Mass aggregations and migrations of millipedes despite numerous attempts to find causes for their occurrences are still an enigma. They have been reported from both southern and northern hemisphere countries, from hig...Mass aggregations and migrations of millipedes despite numerous attempts to find causes for their occurrences are still an enigma. They have been reported from both southern and northern hemisphere countries, from highlands and lowlands of both tropical and temperate regions and they can involve species belonging to the orders Julida and Spirobolida, Polydesmida and Glomerida. According to the main suggestions put forward in the past, mass occurrences in Diplopoda occur：（1） because of a lack of food and a population increase beyond sustainable levels;（2） for the purpose of reproduction and in order to locate suitable oviposition sites;（3） to find overwintering or aestivation sites;（4） because of habitat disruption and changes in the local environment;（5） as a consequence of weather conditions the year（or winter and spring） before. A recent outbreak（November 2014） of a mass migration of the polydesmid Chamberlinius hualienensis Wang 1956 on the Japanese Izu Island of Hachijojima 300 km to the south of Tokyo gave this author an opportunity to review the existing literature on millipede mass migrations and to carry out additional observations on the phenomenon in the field as well as the laboratory. Hitherto unreported heavy infestations with phoretic deutonymphs of the mite Histiostoma sp. as well as dense populations of internal rhabditid nematodes（Oscheius cf. necromena and an unidentified species of the genus Fictor）, suggest that infestations of this kind could be necromenic and either have been a contributing factor for the mass migration or been a consequence of so manyindividuals occurring together at close proximity. It is concluded that mass migrations and aggregations in millipedes do not have one common cause, but represent phenomena that often are seasonally recurring events and appear identical in their outcome, but which have evolved as responses to different causes in different millipede taxa and therefore need to be examined on a case-to-case basis.展开更多
Fish of the Coilia genus play a crucial ecological role by serving as a vital link between marine and freshwater ecosystems.To gain a comprehensive understanding of the ecological patterns,intra-interspecific variatio...Fish of the Coilia genus play a crucial ecological role by serving as a vital link between marine and freshwater ecosystems.To gain a comprehensive understanding of the ecological patterns,intra-interspecific variations,and potential determinants of Coilia from an ecological stoichiometry perspective,analyzed the concentrations of C,N,and P elements in various types of Coilia,including C.nasus,C.mystus,C.grayii,C.brachygnathus,and C.nasus taihuensis,across the Yangtze River basin.The result shows that:1)A broad spectrum of eco-stoichiometric patterns within Coilia species,facilitating their adaptation to diverse ecosystems,including seawater and freshwater.Specifically,the C content in Coilia species from 40%to 70%,while N%and P%range between 4%–12%and 0.5%–3%,respectively.2)Intriguingly,interspecific variations in eco-stoichiometric patterns are predominantly driven by anadromous populations.The anadromous Coilia species,including C.nasus,C.mystus,and C.grayii,exhibit significantly higher C contents and C/N,C/P,and N/P ratios compared to their landlocked and freshwater counterparts(C.nasus taihuensis and C.brachygnathus).However,the trends in N and P content are reversed.3)Intraspecific differences vary among Coilia species,notably observed in C.nasus taihuensis and C.brachygnathus,where there's minimal correlation with body size.Conversely,C.nasus and C.mystus demonstrate a substantial influence of body size,with increasing fish size associated with higher C content,C/N,C/P,and N/P ratios,while N and P content decrease.This suggests that larger fishes store more energy(C%)in preparation for reproductive migration.In conclusion,this study provides a scientific foundation for comprehending the ecological patterns and intra-interspecific variations in Coilia.Furthermore,it contributes to the application of ecological chemometrics in the study of migratory fish,enriching our understanding of the intricate dynamics within this ecologically significant species.展开更多
The Yangtze River and its branches are important habitats for the Japanese Eel(Anguilla japonica),however,there are few data on gonadal development and silvering indices of eels during the downstream spawning migratio...The Yangtze River and its branches are important habitats for the Japanese Eel(Anguilla japonica),however,there are few data on gonadal development and silvering indices of eels during the downstream spawning migration.This study investigates gonadal development in 121 Japanese eels caught downstream from the Jingjiang Reach of the Yangtze River in October 2012.We found that in females the ovaries of most of the out-migrating population developed earlier than the testes in males,that is,the ovaries reached stage 3(F3)or early stage 4(eF4),while the testes were at stage 2(M2)or stage 3(M3).Gonadal development in eels collected in 2012 was earlier than that of samples caught from the same region in 2007e2008 and from the Pearl River Estuary in 1972e1973.The average age,body size and gonadal-somatic index of females were significantly greater than those in males.For both females and males,there were no significant differences between the two stages of gonadal development in any of the morphological indices,which indicates that gonadal development of the Japanese Eel is independent of body size.These results help us to understand the spawning population of Japanese Eels in the Yangtze River.展开更多
