Attraction and food preference behaviour of predatory nematodes, Allodorylaimus americanus and Discolaimus silvicolus (Nematoda: Dorylaimida)

Abstract

Observations were made on the attraction and food preference behaviour of two species of dorylaim predators viz., Allodorylaimus americanus and Discolaimus silvicolus. A. americanus and D. silvicolus reached prey either by chance or wilful movement (in response to prey) secretions). The attraction of predators depended upon the type and physical state (live or excised) of prey and the volume, chemical nature and composition of prey contents as well as the perceptible attraction gradient of the stimuli and the attraction threshold level of the predators. Attraction increased with the increase in the period of observation and varied with dierent species of plant parasitic nematodes. Excised indiiuals attracted more predators than the live or intact. Hirschmanniella oryzae and Xiphinema basiri elicited maximum while Helicotylenchus indicus the least response of the two species of predators. Other species of prey were moderately attractive. A. americanus and D. silvicolus also responded positively to secretions of such species of prey (Hoplolaimus indicus, Helicotylenchus indicus and Hemicycliophora dhirenderi) which are resistant to predation. Predators failed to injure or kill any individual of these species but fed when excised. A. americanus and D. silvicolus prefered the second stage juveniles of Meloldogyne incognita, Anguina tritici and Heterodera mohi most in all combination in which they were tested. Food preference is attributed to the physical, chemical and behavioural characteristics of prey that provide resistance to predation and the ability of the predators to capture and kill the prey.