THE WAY OF AN OYSTER.

Hauraki Plains Gazette, Volume XXXV, Issue 4761, 8 October 1924, Page 3

THE WAY OF AN OYSTER.

LIGHTNING CHANGE OF SEX. INTERESTING RESEARCH WORKThe oyster, as the Romanis knew it and as we know it, is fickle and undecided as to which of the three genders it shall adopt at varying periods of its life. The belief has anciently obtained in the trade (states the ‘‘Morning Post ’) that oysters are able to change their sex, and as long ago as last century serious investigations had been undertaken to determine exactly what did occur. Now, in view of the keen interest in genetics, tire searchlight of the Marine Biological Laboratory at Portsmouth has been turned on to tire oyster, and the facts are even more striking than tire tradehad believed. Though the fact is not pioved, tire evidence points very clearly to the view that every oyster born-into the world starts his existence as a male. If the reason is propitious, with warm sun. calm seas, and what is generally known as good harvest weather, he may have turned into a female, but no sooner will she have shed her spawn than the oyster will reassume the form and functions of a male. Cases, carefully controlled, have been observed in which in little over a year the same specimen has twice in the counse of its existence been a male and twice a female. The normal sequence of events seems to be that at the exact moment when (he female lays her eggs a very rapid change comes over her, which suggests the presence of some fluid circulating in the body that causes the sex reversal. It is a common belief that oysteis may be hermaphroditic. It is known that the dredging of oysteiys in the spawning season will cause the extrusion of the majority of the eggs, though some will be left behind. In thesg circumstances the sex-reversal takes place; the eggs left behind are absorbed or otherwise dealt with, and the oyster ceases to function as a female. It is still admitted, however, a?s a result of modern investigations, that there are puzzling cases of apparent hermaphroditism. The immediate cause that brings about the change still remains a mystery. The change from male to female usually occurs in the winter months, but has also been observed in summer. One .theory put forward is that at birth there is a predisposition to maleness. This •predisposition declines, so that femaleness becomes dominant, but with the shedding of the ova the dominance of femaleness is eliminated and the old male predominance reassumes sway. Does the organism react to one of the hormones that loom so largely in modern biological teaching ? Or is the change based on an accumulation of reserves within the organism ? These are two of the problems on which researches are being undertaken, and when they are solved it is hoped that they may have a bearing on the allimportaiK question for oyster culture of “fishing up” or natural fattening. The oyster is far from being alone in its policy of sex-reversal. At the British Association last year Dr. Crewe quoted a number of cases produced experimentally among highlyorganised animals, but the closest parallel for the oyster is the American slipper limpet, which alternates between male and female, as if by de : sign, to redress when necessary the balance of nature. Anothei problem which is in course of investigation is the chemical changes that the oyster undergoes during the progress of the seasons, and elaborate analyses conducted by Dr. E. S. Russell through the staff of Government chemists have shown that these are considerable.