Horseshoe crabs are iconic and ecologically significant macroinvertebrates in coastal environments.The processes and mechanisms of larval hatching in Asian horseshoe crabs that occurs beneath the sand are largely unkn...Horseshoe crabs are iconic and ecologically significant macroinvertebrates in coastal environments.The processes and mechanisms of larval hatching in Asian horseshoe crabs that occurs beneath the sand are largely unknown.The spawning and developmental ecology of Tachypleus tridentatus and T.gigas are assumed to be similar to their Atlantic counterpart Limulus polyphemus.However,Carcinoscorpius rotundicauda has been cited as an exception owing to their frequent sightings in muddy mangrove areas even during low tides.To reveal the larval hatching mechanisms,in this study,we examined varying hatching responses of C.rotundicauda embryos within the sediment to the environmental conditions under continuous tidal cycles.During the eight-week experiment,the count of hatched larvae ranged 4%–30%per week,while the cumulative emergence rate from the sediment was 0–47%.Embryos were observed to have the highest active rotation activity in the first two weeks after incubation.The inundation of tidal water significantly enhanced the occurrence of hatching,in which hydration,osmotic shock and possibly agitation had triggered or facilitated the eclosion.The larvae were found to remain in the sediment for approximately 2–6 weeks before emergence.In general,C.rotundicauda was found to share a similar hatching mechanism with L.polyphemus.Our findings provide insight into the developmental ecology of Asian horseshoe crabs exposed to varying tidal conditions,and are helpful to the management and protection of their spawning habitats.展开更多
基金the National Natural Science Foundation of China(No.32060129)Guangxi BaGui Youth Scholars ProgrammeGuangxi Recruitment Program of 100 Global Experts。
文摘Horseshoe crabs are iconic and ecologically significant macroinvertebrates in coastal environments.The processes and mechanisms of larval hatching in Asian horseshoe crabs that occurs beneath the sand are largely unknown.The spawning and developmental ecology of Tachypleus tridentatus and T.gigas are assumed to be similar to their Atlantic counterpart Limulus polyphemus.However,Carcinoscorpius rotundicauda has been cited as an exception owing to their frequent sightings in muddy mangrove areas even during low tides.To reveal the larval hatching mechanisms,in this study,we examined varying hatching responses of C.rotundicauda embryos within the sediment to the environmental conditions under continuous tidal cycles.During the eight-week experiment,the count of hatched larvae ranged 4%–30%per week,while the cumulative emergence rate from the sediment was 0–47%.Embryos were observed to have the highest active rotation activity in the first two weeks after incubation.The inundation of tidal water significantly enhanced the occurrence of hatching,in which hydration,osmotic shock and possibly agitation had triggered or facilitated the eclosion.The larvae were found to remain in the sediment for approximately 2–6 weeks before emergence.In general,C.rotundicauda was found to share a similar hatching mechanism with L.polyphemus.Our findings provide insight into the developmental ecology of Asian horseshoe crabs exposed to varying tidal conditions,and are helpful to the management and protection of their spawning habitats.
