34 
James E. Joy and Jeffrey W. Hively 
constitutes the first report of the parasitic mite Unionicola formosa 
(Dana and Whelpley, 1836) from West Virginia. 
MATERIALS AND METHODS 
The subject of this study was a parasitic aquatic mite, Unionicola 
formosa, and its freshwater mussel host, Anodonta imbecillis (Say, 
1829). Work was carried out in two ponds at the McClintic Wildlife 
Station, Mason Co., W.Va. The station, outlined on USGS Topographic 
Map, Cheshire Quadrangle, Ohio— W.Va., is a 2,800-acre (1,135-ha) 
wildlife sanctuary dotted by 35 ponds and managed by the W.Va. 
Department of Natural Resources. Ponds 14 and 27 were chosen as 
study sites because they harbored thriving mussel populations at 
densities of 8.6 (moderate) and 26.0 (high) A. imbecillis individuals per 
m 2 , respectively (Harmon 1987). Pond 14 had a surface area of 
approximately 1.4 ha. It was a shallow pond (maximum depth of 2.4 m) 
with a considerable amount of rooted aquatic vegetation (coon-tail, 
Ceratophyllum demersum) arising from a silt/ clay substrate. Pond 27 
had a surface area of approximately 0.75 ha. It also was shallow 
(maximum depth of 1.6 m) with a silt/ clay substrate. With the exception 
of a few small shoreline patches of cattail, this smaller pond was 
virtually devoid of rooted aquatic vegetation. 
A host sample was collected, by hand, from each pond monthly 
from May through November, 1986. Collections were not random 
because a randomized procedure resulted in a sample containing dispro- 
portionately large numbers of mussels in the shell-length range of 65-79 
mm. Because one goal was to estimate intensity of infestation relative to 
host length, some additional effort was made to collect individuals with 
a shell length <65 mm or >79 mm. 
Each mussel was processed at the site where it was collected: 
cleaned, measured for its shell length with vernier calipers to the nearest 
0.1 mm, and opened by severing the adductor muscles with a # 60 
autopsy scalpel blade. The entire open mussel was then placed in a 
separate, labeled (pond designation, date, shell length) jar containing a 
fixative of 10% buffered formalin acetate. This procedure precluded loss 
of mites and exchange of mites between hosts. Hosts thus collected and 
preserved were transported to the laboratory. In the laboratory mites 
were collected from the bottom of the jars and from host soft tissues 
with jeweler’s forceps and the use of a Zeiss stereomicroscope as 
needed. Only adult mites were counted. Females were easily separated 
from males on the basis of two or more of the following criteria: larger 
body size, presence of eggs, shape of palps, and differences in anal plate 
morphology (Vidrine 1986). The data from two collections made in the 
same month were combined. 
