Effects of male mating frequency and male size on ejaculate size and reproductive success of female spiny king crab Paralithodes brevipes

Abstract

Potential sperm limitation in a fished population of the spiny king crab Paralithodes brevipes was investigated in controlled laboratory experimental and field studies. The laboratory experiments examined the effects of male size and mating frequency on their reproductive potential and the recovery rate of exhausted sperm. The spawning success and fertilization rate of females decreased as the male mating frequency increased. The effects of increased male mating frequency on the spawning success of females and fertilization rates differed between male size classes. Male size and mating frequency have great influences on sperm limitation. Males showed little capacity to regenerate sperm, increasing the likelihood of limited sperm supply to females in fished population with low numbers of males due to male-selective fishing regulations. The field studies examined the structure of a fished population of P. brevipes in Hamanaka, eastern Hokkaido, before and after a change in the fishery regulations that permitted smaller males to be harvested. The results showed that a change in the sex ratio occurred after the fishery regulations were introduced, skewing the population towards females. The results also showed a decrease in the mean male size in the fished population. The results also indicated that a significant percentage of males (42.2%) had depleted sperm reserves just after the reproductive season. Overall, the results indicate that sperm limitation could occur in this fished population of P. brevipes. These observations may warrant a review of the current fishing regulations, particularly the minimum legal size.

Sperm limitation: possible impacts of large male-selective harvesting on reproduction of the coconut crab Birgus latro

“…For example, male mating frequency increases if the sex ratio of a population is skewed toward females. Since males deplete their sperm reserves and decrease ejaculate size through successive matings (Birkhead 1991, Pitnick & Markow 1994, Sato et al 2005), a population with a female-biased sex ratio may have a reduced female fertilization success (e.g. .…”

“…. Larger males have larger sperm reserves (Pitnick 1996, Kendall et al 2001, Sato et al 2005) and pass larger ejaculates to successive mates than do smaller ones in some species (Jivoff 1997, and thus sperm supply can be lower in populations with only small males. Therefore, the probability that females suffer from insufficient sperm supply is closely related to the structure of the population, namely the mean male size and the sex ratio.…”

“…Such harvesting, in addition to the obvious direct effect of reducing the abundance of the resource, also affects the demography of the population by skewing the sex ratio towards females and decreasing mean male body size (Smith & Jamieson 1991, Ginsberg & Milner-Gulland 1994, Sato et al 2005. Females in populations subjected to such biased harvesting may receive reduced sperm supplies that limit their reproductive success, which can result in a decrease in the reproductive rate of the resource.…”

Mutual mate choice in crayfish: large body size is selected by both sexes, virginity by males only

“…Sperm competition is likely to occur in several species of insects, spiders and some crustaceans due to the female ability to store sperm and to mate repeatedly, so that males are also expected to be careful in choosing mates and in allocating their sperm (Wedell et al, 2002). As a consequence, both sexes of some arthropods were found to assess the mating status (MS) of a potential partner, thereby reducing the risk of wasting time and energy (Sato et al, 2005;Sato & Goshima, 2007).…”

Absence of a prezygotic behavioural barrier to gene flow between the two sympatric morphs of the squat lobster Munida gregaria (Fabricius, 1793) (Decapoda: Anomura: Galatheidae)

“…In arthropods, there is a general preference for large mates (Crespi 1989), and body size is positively correlated with mating success and fecundity (Andersson 1994). Larger males are often stronger competitors for females (Hoefler 2007), can provide more sperm (Sato and Goshima 2007a), can mate with several females in a single mating season (Paul and Paul 1990;Paul and Paul 1997;Sato et al 2005), or have an advantage in struggles with females to capture or physically control them during the mating and guarding phases (Lee and Seed 1992). In turn, females may resist mating and copulate only with males that overcome female reluctance to mate (Kokko et al 2003).…”