PREDATORY ABILITIES OF MONONCHOIDES LONGICAUDATUS AND M. FORTIDENS (NEMATODA: DIPLOGASTERIDA) AND FACTORS INFLUENCING PREDATION*

BY

A. L. BILGRAMI and M. S. JAIRAJPURI Section of Nematology, Department of Zoology, Aligarh Muslim University, Aligarh-202002, India

The predatory abilities of all stages of Mononchoides longicaudatus and M. for- tidens were studied in vitro including prey catching and feeding mechanisms, rate of predation by adult and juvenile predators, prey preference, and effect of prey numbers, starvation of predators and temperature on predation. Prey catching and feeding mechanisms were divided into five phases, i.e., encounter with prey, attack response, attack, salivationlextra-corporeal digestion and inges- tionlfeeding. Most phases were comparable in both predators. M. fortidens preyed more frequently and took less time to consume its prey than M. longicaudatus. The latter species probed its prey gently but for longer, while pro- bing by the former was more vigorous but for a shorter time. The rate of predation by male and female predators remained unchanged over twelve days and prey numbers, starvation of predators and temperatures governed preda- tion. Maximum predation took place in a population of 200 prey individuals and when predators starved for twelve days were used at 25-30°C. Acrobeloides sp. Cephalobus sp., Panagrellus redivivus and second stage juveniles of Meloidogyne incognita and tritici were most preferred by both predators. No preda- tion on indicus or Hemicriconemoides mangiferae occurred. Ever since Cobb (1917) first speculated on the possible economic importance of mononchs in agriculture, studies have been made of the predatory abilities of mononchs (Nelmes, 1974; Cohn & Mordechai, 1974; Small, 1979; Bilgrami et al., 1983, 1984; Small, 1987); dorylaims (Wyss & Grootaert, 1977; Shaf'qat et al., 1987) and nygolaims (Bilgrami et al., 1985). However, few attempts have been made to assess the role of diplogasterid predators in the biological control of plant-parasitic . Yeates (1969) first studied in vitro the predatory behaviour of Diplenteron colobocercus (Andrissy). All stages of diplogasterid predators may not be obligate predators as they also feed upon bacteria in the

* Presented at the XIX International Nematology Symposium of the European Society of Nematologists held at Uppsala, Sweden, August 7-13, 1988. 476 absence of prey nematodes (Yeates, 1969). Grootaert et al. (1977) elucidated the feeding habits of Butlerius sp., and assessed its possible use in the biological control of nematodes. Later, Small & Grootaert (1983) evaluated the predation abilities of Butlerius degrissei (Grootaert & Small). Recently, observations have been made of the attraction of Mononchoides longicaudatus (Khera) and M. for- tidens (Schuurmans Stekhoven) towards different prey nematodes (Bilgrami & Jairajpuri, 1988) and pre- and post-feeding aggregation of these predators around a previously injured prey at feeding sites (Bilgrami & Jairajpuri, 1989b). The strike rate of M. longicaudatus and M. fortidens and resistance and susceptibility of different prey nematodes to these predators was also deter- mined (Bilgrami & Jairajpuri, 1989a). In the present work Mononchoides longicaudatus and M. fortidens have been studied in vitro to evaluate their predatory abilities and to determine the effect of biotic and abiotic factors on predation.

MATERIALS AND METHODS

Mononchoides longicaudatus and M. fortidens were cultured by using the tech- niques of Bilgrami & Jairajpuri (1988). All experiments were made in 5 cm diameter Petri-dishes containing a 5 mm thick layer of 1 % water-agar at 28 ± 1 °C. The predator species were tested separately. Twenty-five prey nematodes were subjected to predation by five female predators. The prey and predators were inoculated simultaneously. Observations on the number of prey killed or ingested were made after 24 h. Every experiment was replicated five times. The conditions in all experiments remained the same unless stated otherwise. To maintain consistency, the same species of prey were used for all the experiments with the two predators, i.e., attraction (Bilgrami & Jairajpuri, 1988); resistance and susceptibility of prey (Bilgrami & Jairajpuri, 1989a) and predation (present observations). For comparison free-living, ecto- and endo-parasitic nematodes were used as prey. Second stage juveniles of Meloidogyne incognita and were collected from cultures maintained on tomato and wheat respectively, while free-living nematodes (viz., Acrobeloides sp., Cephalobus sp., Rhabditis sp., Panagrellus redivivus) were isolated from culture dishes maintained in the laboratory. The rest of the species of plant-parasitic nematodes (viz., Tylen- chorhynchus mashhoodi, Xiphinema americanum, indicus, , , Hemicriconemoides mangiferae and Longidorus sp.) were obtained fresh from soil. Prey catching and feeding mechanisms. Observations on prey catching were made by stereoscopic microscope at 60 x magnification on inverted culture dishes containing M. longicaudatus and M. fortidens. To study the feeding mechanism in detail, observation chambers were made of a glass slide with a 2 x 1.5 x 0.5 cm block of 1 % water-agar (Wyss & Grootaert, 1977; Bilgrami et