Underground Animals: Cool Cave Critters, Part Two

Wednesday, January 26th, 2011

Hi everyone! I’m sure that most of you have arrived here after clicking on the link at the end of the first half of the series on Neatorama, but if you haven’t, please click here to check out part one. That being said, enjoy the second part of the series covering arachnids, insects, snakes, fish and more.

Image via Nick See [Flickr]

Arachnids

Kaua’i Cave Wolf Spiders

Also called the “blind wolf spider,” the “no-eyed big-eyed spider” and “pe’epe’emaka’ole” (in Hawaiian) the kaua’i cave wolf spider lives only in a five lava flow caves in the Kaua’i Island of Hawaii. While wolf spiders are known for having two large eyes in the center of their eight eyes, this species has no eyes at all. While most spiders have sensory hairs on their body and legs, these wolf spiders have particularly long hairs that they use to help them compensate with their lack of sight. Its most common food source is the Kaua’i cave amphipod and other arthropods. They are about three quarters of an inch long and present no danger to people.

The Kaua’i cave wolf spider is being threatened with extinction since the introduction of the brown recluse spider to the island, which is competing with the cave wolf spider for food. They also are at risk due to their environment constantly shrinking because the basalt caves they inhabit are constantly filling with sediment at a slow pace, decreasing the size of the caves. To make matters worse, the spiders reproduce at a rate one tenth the speed of most wolf spiders. The female spiders carry the egg sac in their mouth until the offspring hatch and then they carry them on their backs until the babies are ready to survive on their own.

Insects

Kaua’i Cave Amphipod

These small amphipods live in the same caves as the Kaua’i Cave wolf spiders and provide them with their primary food source. They live in a more caves than the wolf spider, but are still endangered and put at risk by many of the same threats. The creatures have no eyes, no pigment and are nearly translucent. They eat the feces of other insects and the roots of plants that grow through the cave roofs.

Tooth Cave Pseusoscorpion

Pseusoscorpions are similar to scorpions, but they have poison in their claws rather than their tails. In fact, they don’t have tails at all. At only about a quarter of an inch, the tooth cave pseusoscopions aren’t much of a threat to humans, but they are a deadly predator to the small insects that reside in limestone caves in Texas.

Unfortunately, because they live in such a small area and already have such a small population, they are at high risk of extinction and the recent introduction of red ants into the area has resulted in a serious threat to the pseusoscorpion’s longevity as the ants eat both the pseuspscorpion and on their food sources.

Arachnocampa

These weird creatures from Australia were originally believed to be related to European glowworm beetles, but they are actually gnats. The majority of their lifecycle occurs during their larvae stage. During this period, they spin a nest of silk on cave ceilings and then hang up to 70 silk threads around their nests. Each thread snare is about a foot long and hung by mucus drop. The larvae light up their bodies and their snares reflect the glow, attracting flying and wall-climbing insects which are then trapped in the threads and eaten by the worms. Some of the worms even have poisonous mucus on their silk threads, making their traps even more effective. If the worm is really hungry, it may even cannibalize other larvae or adult flies.

The creatures are larvae for about 6 months to a year, then they enter the pupa stage, which lasts for about a week or two. At this point, the males stop glowing and the females continue glowing, most scientists believe she keeps the glowing abilities to help attract mates. As flies, they only live a short time and essentially only have time to mate and lay eggs.

Image via TimParkinson [Flickr]

Blind Cave Beetles

These beetles have no eyes, and longer legs and antennae than most beetles. They prefer cave environments with near 100% humidity where the temperature doesn’t exceed 54 degrees Fahrenheit. While olms were technically the first cave species discovered, these were the first to be recognized as animals exclusive to cave life when they were found in 1831.

The cave they were discovered in is now a major tourist attraction as it not only houses these guys, it also contains olms, making it a historical monument to the study of troglobites.

The blind cave beetle feeds on the carcasses of cave animals and on other organic material, including dung. Females lay relatively few eggs compared with other beetles and the eggs take a long time to develop fully. Other than these few details, very little is known about the beetles.

Image via Yerpo [Wikipedia]

Cave Crickets

Unlike the crickets in your backyard, these guys have no wings and even longer legs and antennae, which help them navigate their dark settings. One of the newly discovered cave crickets from Grand Canyon-Parashant National Monument, located in a remote strip of land on the Utah-Arizona border, is notable for having functional pinschers on its rear end, but scientists still have not found a purpose for this strange adaptation.

Because they usually can’t see in their environments, they often jump towards any perceived threat, hoping to scare it away.  Like many cave animals, they lack a lot of pigment and youngsters appear translucent, but they do darken a bit as they get older.

Since food can often be scarce, cave crickets go to desperate lengths to avoid starvation –even eating their own limbs which cannot regenerate back. This seems like a risky venture considering that missing limbs can make food even harder to find.

Image via Gunther Tschuch [Flickr]

Snakes

Cave Dwelling Rat Snake

Snakes generally don’t live in caves because the environment is too cold for them, but the tropical caves of Thailand are just hot enough to support the Cave Dwelling Rat Snake. Living in caves has provided them with a unique coloration as they are beige and colorless in the front half, but fade into a grey black shade (with a cool white stripe) near the tail. They also have blue stripes on their eyes.

The snakes are not venomous and can grow fairly long, to about 7 feet. This length can be quite beneficial when your food source relies on your being able to dangle from crevices near the front of the cave so you can snag bats as they come and go. While the snakes are practically blind while hunting, they rely on special heat sensitive receptors that allow them to see where each bat is based on its body heat.

