Vorticella companula

• It is the long, transparent larva of marine petromyzon.

• Body of ammocoetes is thin and laterally compressed.

• Body is supported by an unconstructed notochord.

• Pharynx is ciliated and perforated by 7 pairs of gills slits.

• Besides resembling amphioxus, ammocoetes closely approaches a generalized chordate plan.

• It is not a ciliary feeder.

• Two major instinctive response of larva are photokinesis and thigmotaxis.

• Migrates downstream to the sea and then grows to a predatory adult.