THE UPTAKE OF TRITIATED WATER BY A BEETLE, Chilocorus cacti (Coleoptera; Coccinellidae), FROM A MITE, Hemisarcoptes cooremani (Acari: Acariformes) by AURAL! E. HOLTE, B.S. A THESIS IN BIOLOGY Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Approved December, 1999 mr'-^'^-"""'^'" .——^—--— •« • "ji» • »j»«p»^"^i^»w /^n^^l C>^i^f ACKNOWLEDGMENTS I thank a number of people for their assistance and support in the completion of iS-f' 7^ this work. First, I would like to thank Dr. Marilyn Houck for her generous encouragement, understanding and guidance, without which I would not have been able to start or complete this project. I also thank the members of my committee. Dr. Nathan Collie and Dr. Richard Deslippe who provided valuable comments and information utilized for this research. Elizabeth Richards, Heather Roberts, and Qingtian Li were encouraging and helpful colleagues in all my endeavors as a graduate student. I also thank a number of people for personal support; foremost, Damon for without his devoted love, constant support and immutable encouragement, I would have not been able to accomplish this work. I v^sh to thank my family for all of the love and understanding they have given me, especially my mother who guided me with her example, demonstrating that I could do anything once I set my mind to it. I also would like to acknowledge all of the other friends and family members who have given me encouragement. Finally, financial support for this research was provided by the Texas Tech University Biology Department and the Bi-National Agricultural Research and Development grants (#IS-1397-87 and #US-2359-93C to M. A. H.). 11 II III iiiiiiiir li y*"*''* * *••»• *''*^«*»*»"J^fcjt * *Mr^f t^^m m'm m w TABLE OF CONTENTS ACKNOWLEDGMENTS ii ABSTRACT v LIST OF TABLES vh LIST OF FIGURES vm CHAPTER I. INTRODUCTION Scale Insects 2 Hemisarcoptes Chilocorus. Biological Control of Scale Insects 6 Coevolutionary Relationship of Hemisarcoptes and Chilocorus 8 Research Objective 9 IL MATERIALS AND METHODS 11 Laboratory Monocultures 11 Experimental Design 11 Cohort Conditions 12 Treatment Condifions 12 Controls 13 Cohort Number 14 Data Analysis 15 III. RESULTS 18 111 ^^r-fl K ^^mimm MM ^<fc ifM I•! 1 '^ •!>^Nr» 1^ « i Tritium Levels 18 Effects of Mite Numbers on Tritium Levels 19 Comparisons 19 IV. DISCUSSION 48 Future Directions 50 LITERATURE CITED 52 APPENDIX 59 IV 3BB h^jja^m i_.>.r»iT.»w;iviir!iiTirii-Trfiinfi tv •—i-, .•-. JT, ABSTRACT Understanding the origin and evolution of symbiotic interactions between extant species plays an important role in comprehending the nature of their ecological relationships. The dynamics of such complex evolutionary relationships must be examined from multiple perspectives, using both field and laboratory methods. Phoresy is a form of symbiotic interaction that results in dispersal. It is a coevolved interaction that benefits the dispersed organism but does not affect the phoretic host. In this thesis, I address a purportedly phoretic interaction between the deutonymphal stage (subadult) of a mite Hemisarcoptes cooremani (Astigmata: Acariformes) and the adult stage of the beetle Chilocorus cacti (Coleoptera : Coccinellidae), two potentially important biological control agents of scale insects. Past radiolabeling studies indicated that the deutonymph of//, cooremani acquired tritiated water from adult C. cacti, challenging the validity of the paradigm that this relationship, and many like it among the Astigmata, is phoretic. Passage of materials from one organism to another can be indicative of a parasitic relationship. This conclusion may be an incomplete assessment of a fuller relationship in which materials are freely passed among symbionts (mutualism). To probe this