Behavioural aspects of the ‘New Zealand flatworm’, Artioposthia triangulata, in relation to species spread

The ontogenetic behavioural patterns for the 'New Zealand flatworm', Artioposthia triangulata (Tricladida: Terricola), are considered in relation to short- and long-distance spread of the species. Intra-specific interaction of siblings within the egg capsule appears to influence the number and size of hatchlings upon emergence, and thereby clutch dispersal into the soil environment. This initial exploratory phase, aimed at acquisition of a suitable habitat particularly with respect to soil micro-climatic conditions and food availability, involves active migration in both horizontal and vertical planes. Habitat suitability also influences the movement patterns of larger juveniles and adults. Movements within the 'home-range' include travel between various resource sites, with mucus-lined runways connecting discrete resting, feeding, excretion, and egg capsule deposition sites. The positive correlation between body size and crawling speed facilitates the longer distance exploratory migrations (over 20 m) of some larger individuals which move away from the population into unexploited habitats.