This study was conducted to provide a five-year database on the breeding seasonality and breeding biology of a Central American cichlid fish Neetroplus nematopus, a biparental substratum-spawning cichlid that cares fo...This study was conducted to provide a five-year database on the breeding seasonality and breeding biology of a Central American cichlid fish Neetroplus nematopus, a biparental substratum-spawning cichlid that cares for its eggs, wrigglers, and fry for up to six weeks. A total of 503 breeding pairs were monitored for breeding success. Breeding pairs of N. nematopus are sexually dimorphic in size, with females averaging 39% of male body mass. Fry emerged from 85% of nesting cavities. After three weeks, only 30% of the broods were present in the nesting cavity; these broods had a 30% survival rate, giving a 9% overall survival rate. Nineteen percent of the successful parents with three-week-old broods adopted foreign fry. A consistent unimodal breeding peak in December was observed for five years. This breeding peak differed dramatically from the bimodal breeding season 20 years found in the 1970s. The effects of extensive grenade fishing practices during the 1980s might have played a substantial role in the observed change. Grenade fishing stopped in 1991, and the number ofN. nematopus pairs increased by 136% from 1990 to 1995. With increased density of breeding fish, the breeding season for this species also expanded. The balance between divergent selection due to competition for breeding sites and stabilizing selection due to predation pressure on offspring is likely to mold the breeding season for N. nematopus and other cichlids of Lake Xilofi. We suggest that brood adoption and synchrony of breeding is a strategy to reduce predation on the parent＇s own young [Current Zoology 56 （1）： 43-51 2010].展开更多
Olfactory cues that indicate predation risk elicit a number of defensive behaviors in fishes, but whether they are sufficient to also induce morphological defenses has received little attention. Cichlids are character...Olfactory cues that indicate predation risk elicit a number of defensive behaviors in fishes, but whether they are sufficient to also induce morphological defenses has received little attention. Cichlids are characterized by a high level of morphological plasticity during development, and the few species that have been tested do exhibit defensive behaviors when exposed to alarm cues released from the damaged skin of conspecifics. We utilized young juvenile Nicaragua cichlids Hypsophrys nicaraguensis to test if the perception of predation risk from alarm cue （conspecific skin extract） alone induces an increased relative body depth which is a defense against gape-limited predators. After two weeks of exposure, siblings that were exposed to conspecific alarm cue increased their relative body depth nearly double the amount of those exposed to distilled water （control） and zebrafish Danio rerio alarm cue. We repeated our measurements over the last two weeks （12 and 14） of cue exposure when the fish were late-stage juveniles to test if the rate of increase was sustained; there were no differences in final dimensions between the three treatments. Our results show that 1） the Nicaragua cichlid has an innate response to conspecific alarm cue which is not a generalized response to an injured fish, and 2） this innate recognition ultimately results in developing a deeper body at a stage of the life history where predation risk is high [Current Zoology 56 （1）： 36-42, 2010].展开更多
基金funded in part by the National Science Foundationthe United States Agency for International Developmentthe Fulbright program to KRM and EvdB
文摘This study was conducted to provide a five-year database on the breeding seasonality and breeding biology of a Central American cichlid fish Neetroplus nematopus, a biparental substratum-spawning cichlid that cares for its eggs, wrigglers, and fry for up to six weeks. A total of 503 breeding pairs were monitored for breeding success. Breeding pairs of N. nematopus are sexually dimorphic in size, with females averaging 39% of male body mass. Fry emerged from 85% of nesting cavities. After three weeks, only 30% of the broods were present in the nesting cavity; these broods had a 30% survival rate, giving a 9% overall survival rate. Nineteen percent of the successful parents with three-week-old broods adopted foreign fry. A consistent unimodal breeding peak in December was observed for five years. This breeding peak differed dramatically from the bimodal breeding season 20 years found in the 1970s. The effects of extensive grenade fishing practices during the 1980s might have played a substantial role in the observed change. Grenade fishing stopped in 1991, and the number ofN. nematopus pairs increased by 136% from 1990 to 1995. With increased density of breeding fish, the breeding season for this species also expanded. The balance between divergent selection due to competition for breeding sites and stabilizing selection due to predation pressure on offspring is likely to mold the breeding season for N. nematopus and other cichlids of Lake Xilofi. We suggest that brood adoption and synchrony of breeding is a strategy to reduce predation on the parent＇s own young [Current Zoology 56 （1）： 43-51 2010].
基金provided by the Undergraduate Research Opportunities Program of Boston University
文摘Olfactory cues that indicate predation risk elicit a number of defensive behaviors in fishes, but whether they are sufficient to also induce morphological defenses has received little attention. Cichlids are characterized by a high level of morphological plasticity during development, and the few species that have been tested do exhibit defensive behaviors when exposed to alarm cues released from the damaged skin of conspecifics. We utilized young juvenile Nicaragua cichlids Hypsophrys nicaraguensis to test if the perception of predation risk from alarm cue （conspecific skin extract） alone induces an increased relative body depth which is a defense against gape-limited predators. After two weeks of exposure, siblings that were exposed to conspecific alarm cue increased their relative body depth nearly double the amount of those exposed to distilled water （control） and zebrafish Danio rerio alarm cue. We repeated our measurements over the last two weeks （12 and 14） of cue exposure when the fish were late-stage juveniles to test if the rate of increase was sustained; there were no differences in final dimensions between the three treatments. Our results show that 1） the Nicaragua cichlid has an innate response to conspecific alarm cue which is not a generalized response to an injured fish, and 2） this innate recognition ultimately results in developing a deeper body at a stage of the life history where predation risk is high [Current Zoology 56 （1）： 36-42, 2010].
