Interactions Between Some Tubificid Oligochaetes and Bacteria Found in the Sediments of Toronto Harbour, Ontario

Abstract

Three species of tubificid oligochaetes and seven heterotrophic aerobic bacteria were identified from the sediment of Toronto Harbour, Ontario. The relative abundance of the identifiable bacteria present in the mud and in the worm feces voided after 18 hr was established using nutrient agar medium. The results indicated a reduction in the relative abundance of bacteria by about 72% and a reduction in the variety of bacteria in the feces as opposed to those detected in the mud. After a starvation period of approximately 1 week, only one type of bacteria was detected in the feces and guts of the worms, whereas all seven were shown to be ingested at one time or another. The surviving bacterium was different in each tubificid species, but Aeromonas sp. was seen to replace this surviving species on some occasions in all three species of worm. The results suggest that the fraction of the bacterial flora investigated forms a part of the diet of tubificids, and that differences between worm species in relation to their use of those bacteria may help to explain the survival of a number of morphologically unspecialized sediment-feeding species in close physical proximity to each other.