Horseshoe crabs,the most well-known example of“living fossils”,are iconic and ecologically important macroinvertebrates in coastal and estuarine ecosystems.Their blood is a crucial resource for manufacturing Limulus...Horseshoe crabs,the most well-known example of“living fossils”,are iconic and ecologically important macroinvertebrates in coastal and estuarine ecosystems.Their blood is a crucial resource for manufacturing Limulus or Tachypleus amebocyte lysate to detect bacterial endotoxins or fungal contamination in drug and medical devices.An enhanced understanding of their ecological roles and trophic interactions in the food webs is fundamental to facilitate resource management for the declining populations in Asia.Foraging information of the Asian species,however,is mainly derived from preliminary,scattered reports from a limited number of study locations.In this study,resource utilization,trophic niche dynamics,and trophic interaction of the juvenile tri-spine horseshoe crab,Tachypleus tridentatus(instars 1–12,approximately 0.5–8 years old)across ontogeny was assessed in diversified nursery habitats along the northern Beibu Gulf,China,using carbon and nitrogen stable isotopes.Our results suggest that:(i)T.tridentatus are ecological generalists given the vast range of carbon isotopic values and trophic niche width estimates exhibited between multiple instar groups;(ii)juvenile T.tridentatus across most habitat types predominantly assimilated energy from a variety of basal production sources in the food web,but primarily depended on sedimentary organic matter and seagrass resource pools;(iii)ontogenetic shifts in juvenile dietary proportions were evident,with decreased reliance on sedimentary organic matter,coupled with increased reliance on benthic macroinvertebrate grazers,detritivores,and omnivores with age;and(iv)nearly all juvenile instars occupied similar trophic positions in the food web with slight shifts in trophic position present with increasing size.Our findings indicate that resource availability and ontogenetic diet shifts strongly influence horseshoe crab trophic dynamics,and age should be accounted when formulating habitat conservation measures based on resource use for Asian horseshoe crabs.展开更多
Figs and fig pollinators are one of the few classic textbook examples of obligate pollination mutualism.The specific dependence of fig pollinators on the relatively safe living environment with sufficient food sources...Figs and fig pollinators are one of the few classic textbook examples of obligate pollination mutualism.The specific dependence of fig pollinators on the relatively safe living environment with sufficient food sources in the enclosed fig syconia implies that they are vulnerable to habitat changes.However,there is still no extensive genomic evidence to reveal the evolutionary footprint of this long-term mutually beneficial symbiosis in fig pollinators.In fig syconia,there are also non-pollinator species.The non-pollinator species differ in their evolutionary and life histories from pollinators.We conducted comparative analyses on 11 newly sequenced fig wasp genomes and one previously published genome.The pollinators colonized the figs approximately 66.9 million years ago,consistent with the origin of host figs.Compared with nonpollinators,many more genes in pollinators were subject to relaxed selection.Seven genes were absent in pollinators in response to environmental stress and immune activation.Pollinators had more streamlined gene repertoires in the innate immune system,chemosensory toolbox,and detoxification system.Our results provide genomic evidence for the differentiation between pollinators and nonpollinators.The data suggest that owing to the long-term adaptation to the fig,some genes related to functions no longer required are absent in pollinators.展开更多
基金This research was supported by the National Natural Science Foundation of China(41706183,41901226)the Guangxi Natural Science Foundation(2017GXNSFBA198181)the Guangxi BaGui Youth Scholars Program,the Guangxi Recruitment Program of 100 Global Experts,and the Guangxi Postdoctoral Innovation Program.
文摘Horseshoe crabs,the most well-known example of“living fossils”,are iconic and ecologically important macroinvertebrates in coastal and estuarine ecosystems.Their blood is a crucial resource for manufacturing Limulus or Tachypleus amebocyte lysate to detect bacterial endotoxins or fungal contamination in drug and medical devices.An enhanced understanding of their ecological roles and trophic interactions in the food webs is fundamental to facilitate resource management for the declining populations in Asia.Foraging information of the Asian species,however,is mainly derived from preliminary,scattered reports from a limited number of study locations.In this study,resource utilization,trophic niche dynamics,and trophic interaction of the juvenile tri-spine horseshoe crab,Tachypleus tridentatus(instars 1–12,approximately 0.5–8 years old)across ontogeny was assessed in diversified nursery habitats along the northern Beibu Gulf,China,using carbon and nitrogen stable isotopes.Our results suggest that:(i)T.tridentatus are ecological generalists given the vast range of carbon isotopic values and trophic niche width estimates exhibited between multiple instar groups;(ii)juvenile T.tridentatus across most habitat types predominantly assimilated energy from a variety of basal production sources in the food web,but primarily depended on sedimentary organic matter and seagrass resource pools;(iii)ontogenetic shifts in juvenile dietary proportions were evident,with decreased reliance on sedimentary organic matter,coupled with increased reliance on benthic macroinvertebrate grazers,detritivores,and omnivores with age;and(iv)nearly all juvenile instars occupied similar trophic positions in the food web with slight shifts in trophic position present with increasing size.Our findings indicate that resource availability and ontogenetic diet shifts strongly influence horseshoe crab trophic dynamics,and age should be accounted when formulating habitat conservation measures based on resource use for Asian horseshoe crabs.
基金supported by the National Natural Science Foundation of China(31830084,31970440 and 32070466)supported by“the Fundamental Research Funds for the Central Universities”,Nankai University(96172158,96173250 and 91822294)。
文摘Figs and fig pollinators are one of the few classic textbook examples of obligate pollination mutualism.The specific dependence of fig pollinators on the relatively safe living environment with sufficient food sources in the enclosed fig syconia implies that they are vulnerable to habitat changes.However,there is still no extensive genomic evidence to reveal the evolutionary footprint of this long-term mutually beneficial symbiosis in fig pollinators.In fig syconia,there are also non-pollinator species.The non-pollinator species differ in their evolutionary and life histories from pollinators.We conducted comparative analyses on 11 newly sequenced fig wasp genomes and one previously published genome.The pollinators colonized the figs approximately 66.9 million years ago,consistent with the origin of host figs.Compared with nonpollinators,many more genes in pollinators were subject to relaxed selection.Seven genes were absent in pollinators in response to environmental stress and immune activation.Pollinators had more streamlined gene repertoires in the innate immune system,chemosensory toolbox,and detoxification system.Our results provide genomic evidence for the differentiation between pollinators and nonpollinators.The data suggest that owing to the long-term adaptation to the fig,some genes related to functions no longer required are absent in pollinators.
