Wood-eating catfishes of the genus Panaque :
gut microflora and cellulolytic enzyme activities


J. A. Nelson*, D. A. Wubah*, M. E. WhitmerÝ, E. A. JohnsonÝ and D. J. Stewart

*- Department of Biological Sciences, Towson University, Towson MD, 21252
-103 Illick Hall, State University of New York-College of Environmental Science and Forestry, Syracuse, New York 13210
Ý-College of Agricultural and Life
Sciences, University of Wisconsin, 1925 Willow Drive, Madison, Wisconsin53706

Running Page Head: Wood-eating loricariid catfishes
*-phone: (410) 830-3945 Fax: (410) 830-2405 E-mail: jnelson@towson.edu

The use of woody plant material as a dietary item is rare among vertebrates and unknown in fishes. Previous observations have shown that loricariid catfishes of the genus Panaque posess teeth which appear to be specialized for gouging and that individual Panaque can be captured with gastrointestinal tracts containing primarily wood shavings. The purpose of the present work was to see whether enzymes involved in the break down of complex carbon polymers found in wood are present in Panaque guts and whether microorganisms cultured from the guts of Panaque have similar enzymatic activity. Fresh gut contents of both Panaque and a generalized loricariid (Liposarcus sp. ) had enzymatic activity directed against both cellulose and hemicellulose. Furthermore, aerobic cultures made from the guts of Panaque exhibited growth on a minimal salts medium containing only crystalline cellulose as a carbon source as well as on a variety of other substrates containing carbon polymers found in wood. Anaerobic cultures made from Panaque guts only grew with glucose as a carbon source. Cultures of whole gut contents grown on a yeast extract basal salts medium had significant cellulolytic activity. However, no culture of individual microbes had significant cellulolytic activity, suggesting that any cellulose breakdown which occurs in loricariid guts is by a consortium of microorganisms. A variety of aerobes, microaerophiles and facultative anaerobes were found in the guts of Panaque ; several of these bacteria appear to be new species.

Key Words : Herbivory, Loricariidae, xylophagy, trophic ecology, nutrition

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