Luciana, looks greatI’ve suggested a few additions not necessary but if helpful you can use them.In text boxes highlighted in yellow
Variation in sperm load unrelated to male morphology or developmental challenges in black widow spiders Luciana Baruffaldi, Maria Modanu, Maydianne CB Andrade University of Toronto, Scarborough
In mating systems in which females are polyandrous. Sperm from different males compete for fertilization. (Parker, et al, 1990) Argiope argentata Sperm competition drives evolution of morphology, behaviour, life history and ejaculate characteristics across taxa
More ejaculated sperm leads to higher paternity. Sperm raffle – paternity split along same ratio as sperm numbers. Thalassoma bifasciatum (Warner et al, 1995)
Male body condition. Evolution of ejaculate size. The risk and intensity of sperm competition. Large males have large ejaculates. Release more ejaculate in the presence of sneaker males. Gasterosteus aculeatus (Parker, 1990; Zbinden, et al, 2001,2004)
Individual decisions about sperm allocation across females According to female promiscuity (releasing more ejaculate with virgin females) Females with large sexual ornaments (superior maternal investment) Invest less sperm in each mating but have more matings (Pizzari et al, 2003)
Latrodectus hesperus Females mate more than once. Males show considerable variation in body size Is this scale bar shifted to the right? Thorax width
Palps Palps: male’s paired intromittant reproductive organs.
Sperm Induction No direct connection between gonads and palps Palps filled with sperm after final moult
Considerable variation in sperm load in the palps Total sperm in one palp
Objective • Analyze the variation in the number of sperm produced by male Latrodectushesperus spiders in relation to: • Male body size and • Experimental injuries
Related to body size Evidence in other taxa. Large males = more sperm Large males = less sperm
Related to injuries Adulthood reached through molting. Injuries can occur during molting. Developmental challenges that occur in nature during the male’s last molt How does damage to a sexual vs. non-sexual structure affect sperm load?
Methods Leg Palp Day 1 amputation N=25 Day 7 N=25 Remove palps Count sperm
Body size Length of tibia-patella Cephalothorax width
P-amp L-amp SPERM IS INDEPENDENT OF THE TYPE OF INJURY
Conclusion • Wide variation in sperm #: • unrelated to male morphology. SURPRISING BECAUSE IS EXTENDE IN ALL OF THE TAXA • Independent of the type of injury. SURPRISING BECAUSE IN NOT THE SAME LOSE A PALP THAN A LEG
Future directions Diet during juvenile stages could affect sperm production? The size of the palp is related to storage of sperm? Or the condition of the male?