Inter- and intraspecific comparison of the bacterial assemblages in the hindgut of humivorous scarab beetle larvae (Pachnoda spp.)

Abstract

The larvae of scarab beetles are model organisms for studying the role of physicochemical gut conditions and intestinal microbiota in symbiotic digestion, particularly of humus. Here, we address the question of whether the enlarged hindgut paunch of Pachnoda ephippiata and Pachnoda marginata, two closely related, but allopatric species, harbors a specific bacterial microbiota. Terminal restriction length fragment polymorphism (T-RFLP) analysis revealed that in both species, the bacterial hindgut community differs strongly from that in the midgut, food soil, and fecal pellets. High intra- and interspecific similarities between the T-RFLP profiles of different larvae indicate the presence of a hindgut-specific microbiota. Nevertheless, we found a clear separation of the two species. A 16S rRNA gene clone library from the hindgut of P. ephippiata identified the major phylogenetic groups as members of the Clostridia, Betaproteobacteria, and Bacteroidetes, followed by Bacillales and Deltaproteobacteria. A comparison with a previously obtained clone library of the same species corroborates both the similarities and the intraspecific variance of the hindgut microbiota.

Distinctive Gut Microbiota of Honey Bees Assessed Using Deep Sampling from Individual Worker Bees

“…Drosophila melanogaster individuals (Diptera) have highly variable gut communities composed of bacterial phylotypes that are the same or closely related to bacteria living in soil or other environments [34], [35]. Scarab beetle larvae also display large intraspecific differences in gut microbiota [36]. Termite species resemble honey bees in being eusocial and in possessing a highly distinctive set of gut microbes that is transferred through social interactions and that plays a central role in digestion of lignocellulytic components of the diet [37].…”

Comparative Digestive Physiology

“…The species richness of the microbiota in the GI tract of many invertebrate animals is apparently an order of magnitude lower than in mammals, commonly with just 10 to 20 taxa per individual (7, 22, 123, 131, 285, 381, 475). Nevertheless, the global diversity of microorganisms associated with the GI tract of invertebrates is substantial with different dominant species, phyla or even kingdoms in different animal taxa.…”

Multiorganismal Insects: Diversity and Function of Resident Microorganisms

“…(67, 120). Archaea generally are not associated with animals (48), although representatives of the Methanoarchaeota (methanogens) and the nonmethanogenic Thermoplasmatales and Halobacteriales are known in insects and are prevalent in the hindgut of cockroaches (order Blattodea), termites (infraorder Isoptera), and larval scarab beetles (family Scarabaeidae) (5, 15). Most of the eukaryotic microorganisms described in insects are fungi, especially ascomycetes (e.g., Clavicipitaceae , Saccharomycetes ).…”

“…With respect to direct effects, food-associated microorganisms ingested by the insect may vary with the composition of the food, and the microorganisms favored in the gut environment likely include those taxa that can best utilize food-derived nutrients in the gut lumen, including compounds intractable to host digestive enzymes. Indirect effects are mediated through the impact of food on gut anatomy, digestive function, and immunity and may be significant in the many insects where the microbiota in the gut and the food overlap weakly (5, 107, 110). The difference between the microbiota in the gut and that in the food can be exaggerated by behavioral adaptations that further promote the dominant gut microbial taxa, including coprophagy, trophallaxis (transfer of gut fluids by anus-to-mouth or mouth-to-mouth feeding), and maternal smearing of gut microorganisms on the eggshell, which is subsequently consumed by the offspring (11, 14).…”