 In animals that mate promiscuously, store sperm and fertilise internally, the sperm from two or more donors usually compete for access to eggs. Such sperm competition often leads to sexual conflict, because traits that are advantageous to the sperm donor can be harmful to the recipient. In species with separate sexes, many recent studies have focussed on sperm competition, sexual conflicts and counter-adaptive arms races, and have shown their severe impact on the evolution of mating interactions, genital morphologies, gametes, seminal products and speciation. For simultaneous hermaphrodites, despite substantial theoretical work, it remains unclear how general sperm competition and the resulting sexual conflicts are. Moreover, the underlying mechanisms are largely unexplored. Our aim is to address these proximate and ultimate questions using the freshwater snail Lymnaea stagnalis. Ultimate issues to be tackled are the evolution of reproductive morphology and allohormones between species as well as the functional significance of differences in lifetime reproductive success they cause within L. stagnalis. Proximate issues include the development of these differences as well as the mechanism underlying mating decisions and differential sperm allocation (e.g. based on pheromones or learning). The integrative nature of this research implies the use of a range of techniques, including quantification of behaviour and resource investment, molecular phylogeny reconstruction, paternity analysis, identification of allohormone-encoding genes, biochemical analysis, immunohistochemistry, micro-surgery, neuroanatomy and electrophysiology. The aim is to integrate the findings into a complete picture of why and how sperm competition and sexual conflict affect these simultaneous hermaphrodites. Such a broad synthesis is expected to significantly contribute to a full and correct understanding of hermaphroditism as a reproductive strategy. Collaboration: Kora Montagne-Wajer, Jeroen Hoffer, Jacintha Ellers, Dick Roelofs, Nico van Straalen (Amsterdam, The Netherlands); Andries ter Maat (Max Planck Institute, Seewiesen); Gregg T. Nagle (University of Texas Medical Branch); Scott F. Cummins (University of Queensland, Australia)  In the animal kingdom there are many examples of ways in which an individual can manipulate its mating partner to its own benefit. One bizarre example is the phenomenon of dart shooting in hermaphroditic land snails. In many species, a so-called "love dart" is forcefully stabbed through the skin of the mating partner. In Cornu aspersum (previously Helix aspersa) this results in the injection of an allohormone that increases sperm storage and paternity, probably via a decrease in sperm digestion. We here aim to investigate dart shape, function and use within and between species. Dart shape (and number) can differ dramatically between species, but smaller differences can also be found between individuals of the same species. Dart function has so far only been unravelled in one species (C. aspersum), therefore it needs to be established for other species whether the dart has a similar effect on the recipient and which component of the dart's mucus is responsible. Finally, dart use differs greatly in the few species looked at so far (ranging from 1 to more than 3000 stabs per partner), thus data on more species are needed for a clear evolutionary picture. This can be achieved via behavioural experiments but can also be deduced from the way the dart shooting organs is built (i.e. functional morphology). Ultimately, all this information about darts and dart shooting is essential for a full understanding of the evolution of this odd reproductive act as well as of the importance of sexual selection in hermaphroditic animals. Collaboration: Satoshi Chiba (Sendai, Japan); Bernardo Reyes-Tur (Santiago de Cuba, Cuba); Johan van Leeuwen (Wageningen University, The Netherlands)  Some simultaneous hermaphrodites exchange gametes reciprocally within one mating interaction, while others perform one sexual role at a time. Much attention has been paid to the evolutionary reasons for such gamete exchanges, but the underlying mechanisms have been left largely unexplored. This project aims to investigate the latter by using two snail species that differ in the mode of sperm transfer but share several important features that indicate that the motivational system may be regulated in the same way. The freshwater snail Lymnaea stagnalis copulates by unilateral sperm donation, where the sperm donor mounts the recipient's shell. Its motivation to donate sperm is determined by the size of the prostate gland, which is detected via a nervous connection between this gland and the snail's central nervous system. Copulation in the land snail Succinea putris also involves shell mounting but intromission of penises and sperm exchange are reciprocal. Interestingly, sexually isolated individuals are more eager to perform the active role, the prostate gland increases in size during isolation and this gland is innervated by a small nerve. We will here explore whether in S. putris the mechanism underlying motivation is similar to that of L. stagnalis. In addition, we will follow this up by also looking at the same mechanism in several (freshwater) species. Collaboration: Kurt Jordaens (Antwerp, Belgium)  During courtship, simultaneously hermaphroditic terrestrial slugs of the genus Deroceras stroke each other with an organ called the sarcobellum. After this elaborate courtship, sperm is transferred reciprocally in a very brief copulation. This transfer occurs externally via the tightly-entwined everted penes. Interestingly, before the partners separate and right after sperm exchange the penial appendages are everted and spread over the partner's body. The function for this intriguing behaviour is still unresolved, but may hint at a sexual conflict, which is why we are interested in investigating it in detail. Collaboration: Heike Reise (Goerlitz, Germany) The evolution of the love dart in land snails The function of the copulatory setae in the earthworm Lumbricus terrestris Manipulation of the mating partner via seminal products The interaction between snails and snail leeches Comparative morphology of dart-possessing land snails Behavioural and neurobiological aspects of dart shooting in the garden snail Helix aspersa (Ph.D.) The function of dart shooting behaviour in the garden snail Helix aspersa (M.Sc.) The nervous control of male mating behaviour of the pond snail Lymnaea stagnalis (M.Sc.) |