Caterpillars lack a resident gut microbiome

Abstract

Many animals are inhabited by microbial symbionts that influence their hosts’ development, physiology, ecological interactions, and evolutionary diversification. However, firm evidence for the existence and functional importance of resident microbiomes in larval Lepidoptera (caterpillars) is lacking, despite the fact that these insects are enormously diverse, major agricultural pests, and dominant herbivores in many ecosystems. Using 16S rRNA gene sequencing and quantitative PCR, we characterized the gut microbiomes of wild leaf-feeding caterpillars in the United States and Costa Rica, representing 124 species from 15 families. Compared with other insects and vertebrates assayed using the same methods, the microbes that we detected in caterpillar guts were unusually low-density and variable among individuals. Furthermore, the abundance and composition of leaf-associated microbes were reflected in the feces of caterpillars consuming the same plants. Thus, microbes ingested with food are present (although possibly dead or dormant) in the caterpillar gut, but host-specific, resident symbionts are largely absent. To test whether transient microbes might still contribute to feeding and development, we conducted an experiment on field-collected caterpillars of the model species Manduca sexta. Antibiotic suppression of gut bacterial activity did not significantly affect caterpillar weight gain, development, or survival. The high pH, simple gut structure, and fast transit times that typify caterpillar digestive physiology may prevent microbial colonization. Moreover, host-encoded digestive and detoxification mechanisms likely render microbes unnecessary for caterpillar herbivory. Caterpillars illustrate the potential ecological and evolutionary benefits of independence from symbionts, a lifestyle that may be widespread among animals.

Black soldier fly larvae (Hermetia illucens) strengthen the metabolic function of food waste biodegradation by gut microbiome

“…). Interestingly, a previous study showed that the gut of caterpillars lacked any resident microbiome and was fully colonized (or invaded) by its food microbiome (Hammer et al ., ). The BG was also significantly affected by exogenous bacteria, similar to the caterpillar gut reported above.…”

Feather mites play a role in cleaning host feathers: New insights fromDNAmetabarcoding and microscopy

“…In these studies, microbiomes composed of highly diverse taxa in low abundance have been interpreted as evidence for microbivory. In contrast, microbiome profiles showing a low diversity of highly abundant taxa are interpreted as evidence of symbiotic or pathogenic bacterial species (Hammer, Janzen, Hallwachs, Jaffe, & Fierer, ; Hubert et al., ). In this way, the prevalence–abundance patterns of the bacteria found here (Table ) suggest a combination of bacteria used as food resource (mostly environmental‐associated genera, which were more prevalent but less abundant, for example , Sphingomonas and Acinetobacter ; Table ) and of potentially symbiotic, commensalistic or pathogenic bacteria (less prevalent but much more abundant when present, for example , Bartonella , Enteroccocus; and the primary endosymbiont, Buchnera ; Table ).…”

Contaminants of emerging concern affect Trichoplusia ni growth and development on artificial diets and a key host plant

“…Many insects rely on microbial communities and endosymbionts to grow and develop; however, it has been shown that Lepidoptera species do not have a vertically transmitted microbial community (54,55). In addition, because the effects of microbial communities on T. ni survival and development have not been documented, we present these data only to show that microbial communities change when exposed to CECs, and not as a proven factor influencing survival.…”

“…Lactobacillaceae have been shown to act as beneficial bacteria in Drosophila (63); however, its function in T. ni is still unknown. Alcaligenaceae has been shown to be present in other moths (60), but Lepidopterans are not thought to have a functional microbiome (55). There are clear patterns regarding the changes in microbial community proportionality according to the heat map (Fig.…”