Freshwater vertebrate and invertebrate prey species commonly rely on chemosensory information, including non-injury released disturbance cues, to assess local predation threats. We conducted laboratory studies to （1...Freshwater vertebrate and invertebrate prey species commonly rely on chemosensory information, including non-injury released disturbance cues, to assess local predation threats. We conducted laboratory studies to （1） determine if urea can function as a disturbance cue in juvenile convict cichlids and rainbow trout and （2） determine if the background level of urea influences the behavioral response to a subsequent pulse of urea （＇background noise＇ hypothesis）. In the first series of trials, juve- nile cichlids and trout were exposed to urea at varying concentrations （0 to 0.5 mg L-1 for cichlids and 0 to 1.0 mg L1 for trout）. Our results suggest that both cichilds and trout exhibited functionally similar responses to urea and conspecific disturbance cues and that increasing the concentration of urea results in an increase intensity of antipredator behaviour. In the second series of trials, we pre-exposed cichlids or trout to intermediate or high concentrations of urea （or a distilled water control） and then tested for the response to a second pulse of urea at at intermediate or high concentrations （versus a distilled water control）. Our results demon- strate that pre-exposure to urea reduces or eliminates the response to a second pulse of urea, supporting the background noise hy- pothesis. Together, our results suggest that pulses of urea, released by disturbed or stressed individuals, may function as an early warning signal in freshwater prey species展开更多
In order to conserve and culture the cichlid fish Archocentrus nigrofasciatus,more information about its reproductive biology and its larval behavior and morphogenesis is necessary.Currently,temperatures ranging from ...In order to conserve and culture the cichlid fish Archocentrus nigrofasciatus,more information about its reproductive biology and its larval behavior and morphogenesis is necessary.Currently,temperatures ranging from 21 to 27°C are used in ornamental aquaculture hatcheries.Lower temperatures are preferred to reduce the costs of water heating,and 23°C is usually the selected temperature.However,there is limited information on culturing protocols for ornamental species and most of the information generated on this topic remains scarce.Thus,the present study examines the morphological development of Archocentrus nigrofasciatus during the yolk-sac period up to the age of 100 h post-hatching in relation to 2 temperature regimes used in ornamental aquaculture:a temperature of 27°C(thermal optimum)and a decreased temperature of 23°C(thermal tolerance).The results of this study suggest that the 27°C temperature generates intense morphological changes in yolk-sac development in a shorter period.This has advantages as it reduces the time of yolk-sac larval development,and,thus,minimizes the transition phase to exogenous feeding and maximizes the efficiency at which yolk is converted into body tissues.The present paper provides necessary information to produce freshwater ornamental fish with better practices so as to increase larval survival and capitalize on time for growth.展开更多
文摘Freshwater vertebrate and invertebrate prey species commonly rely on chemosensory information, including non-injury released disturbance cues, to assess local predation threats. We conducted laboratory studies to （1） determine if urea can function as a disturbance cue in juvenile convict cichlids and rainbow trout and （2） determine if the background level of urea influences the behavioral response to a subsequent pulse of urea （＇background noise＇ hypothesis）. In the first series of trials, juve- nile cichlids and trout were exposed to urea at varying concentrations （0 to 0.5 mg L-1 for cichlids and 0 to 1.0 mg L1 for trout）. Our results suggest that both cichilds and trout exhibited functionally similar responses to urea and conspecific disturbance cues and that increasing the concentration of urea results in an increase intensity of antipredator behaviour. In the second series of trials, we pre-exposed cichlids or trout to intermediate or high concentrations of urea （or a distilled water control） and then tested for the response to a second pulse of urea at at intermediate or high concentrations （versus a distilled water control）. Our results demon- strate that pre-exposure to urea reduces or eliminates the response to a second pulse of urea, supporting the background noise hy- pothesis. Together, our results suggest that pulses of urea, released by disturbed or stressed individuals, may function as an early warning signal in freshwater prey species
基金The authors wish to thank Dr.R.Calado for useful discussions.
文摘In order to conserve and culture the cichlid fish Archocentrus nigrofasciatus,more information about its reproductive biology and its larval behavior and morphogenesis is necessary.Currently,temperatures ranging from 21 to 27°C are used in ornamental aquaculture hatcheries.Lower temperatures are preferred to reduce the costs of water heating,and 23°C is usually the selected temperature.However,there is limited information on culturing protocols for ornamental species and most of the information generated on this topic remains scarce.Thus,the present study examines the morphological development of Archocentrus nigrofasciatus during the yolk-sac period up to the age of 100 h post-hatching in relation to 2 temperature regimes used in ornamental aquaculture:a temperature of 27°C(thermal optimum)and a decreased temperature of 23°C(thermal tolerance).The results of this study suggest that the 27°C temperature generates intense morphological changes in yolk-sac development in a shorter period.This has advantages as it reduces the time of yolk-sac larval development,and,thus,minimizes the transition phase to exogenous feeding and maximizes the efficiency at which yolk is converted into body tissues.The present paper provides necessary information to produce freshwater ornamental fish with better practices so as to increase larval survival and capitalize on time for growth.
