Potamilus alatus (Mollusca: Bivalvia: Unionidae) glochidia-induced histopathology in freshwater drum, Aplodinotus grunniens rafinesque, from the Kanawha River, West Virginia, USA.

Abstract

The gills of 37 of 173 freshwater drum, Aplodinotus grunniens Rafinesque, collected from two locations on the Kanawha River, West Virginia, USA, from 25 May through mid-October, 1986, were infected with glochidia (i.e., larval mussels). Of the 85 hosts captured from 25 May through 21 June, 37 (43.5%) carried glochidia infections. No glochidia were observed in the remaining 88 hosts collected in monthly samples from 22 June through mid-October. Infections gave rise to granulomas that caused a distal “clubbing” of the parasitized gill filaments. The resulting lymphohistocytic response was reminiscent of a type IV hypersensitive reaction seen in mammalian tissues. Development of the definitive and larval mantles, and the gut and digestive glands corroborated findings of previous investigators. The transitory larval adductor, pedal retractors, heart, and gill buds were prominent as well, but the number of glochidia at the necessary stages (ages?) of development was insufficient to adequately describe their origin and subsequent development.