Don't worry, I'll bring some thick gloves and gas masks along.
We''ll need the gloves when we get to all the mucus
Without the stabilizing influence of the notochord tunicates are free to become as weird as they please. We've seen Salps who look like a tube of jelly, Pyrosomes who look like a windsock and Sea Squirts who look like a jug.
Larvacean body. The rest is a tail
Larval Larvaceans also look like Sea Squirt larvae but their metamorphosis is so moderate that even as adults, they still look a lot like Sea Squirt larvae! Most of them will be less than 1 cm (0.4 in) long with a blob for a body a long tail trailing behind.
It's eating. YUCK!
The first thing to do is eat, and this turns out to be a remarkably extravagant affair for Larvacea.
Video: Plankton Chronicles
They secrete a whole load of mucus to form a giant net that completely surrounds them. It's known as a "house" and for at least one Arctic species it can occasionally reach 2 metres (6.5 feet) across! They live in a mucus palace!
By wriggling their tail they can set up a current of water which passes through the house and the corridors within. The house has two sets of filters, one for blocking particles which are too big to be eaten and another for trapping the actual food.
Judging from fig. 1.3 in this pdf I think the red things are the outer filters covered in muck and the white stuff are the food nets
|Image: Neptune Canada|
Larvacea houses are very fragile and almost invisible!
Assuming it doesn't get snapped up by a hungry fish on the way down, these houses are a significant constituent of the marine snow that feeds the abyssal depths of the ocean. It becomes the muck that all those Sea Cucumbers wallow in!
Video: Casey Dunn
The thing about Larvaceans is not just that they leave behind a healthy alternative to the Gingerbread House in their wake, it's also the sheer number of them! With sufficient food they can form dense clouds that rival copepod swarms! Most Larvaceans are also hermaphrodite, though they can't self-fertilize because they release their sperm before their own eggs are developed. The eggs are released by tearing a hole in the body such that the adult dies.
In one species the entire lifespan is known to be about a week or two depending on water temperature. In that time they eat and make merry, build numerous homes for themselves and donate huge amounts of food to the poor and needy in the deep sea. A life well lived!