Aquatic hitchhikers: examining the phoretic associations between blackfly (Diptera: Simuliidae) and mayfly (Ephemeroptera: Heptageniidae, Tricorythidae) larvae in Kenyan river ecosystems

Abstract

The interaction known as phoresy, where one organism (the phoront) utilises another (the host) primarily for transport or access to food resources, has been observed among various aquatic invertebrates in Afrotropical rivers. Although documented in multiple species, phoresy’s underlying causes, ecological dynamics, and evolutionary pathways remain poorly understood, and its broader implications are still under investigation. In this study, we collected and analysed macroinvertebrate samples from seven locations along the Gura River and nine locations along the Mara River in Kenya. We explored phoretic dynamics within a diverse range of macroinvertebrate taxa. We identified a consistent phoretic association between Simuliidae larvae and pupae, and Heptageniidae larvae, at four Gura River sites, noting that the prevalence of these interactions varied with the river’s longitudinal gradient. In the Mara River, we detected phoretic interactions between Simuliidae pupae and Tricorythidae larvae, although this was limited to a single site. These findings expand our understanding of phoresy within tropical river systems and highlight the need for more comprehensive research.