Housekeeping via Defaction

Abstract

Conidia of the entompathogenic fungus Metarhizium anisopliae are common in soil environments. Thus, insects that move through and nest within soil have a high probability of becoming infected with this fungal pathogen. A case in point is the woodroach Cryptocercus punctulatus which nests as family units inside decayed and partially buried wood. This species defecates within their nest. We tested the hypothesis that such fecal material has antifungal properties and prevents roaches and their offspring from becoming infected. Fungal conidia were incubated with five fresh crushed feces for 1, 3, 12 and 24 hours and subsequently plated on potato dextrose agar. Germination rates were recorded and compared with those of conidia in the absence of fecal material. Our results indicated that feces have a significant negative impact on conidia viability. Moreover, conidia germination was negatively correlated with incubation time. Additional experiments indicate that the antifungal compound of roach feces may be a heat sensitive factor of microbial origin. When feces were boiled or when feces were subjected to ultraviolet radiation and subsequently incubated with M. anisopliae, conidia, viability was