Nontarget testing of an insect control fungus:effects of Metarhizium anisopliae on developing embryos of the inland silverside fish Menidia beryllina

Abstract

Developing embryos of the inland silverside f ~s h Menidia Deryllina were exposed to conidiospores of the entomopathogenic fungus Metarhiziurn anlsopljae. Several adverse effects were observed in both embryos and newly hatched larvae. These lncluded transitory effects on the heart resulting in decreased cardiac output or circulation velocity, rupture of the chorion, fungal growth on the mandibles of larvae, focal vertebral abnormalities in larvae and teratogenic expressions in embryos and larvae. An ordinal ranking system was used to enumerate responses to conidiospores. This ranking system allowed significance to be determined by nonparametric analysis of variance. Responses were highly variable with significant (p 5 0.05) adverse effects observed in 5 of the 6 experiments conducted. Heat-killed spores failed to cause significant adverse effects indicating that viable spores were required for the adverse effects.