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Today on animal fact files we're talking about sea spiders. Don't forget to subscribe to keep up with creepy creatures.

Sea spiders are weird. They look like some kind of emaciated face hugger, though they wouldn’t really be interested in attaching to your face. They’re more into invertebrates. Though they might superficially look like spiders, and they are quite distantly related to spiders, sea spiders aren’t really spiders. Sure, they have jointed legs and lack antennae like your average terrestrial arachnid, but they’re bodies are amazingly different when you take a closer look. While many sea spiders have the same amount of legs as spiders, others may have more or fewer than eight walking legs. Sea spiders also have more joints in their legs, and they’re almost completely lacking a “body”. They’re mostly made of limbs. Sea spider legs are connected to a thorax which is typically termed the trunk. This trunk is so small it can’t even contain all the sea spider’s organs, so those get shoved up into the legs instead. That means their stomachs and even their reproductive organs are all housed in those long, spindly legs. Now, let’s be clear, sure, some sea spiders can reach dinner plate sized proportions with one foot (30.5 centimeters) or longer leg spans, but most are just a few millimeters long. The biggest boys are typically found in miles deep water while the smaller species are more intertidal. Sea spiders can be found in every ocean, they’ve only been found in marine waters, and they seem to have a preference for colder polar regions. And, like we said, it’s not like they’re after humans anyway.

While walking along the ocean bottom, sea spiders eat sponges, hydrozoans, worms, and other soft bodied, sessile or slow moving animals. Sea spider larvae especially seem to love clinging to anemones as parasites. Adult sea spiders can’t move really fast, so anything that walks around a lot would just be too much effort for them. To eat, a sea spider will use a triangular shaped mouth attached to the end of a long, thick proboscis. The proboscis in a sea spider is thick to help break down food as it passes through to the stomach. Apparently sea spiders have such weak hearts that their hearts alone aren’t able to create all the circulation in their bodies, so their gastrointestinal tract helps out with this circulation. When they aren’t looking for food, they may be in search of a mate.

There’s still a lot to learn about sea spiders, such as how they choose a mate, and when they are reproductively mature. However, it is clear that there are openings on the legs of sea spiders, called gonopores, through which reproductive material passes. Mating in sea spiders is a leggy affair. Male sea spiders have to precariously position their legs around the legs of female sea spiders to line up their gonopores before he can collect and fertilize the eggs. The male will carry the eggs around on his legs until they hatch into larvae.

When they aren’t eating or mating, they may be cleaning. Sea spiders are generally a cleanly group of animals who regularly groom to keep unwanted hitchhikers from attaching to their legs. As arthropods, sea spiders also molt, but how many times they may do so in a lifetime is still a mystery, mostly because how long they can even live is still a mystery! They may even be able to reach decades in age, especially the big boys!

For more facts on sea spiders, check out the links in the description. Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files.