# Males have a greater mite burden than females, and size does not matter: species- and sex-specific infestation patterns of mites (Uropodina) on burying beetles (Nicrophorus spp.)

## TL;DR

Male burying beetles carry more mites than females, and larger beetles don't necessarily carry more mites, showing complex patterns in mite dispersal.

## Contribution

Reveals species- and sex-specific mite infestation patterns on burying beetles, challenging the assumption that body size influences mite burden.

## Key findings

- Nicrophorus vespillo is most frequently infested with U. nova mites.
- Male beetles have higher mite prevalence and intensity than females.
- Body size does not predict mite infestation levels.

## Abstract

Phoretic mites and their carriers represent a dynamic system shaped by ecological and evolutionary processes. In highly specific phoresy, which involves long-term or permanent associations, profound consequences for phoretics, including cospeciation or the transition to phoretic parasitism, can occur. Mites within the complex of cryptic species of Uroobovella nova are carried exclusively on burying beetles (Nicrophorus spp.). Nevertheless, compared with the Poecilochirus mite-Nicrophorus system, this type of interaction remains poorly understood. In this study, we investigated whether different species of burying beetles play the same role in the local dispersal of U. nova deutonymphs. To achieve this, we compared the infestation patterns of deutonymphs among field-collected beetle species, while accounting for sex and body size.

Our results revealed species-specific patterns in deutonymph infestations, with Nicrophorus vespillo being the most frequently infested species, followed by N. humator and N. interruptus. Furthermore, Nicrophorus vespillo and N. humator hosted the greatest number of deutonymphs, whereas in N. interruptus, the number of carried mites was significantly lower. The infestation pattern of U. nova demonstrated significant sexual bias, with males exhibiting higher mite prevalence and intensity than females. Interestingly, the variation in host body size was not a significant predictor of U. nova infestation. Although more mites were attached to the anterior than to the posterior parts of the beetle body in all the examined species, species- and sex-specific patterns in the distribution of deutonymphs were evident.

Species-specific infestation patterns indicate that, at the local scale, individual burying beetle species play different roles in the dispersal of U. nova mites. Sex-specific infestation patterns suggest that biological differences between females and males may be key determinants of deutonymph infestations. Body size does not drive the prevalence, intensity, or distribution of deutonymphs. The assumption that larger hosts carry more symbionts does not hold universally in ecology.

The online version contains supplementary material available at 10.1186/s12983-026-00601-w.