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 deve-lopmental 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.rotun-dicauda embryos within the sediment to the environmental conditions under continuous tidal cycles.During the eight-week experi-ment,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 devel-opmental ecology of Asian horseshoe crabs exposed to varying tidal conditions,and are helpful to the management and protection of their spawning habitats.

KUANG Yang;TAN Kian Ann;FU Yijian;YANG Xin;XU Peng;ZHEN Wenquan;WANG Xueping;HUANG Xing;ZHU Junhua;WANG Chun-Chieh;KWAN Kit Yue

Guangxi Key Laboratory of Beibu Gulf Marine Biodiversity Conservation,College of Marine Sciences,Beibu Gulf University,Qinzhou 535011,China;College of Fisheries,Huazhong Agricultural University,Wuhan 430070,China;Guangxi Beibu Gulf Marine Research Center,Guangxi Academy of Sciences,Nanning 530007,China

中国海洋大学学报（自然科学英文版）

[1]KUANG Yang;TAN Kian Ann;FU Yijian;YANG Xin;XU Peng;ZHEN Wenquan;WANG Xueping;HUANG Xing;ZHU Junhua;WANG Chun-Chieh;KWAN Kit Yue-.Influence of Tidal Cycles on Embryonic Rotation,Hatching and Emergence of Mangrove Horseshoe Crab,Carcinoscorpius rotundicauda)[J].中国海洋大学学报（自然科学英文版）,2022(03):557-563

Hatching,Mangrove,Horseshoe,Carcinoscorpius,rotundicauda,macroinvertebrates,lopmental,Limulus,polyphemus,sightings,rotun,dicauda

Influence,Tidal,Cycles,Embryonic,Rotation,Emergence,Crab,crabs,iconic,ecologically,coastal,environments,processes,mechanisms,larval,hatching,Asian,horseshoe,that,occurs,beneath,sand,largely,unknown,spawning,ecology,Tachypleus,tridentatus,gigas,assumed,similar,their,Atlantic,counterpart,However,has,been,cited,exception,owing,frequent,muddy,mangrove,areas,even,during,low,tides,To,reveal,this,study,examined,varying,responses,embryos,within,sediment,environmental,conditions,under,continuous,tidal,cycles,During,eight,experi,hatched,larvae,ranged,while,cumulative,emergence,from,was,Embryos,were,observed,have,highest,active,rotation,activity,first,two,weeks,after,incubation,inundation,water,significantly,enhanced,occurrence,which,hydration,osmotic,shock,possibly,agitation,had,triggered,facilitated,eclosion,found,remain,approximately,before,general,share,Our,findings,provide,insight,into,devel,exposed,helpful,management,protection,habitats

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