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Promiscuity, sperm storage and internal fertilization enhance sperm competition, which leads to sexual conflict whenever an advantageous trait for sperm donors is harmful to recipients. In separate-sex species, such conflicts can severely impact the evolution of reproductive characteristics, physiology and behaviours. For simultaneous hermaphrodites, the generality of this impact remains unclear and underlying mechanisms remain largely unexplored. In the hermaphrodite Lymnaea stagnalis several previous studies showed that investment in eggs differs depending on semen receipt, but these were inconsistent about the direction of change. We investigated whether the change in egg laying is caused by a seminal fluid component. By intravaginally injecting animals, we here reveal that a component of the seminal fluid inhibits egg laying, thus providing the first direct evidence for involvement of such components in competition for fertilization in hermaphrodites. We discuss the broad implications that this finding has on a number of previous studies performed in the same species. [ABSTRACT FROM AUTHOR]

The article discusses various reports published within the issue, including one by Lukas Schärer et al on the free-living flatworm Macrostomum lignano, another by Heike Reise on the diversity of genus Deroceras in reproductive morphology and Reyes-Tur and Koene on the mating behavior of snails.

Body size can be a good indicator of the quality of a potential mate in terms of fecundity. In many hermaphrodites, egg production is positively correlated with body size. Especially when donating sperm is costly, a preference for larger partners might be expected. Here we test this prediction for the great pond snail Lymnaea stagnalis. As expected, we find a clear effect of body size on egg production, and show that shell height can be used as a reliable predictor of body size. Additionally, behavioural observations reveal that these snails are not physically limited in mating with a much larger or smaller partner. Nonetheless, both in a choice experiment as well as in spontaneous copulations, we find no evidence of mate choice based on body size. These results contribute to a growing field of research which attempts to understand the evolution of the wide variation in the ways that hermaphroditic species respond to the size of potential mating partners. [ABSTRACT FROM AUTHOR]

Many species of pulmonate land snails are equipped with one or more so-called "love darts". Even though the number and shape of these calcareous darts vary considerably between species, dart use has only been investigated in very few species. Here, we redescribe the mating behaviour of Polymita muscarum because previous reports did not include the use of the dart apparatus. Mating in this hermaphroditic land snail can be divided into three stages: courtship, copulation and post-copulatory activity. During courtship, full eversion of the genital atrium is reached, thus exposing the sensitive zone, genital lobes and dart apparatus. We observed that P. muscarum pushes the everted dart apparatus repeatedly onto different parts of the partner's body and does not lose its dart after stabbing. Dissected specimens had a single, slender dart with a round base, a broad corona and a circular cross-section. We propose that the morphology of P. muscarum 's dart is consistent with the idea of simple darts needing to be stabbed more often in order to increase the transfer of mucus, which contains a biologically active substance (i.e. allohormone) that enhances the chances of paternity. Besides adding to the growing diversity in the use of love darts in land snails, these findings contribute to the understanding of the evolution of this peculiar reproductive act. [ABSTRACT FROM AUTHOR]

A foreword to the December 2009 issue of "Animal Biology" is presented.

The article discusses reports within the December 2008 issue of "Animal Biology," including papers presented at the 14th Benelux Congress of Zoology held in Amsterdam, Netherlands.