Moisture preferences, growth and reproduction of the compost worm Eisenia fetida (Oligochaeta)

Summary

Although moisture requirements of Eisenia fetida are considered to be generally known, very few in-depth studies have been performed. The moisture preferences of juveniles as well as adults of this species were determined in moisture towers containing cow manure with a particle size bigger than 500 and smaller than 1000 μm and an organic matter content of 54%. The clitellate worms showed a wider preference range than the juveniles but deposited most of their cocoons within the narrow range of 65%–70% moisture — a moisture range preferred by 80% of the juveniles. Growth studies of newly hatched worms at various moisture levels over a period of 90 days showed that growth rate and final biomass were influenced by moisture availability with a very low rate of growth at low as well as at high moisture levels. The change in biomass of clitellate specimens as well as their consecutively produced cocoons were monitored at different moisture levels. A clear relationship between mass of cocoons and biomass of the producing worms was established at presumably favourable moisture conditions. Furthermore, the relation between cocoon mass and the production rate of cocoons was also determined, which showed that cocoon mass increased concomitantly with increase in cocoon production. The study also showed that clitellum development was increased at moisture levels above 64%. The onset of cocoon production was, however, earliest at slightly lower moisture levels, from which it is concluded that the optimal moisture level for growth and development of clitella are not necessarily optimal for the production of cocoons.