Birds on the Brain

rhamphotheca:

Pyura chilensis: the Closest Thing to Getting Blood from a Stone

by Becky Crew

Despite appearances, this is not some kind of cruelly bisected alien stone organism or a tomato thunderegg. This is Pyura chilensis, a sea creature that lives on the rocky coast of Chile and Peru. And if (like me, very recently) you’ve never seen one of these before, you’ll probably be interested to know that in Chile, they are fished commercially, and the locals eat them raw or cooked with salad and rice because apparently they’re delicious.

P. chilensis belongs to the Ascidiacea class of non-moving, sac-like marine invertebrate filter feeders that are otherwise known as sea squirts. They belong to the Tunicata subphylum, so-called because they wear thick ‘tunics’ made of tunicin, which is a hardy matrix of molecules that help the animal attach itself to a hard surface on which it will carry out its days. The insides of this tunic are lined with an epidermis and a muscular band, and inside these layers lies the main part of the animal.

P. chilensis has two siphons that connect the animal to the surrounding ocean through its tunicin – one for exhaling and one for inhaling. It eats by inhaling the water and filtering out the edible microalgae using a moving layer of mucus in its enlarged pharynx, or branchial sac, before exhaling the water back out the other siphon. The pharynx is connected to the animal’s digestive tract, which basically acts like a mouth…

(read more: Scientific American)       (photo: uncredited)