish are keystone species in their respective marine communities. Their relatively large sizes, diverse diets and ability to adapt to different environments makes them ecologically important. The term "keystone species" was in fact first used by Robert Paine in 1966 to describe a starfish, "Pisaster ochraceus". When studying the low intertidal coasts of Washington state, Paine found that predation by "P. ochraceus" was a major factor in the diversity of species. Experimental removals of this top predator from a stretch of shoreline resulted in lower species diversity and the eventual domination of "Mytilus" mussels, which were able to outcompete other organisms for space and resources. Similar results were found in a 1971 study of "Stichaster australis" on the intertidal coast of the South Island of New Zealand. "S. australis" was found to have removed most of a batch of transplanted mussels within two or three months of their placement, while in an area from which "S. australis" had been removed, the mussels increased in number dramatically, overwhelming the area and threatening biodiversity.
Coscinasterias muricata
This starfish can reproduce by binary fission; a groove appears on the surface of the disc and the two halves of the starfish pull apart from each other. Each part will then regenerate its missing tissues. This is a form of asexual reproduction, and smaller individuals often divide in this way, while larger individuals have an extended breeding season, releasing sperm and eggs into the sea during spring and summer. The larvae are planktonic, and when sufficiently developed, settle onto the seabed in coralline algae habitats.
Starfish
Most species are generalist predators, eating microalgae, sponges, bivalves, snails and other small animals. The crown-of-thorns starfish consumes coral polyps, while other species are detritivores, feeding on decomposing organic material and faecal matter. A few are suspension feeders, gathering in phytoplankton; "Henricia" and "Echinaster" often occur in association with sponges, benefiting from the water current they produce. Various species have been shown to be able to absorb organic nutrients from the surrounding water, and this may form a significant portion of their diet.
Odontaster validus
"Odontaster validus" does not attack members of its own species but can attack starfish of other species. This seems to be due to chemoreceptors which can identify conspecifics by their odour. Starfish often converge on food sources and a study was undertaken to examine how they do this. It was found that food-deprived individual "Odontaster validus" could distinguish between the odours emitted by satiated and by starved starfish of the same species. They were strongly attracted to the former and took little notice of the latter.
Sydney rock oyster
Oysters are filter feeders, straining planktonic algae from the water. Birds, fish, stingrays, mud crabs, and starfish all eat Sydney rock oysters, with the Australian pied oystercatcher being particularly fond of them.
Molluscivore
In more advanced species of starfish, the cardiac stomach can be everted from the organism's body to engulf and digest food. When the prey is a clam, the starfish pulls with its tube feet to separate the two valves slightly, and inserts a small section of its stomach, which releases enzymes to digest the prey. The stomach and the partially digested prey are later retracted into the disc. Here the food is passed on to the pyloric stomach, which always remains inside the disc. Because of this ability to digest food outside the body, starfish can hunt prey much larger than their mouths.
Echinoderm
The modes of feeding vary greatly between the different echinoderm taxa. Crinoids and some brittle stars tend to be passive filter-feeders, enmeshing suspended particles from passing water; most sea urchins are grazers, sea cucumbers deposit feeders and the majority of starfish are active hunters.
Starfish
The larvae of several species of starfish can reproduce asexually before they reach maturity. They do this by autotomising some parts of their bodies or by budding. When such a larva senses that food is plentiful, it takes the path of asexual reproduction rather than normal development. Though this costs it time and energy and delays maturity, it allows a single larva to give rise to multiple adults when the conditions are appropriate.
Pisaster brevispinus
After settling into a home, the larva changes into a juvenile sea star. This process takes about 2 days. Initially the juvenile starfish has only 5 arms but additional arms develop rapidly as the starfish begins to feed on encrusting algae. At the end of 6 months the starfish is about 1 cm in size and begins to feed on corals. The starfish becomes sexually mature at the end of its second year by which time it has grown to about 20 cm in diameter. After 3–4 years (when the starfish is about 35 cm in size) it is thought to go into a senile phase where growth declines dramatically and reproduction is low. This phase has been identified only in the laboratory. It is not known how long starfish live however, they have been kept in aquaria for as long as 8 years.
