NATURE NOTES

New Zealand Herald, Volume LXXII, Issue 22006, 12 January 1935, Page 1 (Supplement)

NATURE NOTES

POISONED LANCES

BY J. DRUMMOND, F.L.S., F.Z.S.

Fairly plentiful on sandy beaches in New Zealand are empty shells about the same size as an orange, but flattened on one side, and covered with bosses in symmetrical patterns. Tho bosses are ornaments 011 , pieces of shelly plate armour, designed and wrought by the creatures that lived inside. The plates of each shell fit closely edge to edge. They are arranged pentamerously—that is, in fives. Pentamerous symmetry is common in flowers, but is unknown in the animal kingdom except in this group, and not in all of them. When tho occupier was alive long sharp spines fixed on ball-and-socket joints sprang from the bosses. Before waves, rocks and boulders broke the spines off they were distributed over the surface of the shell. They helped slightly in locomotion. They gave the shell tho appearance of a hedge-hog.

In former times a hedge-hog was called an urchin. It has lost that name, but this creature of the sea, which is in no way related to it, retains the title of sea-urchin, solely on account of its spines. In addition, a sea-urchin has tube-feet, equipped with suckers. It can walk on the tips of its spines, but it usually fixes the suckers of its tubefeet to a rock or other object and pulls itself along. The long spines are the most conspicuous appendage, and the tube-feet are the most useful. Another sot of appendages is the most remarkable. They look like secondary spines. They work on the same principle as Eincers or three-bladed scissors. They eep the shell clean, remove anything, dead or alive, that should not be on the shell, sometimes hold a piece of seaweed over the shell in order to conceal it, and, more important, defend the dwelling and the occupier by biting enemies and pouring into the wounds poison stored in bags.

The virulence of the sea-urchins' poison was proved when a bite caused a frog's heart to stop beating. A starfish was seen approaching a sea-urchin aggressively. The latter's long spines separated widely, and the blades were fixed into the starfish, which retreated, wrenching the blades out of their position. The starfish returned to the attack several times, always with th 3 same result. The starfish wrenched off all the blades, wrapped itself over the sea-urchin, and smothered it. A seaworm bitten by the snapping blades took cramp immediately* and died in a few minutes. The blades used in this encounter were torn off at their base. The dead sea-worm was thrust from the sea-urchin's shell. It is not unusual for the blades to hold on to an enemy with a bulldog grip until they are torn off. This may not be serious to the sea-urchin, as it can provide itself with fresh blades. On some sea-urchins all the blades may not be used at the same time. An enemy may bo held ,by two and smashed with the third. Zoologists affirm that a seaurchin is devoid of a brain as the word is generally understood. Each blade and each spine acts on its own responsibility, automatically, by reflex action. A sea-urchin has so many automatic movements that it has been called a republic of reflexes.

Some species of sea-urchins have a poison-bag near the tip of each long spine. If the sharp tip of the spine pierces a person's skin and is broken off, the poison enters the wound. The result, according to Sir J. Arthur Thomson, is a painful wound, often slow to heal. Something of this nature, apparently, happened to a resident of Queen Street, Onehunga, who signs his letter with his initials, " J.D." " When I lived at Apia, Samoa," he writes, " I often went with a friend at low tide to the outer reef. During one visit we saw something in tlie water that looked like a shell with hollow projections, shaped like miniature battleship guns, about five inches long, as thick as a lead pencil. My friend put his hand into the water, but quickly withdrew it. Sticking into the top of one of his fingers there were several fragile shafts about the size of fine sewing needles, absolutely straight, jet black. With a steady pull I withdrew all, but did not break the barbs. The shafts were brittle, and evidently poisonous, as inflammation set in at once and continued for several days. We did not inquire further into the creature's habits, and are ignorant of its identity." In reply to a request the Secretary to the Administration of Western Samoa had many inquiries made on the subject. He has courteously replied that the creature is a species of sea-urchin, which Samoans call "vana."

Maoris used sea-urchins for food. Samoa ns probably use their seaurchins in the same way. Sea-gulls, 'hungry lovers of shellfish, sometimes take sea-urchins in shallow water, fly into the air with them, drop them on to rocks or hard sand, smashing the shells, and devour the sea-urchins. Many enemies beset sea-urchins. They need their cuirasses and their poisoned lances aud blades; but Sir J. A. Thomson noted that an average sea-urchin's most dangerous time is in its early youth. It spends its youth as a tiny being in the open sea, away from tho turbulent life near the shore. It has no resemblance to an adult sea-urchin. Delicate, palatable and defenceless, swimming freely in countless numbers, the water thick with them, youthful sea-urchins are among the edible things of the sea, and the mortality among them is very great.

Sea-urchins in an aquarium were hyper-sensitive to light and shade. Strong light irritated their skins, and they sought the darkest corner. If they continued in the strong light the'ir spines rotated. A Mediterranean sea-urchin, equipped with long spines, reacts to a shadow cast by a cloud or by a passing fish. It erects its spines as if to ward off an intruder. Snapping blades were seen in action when a shower of powdered chalk was poured on a captive sea-urchin. The blades seized the particles, broke up any lumps there were, and reduced the whole to an impalpable powder, which was quickly removed by fine hairs that covered the skin. The blades were brought into action by any prolonged irritation of the skin, sucli as bright light and showers of particles of grit or mud. Acid, applied to a sea-urchin's skin, causes the spines to bend to all points of the compass, to rotate. Under stimulation that is too strong the first spines affected strike those next to them vehemently.

Many naturalists find centipedes and their ways interesting, if not fascinating. Eminent zoologists in England spend hours watching and studying them, and do not consider the time wasted. Tastes differ on this point, as on almost everything else. Cats are general favourites, but some people dislike them greatly. Centipedes are the particular aversion of Mr. P. L. Hill, of Crater Flat, Raglan. He writes: "I would sooner handle snakes than centipedes. I have done so, often putting snakes in my pocket. Apart from a slight smell and a cold touch when it encircles the wrist, with its head showing between thumb and forefinger, there is nothing repulsive in a snake. I have seen innumerable centipedes, big and little, and have had a close acquaintance with them, but nothing stirred me to a friendly feeling for them. I could never bring myself to touch one, and my sentiments in this respect are absolutely fixed. Of all noxious creatures I have known or read about, centinedes are the limit."