Article

The influence of habitat quality on the foraging strategies of the entomopathogenic nematodes Steinernema carpocapsae and Heterorhabditis megidis

Institute of Biological and Environmental Sciences, University of Aberdeen, Cruickshank Building, Aberdeen, AB24 3UU, UK.
Parasitology (Impact Factor: 2.56). 10/2009; 137(2):303-9. DOI: 10.1017/S0031182009991326
Source: PubMed

ABSTRACT

Entomopathogenic nematodes (EPN) are soil-transmitted parasites and their foraging strategies are believed to range from 'ambush' to 'cruise' foragers. However, research on their behaviour has not considered the natural habitat of these nematodes. We hypothesized that EPN behaviour would be influenced by soil habitat quality and tested this hypothesis using 2 EPN species Steinernema carpocapsae (an 'ambusher') and Heterorhabditis megidis (a 'cruiser') in 2 contrasting habitats, sand and peat. As predicted from previous studies, in sand most S. carpocapsae remained at the point of application and showed no taxis towards hosts, but in peat S. carpocapsae dispersed much more and showed a highly significant taxis towards hosts. H. megidis dispersed well in both media, but only showed taxis towards hosts in sand. In outdoor mesocosms in which both species were applied, S. carpocapsae outcompeted H. megidis in terms of host finding in peat, whereas the opposite was true in sand. Our data suggest that these 2 EPN may be habitat specialists and highlight the difficulties of studying soil-transmitted parasites in non-soil media.

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    • "The bioassay investigating temperature response of S. carpocapsae against H. arator adults was similar but used higher nematode dose, had a longer exposure time, and used peat, a medium known to favour host finding by S. carpocapsae (Kruitbos et al., 2010). The same 3 cm diameter 6-chamber multi-well plates were used, but were filled with moist peat, a medium known to favour host finding by S. carpocapsae (Kruitbos et al., 2010). One thousand S. carpocapsae infective juveniles were added to each well, and plates were incubated for two-weeks at the appropriate temperature. "
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    • "Their presence and abundance is associated with a number of biotic and abiotic soil characteristics, including soil texture, temperature and moisture (Lawrence et al., 2006), as well as a combination of additional physical, chemical and biotic conditions (Hoy et al., 2008). Applied EPNs have been found to disperse more actively in soils high in organic matter than they do in mineral soils (Kruitbos et al., 2010; MacMillan et al., 2009; Wilson et al., 2012) and their persistence is strongly correlated with high soil moisture (Grant and Villani, 2003; Jabbour and Barbercheck, 2008). The persistence of EPN populations after they have been applied as a biological insecticide also depends on the availability of invertebrate hosts within the soil environment (Susurluk and Ehlers, 2008). "
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    • "Torr et al. (2004) showed that S. carpocapsae had strong response to a wide range of vibrational cues. Recently Kruitbos et al. (2010) stated that S. carpocapsae is adapted to being active in habitats other than mineral soils (e.g., peat, leaf litter, bark or wood). Our results support this finding and also fit with the habitat preferences of this species; S. carpocapsae prefer woodlands where their soil habitats have much higher organic matter contents (Hominick, 2002). "
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