Sunday 17 April 2011

Sea Spider

Image by Ken-ichi via Flickr
Sea Spiders are incredibly weird creatures. To me, they somehow look like they are barely there at all. I can sort of imagine a normal spider having some kind of personality, at least getting angry or scared or something, but I really can't say the same for the Sea Spider. They're just so ridiculously alien, maybe even austere, but definitely weird.

Sea Spiders really are from the sea, pretty much all seas all over the world. The tiniest ones may be about 1 millimetre across and a lot of the smaller ones are found in shallow waters. But Sea Spiders are one of those creatures that do extremely well in really horrible places, so bigger ones can be found in the Arctic and Antarctic, while gigantic ones of some 90 centimetres (3 feet) across reside in the deep sea.

However, what Sea Spiders certainly are not, are spiders. They are currently placed within the subphylum Chelicerata, along with the arachnids and our very own Horseshoe Crab. There is some argument over this, though. Some believe that they are in fact an extremely ancient group that should be placed alongside all other arthropods. For me, they at least look the part. I find it really hard to think of Sea Spiders as being "akin to" or "a bit like" anything else. They seem utterly unique and bizarre to me. I mean, just look at them! They are... legs.

Image by Vishal Bhave via Flickr
Sea Spiders have almost no body to go along with their lanky limbs, they seem to be nothing more than legs that happen to join up in the middle. Most have 8 of them, others have 10 or 12. It's a good thing they have that many because the abdomen is so small that the guts actually have to extend all the way down those limbs! It actually seems like that is how the legs are fed. Luckily, Sea Spiders are so small and thin they can do all their breathing straight through their skin without need of gills or whatever else taking up yet more valuable space. They also have muscles that each consist of just one cell. Really, these appear to be animals that at all times are just barely clinging to life.

Some of them also cling on to death, since they can be scavengers. Strangely enough, most of them are actually predators. Sea Spiders typically don't like to move around much, so what could they possibly prey upon? Something that CAN'T move around much, of course! Soft bodied creatures like Sea Anemones, Sponges and worms are their usual. The mouth is at the end of a proboscis, the only notable body part that doesn't look like a leg, and it's used to bite into soft flesh so the Sea Spider can suck up the insides. Surrounding this proboscis are 2 other paired appendages, the chelifores and the palps. These can be used to slice off a tentacle from a Sea Anemone so the Sea Spider can run(?) off with it and eat it at leisure. Such horror! Some Sea Spiders don't even have these other appendages, or they have just one or the other. Legs and a way of feeding the legs, that's a Sea Spider.

I should also mention that some Sea Spiders have up to 4 simple eyes, while others have none. Also, some Sea Spiders can swim! How? They use their legs, naturally. It's not like they have anything else to do it with! And some of them are really quite colourful, others are transparent. All great! I think.

Image by asbjorn.hansen via Flickr
Anyway, there's one other pair of appendages on the Sea Spider's head - the ovigers (although some species lack those as well). These are particularly long in the male and they can sometimes even look like yet another pair of legs. Once eggs are externally fertilised, the male sticks them all to his ovigers and cares for them. When they hatch, the larvae are serious rebels; they have NO LEGS! They are composed of just a head with the chelifores, palps and ovigers sticking out! These are used for swimming about and finding food and, you know, survival and life and such. Others live on or in worms, clams or poor old sea anemones and live as parasites for a while. Still others stay attached to Dad's ovigers until they have a few legs to call their own. I'm sure that's a very emotional moment for all involved.

I never would have guessed that such a strange animal would have found such a completely different way of being strange in its early life!


Emma Springfield said...

They look all wiggly and like they would have no solidity of movement of their legs.

Joseph JG said...

"Wiggly", I wish I'd thought of that! It's exactly right. It's kind of like their legs couldn't possibly support their weight, except that their legs appear to make up almost the entirety of their weight.

Crunchy said...

If it has 8 huge legs and is an arachnid, I don't care how many times you tell me it's not a spider. It totally is! I mean, maybe it's missing parts so I guess it's bad at being a spider, but still. Spider!

Joseph JG said...

Haha! I think it's Christmas tomorrow. Maybe I won't get any presents so I guess it'll be a bad Christmas, but still. Christmas!

JJ said...

You write a lot like Will Cuppy (:

Joseph JG said...

I actually had to look that one up, but being compared to a guy who wrote something called "The Decline and Fall of Practically Everybody" just HAS to be good. Thanks!