Uviovo and Beatty1) reported that zinc decreased brood size and body size of young at birth, but had no effect on the intervals between broods in the guppy. Boyd2) reported that a threshold concentration of organochloric insecticides such as DDT, dieldrin, toxaphen and lindane caused the pregnant females of the mosquitofish to abort. However, little attention has been paid to the stage of pregn...

Hypothesis: Fish will exhibit morphological plasticity in response to how (food type: live vs. attached food) and where (orientation: surface, mid-water, benthic) they are fed. Fine-grained resource variation (daily rotation of orientations) will produce intermediate morphologies. Population differences will reflect responses to both predators and resources. Organism: Offspring from two populat...