As climatic changes and human uses intensify,resource managers and other decision makers are taking actions to either avoid or respond to ecosystem tipping points,or dramatic shifts in structure and function that are ...As climatic changes and human uses intensify,resource managers and other decision makers are taking actions to either avoid or respond to ecosystem tipping points,or dramatic shifts in structure and function that are often costly and hard to reverse.Evidence indicates that explicitly addressing tipping points leads to improved management outcomes.Drawing on theory and examples from marine systems,we distill a set of seven principles to guide effective management in ecosystems with tipping points,derived from the best available science.These principles are based on observations that tipping points(1)are possible everywhere,(2)are associated with intense and/or multifaceted human use,(3)may be preceded by changes in earlywarning indicators,(4)may redistribute benefits among stakeholders,(5)affect the relative costs of action and inaction,(6)suggest biologically informed management targets,and(7)often require an adaptive response to monitoring.We suggest that early action to preserve system resilience is likely more practical,affordable,and effective than late action to halt or reverse a tipping point.We articulate a conceptual approach to management focused on linking management targets to thresholds,tracking early-warning signals of ecosystem instability,and stepping up investment in monitoring and mitigation as the likelihood of dramatic ecosystem change increases.This approach can simplify and economize management by allowing decision makers to capitalize on the increasing value of precise information about threshold relationships when a system is closer to tipping or by ensuring that restoration effort is sufficient to tip a system into the desired regime.展开更多
Hearing sensitivity change was investigated when a warning sound preceded a loud sound in the false killer whale(Pseudorca crassidens),the bottlenose dolphin(Tursiops truncatus),the beluga whale(Delphinaperus leucas)a...Hearing sensitivity change was investigated when a warning sound preceded a loud sound in the false killer whale(Pseudorca crassidens),the bottlenose dolphin(Tursiops truncatus),the beluga whale(Delphinaperus leucas)and the harbor porpoise(Phocoena phocoena).Hearing sensitivity was measured using pip-train test stimuli and auditory evoked potential recording.When the test/warning stimuli preceded a loud sound,hearing thresholds before the loud sound increased relative to the baseline by 13 to 17 dB.Experiments with multiple frequencies of exposure and shift provided evidence of different amounts of hearing change depending on frequency,indicating that the hearing sensation level changes were not likely due to a simple stapedial reflex.展开更多
Objective:To examine the effects of fasting and refeeding on intestinal cell proliferation and apoptosis in an opportunistic predator,hammerhead shark(Sphyrna lewini)of elasmobranch fishes which are among the earliest...Objective:To examine the effects of fasting and refeeding on intestinal cell proliferation and apoptosis in an opportunistic predator,hammerhead shark(Sphyrna lewini)of elasmobranch fishes which are among the earliest known extant groups of vertebrates to have the valvular intestine ty pical for the primitive species.Methods:Animals were euthanized after 5-10 d of fasting or feeding,or after 10-day fasting and 5-day refeeding.Intestinal apoptosis and cell proliferation were assessed by using oligonucleotide detection assay,terminal deoxynucleotidyl transferase dUTP nick end labeling staining,and immunohistochemistry of proliferating cells nuclear antigen.Results:Plasma levels of cholesterol and glucose were reduced by fasting.Intestinal apoptosis generally decreased during fasting.Numerous apoptotic cells were observed around the tips of the villi,primarily in the epithelium in the fed sharks,whereas fewer labeled nuclei were detected in the epithelium of fasted sharks.Reeding returned intestinal apoptosis to the level in the fed sharks.Proliferating cells were observed in the epithelium around the troughs of the villi and greater in number in fed sharks,whereas fewer labeled nuclei were detected in fasted sharks.Conclusions:The cell turnover is modified in both intestinal epithelia of the shark and the murines by fasting/feeding,but in opposite directions.The difference may reflct the feeding ecology of the elasmobranchs,primitive intermittent feeders.展开更多
基金Primary funding was provided by the Gordon and Betty Moore Foundation,with additional support to K.A.Selkoe from National Science Founda-tion(BioOCE Award 1260169).
文摘As climatic changes and human uses intensify,resource managers and other decision makers are taking actions to either avoid or respond to ecosystem tipping points,or dramatic shifts in structure and function that are often costly and hard to reverse.Evidence indicates that explicitly addressing tipping points leads to improved management outcomes.Drawing on theory and examples from marine systems,we distill a set of seven principles to guide effective management in ecosystems with tipping points,derived from the best available science.These principles are based on observations that tipping points(1)are possible everywhere,(2)are associated with intense and/or multifaceted human use,(3)may be preceded by changes in earlywarning indicators,(4)may redistribute benefits among stakeholders,(5)affect the relative costs of action and inaction,(6)suggest biologically informed management targets,and(7)often require an adaptive response to monitoring.We suggest that early action to preserve system resilience is likely more practical,affordable,and effective than late action to halt or reverse a tipping point.We articulate a conceptual approach to management focused on linking management targets to thresholds,tracking early-warning signals of ecosystem instability,and stepping up investment in monitoring and mitigation as the likelihood of dramatic ecosystem change increases.This approach can simplify and economize management by allowing decision makers to capitalize on the increasing value of precise information about threshold relationships when a system is closer to tipping or by ensuring that restoration effort is sufficient to tip a system into the desired regime.
文摘Hearing sensitivity change was investigated when a warning sound preceded a loud sound in the false killer whale(Pseudorca crassidens),the bottlenose dolphin(Tursiops truncatus),the beluga whale(Delphinaperus leucas)and the harbor porpoise(Phocoena phocoena).Hearing sensitivity was measured using pip-train test stimuli and auditory evoked potential recording.When the test/warning stimuli preceded a loud sound,hearing thresholds before the loud sound increased relative to the baseline by 13 to 17 dB.Experiments with multiple frequencies of exposure and shift provided evidence of different amounts of hearing change depending on frequency,indicating that the hearing sensation level changes were not likely due to a simple stapedial reflex.
基金Supported in part by Grants-in-Aid for Scientific Research(Grant.17570049 and 19570057 from JSPS)Research Fel owships for Young Scientists(Grant.192156 and 214892 from JSPS)the Japan-USA Research Cooperative Program(Grant 07033011-000122 from JSPS)
文摘Objective:To examine the effects of fasting and refeeding on intestinal cell proliferation and apoptosis in an opportunistic predator,hammerhead shark(Sphyrna lewini)of elasmobranch fishes which are among the earliest known extant groups of vertebrates to have the valvular intestine ty pical for the primitive species.Methods:Animals were euthanized after 5-10 d of fasting or feeding,or after 10-day fasting and 5-day refeeding.Intestinal apoptosis and cell proliferation were assessed by using oligonucleotide detection assay,terminal deoxynucleotidyl transferase dUTP nick end labeling staining,and immunohistochemistry of proliferating cells nuclear antigen.Results:Plasma levels of cholesterol and glucose were reduced by fasting.Intestinal apoptosis generally decreased during fasting.Numerous apoptotic cells were observed around the tips of the villi,primarily in the epithelium in the fed sharks,whereas fewer labeled nuclei were detected in the epithelium of fasted sharks.Reeding returned intestinal apoptosis to the level in the fed sharks.Proliferating cells were observed in the epithelium around the troughs of the villi and greater in number in fed sharks,whereas fewer labeled nuclei were detected in fasted sharks.Conclusions:The cell turnover is modified in both intestinal epithelia of the shark and the murines by fasting/feeding,but in opposite directions.The difference may reflct the feeding ecology of the elasmobranchs,primitive intermittent feeders.
