Possible Growth and Reproductive Benefits of Cannibalism in the Mosquitofish

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Abstract
We used the mosquitofish (Gambusia affinis, Poeciliidae) to test the hypothesis that the ingestion of conspecifics confers nutritional advantages to a cannibal in the form of increased growth or reproduction. We conducted two laboratory experiments in which female mosquitofish were fed one of four dried diets, one of which contained conspecifics. Compared with controls, those fed a cannibalistic diet in experiment 1 experienced significant increases in both wet weight and a reproductive index and produced embryos at a significantly advanced developmental stage. In experiment 2, increases in somatic and total dry weights were significantly greater for cannibals than for controls. Although results of the two experiments were disparate and only a few parameters measured were significant, trends were in the direction predicted by the hypothesis and should stimulate further research into nutritional benefits of cannibalism.