Sea Urchins 3 - Aristotle's Lantern

The mouth of a sea urchin on the underside of the test (in situ above), contains five sharp teeth, which form part of a complicated structure, which I was fascinated to read is called 'Aristotle's lantern' because it was first described by the Greek philosopher in his 'Historia Animalium'. I carefully removed the structure from the test so that I could take photos.

The view from above.

Side view of the structure.

The view from below.

Outer and inner view of an individual tooth.

Sea Urchins 2

 Having found the outer casing or test of a sea urchin a couple of days ago, I was surprised to find another yesterday complete with all its spines still intact. The photo below shows the underside and the mouth which contains five sharp teeth.

Sea Urchin

It's a long time since I've found the shell or test of a sea urchin on the beach in Largo. This was quite small only about 3cm. but the markings still as lovely.

Sea-potatoes

Echinocardium cordatum -a heart-urchin. Lower image shows the underside with the mouth visible in centre.

Due to pressure of work, visitors, holidays and rotten weather, haven't had time to post in the last couple of months. However, yesterday was a lovely warm and sunny day, so headed early to the beach. It was low tide and I found several of these strange looking objects. They were very fragile and some were broken. I thought they might be the test of a sea urchin, and on looking them up found that they are known as sea-potatoes, only they are animal not vegetable. They are known as heart-urchins due to their shape. They are adapted for burrowing and are usually found about 15cm deep in the sand (perhaps that's why they are known as sea-potatoes). When alive they are densely covered in yellow-brown spines.

Sea-Urchins

Found this sea-urchin on the beach today. I think it is the green sea urchin - Psammechinus miliaris. It was stranded on the beach, so not sure whether it was dead or alive. They feed on young barnacles and sea-squirts.

This is the outer casing or test of the edible sea-urchin - Echinus esculentus. I found this one on Lower Largo beach many years ago. At that time there were a lot of these on the beach at Largo Bay, not many whole but a lot of broken ones, but it's a long time since I've even seen a small fragment.