Dart shooting, a bizarre component of mating behaviour seen in several species of terrestrial snails, has bewildered scientists for centuries. The hermaphroditic snail Helix aspersa pushes a calcareous "love dart", covered with mucus, through the skin of its partner at the end of an elaborate courtship. I address both why this dart shooting behaviour is performed and how it is controlled by the brain. I find that the dart cannot serve as a nuptial gift of calcium because it is rarely internalised by the recipient and contains only a small amount of calcium. However, most shot darts penetrate the skin and come into contact with the blood. I demonstrate that mucus, produced by the digitiform glands and carried on the dart, causes contractions in the female organs. The contractions suggest that more sperm will reach the sperm storage organ as a result of dart shooting, which is important in sperm competition because snails store sperm from several partners before laying eggs. This introduction of a bioactive substance can be explained by either mate choice or mate manipulation. My findings show that dart shooting is an optional component of mating behaviour, which supports the mate manipulation hypothesis. I conclude that the dart transfers a substance to manipulate the storage of the donated sperm. Many species transfer bioactive substances into conspecifics. I propose the term "allohormones" for such substances to distinguish them from hormones and pheromones. / To investigate how the central nervous system controls dart shooting and other mating behaviours, I used an in vivo approach. The right mesocerebrum has been proposed as the control centre for mating behaviour based on in vitro findings. I demonstrate, by electrically stimulating and recording from right mesocerebral neurones in the intact animal, that these neurones are involved in dart shooting and penial eversion. I also test the hypothesis that different neuropeptides mediate different mating behaviours, and I find that APGWamide is responsible for genital eversion. From my results, together with data obtained using other gastropods, I conclude that the anteromedial portion of the right cerebral ganglion is an evolutionarily conserved region for the control of mating behaviour.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.36624 |
| Date | January 1999 |
| Creators | Koene, Joris M. |
| Contributors | Chase, R. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001746681, proquestno: NQ64591, Theses scanned by UMI/ProQuest. |
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