Bramble shark
Sluggish in nature, the bramble shark feeds on smaller sharks (including the spiny dogfish, "Squalus acanthias"), bony fishes (including ling, catfishes, and lizardfishes), and crabs. The large size of its pharynx, relative to its mouth, suggests that it may capture prey by suction. This species is aplacental viviparous; females have two functional ovaries and two uteruses. Recorded litter sizes have ranged from 15 to 52, and newly born pups have been estimated to measure long. The dermal denticles in near-term embryos are underdeveloped, appearing as minute spines located within open pits in the skin. The size at sexual maturity is uncertain; the smallest known mature males and females are and long respectively.
Common cuttlefish
During the day, most cuttlefish can be found buried below the substrate and fairly inactive. At night however, they are actively searching for prey and can ambush their prey from under the substrate. Cuttlefish are carnivorous and eat a variety or organisms including crustaceans (crabs and shrimp), small fish, molluscs (clams and snails), and sometimes other cuttlefish which is more commonly seen when the abundance of other prey is low.
Ophiura albida
"Ophiura albida" is a predator and scavenger and feeds on such small invertebrates as polychaete worms, crustaceans and bivalve molluscs. In the Baltic Sea it is the favourite food of the starfish "Luidia sarsi" and is chosen in preference to other brittle stars. In the Irish Sea it is eaten along with the common brittle star ("Ophiothrix fragilis") by the fast-moving seven armed starfish ("Luidia ciliaris").
Rorqual
Rorquals are slender and streamlined in shape, compared with their relatives the right whales, and most have narrow, elongated flippers. They have a dorsal fin, situated about two-thirds the way back. Rorquals feed by gulping in water, and then pushing it out through the baleen plates with their tongue. They feed on crustaceans, such as krill, but also on various fish, such as herrings and sardines.
Echinoderm
Nearly all starfish are detritivores or carnivores, though a few are suspension feeders. Small fish landing on the upper surface may be captured by pedicilaria and dead animal matter may be scavenged but the main prey items are living invertebrates, mostly bivalve molluscs. To feed on one of these, the starfish moves over it, attaches its tube feet and exerts pressure on the valves by arching its back. When a small gap between the valves is formed, the starfish inserts part of its stomach into the prey, excretes digestive enzymes and slowly liquefies the soft body parts. As the adductor muscle of the shellfish relaxes, more stomach is inserted and when digestion is complete, the stomach is returned to its usual position in the starfish with its now liquefied bivalve meal inside it. The same everted stomach process is used by other starfish to feed on sponges, sea anemones, corals, detritus and algal films.
Brisingida
These starfish have between six and 18 long, attenuated arms which they use for suspension feeding. Other characteristics include a single series of marginals, a fused ring of disc plates, the lack of actinal plates, a spool-like ambulacral column, reduced abactinal plates, and crossed pedicellariae.
Blotchy swellshark
Like other members of its genus, when threatened the blotchy swellshark is capable of rapidly inflating its stomach with water or air. This allows the shark to wedge itself inside a rocky crevice, becoming extremely difficult to remove. This species is an opportunistic, highly voracious predator; one recorded female long had 10 fish about long and 15 squid about long in her stomach. Predominantly piscivorous, this species is known to prey upon hagfish and at least 50 species of bony fishes, including fast-swimming types that inhabit open water; significant prey species include the mackerel "Scomber japonicus", the sardine "Sardinops melanostictus", the filefish "Thamnaconus modestus", and the hakeling "Physiculus japonicus". Unusually for such a small shark, it also feeds on at least 10 species of cartilaginous fishes, including lantern sharks, catsharks (particularly the cloudy catshark, "Scyliorhinus torazame", and its eggs), the electric ray "Narke japonica", and skates (including their eggs). It also cannibalizes smaller members of its own species. Cephalopods, mostly the squid "Doryteuthis bleekeri" and the cuttlefish "Sepia" spp., are also frequently taken, while crabs, shrimp, and isopods are occasionally consumed. The dietary composition of juveniles varies notably from place to place.
