Dispersal Behavior Of Mosquitofish (gambusia Holbrooki)

Mosquitofish (Gambusia holbrooki) are native to the southeastern United States but invasive elsewhere, and are dominant predators in many ecosystems that they inhabit. Information on dispersal behavior will help better understand and predict mosquitofish metapopulation dynamics and invasions. I experimentally tested dispersal behavior of individual mosquitofish under a range of laboratory conditions relevant to field situations. Preliminary experiments showed that gender, lighting conditions, hunger and acclimation time did not significantly affect net dispersal rate. Power analysis based on this preliminary experiment determined that 6 replicate fish were sufficient for each subsequent experiment; I used 24 fish, and each fish was tested one time. Three factors that potentially could affect net swimming rate were tested: habitat of origin (permanent vs. temporary waters), water depth (3-24 mm), and the interaction between water depth and leaf litter type (upland and wetland). Fish from a temporary pond dispersed significantly faster than fish from a permanent pond, and fish dispersed significantly faster in deeper water than in shallower water. However, leaf litter significantly inhibited fish dispersal at all depths tested. Based on these experiments, G. holbrooki disperse more readily through relatively open and deeper (several centimeters) pathways between habitats such as roadside ditches, drainage canals and trails in flooded conditions. My results are useful for understanding mosquitofish dispersal behavior based on the abiotic and biotic factors examined in this experiment. I predict that mosquitofish can spread from a point of introduction at about 800 m per day, given and unobstructed path of only \u3e 6 mm depth

Antipredator response to injury-released chemical alarm cues by convict cichlid young before and after independence from parental protection. Behaviour

Summary Injury-released chemical alarm cues are released when predators attack aquatic prey. These cues are generally released only in this context and as such, conspeci c alarm cues form an important component of risk assessment. Minnows (Ostariophysi, Cyprinidae) possess a well-developed chemical alarm system. However, minnows do not respond to conspeci c injury-released alarm cues until 30 to 50 d post-hatch. Non-ostariophysan shes respond to chemical alarm cues with antipredator behavior but the ontogeny of this behavior is not known for any species. Here, we test convict cichlids (Acanthopterygii: Cichlidae), a species known to respond to alarm cues as adults. Convict cichlid parents care for their eggs and defend their developing young from predators for 4 to 6 weeks. In our experiment, we tested the ontogeny of antipredator response to chemical alarm cues in young convict cichlids well within and just beyond the size range typically defended by parents. We found that small convict cichlid young of a size typically defended by parents engaged in area avoidance and grouping behaviors in response to alarm cues and did so as effectively as young that would typically be independent of parental care

Behavioral Constraints For The Spread Of The Eastern Mosquitofish, Gambusia Holbrooki (Poeciliidae)

Eastern mosquitofish (Gambusia holbrooki) are native to the southeastern United States but notoriously invasive elsewhere, and are aggressive predators in ecosystems they inhabit. Information on dispersal behavior is needed to better understand mosquitofish spread upon introduction and potential means to mitigate that spread. We experimentally tested the effects of shallow water depths (3-24 mm) and obstacles (leaf litter) on mosquitofish dispersal behavior, plus a range of conditions relevant to field situations. Mosquitofish dispersed significantly faster in deeper water (p \u3c 0.001) but some dispersed in only 3 mm water depth (i.e., one-half average body depth). Wetland and upland leaf litter at natural densities strongly interfered with mosquitofish dispersal behavior. Based on our results, introduced mosquitofish spread rapidly given unimpeded dispersal corridors (e.g., mowed ditches), and may do so at rates \u3e800 m/day. Also, consistent lack of sexual dimorphism in dispersal behavior indicates that mosquitofish spread is not strongly dependent on female poeciliid reproductive biology. Our results support designation of mosquitofish as highly invasive and suggest that barriers to mosquitofish spread must obstruct dispersal pathways as shallow as 3 mm depth. © 2007 Springer Science+Business Media, Inc

Epidermal ‘alarm substance’ cells of fishes maintained by non-alarm functions: possible defence against pathogens, parasites and UVB radiation

Many fishes possess specialized epidermal cells that are ruptured by the teeth of predators, thus reliably indicating the presence of an actively foraging predator. Understanding the evolution of these cells has intrigued evolutionary ecologists because the release of these alarm chemicals is not voluntary. Here, we show that predation pressure does not influence alarm cell production in fishes. Alarm cell production is stimulated by exposure to skin-penetrating pathogens (water moulds: Saprolegnia ferax and Saprolegnia parasitica), skin-penetrating parasites (larval trematodes: Teleorchis sp. and Uvulifer sp.) and correlated with exposure to UV radiation. Suppression of the immune system with environmentally relevant levels of Cd inhibits alarm cell production of fishes challenged with Saprolegnia. These data are the first evidence that alarm substance cells have an immune function against ubiquitous environmental challenges to epidermal integrity. Our results indicate that these specialized cells arose and are maintained by natural selection owing to selfish benefits unrelated to predator–prey interactions. Cell contents released when these cells are damaged in predator attacks have secondarily acquired an ecological role as alarm cues because selection favours receivers to detect and respond adaptively to public information about predation

parasites and UVB radiation non-alarm functions: possible defence against pathogens, Epidermal 'alarm substance' cells of fishes maintained by References Epidermal 'alarm substance' cells of fishes maintained by non-alarm functions: possible defence again

Many fishes possess specialized epidermal cells that are ruptured by the teeth of predators, thus reliably indicating the presence of an actively foraging predator. Understanding the evolution of these cells has intrigued evolutionary ecologists because the release of these alarm chemicals is not voluntary. Here, we show that predation pressure does not influence alarm cell production in fishes. Alarm cell production is stimulated by exposure to skin-penetrating pathogens (water moulds: Saprolegnia ferax and Saprolegnia parasitica), skin-penetrating parasites (larval trematodes: Teleorchis sp. and Uvulifer sp.) and correlated with exposure to UV radiation. Suppression of the immune system with environmentally relevant levels of Cd inhibits alarm cell production of fishes challenged with Saprolegnia. These data are the first evidence that alarm substance cells have an immune function against ubiquitous environmental challenges to epidermal integrity. Our results indicate that these specialized cells arose and are maintained by natural selection owing to selfish benefits unrelated to predator-prey interactions. Cell contents released when these cells are damaged in predator attacks have secondarily acquired an ecological role as alarm cues because selection favours receivers to detect and respond adaptively to public information about predation