Alien #7 is a flamboyantly-finned larval Spotfin Flounder (Cyclopsetta fimbriata). Body length ~1cm.
While in their larval stage, larval flounder resemble most other fish in the sense that they have one eye on each side of their head. It’s not until they settle and metamorphosize that one eye migrates to the “top” side, as they begin life in the sand.
Several distantly-related fish have conspicuous fin “flags” in their larval stage. One would think advertising one’s self in a fish-eat-fish world of open blackness is a good way to get eaten! Also, the added hydrodynamic drag seems disadvantageous. Add to that the caloric expenditure and upkeep of such flashy fins…it just seems like such a bad idea! But nature always has a reason, and currently, the best theory is that these appendages resemble the tentacles of a stinging siphonophore, which are quite common predators of the open ocean.
Also unique to this photo, is that I’ve caught the flounder in mid-yawn! Many predatory fish stretch their jaws every so often, and catching this behavior is somewhat of an obsession for me!