“Can you explain the fish with two bugs in its mouth ??”
ABSolutely, my friend! Say hello to Cymothoa exigua, the tongue-eating louse. If ye be weak of stomach, slap on your anti-parasite goggles and scroll right on by!
Photo from Futurism
These fellas are very cool as long as they stick to fish and never ever come close to me because they are the only known example of parasite completely and functionally replacing the organ of a host.
Juvenile C. exigua are free-swimming, and will locate a host (usually snappers) and enter via gill slits, where they will attach themselves, as males, in the gill chamber and start growin’. In a beautiful example of protandrous hermaphroditism, one lucky male will get EXTRA big, turn female, dig all seven pairs of her spiky little grabbers into that tongue to cut off all circulation, and bury her butt in the base to replace that sucker once and for all.
In this particular picture, the second lil’ guy in there is one of the males, having crawled up out of the gill chamber to mate with the female. There seems to be some contention on if females mate once or many times, since the development of all ~400 eggs actually completely and utterly disintegrates all her other organs, which argues for a single brood - but drastic variation in sizes of females suggests that they actually regrow basically their entire body and have multiple broods.
Shockingly, the fish isn’t even mildly inconvenienced by any of this whatsoever. C. exigua is a “benign parasite”, and the fish can eat as normally as it always does - rarely is a host even found to be moderately underweight. They just live their lives with tiny isopod freeloaders in their mouths, undoubtedly making snide comments and backseat driving the whole goddamn way