Characterization of the digestive tract of greenlip abalone, Haliotis laevigata Donovan. II. Microenvironment and bacterial flora

Microelectrodes were used to measure pH and dissolved oxygen within the gut environment of adult greenlip abalone (145 to 160 mm), Haliotis laevigata Donovan. Oxygen levels were found to be below the limit of detection for the oxygen microelectrode (0.38 mg DO · L -1), suggesting either microaerophilic or anaerobic conditions. The pH profile of the gut revealed a decrease from the external environment (pH = 8.20) to pH 5.31 within the crop, increasing through the intestine to 6.64 in the rectum. Enrichment cultures of bacteria from within the abalone gut revealed mostly isolates from the family Enterobacteriaceae. These isolates occurred throughout all regions of the abalone gut, and almost all showed hydrolytic ability for one or more carbohydrates. Cytophaga spp. isolates appeared from esophageal and intestinal enrichments of the digestive tract and were all capable of both carboxymethylcellulose and agar hydrolysis. A decrease in diversity of bacterial types in the stomach, crop, and style sac corresponded with reduced pH.