Ammocoetus larva
Phylum: Chordata
Sub - phylum: Vertebrata
Class: Cyclostomata
Order: Petromyzontia
• 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.