Sex-Phenomena in the Common Limpet: (Patella vulgata)

Abstract

IN the course of investigations on the rate of growth and the age at which breeding begins the common limpet was examined, and the following interesting phenomena were observed:—A preliminary examination of batches of limpets of about 2 cm. long, and later still of smaller specimens, revealed the occurrence of a large proportion of males. The proportion of males was so high indeed as to give strong suspicions of a change of sex from male to female (i.e. protandric hermaphroditism), and a sample of about 1000 small ones less than 1 in. was therefore collected from cement piles between 3 ft. and 9 ft. above low-water springs at the Great Western Docks, Plymouth, and the sex examined and recorded. As the common limpet has no penis or uterus, it is necessary to examine the internal sex-organ (the gonad) to determine the sex. Of the 1102 limpets collected, 167 were rejected as being found by experience to be too small to show development of the internal sex-organ; these were mainly about 13 mm. long. Of the remainder, 169 (mostly about 14 mm.) showed no development of gonad on examination, 64 were females mostly about 2 cm. long, and the remaining 702 were males mostly about 15 mm. to 20 mm. long. These males probably comprise the bulk of the limpets in this sample in their first spawning year.