SPATIAL AND TEMPORAL VARIABILITY IN GLYCOGEN CONTENT IN
HEXAGENIA MAYFLIES AND FINGERNAIL CLAMS IN THE UPPER
MISSISSIPPI RIVER.

Teresa J. Naimo, Erika D. Damschen, and Emy M. Monroe
U.S. Geological Survey, Biological Resources Division, Upper
Mississippi Science Center, La Crosse, WI 54602.

Recently, physiological indicators of condition, such as glycogen concentration,
have been used to assess the relative health of benthic invertebrates in laboratory
studies.  However, data on the spatial and temporal variability in
glycogen concentration from field populations are lacking.  We
assessed the glycogen concentration in 5 male and 5 female mayflies
(Hexagenia spp) and 5 fingernail clams (Musculium transversum)
obtained monthly (May-Oct) from 4 sites in Navigation Pool 8 of the
Upper Mississippi River in 1994 and 1995.  In fingernail clams,
glycogen concentration ranged from 0.3 to 51.8 mg/g wet weight
(mean 11.8) and did not differ significantly between years, or among
sites or months.  In mayflies, glycogen concentration ranged from 1.1
to 14.0 mg/g wet weight (mean 4.9) and differed significantly among
months (p=0.001), but not between sexes or years, or among sites. 
In mayflies, glycogen was highest in late spring and declined
throughout the summer and fall.  In both organisms, glycogen content
(mg) was positively correlated with length and weight.  These data
suggest that the variability in glycogen concentration is driven by
temporal, rather that spatial, patterns.  Thus, glycogen concentration
may be a useful indicator of physiological and reproductive condition in
field and laboratory studies if temporal variation is accounted for.

Keywords: glycogen, Hexagenia mayflies, fingernail clams, Mississippi
River

Teresa J. Naimo
U.S. Geological Survey, Biological Resources Division
Upper Mississippi Science Center
2630 Fanta Reed Road, P.O. Box 818
La Crosse, WI 54602-0818
pH 608-783-6451
fax 608-783-6066

Prefer poster presentation (willing to change format)

Non-student presentation