Reproductive biology in the South Western Atlantic genus Buccinanops (Nassariidae): the case of Buccinanops paytensis

Abstract

The reproductive biology of the nassariid Buccinanops paytensis is considered and compared with the other species in the genus. In B. paytensis an average of 42 egg capsules were attached to the shell of each female. A mean of 2738 eggs (246 µm in diameter) occurred per capsule and generally only one embryo developed inside, measuring c. 5 mm in shell length when hatching; eggs at pre-hatching stage are still abundant. Four percent of the egg capsules contained two pre-hatching embryos of unequal size, in which nurse eggs were totally consumed. ‘Larval kidneys’ were recorded at advanced developmental stages (‘pediveliger’). Adaptations to reproduction in soft substrates involve a great amount of energy being invested by the females (nurse eggs and maternal care of the capsules), which enhance the survival of juveniles. Buccinanops paytensis had the highest number of nurse eggs per embryo (c. 2600), but B. cochlidium had more eggs and embryos per female (c. 3100 and c. 800, respectively). Hatching of crawling juveniles occurred in about 4 months in all species. When multiple embryos occur in an egg capsule, food becomes limiting, hatching size is reduced and unequal. Evidence of sibling cannibalism was observed in B. monilifer. Major differences are related to the spawn size, and the amount of nurse eggs and feeding modality of each species, which impact on the reproductive output (number and size of the juveniles) per female. The South African nassariid genus Bullia differs in egg capsule morphology and attachment, but is similar in having nurse eggs and direct development.