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Cellular Localization of Two Rickettsia Symbionts in the Digestive System and within the Ovaries of the Mirid Bug, Macrolophous pygmaeus


Dally, M. ; Lalzar, M. ; Belausov, E. ; Gottlieb, Y. ; Coll, M. ; Zchori-Fein, E. Cellular Localization of Two Rickettsia Symbionts in the Digestive System and within the Ovaries of the Mirid Bug, Macrolophous pygmaeus. INSECTS 2020, 11.

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Like most insects, those that feed on both prey and plant materials harbor symbiotic bacteria in their body. Yet the involvement of bacteria in the feeding habits of these omnivorous consumers has yet to be investigated. In the present study, we took the first step toward testing the hypothesis that bacterial symbionts are involved in the feeding habits of the omnivorous bugMacrolophus pygmaeus. We (I) characterized the microbiome (the assembly of bacteria and fungi) ofM. pygmaeus, and (II) determined the identity and location of the most dominant bacteria species within the host body. We found thatM. pygmaeusmicrobiome is dominated by twoRickettsiaspecies,R. belliandR. limoniae. These bacteria are found in high numbers in the digestive system of the bug, each exhibiting a unique distribution pattern, and for the most part, do not share the same cells in the gut. These results strongly suggest that the host bug may gain some nutritional benefits by hosting the two dominant symbiotic bacteria in its gut. Bacterial symbionts in arthropods are common, vary in their effects, and can dramatically influence the outcome of biological control efforts.Macrolophus pygmaeus(Heteroptera: Miridae), a key component of biological control programs, is mainly predaceous but may also display phytophagy.M. pygmaeushosts symbioticWolbachia, which induce cytoplasmic incompatibility, and twoRickettsiaspecies,R. belliiandR. limoniae, which are found in all individuals tested. To test possible involvement of the twoRickettsiaspecies in the feeding habits ofM. pygmaeus, we first showed that the microbiome of the insect is dominated by these three symbionts, and later described the distribution pattern of the twoRickettsiaspecies in its digestive system. Although bothRickettsiaspecies were located in certain gut bacteriocyes, in caeca and in Malpighian tubules of both sexes, each species has a unique cellular occupancy pattern and specific distribution along digestive system compartments. Infrequently, both species were found in a cell. In females, bothRickettsiaspecies were detected in the germarium, the apical end of the ovarioles within the ovaries, but not in oocytes. Although the cause for theseRickettsiadistribution patterns is yet unknown, it is likely linked to host nutrition while feeding on prey or plants.

Last updated on 12/13/2021