Sea spiders (Pycnogonids) are a relatively common sea creature distributed widely around the world. They aren’t true spiders but the two groups are slightly related.
However, there is no currently living animal group that is closely related to them, so as a species they are out there on their own.
Usually, in more temperate oceans their leg span is only a few centimetres but in the cold, deep waters of Antarctica it’s a different story altogether. There, their leg span can be as much as 70 cm (27 inches)!! This effect is known as ‘polar gigantism’ and researchers are trying to determine why this happens.
The general belief is that growth limits for animals in the deep ocean are set by the amount of energy an animal can find and take in, as well as the amount of oxygen in the water. Colder water has more oxygen in it so the animals in Antarctica tend to get bigger.
Though abundant, with 1300 species worldwide (around 20% of these are found in Antarctica), the Antarctic sea spiders live on the seafloor and can be hard to find.
Little is known about their role in the deep seas of Antarctica but we do know that male sea spiders carry the eggs, and strangely, particular varieties of shrimp will flip the sea spiders over and eat their eggs, before letting them go.
They also breathe through their exoskeleton, mainly their legs. The legs have large pores that allow oxygen to diffuse into the spiders.
They live by eating the innards of various marine animals like sea urchins, and possibly sponges, by inserting a slender proboscis and sucking their juices out, but no-one yet knows if any animal preys on them.
They move very slowly so don’t be afraid, they aren’t going to attack you any time soon.
Because they are a unique animal, researchers are concerned that rising ocean temperatures may lead to their demise. It seems that if you warm water up to more than 5 degrees, they will die but even at lower temperatures where the increase is only 2 or 3 degrees, they lose the ability to do those things necessary for survival.
However, recent research showed that they do have the ability to adapt to warmer temperatures at least in the short term. Whether they can do it in the long term remains to be seen. Check out the article below to learn more.