The migratory eel, Anguilla rostrata, is born and lives the juvenile (immature) part of its life in a freshwater environment, but then migrates thousands of miles through the ocean as an adult in order to breed. These eels are known to regulate their internal water and salt balance. What adaptations would you expect this eel to have in order to transition from fresh water to salt water at these two life stages?
A) The juvenile eels would be better at removing salt from their bodies compared to adults.
B) The adult eels would be better at removing salt from their bodies compared to juveniles.
C) The juvenile eels would spend energy keeping water in their bodies.
D) The adult eels would spend energy keeping salt in their bodies.

Question

Quizplus · Accepted Answer

The question is asking about the adaptations needed to transition from fresh water to salt water at two different life stages. The adult eels migrate through the ocean, which is a saltwater environment, to breed. Therefore, the adult eels would need to be better at removing salt from their bodies compared to juveniles, which live in freshwater environments. The juvenile eels would spend energy trying to keep water in their bodies, but this is not related to salt regulation. Therefore, options A and C are not correct. The adult eels would need to spend energy keeping salt in their bodies so they do not become dehydrated in the saltwater environment, so option D is also correct.

The Migratory Eel, Anguilla Rostrata, Is Born and Lives the Juvenile