Snailfish
The diet of snailfish consists primarily of small benthic crustaceans, mollusks, polychaete worms, and other small invertebrates. Some species are also piscivorous. Specialist species such as "Paraliparis rosaceus" feed exclusively on sea cucumbers.
Star pearlfish
This species is usually found singly in its host, or sometimes as a male and female pair. The fish works its way in through the anus of the sea cucumber. When it is living in a starfish, it enters its host's body cavity through the grooves associated with the tube feet. A pair of fish may release their gametes within the body cavity of the host, and the fertilised eggs may later emerge into the water column. A study designed to discover whether there were genetic differences between the pearlfish living in holothurians and those living in starfish was inconclusive. During the experimental work, a large sea cucumber, "Bohadschia argus", was put in a bucket of relatively cold water, which caused 14 pearlfish to emerge, with a further one remaining inside. This is believed to be the record number of carapid fish ever found in a single holothurian.
Starfish
Several groups of starfish, including Valvatida and Forcipulatida, possess pedicellariae. In Forcipulatida, such as "Asterias" and "Pisaster", they occur in pompom-like tufts at the base of each spine, whereas in the Goniasteridae, such as "Hippasteria phrygiana", the pedicellariae are scattered over the body surface. Some are thought to assist in defence, while others aid in feeding or in the removal of organisms attempting to settle on the starfish's surface. Some species like "Labidiaster annulatus", "Rathbunaster californicus" and "Novodinia antillensis" use their large pedicellariae to capture small fish and crustaceans.
Starfish
The fossil record for starfish is ancient, dating back to the Ordovician around 450 million years ago, but it is rather sparse, as starfish tend to disintegrate after death. Only the ossicles and spines of the animal are likely to be preserved, making remains hard to locate. With their appealing symmetrical shape, starfish have played a part in literature, legend, design and popular culture. They are sometimes collected as curios, used in design or as logos, and in some cultures, despite possible toxicity, they are eaten.
Fish crow
Food is taken mainly from the ground or shallow water where the bird hovers and plucks food items out of the water with its feet. The fish crow is omnivorous. It feeds on small crustaceans, such as crabs and shrimps, other invertebrates, stranded fish, and live fish if the situation favors their capture, eggs and nestlings of birds, small reptiles, the fruits of many trees, peanuts, and grains, as well as human scraps where available.
American oystercatcher
The American oystercatcher feeds almost exclusively on shellfish and other marine invertebrates. Oysters are a staple of their diet, as their name suggests, but they also eat mussels, clams, limpets, sea urchins, starfish, crabs, and worms. In general, they use their bills to catch shellfish. As they walk across a shellfish bed, they look for a mollusk with a partially opened shell. When they find one, they jab their bill into the shell and sever the muscle that causes the shell to clamp shut. This can be dangerous, however, as they are sometimes drowned when they don't completely severe this muscle and the shell clamps down on their bill. A strong, tightly rooted mollusk can hold the bird in place until the tide comes in. They also feed by carrying loose shellfish out of the water and hammering at the shell or by probing the sand for soft-shell or razor clams.
Crayfish
Crayfish, also known as crawfish, crawdads, crawlfish, crawldads, freshwater lobsters, mountain lobsters, mudbugs, or yabbies, are freshwater crustaceans resembling small lobsters (to which they are related). Taxonomically, they are members of the superfamilies Astacoidea and Parastacoidea. They breathe through feather-like gills. Some species are found in brooks and streams where there is running fresh water, while others thrive in swamps, ditches, and paddy fields. Most crayfish cannot tolerate polluted water, although some species such as "Procambarus clarkii" are hardier. Crayfish feed on animals and plants, either living or decomposing, and detritus.
