Influence of mating strategies on seminal material investment in crabs

Abstract

Reproduction involves high energetic costs which are related to behaviour and gamete production. In females energy allocation to gamete production has been well documented. However, estimations of male investment in seminal material are scarce. The present study aims to assess and compare male investment in four brachyuran species by determining biochemical substrates present in the vasa deferentia to subsequently estimate energetic investment during the reproductive cycle. We identified two groups with contrasting energy investments. Two species, Homalaspis plana and Romaleon setosum, showed high investment due to significant quantities of proteins and lipids. Both species are characterised by large and complex vasa deferentia, and the formation of a remarkably large sperm plug deposited to the female after copulation as a sperm competition avoidance strategy. In contrast, Metacarcinus edwardsii and Taliepus dentatus invested little energy in their smaller-sized and simpler vasa deferentia. Morpho-functional traits may play a key role in determining the investment, which may also be influenced by mechanisms (i.e. mating tactics) to prevent sperm competition and the intensity of polygyny. This study emphasises the high amount of energy males invest in seminal material and highlights the diversity of mating strategies in Brachyura, which are reflected even on the physiological level.

Opposites attract: Multiple evidence of sexual antagonistic coevolution driving extreme male-biased sexual size dimorphism inPanopeus meridionalis

“…Females also evolved seminal receptacles with diverse morpho-physiological adaptations that may function in long-term sperm storing, expulsion of sperm masses after mating, denature or digest spermatozoa, encapsulate it, and even manipulate the order in which different sperm masses from sequential matings encounter and fertilize the eggs (Sal Moyano et al ., 2010; Becker et al ., 2011; Pardo et al ., 2013; Klaus et al ., 2014; Vehof et al ., 2014; Becker & Scholtz, 2016; Farias et al ., 2017). On its side, males evolved gonopods with varied species specific morphological features (Becker et al ., 2012) likely aimed to prevent sperm competition and the intensity of polygyny (Pretterebner et al ., 2022). They also have the ability to deposit their spermatozoa encapsulated in spermatophores that provide nutrition and protection to the cells, allocate the volume of ejaculates based on the socio-sexual context, and even sequentially ejaculate sperm and seminal fluid that hardens within the seminal receptacle in order to isolate or displace sperm masses previously deposited by competing males (Sainte-Marie, 2007; Pardo et al ., 2016, 2018).…”