Effect of temperature, predator starvation, prey density and prey incubation on feeding and aggregation activities of predatory nematodes, Mesodorylaimus bastiani and Aquatides thornei

Effects of temperature (5-40 deg C), predator starvation (0-12 days), prey density (25-250 individuals) and prey incubation (4-24 h) were studied in Mesodorylaimus bastiani and Aquatides thornei. Six types of measurements viz., time and rate of site formation, durations of feeding and post-feeding aggregation and number of predators feeding and showing post-feeding aggregation at feeding sites were made during this study. A minimum time to form feeding site, high rate of site formation and short feeding time were considered optimum attributes for predators. Temperatures of 25-35 deg C, duration of predator starvation of 6 to 8 days, prey densities of 200-250 individuals and duration of prey incubation of 12-16 h were the most suitable for predators in our experiments. All parameters were inter-dependent e.g., durations of feeding and feeding sites depended upon the number of predators feeding; number of predators showing aggregation at feeding sites depended upon duration of post-feeding aggregation and rate of site formation depended upon time of site formation, duration of feeding and aggregation activities of predators at feeding sites, etc.. Differential rates of feeding, attraction and aggregation by M. bastiani and A. thornei are attributed to different temperatures, prey densities, prey incubation and predator starvation. Such differences could also be attributed to differential rates of dispersion and degradation of prey attractants and formation of minimum perceptible attraction gradients by attractants. Various temperatures, prey densities, durations of prey incubation and predator starvation influence these characteristics [Sono stati studiati gli effetti di temperatura (5-40 gradi C), digiuno del predatore (0-12 giorni), densità (25-250 individui) e incubazione delle prede (4-24 h) in Mesodorylaimus bastiani e Aquatides thornei. Sono stati effettuati sei tipi di misurazioni, cioè tempo e ritmo di formazione del sito, durata dell´alimentazione e dell´aggregazione dopo l´alimentazione e numero di predatori che si alimentavano e presentavano aggregazione post-alimentazione nei siti di alimentazione. Sono stati considerati attributi ottimali per i predatori un tempo minimo per la formazione del sito di alimentazione, un tasso elevato di formazione del sito e un tempo limitato di alimentazione. Temperature di 25-35 gradi C, durata del digiuno di 6-8 giorni, densità delle prede pari a 200-250 individui e durata dell´incubazione di 12-16 h sono risult