STUDY OF NATIVE SNAILS

Chronicle (Levin), 21 October 1947, Page 4

STUDY OF NATIVE SNAILS

VALUE IN RECONSTRUCTION OF PAST HISTORY While to the average person the study of the species and. distribution of native snails might not seem of any great importance, it actually provided very valuable evidence in reconstructing land . f connections of the past and connrming geological findings, said the assistant director of the Auckland Museum, Mr. A. W. B. Powell, addressing members of the Levin Rotary d!ub yesterday. Identical species ot snails, it had been found, were kept in place by natural geographical features, yet differed aeeording to changes in those same features, he continued. These differences were to be seen in the size of the snails, their coiour, direetion in which the stripes were running and the pecuiianties of the inside callous. They were not haphazard, but could give valuable information on past history. In 1927 Mr. G. L. Adkin, until recently a resident of Levin, had published an interesting paper on ihe geomorphology of the Horowhenua piains, proceeded Mr. Powell. In this he had shown three different courses in which the Ohau River had fiowed. Its earliest was along Queen Street through the point where Horowhenua Lake now was. Drifting sand had caused the formation of Lake Horowhenua and the river had then moved to Ohau, flowing through what was now Lake Papaitonga to the sea. The same thing had oceurred there and the river had again moved, this time to its present course. Mr. Adkin had submitted geological evidence for his theory and, strangely enough, it was borne out by a study of the coiour changes and differentiation in the snails in this area. The study of snails was most fascinating, said Mr. Powell. He had first become interested in them in 1930, when he had found a new species in the Waiopehu Scenic Reserve which he had named Paryphanta traversi. Of recent years he had had the advantage of the field, collecting the results of the .work of Messrs. R. A. and H. S. Prouse, of Levin, who had eombed the coastal forest remnants° from Te Horo to the Manawatu River. They had very generously ofi'ered their fine collection to the Auckland Museum. One variety of snail, Paryphanta superba prouseorum, had been named after them in recognition of their field work. It was the largest native snail in New Zealand and had been found by the Messrs. Prouse in the South Island. The traversi group of snails extended from Te Horo to the banks of the Manawatu, continued the speaker, but in that area there were four races of the same species, each the outcome of geographical changes. One was in the area from Koputaroa to Queen Street, another between Queen Street and Lake Papaitonga, the third in the Ohau district and the fourth south from there again. The presenee of thesedifferent races could all be traced'to the geographical history of the loeality, and it had been discovered that they had come to this district from the South Islarfd before Cook Strait existed. A hyfcrid form was to be found on Mt. Stokes and Mt. Kiwi. The common garden snail was not a native, advised Mr. Powell, but an accidental importation from England to Nelson about 1865. It was a herbivorous snail. The Paryphanta species of native. snail was carniverous and lived entirely on earthworms, while Placostylus, which was not found south of Whangarei m New Zealand, was herbivorous, feeding upon karaka leaves. Its relatives occupied the islands of Lord Howe, New Caledonia, Loyalty, Fiji and the Solomons. At one time there were only four known species of native snails, but as a result of the efforts of the Messrs. Prouse and others like them elsewhere in New Zealand, there were now over 30. In Horowhenua there were four localised subspecies and many smaller races. An experimental colony of snails had been taken from one area and placed in another to observe what changes took place in them, Mr. Powell proceeded. It would be a long term test, taking 100 years or more before the results could be seen, as snails were very slow growing. . "In the past there has been discrimination in the sponsoring of scientific topics," coneluded the speaker, "greater support being given to those working on subjects iikely to- be of benefit to- industry, but it is now more generally realised that pure science has a potential value." Mr. Powell was introduced to the meeting by Dr. S. J. Thompson. At the conclusion of his tal'k he answer ed several questions and a hearty vote of thanks, proposed by Mr. W. H. Walker, was accorded him. t