Comparison of Midgut Bacterial Diversity in Tropical Caterpillars (Lepidoptera: Saturniidae) Fed on Different Diets

ABSTRACT As primary consumers of foliage, caterpillars play essential roles in shaping the trophic structure of tropical forests. The caterpillar midgut is specialized in plant tissue processing; its pH is exceptionally alkaline and contains high concentrations of toxic compounds derived from the ingested plant material (secondary compounds or allelochemicals) and from the insect itself. The midgut, therefore, represents an extreme environment for microbial life. Isolates from different bacterial taxa have been recovered from caterpillar midguts, but little is known about the impact of these microorganisms on caterpillar biology. Our long-term goals are to identify midgut symbionts and to investigate their functions. As a first step, different diet formulations were evaluated for rearing two species of tropical saturniid caterpillars. Using the polymerase chain reaction (PCR) with primers hybridizing broadly to sequences from the bacterial domain, 16S rRNA gene libraries were constructed with midgut DNA e...