Using physiology and behaviour to understand the responses of fish early life stages to toxicants

Abstract

The use of early life stages of fishes (embryos and larvae) in toxicity testing has been in existence for a long time, generally utilizing endpoints such as morphological defects and mortality. Behavioural endpoints, however, may represent a more insightful evaluation of the ecological effects of toxicants. Indeed, recent years have seen a considerable increase in the use of behavioural measurements in early life stages reflecting a substantial rise in zebrafish Danio rerio early life-stage toxicity testing and the development of automated behavioural monitoring systems. Current behavioural endpoints identified for early life stages in response to toxicant exposure include spontaneous activity, predator avoidance, capture of live food, shoaling ability and interaction with other individuals. Less frequently used endpoints include measurement of anxiogenic behaviours and cognitive ability, both of which are suggested here as future indicators of toxicant disruption. For many simple behavioural endpoints, there is still a need to link behavioural effects with ecological relevance; currently, only a limited number of studies have addressed this issue. Understanding the physiological mechanisms that underlie toxicant effects on behaviour so early in life has received far less attention, perhaps because physiological measurements can be difficult to carry out on individuals of this size. The most commonly established physiological links with behavioural disruption in early life stages are similar to those seen in juveniles and adults including sensory deprivation (olfaction, lateral line and vision), altered neurogenesis and neurotransmitter concentrations. This review highlights the importance of understanding the integrated behavioural and physiological response of early life stages to toxicants and identifies knowledge gaps which present exciting areas for future research.

Development and application of the adverse outcome pathway framework for understanding and predicting chronic toxicity: II. A focus on growth impairment in fish

“…Diverse behavioral alterations have been reported to occur in response to a wide range of toxicants, frequently at concentrations much lower than those that induce any visible defects or mortality (Scott and Sloman, 2004;Sloman and McNeil, 2012;Melvin and Wilson, 2013). For example, certain toxicants are known to impair olfaction, interfering with the ability to recognize prey or causing aversion from particular food sources (LangerJaesrich et al, 2010;Tierney et al, 2010), while others can affect appetite (Baker et al, 1996;Gaworecki and Klaine, 2008;Mennigen et al, 2009).…”

“…Indeed, assessment of movement can be done in embryos and it was recently suggested as a potential assay for developmental neurotoxicity testing (Selderslaghs et al, 2010(Selderslaghs et al, , 2013. However, in many cases the patterns of responses as well as sensitivity to certain toxicants significantly differ between embryos and later stages (Airhart et al, 2007;Jin et al, 2009;Lange et al, 2012;Sloman and McNeil, 2012), and one particular disadvantage of embryonic stages is that spontaneous swimming activity is not yet established.…”

A toxic diet: transfer of contaminants to offspring through a parental care mechanism

“…This exposure period coincides with the early developmental period of these fry and hence is considered a sensitive time of exposure (Brinkman and Hansen, 2007). In fish, the toxicity of dietary contaminants to early life stages (Westin et al, 1985) is not as well studied as the effects of aqueous exposures (Sloman and McNeil, 2012), most likely because of practical reasons of diet manufacture, and certainly warrants further study. While it is usually assumed in fish that exposure to contaminants in the water causes greater toxicity than dietborne contaminants, there are circumstances where this might not be the case (Erickson et al, 2011).…”

Effects of embryonic exposure to polychlorinated biphenyls (PCBs) on anxiety-related behaviors in larval zebrafish

“…The zebrafish ( Danio rerio ) is an excellent model system for studying toxicological effects on behavior (Bailey et al, 2013; de Esch et al, 2012; He et al, 2014; Liu et al, 2012; Padilla et al, 2012; Reif et al, 2015; Richendrfer et al, 2014; Sipes et al, 2011; Sloman and McNeil, 2012; Truong et al, 2014). Eggs are fertilized externally and in large numbers, providing an opportunity for immediate large-scale embryonic exposure to toxicants in multiple concentrations and mixtures.…”