IN TOUCH WITH NATURE

Otago Witness, Issue 3808, 8 March 1927, Page 5

IN TOUCH WITH NATURE

THE SHIP-WOBMB. ■ (By J. Drummond, F.L.S., F.Z.S.) ■ A giant ship-worm sent to the Sea-action Committee of the Institute of Civil Engineers by Mr D. Holderness, engineer to ■tire Auckland Harbour Board, was examined with interest by members of the Linnean Society of j London. Although ■the great mollusc has been known by its massive shelly tube for hundreds of years, this is the first time any naturalist has had' an opportunity to examine its soft parts. The specimen, some 13in long, represents only part of the body. It is not a New Zealander, fortunately. It was by Captain Burgess, of the mission, steamer Southern Cross, at the Solomon Islands. Ship-worms, notoriously, are wood-borers. They were a terrible menace to the old wooden ships. Iron and steel hulls have decreased the measure of their destructiveness, but they still menace the woodwork of harbours and other timbers that have been in the sea for a long .time.

The giant ship-worm has been found embedded in mangrove-swamps, and nowhere else. There seems to be no direct evidence that it is a wood-borer, but there is a suspicion that it is the fullygrown stage of a wood-boring species of ship-worm that is set free by the decay oi the wood. In that case, it begins life in normal conditions. Later it finds itself, by the decay of its home, in fresh conditions, but still has abundance of food, to which its extraordinary size testifies. Its tube may be 4ft long and 3in in diameter at the wider end. This remarkable adaptation to fresh conditions has been noted in other creatures. Amongst these is a little boring sponge. Cliona, which perforates oyster shells. In some respects its life-history is parallel with the life-history of. the giant ship■avorm. It begins as a borer, but abandons that vocation .and develops into a giant sponge, almost as unlike its young stage as it can be.

, People who like romance need go no further than- the ■ship-worms'’ life histories. A egg, microscopically small, may be passeßf'out of th*, female’s body'and be fertilised in the sba, or. it may' be fertilised internally arid develop in the gills. A large female ship-worm, .it is estimated, may. lay 100,000j000 eggs. In some species, if'riot in all, the small young ship-worms are males. They become females when they grow up. Grubs ■that emerge from the eggs swim actively for about a month. Settling on timber, they move oh the surface, mooring themselves by threads. They scrape off particles of wood, which they cement over their tiny bodies, about one-hundredth rif an inch long. They lose structures adapted to free swimming; undergo - a transfofmation;. and sink in. j; At the end of two weeks they are expe'ytlbofers.

Boring, mostly, is done by the rasping’ of the margins of shell-valves against the iimbrir. These tools, ■are equipped with, sharp teeth, in ridges.,.As the ridges get. their teeth blunted’ new’ ones are formed;' Purchase in rasping as'; obtained by a soft foot, which adheres to the wall of the .burrow. Tire ship-worms’ food has been discussed. It. swallows the sawdust, but may not feed on it. The sawdust is ejected in'particles through two syphons, one used foi 'the entrance •of ; water, the other to eject the water. Part of the food, probably, is microscopic organisms, swept in with the : water used in. respiration. One view is that ship-worms eke out the sawdust with a diet of microscopic organisms, specially important for the purpose of and repair! “’The belief that sawis digested is the basis of a method of baffling the ship-worm-'by soaking the timber with a poison, as: contact between the poison, and the digestive juices is assured. ■Tho first, men who went-down to the sea in ships;dreadcd the ship worm.. The triremes of Athens and the gglleys of Venice were attacked by it; it .rotted the timbers of. ■Drake’s Golden Hind; 11 it damaged the wooden walls of England; by ravaging the. dykes of Holland,' it threatened a nation. The great Linnaeus was singularly apt when he named it ‘‘Calamitas navium.” Less imaginative naturalists now know it as teredo, Greek for-“to bore.”

The ship-worm is a .mollusc. It is doubtful if in harbours it 'does more damage than the gribble, a crustacean, reported from Auckland, Lyttelton, and Akaroa, and is present probably in many other New Zealand harbours, if. not in harbours in every part of the -world. It is only about a quarter of an. inch .long, but its destruc : tivenesss is. prodigious. . It does not confine itself to timber. Tt attacked guttapercha that covered the inner core of the Cook Strait cable, showing that it goes some distance from harbours and has powers of dispersal that Dr 0. Chilton, of Christchurch, who has studied its habits, hardly expected in a creature so small and with such limited powers of locomotion. It often is associated with another crustacean, both boring into the game block of timber and sharing the blame- Still another crustacean, probably fairly common in New Zealand waters, has. bored into claystone or papa rock used for embankments in harbour works at Wairoa, Hawke’s Bay. It honeycombed the rock, which soon crumbled away. '

• A specimen of a : graceful, attractive, and conspicuous plant has been sent -by MrE. M. Guest, Owenga, Chatham Islands. He . found it in. peaty waste on Owenga station, rooted in a clump of common rushes.* Taking ■ his description, its stem is 36in high, and is somewhat like a celer/ stalk go»e to seed, dark purple at the base, changing to salmon pink._ The plant Was transplanted, to Mr Guest’s garden at Owenga. He wished to leave it until the winter, but the danger from fires, often : started about this time, was too great. He ,had some difficulty in getting it to his Home, five miles away, as it weighed about 401 b, but he managed to carry it bn horseback. After some trouble, he placed it in its proper family, the Umbelliferae, a large ■ .and , extensive cosmopolitan family, with about 2600 species, including the cayrot, the parsnip, the parsley, the celery, the. hemlock, and . the fennel, and he gives w its proper specific riaihe,'Aciphylla Tra-

versii. It is dedicated tri Mr H. H. Travers, a botanist, and son of a botanist; who first collected it on the Chathams. It is limited to those islands, where it is known by its Maori name, taramea, but it belongs to the same group as the Wild Spaniard and the speargrass of the mainland. There seems to be no. more reason for calling it Wild Spaniard than there, is for calling a more plentiful New Zealand plant Wild Irishman.

In Dr A. R. Walla/e’s day a custom sprang up .of explaining all Nature’s ways by utilitarian reasoning. The Wild Spaniard is a very spiny plant. Its leaves are like naked swords, and amongst its flowers are sharp spines. In the absence of native terrestrial mammals to account for the Wild Spaniard arming itself formidably, Wallace fell back on a theory that it might have developed its weapons to preserve it from being trodden down by moas. Miss Marguerite Crookes sets out the views of latter-day botanists by explaining that the Wild Spaniard had a much more powerful and insidious enemy than the moa. In the form of the Wild Spaniard’s leaves she finds the plant’s sblf.-protection against drought. Long and narrow, the leaves have a reduced' surface, which reduces evaporation and prevents the sun and the wind sucking too much water from the leaves. Additional protection is given by hard and rigid structure. The Wild Spaniard has protected its water supply *by thick-walled tissue.’ In some cases it has substituted stronger and more resistent cells for softer ones, which part more readily with their ivater content. In the Wild Spaniard’s seedling form Miss Crookes finds support of this explanation. The young leaves are not stiff, but are flaccid and grass-like. Unprotected at its tenderest and most helpless <jge, the Wild Spaniard ’’is apt to disappear in areas overrun by stock.