The Foraging Behavior of Anax Junius (Odonata: Aeschnidae) and Its Potential As a Behavioral Endpoint in Pesticide Testing Sandra Kaye Brewer Iowa State University
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Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1997 The foraging behavior of Anax junius (Odonata: Aeschnidae) and its potential as a behavioral endpoint in pesticide testing Sandra Kaye Brewer Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Ecology and Evolutionary Biology Commons, Entomology Commons, Environmental Sciences Commons, Fresh Water Studies Commons, Toxicology Commons, and the Zoology Commons Recommended Citation Brewer, Sandra Kaye, "The foraging behavior of Anax junius (Odonata: Aeschnidae) and its potential as a behavioral endpoint in pesticide testing " (1997). Retrospective Theses and Dissertations. 11445. https://lib.dr.iastate.edu/rtd/11445 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. 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UMI A Bell & Howell Information Company 300 North Zed) Road, Ann Aibor MI 4SI06-I346 USA 313/761-4700 800/521-0600 The foraging behavior of Anax Junius (Odonata: Aeschnidae) and its potential as a behavioral endpoint in pesticide testing By Sandra Kaye Brewer A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Animal Ecology (Limnology) Major Professor: Gary J. Atchison Iowa State University Ames, Iowa 1997 Copyright© Sandra Kaye Brewer, 1997. All right reserved. UMI Number: 9725396 Copyright 1997 by Brewer, Sandra Kaye All rights reserved. UMI Microform 9725396 Copyright 1997, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 ii Graduate College Iowa State University This is to certify that the Doctoral dissertation of Sandra Kaye Brewer has met the dissertation requirements of Iowa State University Signature was redacted for privacy. Signature was redacted for privacy. Signature was redacted for privacy. iii DEDICATION Incipit. in beatae memoriae mi matre ex quo didici magnum, opus mi. Hoc erat in votis: non est tanti. et etiam forsan et haec olim meminisse iuvabit. Acta est tabula, de bone et malo. haid ignota loquor hie et ubigue.- Placet!! Finis, coronat opus! Nunc est bibendum. iv TABLE OF CONTENTS ABSTRACT GENERAL INTRODUCTION 1 Dissertation Organization 7 Literature Cited 7 A TEST FOR SWITCHING BEHAVIOUR AS A POTENTIAL MECHANISM OF OPTIMAL FORAGING THEORY 12 Abstract 12 Materials and Methods 16 Results 22 Discussion 26 Acknowledgments 33 References 33 THE EFFECTS OF CHLORPYRIFOS ON CHOLINESTERASE ACTIVITY AND FORAGING BEHAVIOR IN THE DRAGONFLY Anax Junius (ODONATA) 50 Abstract 50 Introduction 50 Materials and Methods 54 Results 60 Discussion 62 Acknowledgments 66 References 67 GENERAL CONCLUSIONS 81 Literature Cited 83 GENERAL ACKNOWLEDGMENTS 86 V ABSTRACT I examined the foraging behavior of the green darner dragonfly nymph. Anax Junius, to assess the suitability of odonate foraging behavior as a sensitive endpoint for monitoring contaminant exposure. Odonates are potentially excellent organisms for work in biomonitoring programs because: 1) they have complex foraging strategies that tightly couple sensory cues and mechanical responses: 2) their ecology is well-studied: and 3) they are often the dominant invertebrate predator in fishless systems. Thus they have the potential to structure communities through predation. I tested 1) the possibility that nymphs may regulate populations through frequency-dependent foraging and 2) the relationship between head capsule cholinesterase (ChE) levels in nymphs exposed to an organophosphorus insecticide and subsequent foraging behavior. Functional response models were developed for nymphs fed exclusively midges or amphipods and for nymphs fed mixed prey. Nymphs fed only midges exhibited a sigmoidal type III response (a prerequisite for frequency-dependent foraging): nymphs fed only amphipods exhibited a hyperbolic type II response. These results were reversed in mixed prey trials. Regardless of densities of prey offered, a higher percentage of midges were eaten compared to amphipods. Dragonflies did follow a simplified optimal foraging model based on energy maximization but they did not consistently exhibit frequency-dependent selection. ChE levels were slightly elevated in treated nymphs and foraging behaviors between treated and control groups were not statistically significant, most likely because of high variability in ChE activities within the control group and across treated groups. My results suggest vi that certain animals may be unsuitable for routine pesticide monitoring and prior to incorporating any species into a biomonitoring program, careful consideration of the species' sensitivity to the contaminant needs to be considered. Further work is needed to determine other factors that may influence ChE levels in species as well. 1 GENERAL INTRODUCTION Because behavior is a biological product of complex physiological interactions, it is an attribute readily altered by stress (Warner et al. 1966: Beitinger 1990). Normal behavioral patterns are critical to the survival of the organism, population dynamics, and community interactions. Disruptions of normal behavioral patterns can be used in place of. or in addition to. traditional endpoints (death, immobility, etc.) because contaminants have been shown to affect many behaviors of terrestrial and aquatic organisms (Little 1990). By integrating biochemical and ecological interactions, behavioral toxicology may provide a better assessment of environmental contamination than traditional methods. Sublethal effects are especially important considerations in aquatic ecosystems where more organisms are exposed to sublethal than acutely toxic concentrations (Kleerokoper 1976: Niimi 1990). Behavioral toxicity tests may provide inexpensive and accurate methods for assessing a chemical's potential to alter aquatic communities (Sandheinrich and Atchison 1990). The development of behavioral endpoints in toxicity assessment has improved the sensitivity and versatility of toxicological studies (Little 1990). Behavioral endpoints are often more sensitive indicators of sublethal toxicity than traditional endpoints (e.g. Sullivan et al. 1978: Giattina and Garton 1983: Goodrich and Lech 1990: Little and Finger 1990). Behavioral responses may also be used to assess the risk of exposure because animals can avoid or "prefer" a contaminated area (Burris et al. 1990: Gray 1990). In addition to their integrative nature and ecological relevance, behavioral tests are generally non-destructive: thus long-term monitoring is possible, which allows for studies on adaptive responses and 2 recovery. Finally, the same organisms used in a behavioral test may also be studied by researchers in related fields (e.g. biochemists, geneticists, physiologists, ecologists), increasing our understanding of how organisms and the environment interact. Although any behavioral response that can be quantified has the potential to be used as a biomarker in the assessment of stress (Beitinger 1990) not all behaviors are equally valid candidates. Any behavioral response or change in behavior must be well described and be biologically relevant to the organism, i.e., somehow contribute to the fitness of the individual. Ecologically relevant behaviors include reactions of individuals of a single species (i.e., avoidance-attraction responses, learning, locomotion), preference for physical-chemical gradients (e.g.. temperature, oxygen), interactions within a species (i.e., social behaviors, reproduction) as well as interactions among multiple species (competition, predator-prey interactions). Research on the effects of toxicants on invertebrate behavior has traditionally focused on pest species that are either physically or economically harmful to humans because more effective