dr. Jutta Schneider: Sex specific plasticity in life-history and the mating system of Nephila senegalensis
Dr. Jutta Schneider z Univerze v Hambrugu bo v sredo, 3. aprila 2019, ob 14. uri predavala v Biološkem središču v Ljubljani.
»The genus Nephila is well known for its extremes, such as the extreme size differences between the sexes, their extremely large golden orb-webs and their curious adaptions to an unusual mating system such as regular sexual cannibalism, mate plugging, male emasculation, one-shot genitalia and spermatogenesis that terminates at maturation. However, species differ in presence-absence and the combination of the above traits. I will present data from several experiments on Nephila senegalensis from Southern Africa, a species with a pronounced reversed sexual dimorphism and a very large variation within the sexes. Using controlled feeding studies in a split-brood design we explore the causes and fitness consequences of this variation and shed some light on sex-specific selection pressures. Staged mating competition between two males from different size classes revealed balanced paternity gains of large, medium and small males although achieved by different means. Genital damage does not occur in N. senegalensis and males can mate repeatedly although they can only charge their pedipalps once. Hence, while males have a potentially unlimited mating rate, the limitation in sperm supplies opens the scene for curious sperm investment strategies explained to some degree by interactions between male and female body sizes. The recent discovery of endosymbiotic bacteria that seem to influence crucial selection parameters such as sex ratio but also growth, adds another level of complexity to this fascinating study system.«