Tuesday, April 24, 2012

Let's Go Spelunking!: Waterfall-Climbing Cave Fish.

As hinted at in yesterday's entry, cave creatures can get pretty darn creepy. They often have pale skin and no eyes- usually enough to create a terrifying effect by themselves. They use senses that are either diminished in humans or completely absent. Troglobites (creatures that live in caves) are about as close as we can get to aliens on earth.  The deepsea abyss is a close second, of course.

Enter the first of the animals this week that will both terrify and fascinate you: the Waterfall Climbing Fish (Cryptotora thamicola).  It makes its home in a special type of limestone cave called a karst. It eats biofilm (i.e. that grimy stuff you might find in pet dishes) off of rocks in the darkness. Native only, and we mean only, to Thailand, it is darn near impossible to see in the wild. I don't think there are any captives, so very little is known about these fish indeed. It is also called the "cave angel fish."

The Waterfall Climbing Fish exhibits many traits common to most animals that spend their lives entirely in caves. It's blind. Its skin is white and slightly translucent. It sends chills through your soul because it looks so much like a regular fish, but not. Welcome to cave life!

Then the Waterfall Climbing Fish takes the weirdness up a notch by making Christians commit mass suicide: It climbs with its fins. Although not truly lobed like the fins of lungfish or coelacanths, the waterfall fish's fins are indeed able to move like feet. In that light, it's also interesting how these not-limbs are positioned (the actual 'body' of that fish isn't that long - on most fish, the hind fins would be way farther back). Give it a few millennia and we may well get an eyeless lizard that has evolved completely independently from all other reptiles. Darwin was right.

There is no endangered status for this fish, but it's so rare that it's listed as vulnerable. There is likely not enough data to truly classify it as endangered. However, nearly all freshwater ecosystems are extremely fragile; there's no reason a single cave in Thailand should be an exception to that. It probably does deserve to be on the endangered list if it's that rare.

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