Abstract
Parasites and symbionts of freshwater mussels are poorly understood, although a diverse assemblage of mussel-associated leeches (Glossiphoniidae) was recently described. Here, we report on the discovery of a fish leech (Piscicolidae) in the mantle cavity of the freshwater mussel Cristaria plicata (Unionidae) in the Russian Far East. It is the first member of this leech family being associated with freshwater molluscs. This leech does not match any known genus and species both morphologically and genetically, and is described here as Alexandrobdella makhrovigen. & sp. nov. It uses mussels as shelter (and probably as a secondary host), while the Amur catfish Silurus asotus (Siluridae) seems to be the primary host. These novel findings indicate that mussel-associated leech assemblage contains at least one piscicolid species. Our fossil-calibrated phylogeny suggests that the crown group of Piscicolidae was originated in the Early Cretaceous. This primarily marine family shares at least five independent colonization events into freshwater environments.
Highlights
Parasites and symbionts of freshwater mussels are poorly understood, a diverse assemblage of mussel-associated leeches (Glossiphoniidae) was recently described
A sample of fish leeches collected from the mantle cavity of the freshwater mussel species Cristaria plicata (Bivalvia: Unionidae) from Lake Khanka (Fig. 1, Tables 1, 2) shares a distinctive set of morphological and molecular characters and is described here as Alexandrobdella makhrovi gen. & sp. nov. (Figs. 2, 3, 4)
Earlier research revealed that global mussel-associated leech assemblage includes at least 12 species belonging to the family Glossiphoniidae[2]
Summary
Parasites and symbionts of freshwater mussels are poorly understood, a diverse assemblage of mussel-associated leeches (Glossiphoniidae) was recently described. None of the fish leeches (Piscicolidae) was known to occur in association with freshwater mollusks, the marine fish leech Pontobdella moorei (Oka, 1910) uses Octopus bimaculatus Verrill, 1883 (Cephalopoda: Octopodidae) as the primary host[7] This leech family contains numerous marine taxa (including several species discovered from oceanic trenches up to 8.7 km deep8) alongside with a few radiations in fresh water[9,10,11]. The family Piscicolidae together with the Ozobranchidae were placed in the separate suborder Oceanobdelliformes[17] This correspondence (1) reports on the first example of an association of a piscicolid leech species (Hirudinea: Piscicolidae) with freshwater mussels; (2) describes this leech as a genus and species new to science; (3) reconstructs a time-calibrated phylogeny of the piscicolid leeches, and (4) discusses the origin of freshwater lineages in this family in a broader evolutionary context
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