what's the frequency of the letter "a" in:
i saw the page on the acoel flatworms which occasionally show up in reef aquaria, and are mistaken for nudibranchs... i can not identify the acoels pictured, although that type of acoel tend to be small predators of copepods, other small flatworms etc.
the most common type of acoel to show up in reef tanks is probably the brick-red to orange convolutriloba sp. (usually referred to convolutriloba retrogemma, but i suspect several species occur). convolutriloba and some other acoels reproduce primarily asexually, by fission, and i've attached a picture showing the densities these worms can attain in aquaria with strong light (they have symbiotic algae) and abundant copepod prey. the picture shows a typical section of the front pane, about 4x3cm, of a heavily infested aquarium.
they are not parasitic, but can reportedly damage corals by shading. at present no easily available predator of these worms is known, although i would speculate that the white star-trek symbol shaped acoels pictured on the flatworm page would probably eat them.
normally, however, the worms disappear on their own accord after a few months, presumably after having exhausted some necessary nutrient. there have been some recent developments regarding convolutriloba in aquaria - specifically two antihelminth drugs have been released, which can be used to destroy these worms with 'fairly' mild repercussions to fish and corals.
thanks very much for the information and the photos. your message is, by chance, an excellent answer to another one i am posting today from kevin hartley.
user
The given text has 121 "a"s.
assistant