Solaster endeca
In Britain, breeding takes place in the spring. Over a period of about a week, the female lays several thousand eggs in batches. These rise to the surface of the water where they are fertilised by sperm liberated by the male. The developing larvae become less buoyant after three days, feed on the yolks of their eggs, swim with cilia, and develop a pair of larval arms. After about 18 days, they sink to the sea bed, where each one attaches itself to the substrate with a sucker. Here it undergoes metamorphosis during which it develops a disc and first five and then more arms, a pair of tube feet, relatively long spines, red eyespots on the tips of the arms, a mouth, and an anus. After six weeks, the sucker is resorbed and the juvenile starfish begins to move about with its tube feet.
Crown-of-thorns starfish
The crown-of-thorns seastar, "Acanthaster planci", is a large starfish that preys upon hard, or stony, coral polyps (Scleractinia). The crown-of-thorns starfish receives its name from venomous thorn-like spines that cover its upper surface, resembling the biblical crown of thorns. It is one of the largest starfish in the world.
Shrimp
Most shrimp are omnivorous, but some are specialised for particular modes of feeding. Some are filter feeders, using their setose (bristly) legs as a sieve; some scrape algae from rocks. Cleaner shrimp feed on the parasites and necrotic tissue of the reef fish they groom. Some species of shrimp are known to cannibalize others as well if other food sources are not readily available. In turn, shrimp are eaten by various animals, particularly fish and seabirds, and frequently host bopyrid parasites.
Reef starfish
Reef starfish (Stichaster australis) is a species of starfish found in the South Pacific Ocean around New Zealand. A keystone species, this carnivorous starfish plays an important role in local biodiversity by reducing the size and spread of mussel populations.
Nurse shark
Nurse sharks are opportunistic predators that feed primarily on small fish (e.g. stingrays) and some invertebrates (e.g. crustaceans, molluscs, tunicates). They are typically solitary nocturnal animals, rifling through bottom sediments in search of food at night, but often gregarious during the day forming large sedentary groups. Nurse sharks are obligate suction feeders capable of generating suction forces that are among the highest recorded for any aquatic vertebrate to date. Although their small mouths may limit the size of prey, they can exhibit a suck-and-spit behavior and/or shake their head violently to reduce the size of food items.
Starfish
While a starfish lacks a centralized brain, it has a complex nervous system with a nerve ring around the mouth and a radial nerve running along the ambulacral region of each arm parallel to the radial canal. The peripheral nerve system consists of two nerve nets: a sensory system in the epidermis and a motor system in the lining of the coelomic cavity. Neurons passing through the dermis connect the two. The ring nerves and radial nerves have sensory and motor components and coordinate the starfish's balance and directional systems. The sensory component receives input from the sensory organs while the motor nerves control the tube feet and musculature. The starfish does not have the capacity to plan its actions. If one arm detects an attractive odour, it becomes dominant and temporarily over-rides the other arms to initiate movement towards the prey. The mechanism for this is not fully understood.
Starry flounder
The starry flounder before metamorphosis is dependent upon planktonic organisms as a food source during its younger stage of life. Feeding is usually done by waiting for the prey to settle to the floor or around eye level of the flounder and then make a quick lunge at the food drawing a mouthful of water also to help pull the prey in. As the fish develops more, they are able to feed upon small clams, some larger fish, invertebrates and also worms. When the starry flounder reaches adulthood the primary stomach contents that has been found are clams. Clams that are too large for ingestion often have their siphons eaten.
Mycale adhaerens
The relationship between the sponge and the scallop on which it lives is mutualistic, each receiving benefits. The scallop is often preyed on by the starfish "Evasterias troscheli" but when the starfish touches the sponge it tends to move away, either being repelled by some secretion from the sponge or by the spicules present in the sponge's tissue. If the starfish does try to force the scallop's valves apart, the tube feet seem unable to obtain a purchase on the sponge. Quite apart from this, the scallop will often try to escape from the starfish by swimming away, and will also try to evade the nudibranchs "Doris odhneri" and "Peltodoris nobilis" which feed on the sponge.
