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LH\i1NOLOGY LIBRARY APR 0 3 2003

FISH BLOOD OSMOLALITY, GILL HISTOLOGY AND OOCYTE ATRESIA AS EARLY WARNING ACID STRESS

INDICATORS

J.H. McCormlck(1), K.M. Jensen(2), R.L. Leino(3) and G.N. Stokes(1)

4J) U.S. Environmental Protection Agency, Environmental ~rch Laboratory • Duluth, &201 Congdon Blvd., Duluth, Minnesota 55804, USA

(2) C.nter for Lillie Superior Environmental Studies, University of Wisconsin-Superior, · Superior, WI 54880, USA

/ 'J 1 9U I

(3) Department of Biomedical Anatomy, SChool of MediCine, Unlvenslty of Minnesota-Duluth, Duluth. MN 55812, USA

Abstra·ct

yellow perch (f!.t.t..ti flavescens), -rock bass (Ambloplltes

bl -ack cnppie'(romoxis niuoma.cu!atus), a~d largemouth bass

.~J..l'.a!~~ salmoid~s) exposed to acidified soft water ran,ing from pH 7.0

maintained blood osmotic homeostasis for up to 30 days·.: At pH 4.0.

od osmotic homeostasis was lost and all but the yellow perch ·aied with in

Blood osmolality decreased from a normal value of · 2B0-320 mmol/kg

a few days before ·death. Yellow perch exposed to pH ·4.1 were ;

death within 58 days. Gill hyperplasia and chloride cell

observed in 'these species a't pH 4. 5 and 4.0. In fathead

exposed to ~cidifled water, the chloride cells developed apical pits

evaginations at pH 5.5. The incidence of these ·chloride cell changes was "'£ ..

&ressi_vely greater at lower pH values, particularly at pH 5.~. Abnormally

'i.. :h numbers or atretic oocyte~ obsirved in -cid exposed fathead minnows were

t prevalent in the latter part of the spaw~in, season.

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