The Phenomena and Conditions of Sex-change in the Oyster (O. edulis) and Crepidula

Abstract

IN NATURE of December 15, 1921 (vol. 108, p. 500), I described an experiment from which a sexually mature male oyster was obtained of a maximum age of 23 weeks, from the River Blackwater. In this experiment a fair number of oysters born in 1921 were obtained on specially prepared shells kept isolated in the sea with the view of determining the conditions of sex at a known age at later intervals. With the aid of a Government grant from the Royal Society it has been possible to follow up the experiment this year with the following highly interesting results. The young oysters this year were found mostly to be sexually mature or had recently spawned. In one sample of 32 examined from shells on the south shore, River Blackwater, most of the individuals were males, but one large individual (28 × 31 mm.) was found on July 3 to be carrying thousands of young oyster embryos. This same individual was taken to Plymouth and kept alive; on July 18 it was again examined and found to be practically ready to spawn as a male.