Eels, particularly the moray eel, are popular among marine aquarists. The eels were more resistant to the venom of the eel specialist sea snake. Endemic fish include the Puerto Rican snake eel and the Puerto Rico coralbrotula. A notable example occurs with the moray eel. Trout may feed on shrimp, mealworms, bloodworms, insects, small animal parts, and eel. Stings by striped eel catfish have killed people in rare cases. The heaviest true eel is the European conger. They open wide enough to swallow a fish larger than the eel itself. The pharyngeal jaws of the moray eel (family Muraenidae) possess their own set of teeth. Gymnotids, such as the electric eel, and the large silurid catfish are among aquatic competitors. The Japanese freshwater eel produces a fluorescent protein. "Unakyu" is a common expression used for sushi containing eel & cucumber. The European eel is a critically endangered species. Another Atlantic eel species is known&colon; the American eel, "Anguilla rostrata". A majority of eel species are nocturnal, thus are rarely seen.