Biology subjects

Shimoji, H.

Publications and source records attributed to Shimoji, H..

4 recordsLinked to original sources

bioRxiv2026

Viral infection patterns in ants are affected by colony structure and phylogenetic lineage

Across ant species, there are differences in how their societies are structured. Single-queened (monogynous) societies only have one reproducing queen in the colony, and new queens disperse and start colonies independently. In multiple-queened (polygynous) societies, the colony instead can contain several reproductive queens, and newborn queens often remain and reproduce within their natal colony. As a result, polygynous societies are comparatively larger, more genetically diverse, and can span large areas through several interconnected nests, whereas monogynous societies are typically smaller in scale. In this study, we investigated how these different social structures, as well as their phylogenetic lineage, affect the diversity (number of virus species per ant sample) and abundance (number of viral sequences per sample) of viruses in ants. We produced pooled RNA sequence libraries from 15 ant species, representing both monogynous and polygynous social structures, and the two largest ant subfamilies: Formicinae and Myrmicinae, with each library containing the RNA of up to 400 individual worker ants from a single population. We identified 168 virus species in total, of which 152 species were new to science. Out of these 168 viruses, 59 were active viruses based on the host immune response. We observed that polygynous ant species harbor a higher diversity of viruses and also tend to have higher virus abundance compared to monogynous species. Also, the ant subfamily Myrmicinae had a higher virus diversity than Formicinae. These findings highlight how social structure and evolutionary history shape viral diversity in ants.

genomics↗

bioRxiv2025

Soil pH as an external filter shaping insect-microbe gut symbiosis

BackgroundMany animals and plants establish intimate symbiotic relationships with specific microorganisms acquired from the environment. Given the immense diversity of environmental microbiomes, selecting appropriate partners from such a vast microbial pool poses a critical challenge for host organisms. To meet this challenge, hosts have evolved sophisticated internal partner-choice mechanisms that ensure stable associations with beneficial microbes. However, because these symbionts primarily inhabit external environments, environmental conditions themselves are also expected to play pivotal roles in the establishment of symbiosis. Despite this expectation, the mechanistic role of external environmental filters in shaping the intended symbiosis remains largely unexplored. Focusing on stink bugs, which acquire their symbiotic bacteria from soil each generation, we investigated how soil properties influence the establishment of gut symbiosis in terrestrial insects. ResultsMicrobiome analyses confirmed that Burkholderia sensu lato overwhelmingly dominates a specific gut organ in six stink bug species from the superfamilies Coreoidea and Lygaeoidea, including serious agricultural pests (relative abundance ranging from 74.5% to 100%). Rearing experiments with isolated Burkholderia revealed that insects were strictly dependent on this symbiont; failure to acquire it from soil severely reduced host growth and reproduction, indicating that the availability of symbionts from soil represents an ecological bottleneck. Field surveys identified patches of exceptionally high stink bug density in weedy fields with soil pH <7.0, whereas such aggregations were absent in fields with pH [≥]7.0. Laboratory experiments with collected field soils showed that the abundance of Burkholderia in soils was negatively correlated with soil pH, and stink bugs readily acquired their symbionts from soils with pH <7.0 but rarely from soils with pH [≥]7.0. Experimental manipulations of soil pH followed by rearing experiments confirmed that increasing soil pH to 7-8 markedly suppressed symbiont acquisition by the host, likely by impairing symbiont growth and motility. ConclusionsWe demonstrate that, beyond host-intrinsic mechanisms, a soil chemical property externally filters symbiotic bacteria prior to colonization inside the host. These findings reveal that, alongside host physiology, environmental conditions--mediated through the soil and host gut microbiomes--shape the assembly, maintenance, and evolution of host-microbe symbiotic associations.

microbiology↗

bioRxiv2022

Cryptic functional diversity in ant tandem runs

Ants have evolved diverse recruitment methods to guide colony members to valuable resources, such as food or nest sites. One of these methods, tandem running, consists of an informed leader directly guiding a naive follower every step of the way from nest to resource. Although this behavior appears superficially similar in the different ant taxa in which it has independently evolved, this similarity could conceal underlying functional and mechanistic differences. Here we present a combined network and information-theoretic analysis, which reveals fundamental differences in the tandem recruitment between two distantly related ant genera, Temnothorax and Diacamma. Temnothorax uses tandem running to recruit additional recruiters, whereas Diacamma uses it principally to move the passive majority of the colony, a task that Temnothorax accomplishes with a different behavior, social carrying. Accordingly, the structure of the tandem run recruitment networks of Diacamma was different from those of Temnothorax, with Diacamma networks more closely resembling the social carrying networks of Temnothorax. Furthermore, an information-theoretic analysis of the spatial trajectories of leaders and followers revealed that Diacamma tandem runs lack bidirectional information flow, the signature of route-learning in Temnothorax tandem runs. These results suggest that Diacamma uses tandem runs not to share information, but to transport nestmates. By quantifying the cryptic diversity of communication behavior, this study increases the resolution of our understanding of animal societies.

animal behavior and cognition↗

bioRxiv2017

Caste-biased movements by termites in isolation

The caste system of termites is an example of phenotypic plasticity. The castes differ not only in morphology and physiology, but also in behavior. As most of their behaviors within colonies involve nestmates, it is difficult to extract innate differences among castes. In this study, we focused on movement patterns of isolated individuals of Hodotermopsis sjostedti. We observed distinct clusters in movement patterns over 30 min, which indicates that termites have multiple innate modes of movement. The use of these modes is biased among castes, among which neotenics had a caste-specific mode and soldiers moved more actively than workers or neotenics. These caste biases may reflect different adaptive responses to social isolation. Our study provides a basis for a deeper understanding of the roles of individual movements in social behaviors.\n\nSummary StatementMovement patterns of termites in isolation were described for different castes. We proposed movements as a novel caste-specific characteristics in social insects.

animal behavior and cognition↗