An Indigenous Gut Bacterium, Enterococcus faecalis (Lactobacillales: Enterococcaceae), Increases Seed Consumption by Harpalus Pensylvanicus (Coleoptera: Carabidae)
Keywords:
bacteria, Carabidae, Chenopodium album, granivore, seed predation, symbiontAbstract
Microbial symbioses likely drive the evolution of diet within animals, yet these symbiotic relationships remain poorly understood for many organisms. The bacterial endosymbiont Enterococcus faecalis is found in the intestinal tract of the beetle Harpalus pensylvanicus (DeGeer) (Coleoptera: Carabidae) and is thought to contribute to the digestion of the insect’s seed diet. We tested whether E. faecalis increases seed consumption by H. pensylvanicus. The feeding assay consisted of 4 dietary treatments fed: 1) antibiotics and E. faecalis; 2) antibiotics and no E. faecalis; 3) no antibiotics and E. faecalis; and 4) no antibiotics and no E. faecalis, in which seed consumption of the beetles was measured. Beetles administered antibiotics and then E. faecalis consumed greater weights of seeds and had both decreased efficiency of conversion of ingested material to biomass (E.C.I.) per beetle and decreased efficiency of conversion of digested material (E.C.D.) to biomass per beetle. These data provide further evidence that a gut microbiota dominated by E. faecalis facilitate seed consumption by H. pensylvanicus, possibly by contributing digestive enzymes to their host. Further research is needed on the evolutionary relationship between E. faecalis and granivorous insects, and on how these facultative symbioses could influence the trophic placement of animals within complex food webs.
La simbiosis microbial probablemente impulsa la evolución de la dieta dentro de los animales, sin embargo, estas relaciones simbióticas siguen siendo poco conocidas para muchos organismos. Se encuentra la bacteria endosymbionte Enterococcus faecalis en el tracto intestinal del escarabajo Harpalus pensylvanicus (DeGeer) (Coleoptera: Carabidae) y se cree que contribuyen a la digestión de la dieta de semillas de este insecto. Probamos si E. faecalis aumenta el consumo de semillas de H. pensylvanicus. Esto fue probado a través de un ensayo de alimentación de laboratorio que consistió de un tratamiento con antibióticos, para eliminar la flora intestinal natural, y un tratamiento con E. faecalis. El ensayo de alimentación consistió en 4 tratamientos dietéticos alimentados con 1) antibióticos y E. faecalis 2) antibióticos y no E. faecalis, 3) no antibióticos y no E. faecalis y 4) antibióticos y no E. faecalis, en el que se midió el consumo de semillas de los escarabajos. Los escarabajos que recibieron los antibióticos y luego E. faecalis consumieron un peso mayor de semillas y tenían una eficacia disminuida de la conversión de los alimentos ingeridos a la sustancia corporal (ECI) y una eficiencia de conversión del alimento digerido a la sustancia corporal (ECD). Estos datos proveen más evidencia de que una microbiota intestinal dominada por E. faecalis facilita el consumo de semillas por H. pensylvanicus, posiblemente contribuyendo enzimas digestivas para su hospedero. Se necesita más investigación sobre la relación evolutiva entre E. faecalis y los insectos granívoras y cómo estas simbiosis facultativas podrían influir en la colocación trófica de los animales dentro de las redes alimentarias complejas.
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