Have you seen any weird/unusual creatures underwater?
- From Kim Kalantzis' 5th grade class at Kendall Elementary School in Illinois

We see all kinds of unusual creatures underwater. On land the only animals we see are the South Polar Skua and very occasionally, an Adelie or Emperor penguin, or even more rarely a snow petrel. In the sea, there is a huge variety of life, and if it weren't for the cold water stinging your lips and slowly numbing your extremities, you might even think you were on a coral reef.

This is one of my favorite underwater Antarctic pictures, because behind the colorful reef you can see the hole that is drilled through the ice, looking like a moon overhead.

The most obvious animals are the sponges and seastars. The sponges can be huge, sometimes even as large as a diver. Some of the seastars are predators on the sponges.

White vase sponges and common red seastars. The sponges are a type of glass sponge, and these seastars are scavengers, not predators.

We also see soft corals and bryozoans, tunicates, anemones, urchins, scallops; many animals that are familiar from temperate climates. One of my favorite animals is the pycnogonid, or sea spider. These are slow moving predators that find sessile animals - animals that can’t move - and use their specialized mouthparts to suck out the body fluids; like a marine vampire on sponges and soft corals.

Some of the diversity of invertebrate animals we see underwater in Antarctica: the soft coral Alcyonium, the tunicate Cnemidocarpa (the small blob in the middle), the anemone Isotealia, the urchin Sterechinus (wearing a nudibranch as a hat), and the scallop Adamussium.

Antarctic pycnogonids, or sea spiders, exhibit gigantism, but why they are so large is one of remaining unsolved questions about marine life in Antarctica.

The fascinating thing about Antarctic pycnogonids is that they show gigantism; they are much larger than related species found elsewhere in the world. So where these nightmarish creatures are usually only a few millimeters long, here they can be 20 cm or as big as your hand. Gigantism is a relatively common trait in Antarctica, and there are several hypotheses about why this might be. One is that this could be the result of the smaller surface to volume ratio in large animals, which can decrease heat loss and may help prevent freezing. Another is that periodic nearshore glaciations (even though Antarctica is now cold, it has been colder in the past during ice ages) caused much of the shallow water fauna to go extinct as the ice pushed offshore and eliminated their habitat. When the ice retreated, the only place animals could reinvade from was the deep sea, because the continent is isolated geographically and by the currents that encircle it. Gigantism is a common trait in deep sea animals. I favor this hypothesis because it also helps explain why we see so many deep-sea related creatures in shallow water here – for example, crinoids and glass sponges. Of course this leads to the further question of why deep sea animals would be gigantic, and of course, we have a hypothesis for that too. In the deep see, food is generally scarce, and if you are larger, you are able to get your sensory organs higher off the bottom and into faster flowing currents. Friction slows currents near the seafloor, so the higher you can get, the further away you can detect food, and the more food you can get, the better you are at surviving and reproducing. It's a pycnogonid eat sponge world.

A crinoid, another typical deep sea animal that we find living shallow in the Antarctic (the red dots are our laser scaling system, 20 cm apart), and a pycnogonid crawling over potential prey, a red sponge.