IN TOUCH WITH NATURE

Lyttelton Times, Volume CXVII, Issue 17078, 29 January 1916, Page 6

IN TOUCH WITH NATURE

NOTES ON NATURAL HISTORY IN NEW ZEALAND. (By J. DRUMMOND, F.L.5.,F.Z.5.) Most species of mussels in New Zealand, as in other countries, live in the sea; but there are also several species that live in fresh water, and Mrs F. W. Hutton has sent mo two exceptionally large specimens, about five inches long, which her grandson found in the bed of a pond at Longboach, near Ashburton. When the specimens were found, at the end of December, the ponds, on account of a long drought, were quite dry, and the mussels were exposed. They are commonly called the pearl-mussel; the Maoris know them as an item in-the food supplies by the name of kakahi. The species inhabits ponds, rivers, creeks and lakes in many parts of both islands of the Dominion, feeding on microscopical creatures, notably diatoms and very tiny crustaceans. These are wafted into the mussels' mouths by minute filaments endowed with vibratory action, which set the current of water in motion. The mussels have a stomach, but no head, gills but no jaws, organs to smell and hear with but no eyes—although they are imperfectly sensible to light—colourless blood, a nervous system, and a foot like a ploughshare.

They are sluggish in habits and sedentary bv nature, and their lives are <-oent in feeding, producing young and protecting themselves from enemies. Amongst the most formidable of these are star-fishes, worms, fishes, birds and, finally, men. The hard bivalve shell in which the animal lives, apparently, is its shield and buokler. The shell is made by excretions from the skin of a mantle that enfolds.the animal inside. The valves of the shell are united by a hinge at the back. This hinge is an elastic ligament. The valves are closed or opened by two muscles, which, when the valves are shut, always are pulling backwards. The muscles are relaxed hy the action of nerves, and the elasticity of the hinge allows the valves to open. A writer in a zoological publication has compared the device to a book with an elastic binding. When the book is closed by clasps, the binding is stretched; when the clasps are released the book springs open. This action, -t has been pointed out, makes it easier for the mussel to open the valves than to keep them closed, as, in the latter case, sustained muscular effort is required. Fresh water mussels belong to the groat order Eulamcllibranchia—-gills-woll-covered-with-plates. This title has been given on account of two largo gill-plates. These are equipped with hair-like processes, which waft particles of food into the mouth, as stated before. In addition, blood is purified on the surfaces of the gill-plates by the washing currents of water, and the females use the outer plates as a means of sheltering and nourishing the eggs and young.

The hard shells possessed by mussels have been preserved in rocks, and have left a fairlv complete record through the ages. The palffiontological history of bivalves begins a long way down, in the old Palreozoic rocks, before insects, fishes, reptiles, birds, mammals or even land-plants had come into the scheme of creation. Probably they followed the worms and' immediately preceded the crabs and other crustaceans. 1 hey did not become abundant until the Silurian Period, at the end of the Pakeozoic Era. when fishes were supreme. Manv of the species have been dismissed from the universe, but about 5000 living species have been catalogued. At least ono extinct, fresh water species has been recorded in New Zealand. Its remains were found in coal-measures at Moreley Creek, Southland. It probably lived in the Eocene Period, before the time of man, but when the primates had developed in other parts of the world. The fresh water species seem to have appeared later than the species that live in the sea. This is what might be expected. The order of mussels, originated in the sea, but some members wandered up creeks and rivers, where thev established themselves. In time their descendants lived in fresh water exclusively. Birds and insects carried their eggs from the creeks and rivers to ponds and lakes, and their distribution became world-wide.

' Mr A. T. G. Symons, of Christchurch, writes complaining of an injustice done to the gentle, harmless kakapo. "When he first came to New Zealand, in the "eighties," his people had a sheep station at the nead of Lake Wanaka. In those days the district was very rich in respect to the native fauna. The head : o f the station, which was situated to- : wards the Haast Saddle, was speoially adapted as a place where native birds I could live and increase, Mr Symons I became well acquaintea with the different species, notably the kea and the Kakapo.. Last year he visited a country; town in Australia. In the museum he i saw a case of New Zealand birds. Amongst them was a specimen of his old friend, the kakapo, and attached to its stand, to his surprise, _he read a I full account of the methods it followed ! in its sheep-killing raids. The kea, he says, should be made to. take the full blame for the position it has taken as , the Hun of New Zealand bird life. ' Black swans, which were introduced jto the Chatham Islands many years ago, have increased there until now they are present in their tens of thousands. They find rich food supplies in the bottoms of lakes and lagoons, which sometimes seem to bo black with them.. \ Mr B. S. K. Cox, however, states that some time ago these birds received a check. Floods destroyed large areas of their feeding ground, and many jiwans were found dead, while others vrere in poor condition, and were so feeble 'that they could be almost caught I by the hand.