Growth and fecundity of Pisidium amnicum (Müller) (Bivalvia: Sphaeriidae) in the Tadnoll Brook, Dorset, England

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J. A. B. BASS
(1979)
Volume
30
Part
2
Page from
129

In a chalk stream in southern England Pisidium amnicum (Müller) released one annual brood of young in May. A small proportion of the largest adults, surviving brood release, initiated a second brood during August. In the present study these adults died before the young were fully developed. It is suggested that an extended life cycle may occur in other habitats. A slow-growing embryo brood developed in a steadily increasing proportion of the adults from August to April. The number of embryo shells was related to adult shell length. Mean brood size was 13 individuals, with a maximum of 37 recorded from adults of 80 and 85 mm.