Let's Go Spelunking: Mexican Tetra.

Just when you thought cave animals could not get any weirder, this happens:



Those are both the same species of fish, the Mexican tetra (Astyanax mexicanus). It ranges from the Rio Grande in Texas to Central Mexico, both in caves and in surface rivers. The main (but not only) difference between them is simple: One has eyes and one does not.

The eyed and eyeless Mexican tetras have several differences. While the Mexican tetra's surface form looks like, well, a normal silvery fish, the cave form is albino, almost see-through, and, most obviously, eyeless. On the slightly less noticeable side of things, cave tetras store more energy as fat and have much better senses of smell and hearing than their sunlight-dwelling brethren. If you want to see how stuff that evolved in caves is different from its counterpart on the surface world, Mexican tetras are a great place to start. 

Love is blind! (c) Richard Borowsky.

When the blind specimens are born, they have eyes. As the fish grows, opaque skin grows over the eyes, rendering the fish completely blind. The eyes themselves also degenerate as the fish grows older. The coding for eyes is there, it just gets overridden as the fish matures. Nobody knows precisely why, but theories such as protein conservation and sheer dumb luck have both been tossed around.

The exotic pet trade loves these fish, particularly the blind ones. They recommend putting natural rocks into the tank and keeping them in semi-aggressive schools. The appeal is obvious: pet hobbyists, regardless of what sort, like different things.  It's hard to get more different than a blind fish with a see-through body. 

Creationists also love picking on this fish as evidence against evolution. Without factoring in the extensive adaptations this fish has made to cave life, it seems weird that an animal would develop eyes, then suddenly lose them. Clearly they are not familiar with the sheer amount of junk traits humans have retained over time, like our ill-adjustment to something as basic as being bipedal.

Let's Go Spelunking: Cave Shrimp + Crayfish

(Apologies: I went to take a nap and wound up sleeping longer than intended. Come hither, Hell Week...)

Remember when I mentioned that cave creatures had a strange aesthetic to them? Well, to be more specific, creatures that spend their lives exclusively in caves tend to have a few features in common.  These include pale skin, poor or absent eyesight, reduced size, and enhanced senses of hearing, touch, and smell. In human terms, 3/4 isn't bad, nerds.

Lincoln approves of cave shrimp?

Enter the Kentucky and Alabama cave shrimp (Palaemonias). They are both native to the Southwestern U.S. as their names imply. Yes, apparently the South has a lot of neat cave life. They eat anything that washes into the sediments underground. (FYI: Since several kinds of shrimp do in fact eat dirt like this, they are probably not the healthiest seafood in the world.) As the picture above demonstrates, they are smaller than a penny.

Cave shrimp are a prime example of what happens to 'normal' animals once they adapt to cave life. These shrimp are not just blind - they're completely eyeless. They're pure white with translucent skin. If they ever left the safety of the caves, they would die in a heartbeat. Even as they are, they have predators in other cave creatures such as salamanders, raccoons, and equally-blind cave crayfish (a case of the blind eating the blind).

Yes, crayfish live in the caves, too. There are several species (Cambarus pecki in Alabama; Procambarus elsewhere), several of which live in Florida and all of which are endangered. They look a lot like cave shrimp, only bigger, nastier, and with pincers. Like the shrimp, their skin is so light you can see through it - who needs melanin when you live in depths in which nothing can see? It's amazing; we could have saved so much mess in biology if some smart soul had bred translucent crayfish for us to study.

Both species of cave shrimp and all cave crayfish are endangered. The main cause for this classification is poisoned groundwater. As we've said before, freshwater ecosystems are fragile. So are species that are highly adapted to one environment. Cave shrimp will probably not be around much longer, so enjoy them while you can.

Let's Go Spelunking: Dismalites.

As you all probably know, I'm a huge fan of things that glow in the dark. Bioluminescent animals are of particular interest to me. Go figure that caves have some creatures that glow in the dark. Bioluminescence occurs wherever there's darkness - you just need to know where to look for it.

If fireflies and mushrooms are not your cup of tea and you still want to see something glow in the dark on land, look no further than the caves in Dismals Canyon, Alabama. The caves there are chock full of glowing worms called dismalites (Orfelia fultoni). They are related to the Arachnocampa of New Zealand. They make the inside of a cave look covered in cyan stars. 

Beware, looks are deceiving! That light show looks like a starry sky for many invertebrates flying into the cave, too. The glowing spots are just a trap to lure in tasty moths, larger flies, and other creepy crawlies, including mosquitoes. The glowly spots conceal an intricate web of mucous strings that works almost like a spiderweb, snatching prey in mid-air. Although we may be big enough to avoid getting caught in the web, other insects are not so bright and get stuck in the sticky strands. The larvae then feed on the helpless bugs to their hearts' content. If other bugs are not available, they resort to eating their own pupae.

