IMMUNOFLUORESCENCE ASSAY FOR EFFECTS ON FIELD ABUNDANCE OF A NATURALLY-OCCURRING PSEUDOMONAD DURING PASSAGE THROUGH THE GUT OF A MARINE DEPOSIT FEEDER, ABARENICOLA-PACIFICA

In a seasonal study we used immunofluorescence to follow a specific ba cterial population, as well as total numbers, through the fore-, mid-, and hindgut of a deposit feeder, Abarenicola pacifica. We chose a pse udomonad because of its high ambient abundance. On five dates, we coll ected A. pacifica gut contents, with concurrent measurements of sedime ntary food quality (chlorophyll a, protein, bacterial abundance), anim al egestion rates (inversely proportional to gut residence time), and temperature. Increasing bacterial numbers from ingested sediment to fo regut contents, and decreases from foregut to midgut indicate signific ant selection and digestion, respectively, of both the-pseudomonad and the total bacterial community. Inverse correlations between egestion rate and digestive removal of bacteria offer some support for the pred iction that digestion of bacteria is proportional to time spent expose d to digestive enzymes, although the significance of the associated st atistical tests is marginal. No hindgut growth of the pseudomonad was observed, likely due to the short gut residence time of A. pacifica. T he pseudomonad showed variation of less than a factor of 3 in its ambi ent sedimentary abundance over the year.