A Porcupine of the Sea

Among the weirdest creatures of the deep is also one of the latest to become known to science—the sea urchin (closely related to star fish) astropyga magnifica. It is the largest sea urchin yet found in the Atlantic. It has approximately 200 bright blue eyes arranged in double rows. The body is covered with several hundred sharp, barbed black spines nearly a foot long.

That so conspicuous an animal, living in such a densely populated region—one of the most intensively studied in the world by biologists—should have remained undiscovered so long probably is due to two reasons. First, if its habits are at all comparable to those of its nearest relatives, it is strictly nocturnal and comes out to forage on the coral sands of the shallow sea bottom only after light has ceased to penetrate the water. During the day the creatures remain secluded, often congregated in great numbers, in holes and caves of the sea floor and under the coral.

Second, it is quite similar in appearance to another smaller member of the sea urchin race with spines as much as 18 inches long which is greatly dreaded and is even reputed to have caused the death of children who have fallen on it. Anybody coming upon a daytime bed-chamber of these fantastic creatures would be likely to leave them strictly alone.

This particular sea urchin is especially interesting in the development of its eyes. These appear to be true sight organs. If a hand is placed in the water near one of the animals the long barbs immediately are pointed in the direction of the intrusion, and as the hand moves the barbs move. Such a creature is practically impregnable. It never, however, takes the offensive. It cannot “throw” its barbs, but they enter the flesh easily and cause painful local irritation. Some species inject a virulent poison which may even kill a human being. There is no evidence that this species is toxic.

Astropyga magnifica, which has more the appearance of a porcupine than of any other land animal, is a scavenger of the sea bottom. It gathers and devours the accumulated debris that falls through the water. It never kills its own food, so far as is known. It has five sharp teeth in its mouth, located on its under surface, with which it can chew away the flesh of dead animals.

This sea porcupine has a peculiar system of locomotion in common with most of its relatives. It has literally thousands of sucker-like feet, which are hollow and attached to tubes within its shell. It moves by forcing water through the tubes and into the particular “feet” which it wishes to use. When these are out of use they are contracted by withdrawing the water. Being a radially symmetrical animal, the creature can move with equal ease in any direction. It has no head—that is, the development of its nervous system and the direction of its locomotion are not fixed in a forward direction, as is the case with vertebrates and insects.

Some members of the sea urchin family have hoof-like formations on the ends of some of their spines, with which they are enabled to walk over the sea bottom without using the suction disks. About the only enemy of these fearsome nightmares of the deep is man. Some species are used extensively for human food, notably among the Mediterranean coast and in the West Indies. The developing eggs are taken from the body and eaten either raw or cooked. Even if it should prove suitable for human food, it is unlikely that the sea porcupine ever will be a rival in this respect of its rival, the “sea rabbit.” It is too secluded in its habitat.