These enchanting, yet vicious, little glow-worms are members of the family Diptera, which also contains the ever-popular fruit flies and garbage-eating houseflies. The adult form of these glowing larvae is a type of fungus gnat. They stay a long time in their larval form, however - if Arachnocampa are any indication, anywhere from 6 months to a year, which is like eons to a fly. Beelzebub would be so proud to see humans ogling his not-as-repulsive familiars.

As one may have suspected, there are a lot of larvae up there. This is an immense gathering of flies that just so happens to look attractive to us humans. They need very specific conditions to gather in such numbers. Along with keeping cave water clean for human use, let's preserve cave ecosystems to keep the second starry sky alive.

Let's Go Spelunking/They Actually Eat That: Bats.

It was difficult to pick a "They Actually Eat That" for this week. One, this week is Hell Week, meaning that a lot of tests and reports are due this week. Two, humans don't live in caves, so we haven't had that much time to turn the life there into cuisine. Three, umm, people eat bats, even if they aren't necessarily the cave-dwelling kind.



No, not like that! If you look up bat recipes, you get a million fake Halloween bat cupcakes, "bat wings" (black chicken wings made by Martha Stewart. May contain some seasoning from hell, but still not real bat), and so on. In America, we love eating bat-shaped things around Halloween...so long as no actual bats are involved.

Actually, a lot of places eat bat. If a place has bats, specifically flying foxes, someone will find a way to eat them. This restricts chiropteran cuisine to Africa, India, and Southeast Asia. China eats everything; no surprise that bats are on the menu. Sometimes, you can even find bat in Australia. A few places may eat microbats, but by and large, it's only flying foxes on the menu.


(This does not look like a flying fix to me...but there may be a scale issue.)

Eating flying foxes may not be particularly good for you. There is at least one flying fox species that has become endangered due to over-hunting. Flying foxes have also been linked to a number of diseases, including, but not limited to, SARS, Ebola, and Nipah virus. No offense to the cultures that regularly have bat on the menu, but there is a perfectly logical reason that some of us avoid it. Not that beef is really good for you, either...but that's for another entry.

As for what it tastes like? Rumor has it that bat meat smells, but otherwise tastes like chicken. It can be roasted like chicken, seasoned like chicken, and thrown in a stir fry like chicken. There really not much special about bat meat to most people except its sheer oddity.  It's mostly a big treat for foodies.

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.

Bio-Art/ Let's Go Spelunking: The Descent.

In a move expected by hopefully no one, the last week before finals will be a Theme Week! Thisweek's theme will be subterranean life. Although this may sound cheesy, life underground can be just as terrifying as life in the deepsea abyss...only it's on land, so one wrong evolutionary move and we may well have a monster on our hands with easy access to meat. This threat has not gone unnoticed by filmmakers.

The Descent is a British 2005 horror film about a group of ladies who go on a spelunking trip. Unfortunately, they wander into the wrong cave and come face to face with a number of problems - the least of which is that they do not have a map. Their equipment starts to malfunction as they wander deeper into the caves, one of their party breaks a leg, and they find hundred-year-old equipment. Oh, and they meet these guys:


Meet the crawlers, the monsters of The Descent. They appear at roughly 50 minutes into the movie, but their presence is preceded by a series of clicks and occasional flashes of humanoid figures in the caves. These are not aliens - they're cavemen who never really left the caves and evolved over millennia. As per the director Neil Marshall: "I didn't want to make them aliens because humans are the scariest things." So true.

Right off the bat (ha ha), it is easy to tell that a ton of effort went into making these things not only creepy, but also well-adapted to their environment. Like many cave creatures, they have pale skin and are completely blind. They hunt entirely by sound (as confirmed both by their clicks and a rather annoying alarm clock), just like microbats. Although hard to catch, I'm pretty sure their limbs are not only adapted to scale walls, but also slightly longer than those of an average human. Basically, the women were doomed as soon as they wandered into the wrong cave...but they put up one helluva fight until the end. (No, it does not end well - the 'happy' American ending was a hallucination in the original British version.)

Besides making them perfect cave hominids in terms of adaptations, the directors were careful to show that these creatures had families very much like humans do. Female and child crawlers can be seen in the film as well. Unlike Clover, who was meant to illicit sympathy on some level but never really made it, The Descent's crawlers touch a human nerve. Even with the fear factor going, once one sees that these things have lives of sorts, one can't help but wonder who the real monsters are. There are a few jarring scenes that make the parallel between humans and crawlers particularly close - for example, when one of the women stabs a crawler to death, then immediately goes nuts on a fellow party member. A natural reaction, but ouch. (I'll snap one tomorrow, K?) 


The Descent is definitely one of the better horror flicks I've seen in my lifetime. A lot of thought went into the monsters, the characters, and the setting - my summary is extremely condensed. I'll be rewatching it at least once because I likely missed something (And owe you all a cap.) . Still deserves the relatively good ratings from online critics like Rotten Tomatoes and IMDB, so give it a shot if spelunking horror is up your alley. Avoid the American knockoff, The Cave, like the plague.