FIGURE 5.

Zebrafish behavioral responses to 4-hydroxyphenylacetic acid. A, fish were exposed to a point source (arrow) of 4-hydroxyphenylacetic acid (1 mm), and their movements were video tracked 5 min before and after stimulus addition. A representative track is shown, orange, prestimulus; brown, poststimulus. B, quantitative evaluation of tracks shows no evidence for attraction or aversion by 4-hydroxyphenylacetic acid (pHPAA), n.s., not significant. For comparison, attraction by food extract (food) and aversion to cadaverine is shown, raw data for these panels, see Ref. 11. C, no difference in motility was seen after exposure to 4-hydroxyphenylacetic acid. Motility is measured as average velocity and expressed as percent of the prestimulus value. D, oviposition frequency of zebrafish mating pairs is increased after exposure to 4-hydroxyphenylacetic acid, final concentrations as indicated. Blue line indicates control value (left gray bar). All three concentrations of 4-hydroxyphenylacetic acid are active, ***, p < 0.001. Naris closure (right gray bar) abolishes the increase in oviposition events, **, p < 0.02. E, schematic representation of the olfactory-mediated response of zebrafish mating pairs to 4-hydroxyphenylacetic acid.