Influence of food particle size on inter- and intra-specific interactions of Allolobophora chlorotica (Savigny) and Lumbricus terrestris: The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

Abstract

The inverse relationship between the particle size of food resources and earthworm growth rate is widely recognised. The aim was to determine the effects of the particle size of food on interactions between combinations of adult and hatchling A. chlorotica and L. terrestris under laboratory conditions. Treatments were set up in 1 litre mesocosms, maintained in darkness at 15 ± 1 °C. Separated cattle solids (SCS) were used as food either unmilled or milled to <1 mm. The latter led to a 185 and 54% increase in the mass of A. chlorotica and L. terrestris respectively, compared with unmilled SCS. Intra-specific competition in A. chlorotica was detected in adult and hatchling pairings. A positive inter-specific interaction was recorded with hatchling A. chlorotica and mature L. terrestris fed unmilled SCS with growth of the former significantly greater (P<0.01) than in conspecific monoculture. Clitellate A. chlorotica were only recorded in unmilled SCS treatments when paired with L. terrestris (week 18). In milled treatments, 100% maturation was achieved in monoculture and in pairings with hatchling and mature L. terrestris by week 14. The final mass of initially hatchling L. terrestris (3.23 g) fed milled SCS in monoculture was significantly greater (P<0.01) than in pairings with hatchling A. chlorotica and mature conspecifics. With unmilled SCS, lowest initially hatchling L. terrestris mean mass (1.04 g) was recorded when paired with mature conspecifics. Growth of both species was significantly enhanced by decreased food particle size and this effect was size specific. The intensity of competitive interactions was influenced by food particle size and stage of earthworm development. Results suggested a positive association between the two species and mechanisms for this are proposed.