Abstract
Both constitutive and inducible antipredator strategies are ubiquitous in nature and serve to maximize fitness under a predation threat. Inducible strategies may be favored over constitutive defenses depending on their relative cost and benefit and temporal variability in predator presence. In African temporary ponds, annual killifish of the genus Nothobranchius are variably exposed to predators, depending on whether larger fish invade their habitat from nearby rivers during floods. Nonetheless, potential plastic responses to predation risk are poorly known. Here, we studied whether Nothobranchius furzeri individuals adjust their life history in response to a predation threat. For this, we monitored key life history traits in response to cues that signal the presence of predatory pumpkinseed sunfish (Lepomis gibbosus). While growth rate, adult body size, age at maturation, and initial fecundity were not affected, peak and total fecundity were higher in the predation risk treatment. This contrasts with known life history strategies of killifish from permanent waters, which tend to reduce reproduction in the presence of predators. Although our results show that N. furzeri individuals are able to detect predators and respond to their presence by modulating their reproductive output, these responses only become evident after a few clutches have been deposited. Overall our findings suggest that, in the presence of a predation risk, it can be beneficial to increase the production of life stages that can persist until the predation risk has faded.
Highlights
Before the end of an inundation, amphibians and many aquatic insects need to complete metamorphosis to escape, whereas others such as killifish and many crustaceans need to produce dormant life stages to survive the drought in situ (Williams, 2006)
In Nothobranchius killifish, lifespan may be linked to the typical lengths of the inundations that they experience in their local habitat (Terzibasi Tozzini et al, 2013; Terzibasi et al, 2008)
Nothobranchius may still retain some flexibility in dealing with impending pond drying as it has been shown that desiccation risk simulated by means of a drop in water level resulted in a plastic increase in egg deposition at the cost of a shorter lifespan (Grégoir et al, 2017)
Summary
All fish were kept in a climate controlled room at 24°C, under a 14-h :10-h light:dark regime. From the first day after hatching, healthy larvae were kept individually in jars filled with 250 mL dechlorinated tap water. At day five, this volume was increased to 1L. For the first three weeks of their lives, fish were fed ad libitum with newly hatched Artemia nauplii twice daily (Ocean Nutrition, Essen, Belgium). They were fed ad libitum with frozen Chironomus larvae twice a day. All jars and aquaria were cleaned three times per week from day five onwards by suctioning all debris and replenishing three quarters of the water volume with dechlorinated tap water. Pumpkinseed sunfish, used as predators, were housed in a large 80-L aquarium when not co-housed with Nothobranchius to impose a predation risk (see Experimental setup) and fed with frozen Chironomus larvae every second day
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