Observations on feeding and population structure of five New Zealand terrestrial planarians which prey on lumbricid earthworms

The feeding of five terrestrial planarians found in New Zealand on European lumbricid earthworms was studied. Under laboratory conditions between 60-83% of Artioposthia spp. fed in the first 24 h compared with 21-40% of Australoplana spp. The mean percentage weight gain varied from 31% for Australoplana sanguinea var. alba to 113% for Artioposthia sp. 1. Analysis of the weights of the planarian species showed a mean 11-fold difference between Australoplana sanguinea and Artioposthia triangulata and that these body weights were not related to mean percentage weight gains after feeding. The relationship between the weights of egg capsules and pregnant female planarians was similar for Australoplana sanguinea var. alba (11%), Artioposthia triangulata (12%) and Artioposthia testacea (13%). This study confirms that there are terrestrial planarians in New Zealand which have the potential to prey upon European lumbricid earthworms but which have not been detected in Europe. Greater knowledge of their biology is necessary to control the spread and impact of these organisms around the world.