The edible volutid snail Adelomelon ancilla occurs on the Argentine coast and may have the capacity to serve as source of support for local Wsheries. However, knowledge of its reproduction is lacking. Over 3 years (from September 2000 to July 2004) we studied the oviposition at Golfo Nuevo, Patagonia by diving. Monthly collections were performed to examine gonadal stages histologically during 2002-2003. Gamete development stages corresponded with the expected period for oviposition occurring from July to November, a time of increasing day length. Oviposition also took place in March when water temperature attained a maximum of 18°C. Following the spawning period, remaining gametes were resorpted in both sexes. Males contained sperm throughout the year, parasperm and eusperm forms were found within the same acinus. Oogonia/oocytes ranged from 20 to 240 m in diameter during oogenesis. Females commenced laying egg capsules from a shell length of 114 mm. Reproduction is compared with other Wshable volutid snails from the Argentine shelf, and suggests the need to apply certain Wshing restrictions if the resource begins to be utilized commercially. The imposex condition was found in snails from some shipping areas. The frequency of this condition declined with distance from the port.Communicated by M. Byrne.

Intracapsular embryonic development is common in marine gastropods. In many species, embryos obtain nutrition during ontogeny by ingesting substances contained in the intracapsular fluid. South American volutids spawn egg capsules containing relatively few eggs, and development is entirely intracapsular, with young hatching as crawl-away juveniles. The spawning habits, egg capsules morphology and embryonic development of the South American volutid Adelomelon ancilla is described in this work. Egg capsules of A. ancilla (n = 42) contained 3.0 ± 1.4 (mean ± SD) embryos with a range of 1-6 eggs or embryos. The embryonic morphological changes and body spiralization occur simultaneously with embryo feeding. All embryos within a single egg capsule shared the same developmental stage. No evidence of cannibalism or intracapsular competition was found, suggesting that food is not a limiting resource as in other volutid species. Estimated intracapsular developmental time varied between five and six months (between 12-14°C). The long developmental time and low number of embryos inside the egg capsules, together with late reproductive maturity and longevity of adult individuals, reinforce the statement that the neogastropod Adelomelon ancilla is a fragile resource that must be conserved in Argentinean benthic communities.