Drhoz! (drhoz) wrote in wtf_nature,
Drhoz!
drhoz
wtf_nature

Tunicates

Another post to dazzle your brain.

Down at the far end of the vertebrate family tree are all those animals that have a notochord, but no actual backbone yet. Some of them don't even have that, but are still our distant relatives. The biggest group of these are the tunicates - divided into four classes.

The Ascidians are known for their somewhat tadpole-like larvae, and tendency to glue their heads to a rock and digest their own brain when they want to grow up. At least one colonial species then engages in sex wars against their neighbours, invading each other's tissue and trying to take over their gonads.

Here's Haeckel's illo of a few, complete with helpfully dissected specimen in the lower-middle.



Most of them are filter filters - it's a feature of the entire subphylum - but one species Megalodicopia hians resembles a Venus Flytrap made of jelly and OM NOM NOM NOMs anything that swims between the 'jaws'. (The class Sorberacea are also happy little carnivores, but I can't find much about them on-line. This makes me sad)

On the other hand a number of the solitary species are collected for food by humans. Altho you might want to avoid the following.

Sea pineapple (Halocynthia roretzi) is cultivated in Japan (hoya, maboya) and Korea (meongge) and, when eaten raw, has been described by Lonely Planet as tasting like "rubber dipped in ammonia". The peculiar flavour is attributed to an unsaturated alcohol called cynthiaol.


They also collect and store vanadium and other poisons in their tunic.

Thaliaceans don't bother to glue themselves down - they just float around suck water in one end and pump it out the other, propelling themselves slowly thru the water. The colonial species can be many metres long, and they breed in huge numbers whenever there's anything in the water to eat. Here, a diver goes ZOMG!!!!1 looking at a smaller colony. More info here

But there's also the tunicates that never grew up, the Peterpanea Appendicularians, aka Larvaceans. They never settle down, but stay as 'tadpoles' their whole lives. They can still happily breed however, indeed most of what looks like a head in the below photo is actually gonad, with a few other organs stuffed in alongside.



But how do they feed? By making an astonishingly intricate house out of snot and straining the oceans for single-celled food.

The larvacean's home is large compared to the animal, and made from protein and cellulose it forms into coarse mesh, super-fine filters capable of collection things less than 1/1000 of a millimeter, exhaust ports and escape tunnels. After it's done building the little larvacean gets to work wriggling away, drawing in water thru the coarse filters, and inhaling the single-celled protozoans that collect on the fine filters.



That's the fine filters in the middle, there.

Animated gif of Oikopleura in action, here

Those fine filters have been used to collect marine microbes for scientific research. Of course the larvacean hates being interrupted and flees out the escape hatch, but no matter. Shi would have abandoned it to build a new house the next day anyway. After THAT, the old home collapses and plunges to the sea floor kilometres below, becoming one of the larger chunks in the constant shower of shit that feeds the deep sea.
Tags: deep sea, feeding, invertebrate, sea squirt, sex
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