Die lewensloop en vogbehoeftes van die oriëntaalse komposwurm, Perionyx excavatus (Oligochaeta)

Abstract

THE LIFE CYCLE AND MOISTURE REQUIREMENTS OF THE ORIENTAL COMPOST WORM, PERIONYX EXCAVATUS (OLIGOCHAETA)

The oriental compost worm, Perionyx excavatus, can potentially be implemented as a waste decomposer and a protein source. To determine abovementioned potential P. excavatus will have to be reared in significant quantities. The moisture content of the substrate is one of the basic parameters that govern the survival, growth and reproduction of earthworms. The present study was therefore undertaken to determine the life cycle and moisture requirements of Perionyx excavatus. The experiments were all conducted in a controlled environment (25 °C) with cattle manure as culture medium. The life cycle was determined by placing batches of five worms each, into glass jars containing 50 g prepared culture medium (80,7 % moisture). The worms were fed fresh cattle manure regularly. By day 20, 49,4 % of the worms were clitellate (mature), while 100 % were clitellate by day 45. The mean number of cocoons produced per worm per day was 1,24, the mean incubation period of the cocoons was 18,5 days and the mean number of hatchlings per cocoon was 1,0. The moisture requirements were determined by keeping newly hatched specimens in glass jars containing culture medium with different, but constant, moisture levels. At moisture levels of 50 % and 55 % all the worms had died by day 10. The growth rate was highest at 83,2 % moisture, but the worms at 80,0 % reached maturity earliest. The highest rate of cocoon production per worm per day - was reached at a moisture level of 80,0 %. The moisture preferences of clitellate and juvenile specimens were determined by keeping the worms in undivided moisture towers in which a moisture gradient had been allowed to develop. The distribution of the worms as well as the deposition of cocoons in the different segments of the moisture towers, were determined regularly. The clitellate and juvenile worms preferred a moisture content of 81 - 82 % and most of the cocoons were deposited at a mo i sture level of 78,5 %. It can be concluded that the moisture content of the culture medium must be maintained at a relatively high level to rear P. excavatus maximally. Further it was clear that at 25 °C and 80,7 % moisture, P. excavatus has a relatively short life cycle (42 days) compared to those of other vermicomposting species such as Eisenia fetida and Eudrilus eugeniae.