This week let’s learn about some animals that live in caves!

The dipluran Haplocampa:



Oilbirds and their big black eyes:



A swiftlet:



The angel cave fish that can walk on its fins like a salamander walks on its feet:



Leptodirus, carrying around some air in its abdomen in case it needs some air:



The cave robber spider and its teeny hooked feet:



The devils hole pupfish:



Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

Way back in episode 27 we learned about some animals that live deep in caves. Cave dwelling animals are always interesting because of the way they’ve adapted to an unusual environment, so let’s learn about some of them!

We’ll start with an invertebrate. Diplurans are common animals that are related to insects but aren’t insects. They live all over the world, with hundreds of species known to science, but most people have never seen one because of where they live. They like moist, dark areas like soil, dead leaves, and caves. They’re also small, usually only a few millimeters long, although a few species grow larger, up to two inches long, or five cm.

Diplurans have long bodies with a number of segments, six legs, long antennae, and a pair of tail appendages called cerci. Depending on the species, the cerci may just be a pair of straight filaments like an extra pair of antennae, or they may look like pincers. Diplurans with pincer-like cerci use them to help capture prey, while ones with antennae-like cerci eat fungi and plant material.

Diplurans also don’t have eyes. They don’t need eyes because they live underground where there’s little or no light. A lot of species are pale in color or lack pigment completely.

Diplurans have been around for something like 350 million years, although we don’t have very many fossil diplurans. But recently, a new species of dipluran was discovered in North America that has raised some interesting questions.

Vancouver Island is a large island on the west coast of Canada, near the city of Vancouver. It’s prone to earthquakes and contains a lot of caves, and last summer, in June of 2018, a party of cavers and scientists explored two of the caves and found a new dipluran, which has been named Haplocampa wagnelli. This dipluran is chunkier than most other known diplurans, with shorter antennae, which researchers think points to a more primitive body plan. Since the dipluran is so different from most other diplurans known, and because the caves where it was found were under a thick ice sheet until around 18,000 years ago, researchers are trying to figure out if it found its way into the caves after the ice sheet melted or if it survived in the caves while they were buried under ice.

Haplocampa seems to be most closely related to a few diplurans found in Asia. Asia was connected to western North America during the Pleistocene when sea levels were much lower, since so much of the world’s water was frozen, so it’s possible the ancestors of Haplocampa migrated from Asia after the ice sheets started to melt but before the Bering Land Bridge was completely submerged. Possibly its eggs were accidentally transported by birds who foraged in leaf litter where its ancestor lived.

A lot of animals that live in caves are only found in one particular cave system. This happens when a species of animal that lives near a cave moves into the cave, either full-time or part-time. As its descendants grow up, they become more and more adapted to cave life, until eventually they couldn’t live outside of the cave. Since there’s no way for them to travel from one cave system to another, they are confined to that single cave. And since caves are largely difficult for humans to explore, that means there are lots and lots and lots of animals unknown to science living out their quiet lives deep within caves where humans have never visited. Every so often a group of adventurous and brave scientists explore a ...