Shortnose spurdog
Though sharks across separate ecosystems do favor similar diets despite their location, their diet diversity does slightly differ depending on the ecosystem. Specifically, shortnose spurdog sharks live off the east coast of Australia show an increased level in their diet diversity when compared to other population groups in Australia. Size also plays a role in diet. While larger, sexually mature sharks typically go after prize pray such as mollusks, smaller sharks rely more heavily on crustaceans. This is primarily because squids, octopuses and other mollusks on the menu for the shortnose spurdog are often free swimming and easier to catch. This makes it more difficult for smaller sharks to rely on them as a source of food. Instead the smaller shortnose spurdogs will rely on benthic prey since benthic prey live on the surface of the ocean floor.
Asterinidae
Most of the species feed on food fragments and algal or bacterial mat covering the substratum, evaginating their stomach on their food (a frequent feeding mode in sea stars). However, some species like "Stegnaster inflatus" takes advantage of their webbed shape to form a "trap" by heightening on the tip of their arms, and suddenly falling on a prey which would have believed to find shelter there.
Mollusca
Most molluscs are herbivorous, grazing on algae or filter feeders. For those grazing, two feeding strategies are predominant. Some feed on microscopic, filamentous algae, often using their radula as a 'rake' to comb up filaments from the sea floor. Others feed on macroscopic 'plants' such as kelp, rasping the plant surface with its radula. To employ this strategy, the plant has to be large enough for the mollusc to 'sit' on, so smaller macroscopic plants are not as often eaten as their larger counterparts.
Filter feeders are molluscs that feed by straining suspended matter and food particle from water, typically by passing the water over their gills. Most bivalves are filter feeders.
Molluscivore
Starfish: Primitive starfish, such as "Astropecten" and "Luidia", swallow their prey whole and start to digest it in their cardiac stomachs. Shell valves and other inedible materials are ejected through their mouths. The semi-digested fluid is passed into their pyloric stomachs and caeca where digestion continues and absorption occurs. The margined sea star ("Astropecten articulatus") is a well known molluscivore. It catches prey with its arms which it then takes to the mouth. The prey is then trapped by the long, moving prickles around the mouth cavity and swallowed food.
Bigeye thresher
The large eyes of the bigeye thresher are adapted for hunting in low light conditions. It is one of the few sharks that conduct a diel vertical migration, staying in deep water during the day and moving into surface waters at night to feed. To protect its sensitive brain and eyes from the temperature changes accompanying these movements, the bigeye thresher has a vascular exchange system called the rete mirabile around those organs. This species feeds mainly on fish and squid, which are stunned via whip-like strikes of the long tail. Bigeye threshers are ovoviviparous, usually bearing litters of two pups. The embryos are oophagous and feed on ova produced by the mother while inside the uterus. This shark is caught by commercial fisheries across its range; the meat is not highly regarded but the skin, fins, and liver oil are valued. It has been assessed as Vulnerable by the International Union for Conservation of Nature (IUCN).
Crown-of-thorns starfish
By Day 1 the embryo has hatched as a ciliated gastrula stage (photograph). By Day 2 the gut is complete and the larva is now known as a bipinnaria (photographs). It has ciliated bands along the body and uses these to swim and filter feed on microscopic particles, particularly unicellular green flagellates (phytoplankton). The SEM photograph is a scanning electron micrograph, which clearly shows the complex ciliated bands of the bipinnaria larva. By Day 5 it is an early brachiolaria larva. The arms of the bipinnaria have further elongated, there are two stump-like projections in the anterior (not evident in the photograph) and structures are developing within the posterior of the larva. In the late brachiolaria larva (Day 11)(photograph) the larval arms are elongate and there are three distinctive arms at the anterior with small structures on their inner surfaces (photographs). To this stage the larva has been virtually transparent, but the posterior section is now opaque with the initial development of a starfish. The late brachiolaria is 1-1.5 mm. It tends to sink to the bottom and test the substrate with its brachiolar arms, including flexing the anterior body to orient the brachiolar arms against the substrate.
