It’s hard to believe that something so cute can lie at the bottom of the sea, but don’t let the appearances fool you. Sea squirts don’t have a face, and they’ve basically digested their own organs. Yes, really.
Sea squirts, or tunicates, are marine invertebrate animals. They are marine filter feeders, with a water-filled, sac-like body structure and two tubular openings, known as siphons, through which they draw in and expel water. They’re basically a big stomach inside a sack.
Some of them live as isolated individuals, but others form big colonies. They are hermaphrodites, which means they have both male and female reproductive organs, and they spawn by releasing eggs and sperm into the ocean. Their maturing process is quite intriguing.
When they are larvae, they look a lot like tadpoles, swimming around freely. They are able to reproduce sexually as larvae, which is a bit strange, but they are unable to feed at this stage.
In order to be able to feed, they must give up on their swimming freedom and permanently fixate on the ocean floor. But that’s not all they give up – in the process, they absorb and digest the body parts they no longer need – including their tail, gills, and brains. Yikes!
Strangely, this system has worked out efficiently for hundreds of millions of years. There are thousands of species, and they’ve been around since the mid-Cambrian, over 500 million years ago.
As if that wasn’t enough, their blood is also strange. It contains unusually high quantities of a metal called vanadium, contained by vacuoles which also containing sulphuric acid. Biologists and doctors are now studying the potential medical applications of tunicates, after it was revealed that their bodies contain several compounds which can be used to fight different types of cancer.
All in all, sea squirts are apparently simple creatures, but they come with a complex story behind them. They’re more than just a pretty face… because well, they don’t have a face, and even if they did they would have probably digested it.
