UA ENTO 446 - Behavioral Ecology of Entomopathogenic Nematodes (14 pages)

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Behavioral Ecology of Entomopathogenic Nematodes



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Behavioral Ecology of Entomopathogenic Nematodes

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Pages:
14
School:
University of Arizona
Course:
Ento 446 - Insect Pathogens: Biocontrol Agents Biological Models
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Biological Control 38 2006 66 79 www elsevier com locate ybcon Behavioral ecology of entomopathogenic nematodes Edwin E Lewis a b James Campbell c Christine GriYn d Harry Kaya a b Arne Peters e a Department of Nematology University of California Davis Davis CA 95616 USA Department of Entomology University of California Davis Davis CA 95616 USA c USDA ARS GMPRC 1515 College Ave Manhattan KS 66502 USA d Department of Biology and Institute of Bioengineering and Agroecology National University of Ireland Maynooth Co Kildare Ireland e E Nema GmbH Klausdorfer Str 28 36 D 24223 Raisdorf Germany b Received 9 June 2005 accepted 16 November 2005 Available online 18 January 2006 Abstract We discuss the behavior and ecology of entomopathogenic nematodes in relation to their successes and failures as biological control agents Four categories of studies have been reviewed herein infective juvenile foraging strategies recognition and evaluation of the host by infective juveniles the actual behaviors of infective juveniles that result in infection and the protective role of the symbiotic bacteria during nematode reproduction in the cadaver This constitutes a chronological order of events Two challenges are suggested First the data on entomopathogenic nematode behavioral ecology while very extensive for some species are almost completely lacking for most described species We need to approach future studies paying more attention to phylogenetic origins of the traits that we study Second there is little consensus on exactly what are the traits that are worth studying By reviewing and synthesizing current work we make some suggestions about where future research should be directed 2005 Elsevier Inc All rights reserved Keywords Behavior Ecology Entomopathogenic nematode Infection Host Parasite Insect Steinernema Heterorhabditis 1 Introduction The behavior and ecology of entomopathogenic nematodes i e steinernematids and heterorhabditids have been studied in the past in attempts to make them better biological control agents Indeed their utility as biological control agents has spurred most of the research that has been conducted Much of this work has been focused on their behavioral interactions with hosts Several reasons have been put forward to explain the need for further understanding of entomopathogenic nematode behavior and ecology Many of the papers published in this area and grant proposals as well have begun with a sentence resembling the following Entomopathogenic nematodes have great potential as biological control agents but because of signiWcant gaps in our Corresponding author E mail address eelewis ucdavis edu E E Lewis 1049 9644 see front matter 2005 Elsevier Inc All rights reserved doi 10 1016 j biocontrol 2005 11 007 knowledge of their foraging behavior or infection strategies host associations etc this potential has not been realized Only relatively recently have entomopathogenic nematodes been the subject of more basic studies where entomopathogenic nematodes are viewed as model organisms with which to ask questions about parasite biology in general Entomopathogenic nematodes are excellent models for this purpose since they share the trait of having an active third stage infective juvenile IJ as the infective stage with many other parasitic nematode species They have distinct experimental advantages over many animal parasites they are easy and cheap to culture they live from several weeks up to months in the infective stage and there is a large group of species which facilitates comparative studies However entomopathogenic nematodes diVer from other parasitic nematodes because of their mutualistic association with bacteria In this review we address the basic studies that attempt to examine the theoretical underpinnings of E E Lewis et al Biological Control 38 2006 66 79 entomopathogenic nematode behavior and the potential applications of these Wndings to biological control of insect pests We cannot know all biological aspects of all species of entomopathogenic nematode Therefore we must pick and choose our questions and experimental subjects well Here we ask which aspects of entomopathogenic nematode biology are most important to understand to improve their success as biological control agents We divide this review into four sections that describe the behavioral and ecological aspects of the infection process for entomopathogenic nematodes in chronological order The Wrst section describes host Wnding behaviors and strategies The second section and next step in infection is a mechanistic look at how IJs recognize hosts and how they gain entrance into the host hemocoel Third is a section on infection strategies and the interaction between nematodes inside and outside the host Finally we examine the defense of the host cadaver from opportunistic competitors speciWcally ants 2 Foraging strategies How organisms forage for resources can be described using diVerent conceptual models These models were originally developed for foragers other than entomopathogenic nematode infective stages but are broadly applicable to many taxa and life histories Two broad categories of conceptual models are 1 those based on the behavioral responses to sequentially encountered stimuli that vary in the quality of information that they convey and 2 those based on how searchers move through their environment Both types of models can be applied to infective stage juvenile host foraging behavior In the Wrst category of models host search is divided into a hierarchical process of host habitat location host location host acceptance and host suitability Doutt 1964 Laing 1937 Salt 1935 This conceptual model has been widely adopted and has proven useful for understanding parasitoid host search behavior Godfray 1994 This hierarchical set of behaviors is not necessarily rigid Vinson 1981 and more recent models have emphasized the dynamic ranking of stimuli based on how closely they are associated with the host forager internal state and the amount of directional information provided by the cue Godfray 1994 Lewis et al 1990 Vet et al 1990 Using the second category of models foraging strategies are divided into two broad categories cruise widely foraging and ambush sit and wait Echkhardt 1979 Huey and Pianka 1981 McLaughlin 1989 Pianka 1966 Schoener 1971 ClassiWcation is based on diVerences in how foraging time is allocated to motionless scanning versus moving through the environment Huey and Pianka 1981 O Brien et al


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