Missing Dorsal Fin Streamer

My McCoskers Wrasse, who is a young male in good health, has somehow lost the streamer on his dorsal fin. He is housed with peaceful fish and I don't see any of them picking on him or nipping him. My Linespot Wrasse used to flash a lot, but they never had any real aggression towards each other. Now the McCoskers spends a lot of time hanging out with the Linespot. Is it possible that he's reverting, to a certain extent, back to a female if the Linespot has established dominance? If the damage occurred due to trauma, will it grow back?

 

It happens. But I highly doubt it's due to a reversion; 90% likely it was ripped/chomped off.

As it's a soft ray, it will grow back. (Unless the dorsal fin is damaged down to where it meets the body)

 

The damage is just to the streamer, the rest of the fin looks normal, so hopefully it grows back.

While I have your ear Evolved, will he start flashing as he matures? He's very small and he's never flashed. His blue lines rarely glow, but they do sometimes if he's excited from eating.

 

Probably, but it all depends on tank dynamics and relationships; social roles.