External Microflora of a Marine Wood-Boring Isopod

Bacteria associated with the marine wood-boring isopodLimnoria lignorum were enumerated by acridine orange epifluorescence microscopy and by plate counts on several media; the plate-viable bacteria were isolated and identified. Similar procedures were followed to enumerate and identify bacteria associated with the wood substrate from which the isopods were collected and with the surrounding water from the isopod habitat. Approximately 1.4 × 107 bacterial cells were associated with each individualL. lignorum. Aeromonas hydrophila, Pseudomonas , andVibrio were the most common genera in the isopod microflora. Wood fromL. lignorum burrows had an associated bacterial flora of 1.6 × 107 cells per mg (damp weight).A. hydrophila also predominated in the wood microflora. The water from which the isopod population was collected contained 2.3 × 106 bacteria per ml.Pseudomonas andVibrio species were very common in the water microflora, butA. hydrophila was not detected. Interactions between the isopod, its associated microorganisms, and the microorganisms within the wood substrate are discussed in the light of the known absence of a resident digestive tract microflora in these animals.