Capacités cellulolytiques de la flore digestive de deux cyprinides, la carpe Amour (Ctenopharyngodon idella) et le carassin doré (Carassius auratus) à 14 °C

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Summary

Cellulolytic activity of the digestive flora of two cyprinids, the Amur carp (Ctenopharyngodon idella) and the gold fish (Carassius auratus) at 14 °C

The cellulolytic ability of bacterial flora living in the digestive tract was studied in two cyprinids reared at 14 °C: the Amur carp, Ctenopharyngodon idella, a herbivorous reputed species, and the goldfish, Carassius auratus, an omnivorous species. The reducing capacity of released sugars was determined by spectrophotometric measure of the 3–5 dinitrosalicylic acid reduction after incubating 24 h at 24 °C. Results showed a low carboxymethyl cellulase activity in the digestive tract of fishes.

The quantitative study of bacterial populations indicated that this flora, aerobic or anaerobic, was light compared with that of higher vertebrates. At 14 °C, the goldfish has a heterotrophic flora more abundant than that of the Amur carp. Functional activity was different according to the hostspecies; in the best conditions, the cellulolytic flora reached 10⁴ bacteria per g of intestine in the herbivorous species, C. idella.

All the results inicate that, at 14 °C, the bacterial flora is not rich enough to allow enzyms to have any activity on the host-animal. One cannot consider these two cyprinids to be able to digest cellulose.