文摘Mass aggregations and migrations of millipedes despite numerous attempts to find causes for their occurrences are still an enigma. They have been reported from both southern and northern hemisphere countries, from highlands and lowlands of both tropical and temperate regions and they can involve species belonging to the orders Julida and Spirobolida, Polydesmida and Glomerida. According to the main suggestions put forward in the past, mass occurrences in Diplopoda occur：（1） because of a lack of food and a population increase beyond sustainable levels;（2） for the purpose of reproduction and in order to locate suitable oviposition sites;（3） to find overwintering or aestivation sites;（4） because of habitat disruption and changes in the local environment;（5） as a consequence of weather conditions the year（or winter and spring） before. A recent outbreak（November 2014） of a mass migration of the polydesmid Chamberlinius hualienensis Wang 1956 on the Japanese Izu Island of Hachijojima 300 km to the south of Tokyo gave this author an opportunity to review the existing literature on millipede mass migrations and to carry out additional observations on the phenomenon in the field as well as the laboratory. Hitherto unreported heavy infestations with phoretic deutonymphs of the mite Histiostoma sp. as well as dense populations of internal rhabditid nematodes（Oscheius cf. necromena and an unidentified species of the genus Fictor）, suggest that infestations of this kind could be necromenic and either have been a contributing factor for the mass migration or been a consequence of so manyindividuals occurring together at close proximity. It is concluded that mass migrations and aggregations in millipedes do not have one common cause, but represent phenomena that often are seasonally recurring events and appear identical in their outcome, but which have evolved as responses to different causes in different millipede taxa and therefore need to be examined on a case-to-case basis.
基金supported by Science and Technology Commission of Shanghai Municipality(19590750500).
文摘Fish of the Coilia genus play a crucial ecological role by serving as a vital link between marine and freshwater ecosystems.To gain a comprehensive understanding of the ecological patterns,intra-interspecific variations,and potential determinants of Coilia from an ecological stoichiometry perspective,analyzed the concentrations of C,N,and P elements in various types of Coilia,including C.nasus,C.mystus,C.grayii,C.brachygnathus,and C.nasus taihuensis,across the Yangtze River basin.The result shows that:1)A broad spectrum of eco-stoichiometric patterns within Coilia species,facilitating their adaptation to diverse ecosystems,including seawater and freshwater.Specifically,the C content in Coilia species from 40%to 70%,while N%and P%range between 4%–12%and 0.5%–3%,respectively.2)Intriguingly,interspecific variations in eco-stoichiometric patterns are predominantly driven by anadromous populations.The anadromous Coilia species,including C.nasus,C.mystus,and C.grayii,exhibit significantly higher C contents and C/N,C/P,and N/P ratios compared to their landlocked and freshwater counterparts(C.nasus taihuensis and C.brachygnathus).However,the trends in N and P content are reversed.3)Intraspecific differences vary among Coilia species,notably observed in C.nasus taihuensis and C.brachygnathus,where there's minimal correlation with body size.Conversely,C.nasus and C.mystus demonstrate a substantial influence of body size,with increasing fish size associated with higher C content,C/N,C/P,and N/P ratios,while N and P content decrease.This suggests that larger fishes store more energy(C%)in preparation for reproductive migration.In conclusion,this study provides a scientific foundation for comprehending the ecological patterns and intra-interspecific variations in Coilia.Furthermore,it contributes to the application of ecological chemometrics in the study of migratory fish,enriching our understanding of the intricate dynamics within this ecologically significant species.
基金This study was supported by the National Natural Science Foundation of China(No.31201995)the Shanghai Municipal Agricultural Commission(No.20132-2)+1 种基金the Shanghai Municipal Science and Technology Commission of Chongming(No.13231203504)the Open Foundation of Engineering Research Centre of Modern Industrial Technology for Eels,Ministry of Education,China(No.RE201501).
文摘The Yangtze River and its branches are important habitats for the Japanese Eel(Anguilla japonica),however,there are few data on gonadal development and silvering indices of eels during the downstream spawning migration.This study investigates gonadal development in 121 Japanese eels caught downstream from the Jingjiang Reach of the Yangtze River in October 2012.We found that in females the ovaries of most of the out-migrating population developed earlier than the testes in males,that is,the ovaries reached stage 3(F3)or early stage 4(eF4),while the testes were at stage 2(M2)or stage 3(M3).Gonadal development in eels collected in 2012 was earlier than that of samples caught from the same region in 2007e2008 and from the Pearl River Estuary in 1972e1973.The average age,body size and gonadal-somatic index of females were significantly greater than those in males.For both females and males,there were no significant differences between the two stages of gonadal development in any of the morphological indices,which indicates that gonadal development of the Japanese Eel is independent of body size.These results help us to understand the spawning population of Japanese Eels in the Yangtze River.
