CHEMOSENSORY RESPONSES OF PREDATORY NEMATODES TOWARDS KAIROMONES EMITTED BY PREY NEMATODES BELONGING TO DIFFERENT TROPHIC GROUPS

Abstract

Observations were made on the attraction and migration of Mesodorylaimus bastiani and Aquatides thornei towards kairomones/attractants emitted by prey nematodes belonging to different trophic categories viz., saprophagous, predators and epidermal, endodermal, migratory semi-endodermal and cortical feeders. Both species of predators responded positively and significantly to prey kairomones but showed variations in their attraction and preferential behaviour. Predators responded maximally towards excised prey individuals. As a prey trophic group the epidermal feeders were most attractive to predators whereas migratory semi-endoderma1 feeders were the least. The differential responses of predators towards different species of prey are attributed to differences in the inert behaviour of predators, their preference for a particular species of prey and chemical composition, concentration, quality and quantity of prey attractants and formation of minimum perceptible attraction gradient by prey attractants and minimum response threshold of predators. Various factors such as prey density, period of prey incubation and starvation of predators, temperature, agar concentration, agar thickness and distance of predators from the source of attraction (prey) governed chemosensory responses of predators. Both species of nematodes responded maximally towards prey kairomones when tested as ten day starved predators in agar plates containing 2 mm thick layer of 1% water agar with 200 prey individuals previously incubated for 12-16 h at 30 °C. Prey kairomones were most attractive when M. bastiani and A. thornei were tested at a distance of 2 to 3 cm.