35 
Unionicola formosa in West Virginia Mussels 
Counts of female and of male mites were transformed (log j q [Y] 
for female mites; logjQ [Y+l] for male mites). These data were then 
backtransformed to show mean intensity levels (as mean number of 
mites per infested host) with 95% confidence limits (Fig. 1A-C). To 
detect seasonal differences in means, log-transformed data were used in 
calculating F-values (ANOVA) on an AT&T PC 6300 computer with 
Microstat® general-purpose statistics package developed by ECOSOFT, 
Inc. A Texas Instruments statistial calculator was used for Mests (Table 
1) and regression analyses (Fig. 2 and 3). 
RESULTS 
A total of 169 Anodonta imbecillis individuals— 90 from Pond 14 
and 79 from Pond 27 — were examined for Unionicola formosa during 
the 7-month study period. All host mussels were infested by female 
mites (Fig. 1A), but male mites were recovered from only 57 of 90 
(63.3%) and 60 of 79 (75.9%) hosts in Ponds 14 and 27, respectively 
(Fig. 1B-C). The sex ratio of U. formosa was 10.7:1 (794 females: 74 
males) in A. imbecillis from Pond 14 and 18.5:1 (1,737 females: 94 
males) for the host sample drawn from Pond 27. 
Mean intensity levels of female U. formosa in A. imbecillis 
individuals from the high-host-density Pond 27 were significantly higher 
than mean intensities for hosts in the moderate-density Pond 14 for 
every month sampled from May through September (Table 1; Fig. 1A). 
There was no statistical difference between the means for October, and 
no comparison could be made for November when no mussels were 
taken from Pond 27 (Table 1). Conversely, mean intensity levels of male 
U. formosa in A. imbecillis were essentially the same for both ponds in 
every month in which comparisons could be made (Table 1; Fig. 1B-C). 
Although mean intensities of female mites increased seasonally 
from May through September in Pond 27 (Fig. 1A), those increases 
were not significant as determined by ANOVA on log-transformed data 
{F - 2.166, 73 df; P - 0.0671). Seasonal variations in log-transformed 
means for female mites in Pond 14 mussels (Fig. 1A) were, however, 
significantly different ( F - 2.504, 83 df; P = 0.0282). An ANOVA on 
log-transformed data revealed no significant differences in mean numbers 
of male mites by season in either pond {F = 0.059, 54 df; P- 0.7681 and 
F - 1.861, 50 df; P - 0.1062 for male mites in mussels from Ponds 27 
and 14, respectively). 
Adult mites were positively correlated with host shell length in the 
high-host-density Pond 27 for every month sampled (Fig. 2). Cor- 
relations between adult mites and host length in the moderate-host- 
density Pond 14 were, however, largely nonexistent (Fig. 3). 
