|Studies on the reproductive cycles of Cardium edule and C. glaucum|
Kingston, P.F. (1974). Studies on the reproductive cycles of Cardium edule and C. glaucum. Mar. Biol. (Berl.) 28(4): 317-323
In: Marine Biology. Springer: Heidelberg; Berlin. ISSN 0025-3162, more
Reproductive cycle; Cardium edule Linnaeus, 1758 [WoRMS]; Cardium glaucum Bruguière, 1789 [WoRMS]; Brackish water
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Two allopatric populations of Cardium edule and two of C. glaucum were sampled over a period of 16 months and their gonad maturity cycles compared by histological methods. The onset of both spermatogenesis and oogenesis in C. edule took place between September and October; in C. glaucum it was slightly later, between October and November. Development of the gonads continued slowly throughout the winter, C. glaucum developing marginally faster than C. edule. Maturation accelerated in April and May, with the gonads of both species becoming fully ripe in late May and early June. Spawning of the two species approximately coincided at all the localities investigated. Spawning in C. edule was better coordinated than in C. glaucum. Transplanting cockles of one species to the typical habitat of the other did not appreciably alter the spawning period. The separation of spawning periods in sympatric associations of the two cockles is discussed.