Abstract
Organisms are exposed to a wealth of chemical information during their development. Some of these chemical cues indicate present or future dangers, such as the presence of predators that feed on either the developing embryos or their nearby parents. Organisms may use this information to modify their morphology or life-history, including hatching timing, or may retain information about risk until it gains relevance. Previous research has shown predation-induced alterations in hatching among embryonic minnows that were exposed to mechanical-injury-released alarm cues from conspecific embryos. Here, we test whether minnows likewise hatch early in response to alarm cues from injured adult conspecifics. We know that embryonic minnows can detect adult alarm cues and use them to facilitate learned recognition of predators; however, it is unknown whether these adult alarm cues will also induce a change in hatching time. Early hatching may allow animals to rapidly disperse away from potential predators, but late hatching may allow animals to grow and develop structures that allow them to effectively escape when they do hatch. Here, we found here that unlike embryonic fathead minnows (Pimephales promelas) exposed to embryonic cues, embryonic minnows exposed to adult alarm cues do not exhibit early hatching. The ability of embryos to recognize adult alarm cues as a future threat, but not a current one, demonstrates sophisticated ontogenetic specificity in the hatching response of embryonic minnows.
Highlights
Animals facing predation must continually weigh the gains of activities such as foraging and mating against the risk of being injured or killed by a predator
Our results provide strong evidence that hatching rates were not affected by the presence of adult alarm cues
It may seem inconsequential to have examined a factor that does not induce an effect. What makes this observation interesting is the fact that embryonic minnows seem to be differentiating between this and other highly similar pieces of information
Summary
Animals facing predation must continually weigh the gains of activities such as foraging and mating against the risk of being injured or killed by a predator. The behavioural impacts are well studied; animals typically exhibit fright behaviours, such as reduced movement and foraging [1], and in the case of fish, increased shelter use and shoaling [2]. These behaviours may significantly decrease their risk of predation [3, 4]. Individuals that are under a constant threat of predation may even begin to demonstrate neophobia–a fear of all novel stimuli [5] These more drastic behavioural responses may come at a greater cost, as exhibiting fear of everything may prevent low-risk gains–a willingness to take opportunities when the threat is low rather than non-existent [1]. Individuals that experience extended exposure to predation risk at certain life stages
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