Winged mapleleaf glochidia metamorphose on channel catfish
Mark Hove1, Dave Heath2, Ronald Benjamin3, Mark Endris3, Byron Karns4,
Rhonda Kenyon3, Bob Whaley4, Jeff Woods4, and Anne Kapuscinski1. 2000. Triannual Unionid Report. In press



1 Univ. of Minnesota, 1980 Folwell Ave. St. Paul, MN 55108. (612) 624-3019 Mark.Hove@fw.umn.edu,
2 WI DNR, 107 Sutliff Ave., Rhinelander, WI 54501. (715) 365-8979 HEATHD@dnr.state.wi.us
3 WI DNR, 3550 Mormon Coulee Rd., La Crosse, WI 54601. (608) 785-9012 benjar@mail01.dnr.state.wi.us
4 St. Croix National Scenic Riverway, P.O. Box 708, St. Croix Falls, WI 54024. (715) 483-3284
 

During fall and winter 1999 we attempted to identify host(s) for the federally endangered winged mapleleaf (Quadrula fragosa (Conrad, 1835)). Unlike most Amblemines, which brood glochidia during spring and summer, winged mapleleaf brood glochidia during a relatively short period in September and October (Heath et al. 1999). A brooding winged mapleleaf collected in October 1999 released glochidia that were used in host suitability tests. Trials were conducted using standard protocol (Neves et al.1985) at water temperature 11±1 0C.Eleven fish species (three families) were tested. Glochidia grew while attached to Ictalurids. Two juveniles excysted from a channel catfish (Tables 1 and 2).

Table 1. Glochidial transformation observed.

 
Species
Number tested
Juvenile collection period (d)
channel catfish*
1
117-123
* Test subject died before end of study.

 Table 2. Glochidial transformation not observed.

 
Species
Number tested
Excystment period (d)
slender madtom
1
94-95
flathead catfish I
3
74-82
blue catfish*
29
46-48
flathead catfish II*
43
39-43
yellow bullhead
9
108-118
black bullhead
20
61-68
stonecat
2
1-4
tadpole madtom
4
1-4
freshwater drum
4
4-9
orange spotted sunfish
2
1-4
* Test subject died before end of study.

Additional juveniles might have been collected from the catfish but a low-grade Ich infection flared during the excystment period killing the fish. Glochidia collected from most Ictalurids exhibited growth after four weeks. The shell diameter doubled by six weeks, and by twelve weeks the shell diameter of several individuals was triple the glochidial shell diameter (figures 1 and 2).
Figure 1. Winged mapleleaf glochidia.
Figure 2. Winged mapleleaf glochdium exhibitinggrowth. 
During fall 1999 we tried to collect Ictalurids naturally infested with winged mapleleaf glochidia from the St. Croix River. Using SCUBA we searched a 60 ft deep pool and found several young and one older channel catfish. One small catfish was brought to the laboratory and two non-winged mapleleaf juvenile mussels excysted. We will attempt to collect catfishes again this year in hopes of obtaining juvenile winged mapleleaf from naturally infested fishes.

We thank Robert Hay of the WI DNR. Funding was provided through federal aid under Section 6 of the Endangered Species Act with matching funds from the WI DNR, MN DNR, and MN Environment & Natural Resources Trust Fund.

Literature Cited

Heath, D., M. Hove, R. Benjamin, M. Endris, R. Kenyon, and J. Kurth. 1998. Quadrula fragosa exhibit unusual reproductive behaviors. Triannual Unionid Report 16: 33.

Neves, R. J., L. R. Weaver, and A. V. Zale. 1985. An evaluation of fish host suitability for glochidia of Villosa vanuxemi and V. nebulosa (Pelecypoda: Unionidae). American Midland Naturalist 113(1): 13-19.