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How does an eel larva differ in appearance from an adult eel?
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eel
The American eel (Anguilla rostrata) is found in habitats along the coast of eastern North America.
Eel larvae, known as leptocephali, differ significantly in appearance from adult eels. While adult eels typically possess an elongated, cylindrical, and streamlined body, the leptocephalus is characterized by a transparent, gelatinous, and leaflike shape that is laterally compressed.12
Key differences include:
- Body Structure: Larvae are often thin and deep-bodied, sometimes resembling a small dinner plate, whereas adults are streamlined and often attenuated.1
- Pigmentation: Leptocephali are transparent and feature larval melanophores in various patterns, which disappear during metamorphosis.12
- Features: Larvae possess sharp, forward-pointing teeth and a subterminal anal vent. During metamorphosis, these teeth are lost, the snout becomes rounded, and the anal vent shifts toward the midpoint of the body.12
- Bulk: The body of a larva is significantly reduced in bulk—sometimes by as much as 90 percent by weight—as it transforms into the cylindrical form of an adult.2
These dramatic structural changes allow the leptocephalus to survive as a planktonic organism in the open ocean before transitioning to the distinct habitat and lifestyle of an adult fish.2