While many cave species are endangered, the cave dwelling rat snake is doing just fine –to the point where many people keep them as pets. They are popular due to their distinct markings and seem to survive just fine on a diet of rats in place of bats.

Image via Ricky Romero [Flickr]

Bacteria

Snotties

Ordinarily, I wouldn’t include bacteria in an article about animals, but snotties are pretty cool -in a disgusting way. These single-celled bacteria survive in some of the most extreme environments on earth. They thrive in caves containing volcanic sulfur compounds including hydrogen sulfide and sulfuric acids.

The bacteria live together in massive colonies that hang from the ceiling and resemble stalactites made from mucus. Because they live in such extreme environments, their waste products are incredibly acidic and have similar properties as battery acid.

Cavefish

There are at least 80 varieties of cavefish, but one thing they have in common is a small size –most are smaller than 5 inches when fully grown. Because they live in the dark, the fish have all found their own way to adapt to their surroundings by using sensory organs on their skin to help them navigate. All cavefish rely on some source of fresh water, so they are only  found in caves that have streams running into them.

Waterfall Climbing Cave Fishes

While scientists still don’t know much about this species that is only found in Thailand, the little bit they do know is absolutely fascinating. They have no pigment and no eyes, like many cave species, and have managed to develop their own incredible specialization for survival.

The fish has microscopic hooks on its fins which allow it to grab onto rocks and climb up nearly vertical terrain. This ability has allowed the species to survive inside of cave waterfalls, where they eat bacteria that grows on the rocks and flows in the water.

Blind Cave Tetras

As its name implies, these fish are blind. The young fish are born with eyes, but as the fish ages, skin grows over its eyes, which then degenerate. They use lateral lines on the sides of their body to navigate through the water based on fluctuating water pressure.

While many cave species are unrelated to any above surface animals, the blind cave tetra is just like the Mexican tetra, only blind and pigmentless. The two can still interbreed.

Like the cave dwelling rat snake, they are not at risk of endangerment and, as such, are a popular addition in aquariums. Owners even claim that, despite having no eyes, the fish are able to grab the falling food in the tank faster than their sighted relatives. This may have to do with their improved sense of smell and the special organ in their brains that is light-sensitive and can thus sense the fish flakes overhead.

Image via OpenCage [Wikipedia]

Devil’s Hole Pupfishes

Native to only one geothermal pool named The Devil’s Hole, inside a limestone cavern in Death Valley, these fish are famous for surviving for tens of thousands of years with a reliance on a submerged limestone shelf that is no more than 90 square feet in size.  While their total territory expands a bit beyond the reach of the shelf, they use it for spawning and find most of their food on the shelf.

Ecologists and scientists are fascinated by the fish’s ability to survive so long in such a small area, but they also use it as a poster child for eco-friendly practices. If humans destroy the aquifer through polluted water or by using too much groundwater, the fish will be done for. At any given time, there are no more than 500 Devil’s Hole pupfish on earth and their numbers dwindle to half of that each winter.

Ozark Cavefish

This cavefish not only lacks visible eyes (like other cave animals, its skin has grown over them), it lacks any optic nerves. They are small, reaching no more than two inches long and have no skin pigment. To compensate for its lack of vision, the fish rely on sensory organs on their skin to catch microorganisms, insects, fungi, small crustaceans and salamander larvae. When food is really scarce, they’ve been known to eat their young. They get most of their nutrients through the tree roots from above the surface, bat guano in the water and brown leaf litter that has washed into the cave.

There are currently 15 caves in the Ozarks that are known to have these species. Some of them are linked to springs and wells that were used by early settlers. When these people pulled up a bucket of water with a cavefish in it, they considered it to be a sign of good luck.

Alabama Cavefish

This eyeless, pigmentless cavefish is one of the rarest in the world as it only lives in the underground pools of Key Cave in Alabama. Scientists believe there are only 100 of the fish left on the planet. Like the Ozark cavefish, it survives largely thanks to the nutrients derived from guano dropped into the water. Also like the Ozark fish, it uses sensory organs on its skin to navigate its dark home.

The fish is believed to incubate its young in its mouth to protect its young. Their population growth is the slowest amongst all cave dwellers, making them one of the most at risk species on earth.

Cave Crayfish

There are approximately 40 species of cave crayfish in North America. Many are isolated to single caves and most are albino or translucent in color. Perhaps one of the most interesting things about these crayfish though is their longevity. Because they have such low metabolisms and sedentary lifestyles, they live rather long, many up to 75 years. One species, the Orconectes australis of Shelta Cave in Alabama, can still mate when its 100 years old and can live up to 175 years old.

Image via Marshal Hedin [Wikipedia]

Kentucky Cave Shrimp

Also called the “blind cave shrimp,” this little troglobite has no eyes and no pigment like many other cave species. They serve as a perfect example of the dangers faced by many cave animals as one of the three populations of the species was almost wiped out in the eighties when a truck carrying cyanide salts overturned near Mammoth Cave and almost destroyed the entire ecosystem.

Cave animals are some of the weirdest, most specialized animals on the planet. But this list, while long, is by no means exhaustive. If you know anything about any other cave animals, share it in the comments! Also, I’d just like to remind you all that if you haven’t yet read the first half of the series over on Neatorama, here’s the link.

Sources: Wikipedia #1, #2, #3, #4, #5, #6, #7, #8, #9, #10, #11, #12#13, Earlham College, Cornell University, The Book Of Animal Ignorance, Discovery Channel #1, #2, Fox News, Missouri Conservationist, WebEcoist and Unusual Kentucky

Advertisement