Growth of the Earthworm Eisenia Foetida in Relation to Population Density and Food Rationing

At 250C Eisenia foetida hatches from its cocoon about 3 weeks after fertilization and follows a logistic growth pattern. It grows slowly for about three weeks and then enters a rapid phase whose slope is useful as an index to the nutritional quality of its food. The rapid phase is followed by a steady state maintenance phase, or by a phase of weight decline whose slope can be used as an index to a property of the food which is related to starvation latency. The slope of the rapid phase for individually grown worms was steeper on activated sludge than on cow manure and steeper on the latter than on horse manure. The maximum weight achieved by individually tested E. foetida was significantly greater with activated sludge than with either manure as food. The manures provided nutrients at a rate suboptimal to genetic capability for growth but either served as a better source of food than sludge when submaintenance levels remained, or were less toxic as castings. In a volume of about 30 cc over an area 78 cm2 the carrying capacity of 250 g horse manure on 50 g silt loam was 6 g live weight E. foetida; this value for these periodically disturbed systems is considerably less than what can be achieved in undisturbed systems published elsewhere. Carrying capacity was not achieved in the same volume-area-time relation with activated sludge in place of manure, though more than 23 g could be supported; more than ten times as much biomass of E. foetida can be supported per unit area of soil overlain by activated sludge than has been reported for earthworms in natural ecosystems.