Current fishing practices may induce low risk of sperm limitation in female swimming crab Portunus trituberculatus in the East China Sea

Abstract

Potential sperm limitation of the swimming crab Portunus trituberculatus was examined during the reproductive season from September 2006 to April 2007 in the East China Sea. We documented developmental variations between the spermatheca and ovary and distinguished these into 5 stages. We counted the number of stored sperm in paired spermathecae and found that more than 50% of sperm initially received during mating disappeared as the sperm plug degenerated; around 1.70 × 10 8 were used for final fertilization, and there was significant correlation between the final number of stored sperm and female carapace width. Lastly, using knowledge of the reproductive characteristics of P. trituberculatus, we calculated potential sperm:egg ratios of 221:1 or 153:1 for the first brood, and 55:1 or 38:1 for lifetime broods -either from the perspective of a fishery resource assessment or from the perspective of seed production. From comparison to sperm:egg ratios of Callinectes sapidus (for lifetime broods this ranges from 10:1 to 42:1), we can infer that female P. trituberculatus in the East China Sea may be at low risk of sperm limitation under current fishing practices. This may be the result of greater fishing mortality of females, causing an increase in the operational sex ratio. The present study improves our knowledge of sperm limitation in brachyurans as fishing management in China is non-selective, which differs from other exploited decapod crustacean species around the world. KEY WORDS: Portunus trituberculatus · Sperm limitation · Non-selective fishing · East China SeaResale or republication not permitted without written consent of the publisher Aquat Biol 20: 145-153, 2014 (OSR) of males to females (Hines et al. 2003, Carver et al. 2005. Therefore, sperm limitation can contribute to the structure of mating systems (Wedell et al. 2002), and knowledge of the process of sperm limitation may be beneficial to conservation and management efforts (Conover & Munch 2002, Sainte-Marie et al. 2002.A critical step in estimating the risk of sperm limitation in brachyurans is to determine whether the final quantities of sperm stored in female spermathecae are 'sufficient' to meet the possible minimum ratio of spermatozoon to oocyte for fertilization, to ensure reproductive success. However, there are relatively few reports concerning these important reproductive parameters. In Chionoecetes species, ratios for high fertilization success are reported to range from 'several' sperm per egg (Adams & Paul 1983) to actual expenditure of an estimated 70 stored sperm per egg for the first clutch extruded (SainteMarie & Lovrich 1994); females failed to extrude any eggs when the sperm:egg ratio was below 7:1 (SainteMarie & Lovrich 1994). In comparison, sperm:egg ratios in C. sapidus were estimated at 100:1 to 400:1 for the first brood, and only 20:1 to 30:1 for maximum lifetime broods over the 2 possible reproductive seasons, suggesting that approximately 67 × 10 6 sperm are used per brood of 3 × 10 6 eggs (Hines et al. 2003)....

Fishery Induces Sperm Depletion and Reduction in Male Reproductive Potential for Crab Species under Male-Biased Harvest Strategy

“…In the case of the Chilean crab fishery, a ban seasonal could be applied during the mating season to provide some protection to males. Alternatively, non sex-selective harvesting strategy could be applied as in some other crab fisheries [ 30 , 31 ], and could be complemented with a maximum catch quota.…”

De novo transcriptome sequencing and analysis of male and female swimming crab (Portunus trituberculatus) reproductive systems during mating embrace (stage II)

“…A total of 10 pre-pubertal females (distinguished by the differences in the abdominal shape and the coloration of the second-to-last segment of the swimming appendage) [ 9 ] and 10 mature male crabs (CW > 100 mm, gonadal maturity) [ 42 ] were obtained in September 2006 (close to the mating peak) [ 43 ] from a local fishing port in Sheyang in Jiangsu Province. The crabs are transferred to the laboratory in Jiangsu key laboratory for bioresources of saline soils at Yancheng Teachers University and then pairs of crabs (1 male and 1 female) were randomly grouped and reared in ten 200-l aquaria at 25 °C and salinity of 30 for mating observations.…”

Reproductive potential of individual male Chinese mitten crabsEriocheir japonica sinensisin a local pond-reared broodstock: Implications for parent crab selection and sex ratio optimization

“…Therefore, if the total delivered sperm for each mating act is completely used to fertilize the first brood, the potential sperm‐to‐egg ratio can reach 10 4 :1 (Xuan et al, ). This ratio is far greater than the ratio of 100:1 to 400:1, the ratio for the blue crab Callinectes sapidus (Hines et al, ), and of 153:1 or 221:1 for the swimming crab Portunus trituberculatus (Xuan et al, ). Besides, the schedules for broodstock mating activities in the pond are usually 20–30 days, which may allow males to replenish their consuming sperm load as blue crabs, later required approximately 9–20 days to fully recover the sperm load after two successive mating activities (Kendall et al, ).…”