how would you describe the structure of their heart?
They have a main systemic heart that pumps blood around the body as part of the general circulatory system, and two branchial hearts.
Squid
. Squid have a main systemic heart that pumps blood around the body as part of the general circulatory system, and two branchial hearts. 
squid are members of what phylum and what class They are members of the class Cephalopoda, subclass Coleoidea. with reference to the class mentioned, what is the meaning of the name it derives? UNANSWERABLE with reference to the creature mentioned, how would you describe its physical appearance? The head and foot of the squid are at one end of a long body, and this end is functionally anterior, leading the animal as it moves through the water. A set of eight arms and two distinctive tentacles surround the mouth; each appendage takes the form of a muscular hydrostat and is flexible and prehensile, usually bearing disc-like suckers. from which part of their body do these creatures release ink? The ink gland and its associated ink sac empties into the rectum close to the anus, allowing the squid to rapidly discharge black ink into the mantle cavity and surrounding water. why do these release this substance? Squid distract attacking predators by ejecting a cloud of ink, giving themselves an opportunity to escape. what are the features of their nervous system? Squids have a complex brain in the form of a nerve ring encircling the oesophagus, enclosed in a cartilaginous cranium. Paired cerebral ganglia above the oesophagus receive sensory information from the eyes and statocysts, and further ganglia below control the muscles of the mouth, foot, mantle and viscera. do these creatures have a specific breeding season? Courtship in squid takes place in the open water and involves the male selecting a female, the female responding, and the transfer by the male of spermatophores to the female. In many instances, the male may display to identify himself to the female and drive off any potential competitors. what is the maximum length the largest species can grow? UNANSWERABLE what do these creatures feed on? Squid are carnivores
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Squid [SEP] Cardiovascular and excretory systems
The squid mantle cavity is a seawater-filled sac containing three hearts and other organs supporting circulation, respiration, and excretion. Squid have a main systemic heart that pumps blood around the body as part of the general circulatory system, and two branchial hearts. The systemic heart consists of three chambers, a lower ventricle and two upper atria, all of which can contract to propel the blood. The branchial hearts pump blood specifically to the gills for oxygenation, before returning it to the systemic heart. The blood contains the copper-rich protein hemocyanin, which is used for oxygen transport at low ocean temperatures and low oxygen concentrations, and makes the oxygenated blood a deep, blue color.