http://mollus.oxfordjournals.org Journal of Molluscan Studies - RSS feed of articles 1464-3766 Journal of Molluscan Studies 0260-1230 http://mollus.oxfordjournals.org/cgi/content/short/eyn021v1?rss=1 The malacofauna associated with Zostera marina beds in the Marine Protected Area ‘Acantilados de Maro-Cerro Gordo’ (southern Spain) includes a high number of species, but Jujubinus striatus is the dominant species throughout the year (dominance of 79.5% during day and 60.3% at night). The density of this trochid is maximal in the spring and summer months (up to 172.8 ± 62.4 individuals/m²) and ultrajuveniles (shell height <1 mm) occur in the eelgrass bed from February to October. The temporal dynamics of this species abundance is linked to that of the foliage of Z. marina over its annual cycle. Jujubinus striatus reproduces from at least March to November, according to a histological study of the gonads. The reproductive potential of the population is enhanced by early sexual maturity (at 2 mm size) and by the ability of a single individual to reproduce more than once a year. These reproductive features may be of importance for maintaining the J. striatus population at a high dominance level in this habitat.

]]> 2008-07-28 info:doi/10.1093/mollus/eyn021 The Malacological Society of London 2008-07-28 ARTICLE http://mollus.oxfordjournals.org/cgi/content/short/eyn020v1?rss=1 Mate choice based on mating history is one way to optimize the distribution of one's sperm. This is especially pertinent when donating semen is costly. Owing to sperm competition many species allocate different amounts of sperm depending on their partners' mating histories. The hermaphroditic Lymnaea stagnalis has a preference for inseminating different partners, rather than the same one twice. Moreover, virgin partners receive more sperm than nonvirgins. Here we aim to determine whether these hermaphrodites prefer to inseminate virgins. Therefore, focal animals were offered a choice between one mating partner raised in isolation and one raised in a group. For each rearing condition we also measured individual growth, onset of egg laying (waiting time) and hatching success. Of the growth parameters we found that only the asymptotic size differed, with the virgins attaining a larger size. This coincides with the delayed onset of laying selfed eggs by virgins. Selfed eggs did not differ in hatching success from outcrossed eggs. The choice experiment revealed that focal individuals mated randomly with animals raised in isolation (virgins) and raised in groups (nonvirgins). This leads us to conclude that the decisions about whether to mate with an encountered individual and how much sperm to donate to this individual are two separate processes.

]]> 2008-07-28 info:doi/10.1093/mollus/eyn020 The Malacological Society of London 2008-07-28 ARTICLE