Hooded Shrimp

Image via Wikipedia

It's always a bit odd when you come across something that doesn't appear to have a head. Hooded Shrimps seem to be missing a whole load of legs as well, not to mention some simple details of something on half its body. It looks like a weird seed on the end of a weird stem.

Of course, as the name suggests all those things are actually there, they're just hidden beneath a hood. This covering is actually a really big carapace, which is the same head-and-thorax shield that all crustaceans have. The difference here is that it almost entirely encloses the front part of this "shrimp", sort of like those old, unwieldy helmets.

Hooded Shrimp aren't really true shrimp, they actually have an entire order to themselves called Cumacea, composed of over 1,500 species known thus far. They're tiny, at just 1 to 30 mm in length, and are mostly found at the bottom of shallow sea waters though some can make it into brackish water or live at great depths.

Image via Wikipedia

Inside that large hood are a whole host of organs for feeding. Cumaceans can eat various tiny organisms from the sediment, some filter out food from mud, others will browse tiny mouthfuls from individual grains of sand. Some are miniature predators, their mandibles used to pierce other crustaceans and eat them.

Then there are the two pairs of maxillae and three pairs of maxillipeds, all little leg type things that are used for feeding and all completely hidden from view.

While some Hooded Shrimp have a bulbous carapace and a long, thin abdomen, others have a long, thin abdomen with a carapace that isn't much thicker. These look almost like worms, and some are flattened and live in a load of mucus so that they look like a really disgusting worm. The actual carapace can also be smooth or have all sorts of spikes and ornaments sticking out. For such minute, little known crustaceans they are wonderfully diverse.

Males and females of the species can differ quite a lot, too. It seems that males become larger and their antennae become bigger, this, plus some other adaptations, help him to swim around and find females more easily. The females on the other hand have a marsupium or brood pouch where she carries the eggs. Her young will stay there and moult several times before they emerge looking much like tiny versions of the adults.

It seems so strange to me that for all these years that I had never heard of these creatures, there have been people researching them and going into formidable detail as to what exactly makes a Hooded Shrimp a Cumacean. Viva la people! I hope one day a Hooded Shrimp turns out to be the cure for "mysterious aches and pains" or something, then we'll never stop hearing about them.