Responses of the predatory rotifer Asplanchna intermedia to prey species differing in vulnerability: laboratory and field studies

Abstract

1. We have studied the numerical and functional responses of campanulate morphs of Asplanchna intermedia fed five species of rotifer (Brachionus rubens, B. patulus, B. calyciflorus, Hexarthra mira and Filinia longiseta). The vulnerability of the prey varied with their morphology and mode of swimming. 2. To test the numerical and functional responses, prey species differing in their morphology and mode of swimming were provided. Responses were also tested with mixtures of evasive and non‐evasive prey provided in three different ratios. 3. A. intermedia showed a type II functional response to all the prey species provided. 4. The population growth rate of A. intermedia on the various prey species provided ranged from a minimum of –0.24 to a maximum of 0.68. There was a significant correlation between the capturability of a prey species and the population growth rate of the predator feeding on it. The capturability of a prey species also has a significant influence on the maximal predator density but not on the time taken to reach it. 5. Observations from a field study undertaken over a 10‐month period to study the prey preferences of A. intermedia in nature were corroborated by the laboratory findings.

Inducible Defenses and Trophic Structure

“…Unit Interpretation Dumont et al (1975);3, Jørgensen et al (1991); 4, Gilbert and Waage (1967);5, Gilbert (1976);6, Walz (1993);7, Nandini and Sarma (1999);8, Lü rling and Van Donk (2000);9, Laroque et al (1996); 10, Stemberger (1990); 11, A.M. Verschoor (unpublished data); 12, Iyer and Rao (1996);13, Gilbert (1967).…”

Comments on the diet of Asplanchna priodonta (Gosse, 1850) in the Dobczycki dam reservoir on the basis of field sample observations

“…Comparative studies on different populations of the widespread A. priodonta have demonstrated enormous plasticity in its diet, ranging from exclusively zoophagous populations, through omniphagous, to exclusively phytophagous populations (Guiset 1977;Hofmann 1983Hofmann , 1985Kappes et al 2000;Wilk-Woźniak et al 2001). A. priodonta has been reported to feed on other rotifers, such as Keratella cochlearis (Gosse) and on certain cladocerans (Ejsmont-Karabin 1974;Guiset 1977;Salt 1977;Hofmann 1983Hofmann , 1985Iyer and Rao 1996;Kappes et al 2000). However, planktonic crustaceans usually do not form a significant part of Asplanchna's diet, as was illustrated by a study of 17 populations in Spain (Guiset 1977).…”

Comparative morphology of the somatic musculature in species of Hexarthra and Polyarthra (Rotifera, Monogononta): Its function in appendage movement and escape behavior

“…For example, Gilbert (1987) found that 97% of individuals of Polyarthra remata caught in the inhalant current of Daphnia could escape. Similarly, species of Polyarthra and Filinia terminalis use their appendages, albeit differently, to escape predation by the predatory rotifer Asplanchna intermedia (Iyer and Rao 1996) and the Fig. 7.…”

“…Still, a series of observations and experiments over the past two decades have shown that appendage-bearing species can evade potential predators much more effectively than species without appendages (e.g., Kak and Rao 1998;Walton 1988;Williamson 1987;Iyer and Rao 1996;Hampton and Starkweather 1998). These species generally rely on saltation that in many cases, not only distances the prey from the predator, but also removes the prey from the predator's ''line of sight'' through haphazard rotations of the prey's body and its corresponding movement in erratic directions.…”