MARINE NATURE NOTES

Otago Daily Times, Issue 22628, 20 July 1935, Page 23

MARINE NATURE NOTES

Written for the Otago Daily Times By David H. Graham, F.R.M.S., P.Z.S. SPECIMENS FROM CORRESPONDENTS. Ever since these articles were started readers from many parts of New Zealand have supplied me with specimens of marine life concerning which they wanted some information. My article on “ Nereides or Bristle Worms ” have caused a number or readers to send me worms they have collected around the sea shore. Two most unattractive looking worms have been sent in—one from Owaka and one from Seacliff. Both belong to the species of an aphrodite commonly known as sea mouse. It is a species that prefers deeper water than shore worms, but sometimes conies ashore with a heavy sea, and may be found at very low tide under stones and rocks, clinging to the under surface. As the body of each specimen measured four inches in length and about an inch and a-half in width and possibly threequarters of an inch in thickness, it is no small worm. This worm has often been mistaken by collectors for a hairy slug and, indeed, it is not unlike one that is covered with fine hairs. Oval in form and of a much larger shape than most worms, the animal may be distinguished by the enormous development of the bristles, some of which are highly iridescent and occupy the. sides of the body, while others are long and hairlike and woven into a kind of felt protecting the whole dorsal surface. If this thick coating of hair-like bristles is removed, 15 pairs of scales will be found covering the body. This worm is covered with a thick frown felt, thinner in the middle, from which emerge long, brown bristles and hairs of yellow and green that are so iridescent as to reflect all the colours of the spectrum. The body of the animal, which can best he seen from the undersurface, consists of from 35 to 40 segments, beginning at the head, broadening at the middle, and tapering off, and that v the last dozen segments are very small. - Once seen, this worm cannot be mistaken. It always attracts the notice of collectors and others who are observers of nature. It is known to grow to a length of eight inches, but the largest found by the writer was five and a-ha!f inches, and was brought up in the codend of a trawl seven miles off Otago Heads in 17 fathoms. In life nothing/ can .exceed the splendour of these apparently apathetic creatures. They yield indeed in no respect to the most gorgeous tints of tropical birds, or, to the brilliant decorations of insects from the warmer climates. All the hues of iris play upon them with the changing light and shine with metallic effusion. But it is not for their dazzling beauty merely that the bristles of aphrodites are remarkable; they are really important weapons of defence and exhibit a complexity of structure far beyond anything met with in the hairs of higher animals. They are perfect harpoons, the points of each being provided with a double series of strong barbs, so that when the creature erects its bristles, many enemies scarcely venture to attack it. Animals, like fish, red cod, for instance, are very fond of sea mice, and swallow them whole. Nature has provided these hairy animals with another provision in the construction of the lance-like spines. bundles of bristles are all retractile, and can bo drawn into the interior of the body by the aid of a muscular tube from which they spring. Every barbed spine furnished with a smooth, horny sheath, composed of two blades, between which it is lodged, and these close upon the barbs when they are drawn inwards. Two stiff-looking palps or antennae about half an inch in length issue from the head parts and a row. of feet furnished with stiff bristles borders each side of the body. Strange to say, however, when in confinement the animal is exceedingly sluggish and scarcely ever stirs, but always remains in a languid state, remaining nearly in, the same position with the posterior tremity of the body recurved and dis- I charging a stream of water from a hole near the hinder part of its back. In their natural habitat, however, sea mice are very swift, moving along in a halfrunning, half-swimming manner, and at times they swim with great facility. Sea mice prey upon living creatures and do not spare their own species either. I well remember keeping two specimens in an aquarium jar, both having been procured at the same time. One was a large five-inch specimen; the other not quite half as long but proportionately broader. After living peaceably together during the first two or three days, the larger specimen was found attempting to devour his companion. One piece was already eaten, as the victim struggled desperately to be freq. In the struggle the assailant was compelled to let go, but the suffering animal’s back was injured and some of the scales ruffled off by the assault. Next morning only half the dead worm remained, the other portion having been devoured, and the victor darted out its proboscis repeatedly as it lay in the corner of the tank.

Respiration is performed on a novel principle, of which no illustration occurs in any other family of worms. The whole back is covered over with a series of scales or membraneous plates, which exhibit periodical movements of elevation and depression. Overspread by a coating of felt, readily pervious to water, the space beneath the scales during their elevation becomes filled with water, which, during the descent of the scales, is forcibly ejected at the posterior end of the body, thus, like a pair of water-bellows, supplying a constant flow of the respired element over the back surface of the worm’s body. These worms are extrernedy timid. They roam About at night or in daylight in darkened situations apparently in search of prey, but always quit their retreat cautiously, as if dreading the vicinity of a foe. The aphrodite reproduces an immense number of eggs, probably no fewer than 10,000 or so, perhaps, laid at one time. This great profusion, accumulated on the bottom of a glass vessel one day in captivity, was of a reddish hue, each individual egg being minute, white, and globular to the naked eye. My method of preserving aphrodite was to place the specimens into a flat basin of clean sea water until they had moved about and left as much grit as possible on the floor of the dish when the water was changed, fresh water being gradually added till they were lying in pure fresh water. They were left in this for 10 or 15 minutes, when they died, well extended, practically no hairs or bristles being lost. They can then be placed in 70 per cent, methylated spirits or 5 per cent, formalin, and, after a week or so, again removed to a similar strength of whatever is being used. While I am pleased to identify specimens from readers, I would appreciate it if self-addressed and stamped envelopes were forwarded for replies.