What specific facial features develop prominently on mature male Wolf Eels?

A noticeable head crest and notably large lips.

Sexual maturity in the Wolf Eel brings about distinct physical differences between males and females, a form of sexual dimorphism observable on the face. Male Wolf Eels develop exaggerated features that contribute to an overall thicker appearance of their jaws. Specifically, males commonly develop a prominent protuberance on the top of their head, referred to as a head crest. Concurrently, they exhibit notably larger lips compared to their female counterparts. These combined characteristics alter the male's visage, contributing to the intimidating facial structure from which the 'wolf' moniker is partially derived. While females may exhibit slight color variation, these specific cranial and labial growths are hallmarks of the mature male.