Molluscivore
The black carp ("Mylopharyngodon piceus") commonly feeds by crushing large molluscs with pharyngeal teeth, extracting soft tissue, and spitting out shell fragments. Four-year-old juveniles are capable of consuming approximately 1–2 kg of molluscs per day. This bottom-dwelling molluscivore was purposely imported into the United States in the early 1970s for use as a food fish and also as a biological control agent for snails—an intermediate host for a trematode parasite in fish reared on fish farms. Two snail-eating cichlids, "Trematocranus placodon" and "Maravichromis anaphyrmis", have been tried as biological control agents of schistosomes in fish ponds in Africa. Redear sunfish ("Lepomis micropholus") and bluegill ("Lepomis macrochirus") have been used to control quagga mussels ("Dreissena bugensis") in the lower Colorado River in the US.
The common name of some fish reflects their molluscivorous feeding, for example, the "snail-crusher hap" ("Trematocranus placodon"), ""red rock sheller" ("Haplochromis sp."), "Rusinga oral sheller" ("Haplochromis sp.") and "rainbow sheller" ("Haplochromis sp."). The redear sunfish is also known as the "shellcracker".
Porcupine Abyssal Plain
The ecosystem is profoundly changed by the reworking and consequent aeration of the seabed surface layers. The starfish "Psilaster andromeda" which feeds mainly on molluscs is present on the abyssal plain. The detritivore starfish "Hyphalaster inermis" and "Styracaster chuni", both of which feed by ingesting mud, are also common. There are a number of species of sea anemone present, also sea spiders, tunicates and dumbo octopuses ("Grimpoteuthis" spp).
Asterias forbesi
Starfish can locate their prey by chemoreception. In a trial, sixty "Asterias forbesi" that had not been fed for a week were used. The bait was a piece of mussel flesh in a tank of slowly circulating water. Test starfish were placed in the downstream odour plume, one metre (3 ft 3 in) away from the food source and the movements of each starfish were recorded on videotape. A control was provided using the same flow conditions but without an odour being present. 12 of the test starfish (20%) moved towards the target and got within of it in the allotted 15 minute timespan. The direction of movement became more accurate as the distance from the bait shortened. The rate of movement was slower than that of the control starfish and it was thought that this slower speed might improve the ability of the starfish to taste the water and make accurate comparisons of odour concentrations. None of the control starfish moved purposely in any direction, tending to move in random directions, circling and crossing their previous paths. It was proposed that more starfish would have moved towards the bait if they had previously been starved for a longer period. Other similar trials have involved starving starfish for two months prior to the experiment and this provides greater motivation to seek prey.
Henricia lisa
Members of the genus "Henricia" are suspension feeders, and feed efficiently on phytoplankton. For this purpose, the starfishes have Tiedemann pouches at the bases of the digestive glands; these create water currents by use of flagellae. These starfishes are often found in association with sponges, benefiting from the current of water they create.
