37 
Unionicola formosa in West Virginia Mussels 
Table 1. Mean numbers of adult Unionicola formosa in Anodonta imbecillis in two ponds 
compared by month. 3 
Female mites/host Male mites/host 
Pond 27 Pond 14 
calculated 
/-value 
(two-tailed test) 
Pond 27 Pond 14 
calculated 
/-value 
(two-tailed test) 
May 
18.48 
4.67 
'0.05,38 r 5 - 05b 
1.82 
1.18 
'0.05,26 r L535 
[1.19] 
[0.63] 
[= 6.75] b 
[0.42] 
[0.33] 
[= 1.585] 
Jun 
19.47 
8.25 
'0.05,27 = 3 - 86b 
1.43 
1.63 
'0.05,20 r ~0-662 
[1.24] 
[0.83] 
[= 4.4 l] b 
[0.37] 
[0.41] 
[--0.667] 
Jul 
23.50 
8.10 
'0.05,21 r 3 - 8gb 
1.64 
1.43 
'0.05,16 r 0 693 
[1.31] 
[0.85] 
[= 4.3 l] b 
[0.41] 
[0.38] 
[= 0.634] 
Aug 
29.56 
12.10 
'0.05,31 r 4 - 4lb 
1.46 
1.50 
'0.05,21 = ~°- 1 56 
[1.42] 
[0.98] 
[=4.3 1 ] b 
[0.38] 
[0.38] 
[=-0.023] 
Sep 
27.30 
6.80 
'0.05,16 r 7 09b 
1.00 
1.00 
'0.05,9 = nd ° 
[1.44] 
[0.73] 
[= 3.77] b 
[0.30] 
[0.30] 
= [nd] c 
Oct 
20.60 
12.80 
'0.05,16 3 L17b 
1.33 
1.00 
'0.05,5 r L ' 187 
[1.19] 
[0.93] 
[= 1-36] 
[0.36] 
[0.30] 
[= 1.168] 
Nov 
- 
10.50 
- 
- 
1.33 
- 
- 
[0.92] 
- 
- 
[0.36] 
- 
a Initial /-tests based on raw data followed by log-transformed data in brackets. 
^Significantly different at a - 0.05. 
C nd - not determined (mean - 1.0 and variance - 0 for male mites in mussels 
from both ponds). 
DISCUSSION 
The impetus for this study came primarily from two sources: (1) 
Vidrine’s (1980) suggestion that concentrated populations of mussels 
harbored more U. formosa individuals than mussels in areas of lower 
density; and (2) Dimock’s (1985) statement that “no association between 
the population biology of the host and that of symbiotic mites has yet 
been established.” Vidrine’s empirical observation should be evaluated 
with consideration of his extensive work on aquatic mite/freshwater 
mussel relationships. The present investigation strengthens, quantita- 
tively, his generalization that mussels in a high-density population (as in 
Pond 27) harbor significantly greater numbers of female mites than host 
mussels in a moderate-density situation (as in Pond 14) (Table 1; Fig. 
1A). Differences were so striking that mean numbers of female mites 
