Host Specificity Among Unionicola Spp. (Acari: Unionicolidae) Parasitizing Freshwater Mussels

Abstract

Water mites of Unionicola spp. are common parasites of freshwater mussels as adults, living on the gills, or mantle and foot of their hosts and using these tissues as sites of oviposition. The present study addresses specialization among North American Unionicola mussel-mites using 2 measures of host specificity: (1) the number of host species used by a species of mite; and (2) a measure that considers the taxonomic distinctness of the hosts utilized by mites, weighted for their prevalence in the different hosts. Results of this study indicate the Unionicola spp. mussel-mites are highly host specific, with most species occurring in association with 1 or 2 species of hosts. If 2 or more host species are utilized, they are typically members of the same genus. These data are consistent with studies examining the dispersal abilities and host recognition behavior for members of the group. When the average values of host specificity for Unionicola subgenera were mapped on a phylogenetic tree for these taxa, a clade comprised of gill mites appeared to be more host specific than a clade consisting of mantle mites. There were, however, no apparent patterns of host specificity within each of the clades. Differences in specificity between the 2 lineages may reflect either a long evolutionary history that gill mites have had with host mussels or the intense competition among gill mites for oviposition sites within unionid mussels, leading to increased host specialization.

The invasive Chinese pond mussel Sinanodonta woodiana (Lea, 1834) as a host for native symbionts in European waters

“…The presence of the water mites in fish ponds, where the high number of chironomids was noted, is not surprising, as unionicolids use the chironomid larvae as hosts in the life cycle (Baker, 1991). The adult forms of unionicolid water mites are attached to the gills of mussels and cause displacement, rupture, and erosion of the gill epithelium (Baker, 1976;Edwards and Vidrine, 2006;Fisher et al, 2000;Gangloff et al, 2008).…”

Regionally widespread parasitic water mites have relatively broad host-species ranges

“…The majority of the Arrenurus species in this study infect several host species spanning at least two coenagrionid damselfly genera, which overlap within freshwater wetlands. Being generalists makes them different from Unionicola Haldeman, 1842 mites infecting mussels (Edwards and Vidrine 2006). Unionicola mites Pagination not final (cite DOI) / Pagination provisoire (citer le DOI) Fig.…”

“…If the parasite is not present in the same habitat or at the same time as a particular host species or when that species is abundant, then that parasite will not be able to infect that host species effectively or at all (Poulin 2007). Other biological factors presumably include host defenses, parasite exploitation, and transmission mechanisms that might be subject to phylogenetic constraints (Edwards and Vidrine 2006;Mouillot et al 2006) and that might influence local adaptation (Lajeunesse and Forbes 2002).…”

Genetic Differences Among Sibling Species of the SubgenusDimockatax(Acari: Unionicolidae:Unionicola): Heterogeneity in Dna Sequence Data Supports Morphological Differentiation

“…An examination of the specificity of the host recognition behavior of U. tiimida and U. eriistirigi will be required before we can conclude that these mites exhibit species-specific associations toward their mussel hosts. Collectively, North American Unionicola mussels-mites are known to exhibit highly variable patterns of host specificity, with some species occurring in association with a long list of host species and others utilizing one or at most a few species of hosts (Vidrine 1996c;Edwards and Vidrine, 2006). An examination of both interspecific and intraspecific diversity of molecular sequence data among host-associated populations of these mites will play a valuable role in testing hypotheses about current species designations and potentially uncovering sibling species of Uiiionicolu mussel-mites.…”