Speculative Biology Sunday: Land Fish

28 Feb

Once upon a time, a long time ago (somewhere in the order of 350 million years ago) fish evolved to to such a point that they could comfortably leave the comfort of the water for long periods of time, eventually to the point that they could live most of their lives out of the water.
As far as we know, that was the only time this has happened. Why not?
Well mostly because any fish that starts to evolve terrestriallity is hastily outcompeted by the multitude of land critters that have long ago mastered living out of water.
But what if by some amazing set of circumstances, fish did get the chance to have another shot at conquering dry land?
There are quite a few species of semi amphibious fishes floating around at the moment. Mudskippers, and the Climbing Gouramin are good examples of this.
But the one I want to focus on in this post is the Walking Catfish.

Walking Catfish
Modern Walking Catfish are already accomplished landsmen. On being introduced to florida, they have become a rather troublesome pest species, moving overland to get to new ponds, rivers and swampland. They have a snakelike thrashing mode of walking, using their spiney pectoral fins to provide traction. Their gills have a branching supportive gill arches that support their gills out of water, allowing them to breathe air with them.

Add more selection towards landlubbing and bake for a million years or so and I think you would have something akin to this.

Future Catfish
The ray fins proving to hard to associate together in a way able to support body weight without further and extreme selection, these terrestrial catfish have opted for a more snakelike form of locomotion, using their spiney fins as purchace on slipperier terrain.
The surface area and volume of their gills has increased to improve their oxygen uptake from the air. They also absorb oxygen through their skin.
Their elongated body aids the serpentine form of locomotion.
Their barbels still function as sensory organs and so are constantly waving around and touching things in the path of any given individual, resembling an ants antennae.
Their swimming fins are greatly reduced. The eel-like dorsal fin is elongated down the back of the tail and replacing the absent caudal fin.

Mostly insectivorous, but otherwise oppurtunistic omnivores.

That is all for now. Might do another post in the future about where they go from here.
I actively encourage questions 🙂

TYFYT

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2 Responses to “Speculative Biology Sunday: Land Fish”

  1. Margaret Pye April 29, 2010 at 7:26 pm #

    How exactly do the gills work in air? How do they avoid dessication?

  2. mitchbeard April 30, 2010 at 12:57 am #

    The modern walking catfish already have the mechanisms in place to work in air. They have supporting structures in the a couple of their gill arches that stop them collapsing when not supported by water. There was more detail on this on the walking catfish’s wikipedia page, but it is unfortunately not on their anymore. From how it was described it sounded a lot like a book lung that some terrestrial arthropods use.
    They also avoid dessication by not drying out, as tautalogical as it sounds. The animal I have proposed here is not perfectly adapted to a terrestrial lifestyle, and is more analogous to an amphibian.

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