Speartooth shark
The speartooth shark seems to be relatively sluggish in nature, moving with the tides so as to conserve energy. Its activity levels are unaffected by day or night, reflecting the constant darkness of its environment. Small eyes and abundant ampullae of Lorenzini suggest that this shark relies more on electroreception than sight to hunt, while the large second dorsal fin enhances its ability to maneuver at slow speeds in fast currents. It has slender teeth adept for catching bony fishes and crustaceans, mostly on or near the bottom. Known prey of juveniles include "Macrobrachium" prawns, "Taenoides" or "Trypauchen" burrowing gobies, ariid catfish, the threadfin "Polydactylus macrochir", the gudgeon "Prionobutis microps", the benthic croaker "Nibea squamosa" and the bream "Nematalosa erebi". Very little is known about the feeding habits of adults, but many bony fish spines and a stingray spine were found embedded in the jaws of the only documented adult female. As in other requiem sharks, the speartooth shark is viviparous: when the developing embryo exhausts its supply of yolk, the yolk sac develops into a placental connection through which the mother delivers nourishment. Birthing seems to occur from October to December, near the end of the dry season, with newborns measuring around long. Upon being captured a female gave birth to a single fully developed pup, about long, and anecdotal information indicates a litter size of six to seven. The growth rate of young sharks is probably around per year.
Fromia nodosa
This starfish has a nocturnal activity and feeds mainly on bivalve molluscs, corals, detritus and microalgae. To ingest its food, it needs as all other sea stars to externalize its stomach, this action is also called devagination, and has to make an external digestion.
Blue shark
Squid are important prey for blue sharks, but their diet includes other invertebrates, such as cuttlefish and pelagic octopuses, as well as lobster, shrimp, crab, a large number of bony fishes, small sharks, mammalian carrion and occasional sea birds. Whale and porpoise blubber and meat have been retrieved from the stomachs of captured specimens and they are known to take cod from trawl nets. Sharks have been observed and documented working together as a "pack" to herd prey into a concentrated group from which they can easily feed. Blue sharks may eat tuna, which have been observed taking advantage of the herding behaviour to opportunistically feed on escaping prey. The observed herding behaviour was undisturbed by different species of shark in the vicinity that normally would pursue the common prey. The blue shark can swim at fast speeds, allowing it to catch up with prey easily. Its triangular teeth allow it to easily catch hold of slippery prey.
Novaculichthys taeniourus
The fish feed on benthic invertebrates including molluscs, crabs and polychaete worms. One fish turns or shifts large pieces of debris or rubble, grabbing or pulling it with its mouth or pushing it with its snout. When the working member of the pair has revealed the prey, the other fish quickly grabs and eats it. Juveniles do not usually work in pairs, doing all the work themselves. Facing danger, these wrasses quickly dive into the sand for protection.
Starfish
Echinoderms, including starfish, maintain a delicate internal electrolyte balance that is in equilibrium with sea water. This means that it is only possible for them to live in a marine environment and they are not found in any freshwater habitats. Starfish species inhabit all of the world's oceans. Habitats range from tropical coral reefs, rocky shores, tidal pools, mud, and sand to kelp forests, seagrass meadows and the deep-sea floor down to at least . The greatest diversity of species occurs in coastal areas.
Astropecten armatus
"Astropecten armatus" is an agile starfish. It can "glide" across the surface of the sand with its mobile tube feet. If turned upside down it can right itself with a flip and if several are stacked on top of each other, they will quickly disperse. It is a predator and primarily feeds on the olive snail ("Olivella biplicata"). It can consume these at the rate of one each day but, when they are less plentiful, it will turn to other food sources and eat sand dollars and sea pansies ("Renilla reniformis") and scavenge on dead fish.
Starfish
The lifespan of a starfish varies considerably between species, generally being longer in larger forms and in those with planktonic larvae. For example, "Leptasterias hexactis" broods a small number of large-yolked eggs. It has an adult weight of , reaches sexual maturity in two years and lives for about ten years. "Pisaster ochraceus" releases a large number of eggs into the sea each year and has an adult weight of up to . It reaches maturity in five years and has a maximum recorded lifespan of 34 years.
Asterias forbesi
The sexes are separate in "Asterias forbesi". Sperm and eggs are liberated into the sea and fertilization is external. The starfish in any area may synchronise their emission of gametes which will increase the chance of fertilization taking place. The eggs hatch into bipinnaria larvae which form part of the zooplankton and develop over a period of about three weeks before settling on the seabed and undergoing metamorphosis into juvenile starfish.