Fig. 7. Structural specificity of the sperm response to L-tryptophan. Red abalone
sperm were assayed for behavioral responses to natural egg-conditioned sea
water (ESW), and to synthetic standards tested at 10-7 mol
l-1 concentration. Both the natural L-enantiomer (L-trp) and the
unnatural D-enantiomer (D-trp) of tryptophan were tested to determine the
stereospecificity of sperm response. Serotonin, or 5-hydroxytryptamine, is a
neuroactive metabolite of L-tryptophan known to activate sperm in other
molluscan species. Filtered sea water (FSW) was used as a negative control.
Values are means ± S.E.M.; means not linked by a horizontal bar
differed significantly (one-way ANOVA with post-hoc Scheffé
test, P<0.05). (A) Change in sperm swim speed in response to
tested solutions. (B) Change in cell density due to sperm chemotaxis.
