Today I wondered about the smartest fish in the sea, and this is what I found. The top hit was an article by Karl Gruber (Our Blue Planet/BBCearth), titled “These are the world’s smartest fish”. Well, Gruber says the Killfish are a super smart/adept species, because apparently the mangrove rivulus aka killfish (Kriptolebias marmoratus) has no qualms being a “discriminating” cannibal and will eat the eggs of other fish but not eat the eggs of it’s own kind.

You can read more about this fish and others in Grubers, Our Blue Planet article here.

Kriptolebias marmoratus, image by
By Cardet co6cs CC BY-SA 3.0

But wait, there’s more! Intrigued by this fish, I did the usual Wikipedia check for more info and found that the killfish can live on land for about 2 months by adjusting its gills to retain water and nutrients, while nitrogen waste is excreted through their skin. The process is reversed once the fish returns to ocean water. That’s right! They can live for over two months on dry land! However, most are only 2″ inches long and not very good eating I would guess. Some research indicates killfish have been self replicating as an exact copy of itself for over 200,000 years.

Not only that, while on land, Killfish can do tail flips to move in the direction of the most desirable real estate! And here’s yet another odd twist, killfish are mostly hermaphrodites and can self reproduce, yet some “males do exist” and there is some outcrossing among this species which is noted by “these three-guys“, in a scientific paper from 2006, (Royal Society B: Biological Sciences).

So, imagine that, fish that can vacation 66 days (or so) a year on dry land, make their own babies, and recognize eggs of their own kind to avoid eating them as a snack. Now that’s evolution 101….Don’t eat your babies! post by Stu C.