Microflora in the alimentary tract of gray mullet. II. A comparison of the mullet intestinal microflora in fresh and sea water.

Abstract

The purpose of this study was to determine the changes in microflora in the intestine of the gray mullet Mugil cephalus, an amphidromous fish with an undeveloped stomach, under different conditions. Samples were taken from fishes kept sequentially in fresh water, then in a half fresh and half sea water mixture, then in sea water, again in half fresh and half sea water, and finally returned to fresh water. The intestinal bacterial flora of the mullet in fresh water were composed primarily of Enterobacter, Bacillus, and Micrococcus. When the mullets were transferred to sea water, however, the flora changed; the dominant genera were Vibrio, Pseudomonas, and Aeromonas. After the return to fresh water the microflora consisted of only one genus, Enterobacter, the predominant one usually found in fishes from fresh water. The other bacterial genera did not appear to survive the transition through the water changes used.