Gut Microflora and Microfauna of Earthworm Species in the Soils of the Research Farms of the University of Agriculture, Abeokuta, Nigeria

The present study investigated the microbial biomass (microflora and fauna) present in soil samples, gut sections and casts of earthworms collected from research farm areas on the campus of the University of Agriculture, Abeokuta. Keffia proxipora, Libyodrilus violacaeus and Hippoporera nigereae were the earthworm species identified from the soil samples. Isolated microflora included bacteria, yeasts and moulds while microfauna identified were protozoa and nematodes. For all samples of soil, casts and earthworms, the differences observed in counts of microflora and microfauna were significant at a level of p < 0.05. Casts stored for 2 weeks had higher pH and bacterial counts than those obtained from fresh castings. However, the pH values and nitrogen contents of both the fresh and stored casts were significantly higher than those for un-ingested soil samples. Among the earthworms identified, Libyodrillus violacaeus recorded the highest values of microflora and microfauna counts, significantly higher than values obtained for the other earthworm species. The hind gut of Libyodrillus violacaeus also had the highest bacterial, protozoal and yeast counts as well as total viable counts of microflora. Both micro-flora and fauna were found to increase in numbers during gut passage in all worms collected except for nematodes which were observed to reduce significantly in numbers during gut passage, with total disappearance in the mid and hind gut sections of some earthworm species.