Hemisarcoptes- Chilocorus relationship, I conducted a tritiated radiolabel study, similar to the previous test, to determine whether materials were being passed from the deutonymphs to the beetles. The explicit research hypothesis was that tritiated water could be passed from the deutonymphs to the beetles during the symbiotic interaction. To test this hypothesis, wr^arntmmnmK*-^. * •^'»j'?'a£iL^lQ3MMMW)ottiiaCT-iflin«PirTi nr itrrnramniiiriri ft^J^M»M"~T. deutonymphs of//, cooremani were radiolabeled and then allowed to attach to C cacti. After remaining attached for 48-Hours, the beetles were tested for tritium concentrations. The results of this experiment demonstrated that beetles acquired tritium from the deutonymphs. Both the elytra and the body of the beetle showed significantly higher levels of tritium when mites were attached than when they were not. These results have interesting implications for understanding the complex relationship between Hemisarcoptes and Chilocorus. I propose that we now tentatively redefine this relationship as mutualistic. However, this judgment must be held in reserve until verified by examination of the potential fitness advantages conferred on both members of this interaction. VI asaBSBSss esacs^^-, - iT.^ - .-*<wt^ -ijiwi»M«gw||Tit-i^'inr''TT«iiflTfiftfmftiTifirtfiim^^ i i LIST OF TABLES 2.1 Full-Blocked Design of Experiment (Treatment and Controls) 16 2.2 Experimental Blocked Design of the Treatment and Controls 17 3.1 Summary of Tritium Concentrafion in Beetle Bodies at the End of the 48-Hour Experimental Exposure 22 3.2 Summary of Tritium Concentration in Beetle Elytra at the End of the 48-Hour Experimental Exposure 22 3.3 Number of Mites Attached to Each Beefie in the Treatment and Control #1 23 3.4 Results oft-test for All Pair-Wise Comparisons of Tritium Concentrations in the Beetle Bodies after the 48-Hour Experimental Exposure 24 3.5 Results oft-test for All Pair-Wise Comparisons of Tritium Concentrations in the Beetle Elytra after the 48-Hour Experimental Exposure 24 3.6 Results of Mann-Whitney test for All Pair-Wise Comparisons of Tritium Concentrations in the Beetle Bodies after the 48-Hour Experimental Exposure. 25 3.7 Results of Mann-Whitney test for All Pair-Wise Comparisons of Tritium Concentrations in the Beetle Elytra after the 48-Hour Experimental Exposure. 25 A. 1 Tritium Concentrations (dpm) from Beetle Bodies after the 48-Hour Experimental Exposure 60 A.2 Tritium Concentrations (dpm) from Beetle Bodies after the 48-Hour Experimental Exposure 61 Vll JB ^7^-.^. ^,. ,-^,>. ........1.-.., • ,».. ^.....^ •„„.^ LIST OF FIGURES 3.1 Trifium Concentrations from Beetle Body after 48-Hour Exposure of Treatment 26 3.2 Frequency Distribufion of Tritium Concentrafion in Beefie's Bodies after 48-Hour Exposure of Treatment 27 3.3 Tritium Concentrations from Beetle Elytra after 48-Hour Exposure of Treatment 28 3.4 Frequency Distribution of Tritium Concentration in Beetle's Elytra after 48-Hour Exposure of Treatment 29 3.5 Tritium Concentrations from Beetle Body after 48-Hour Exposure of Control #1 30 3.6 Frequency Distribution of Tritium Concentration in Beetle's Bodies after 48-Hour Exposure of Control #1 31 3.7 Tritium Concentrations from Beetle Elytra after 48-Hour Exposure of Control #1 32 3.8 Frequency Distribution of Tritium Concentration in Beetle's Elytra after 48-Hour Exposure of Control #1 33 3.9 Tritium Concentrations from Beetle Body after 48-Hour Exposure of Control #2 34 3.10 Frequency Distribution of Tritium Concentration in Beetle's Bodies after 48-Hour Exposure of Control #2 35 3.11 Tritium Concentrations from Beetle Elytra after 48-Hour Exposure of Control #2 36 3.12 Frequency Distribufion of TriUum Concenlration in BeeUe\ Elytra after 48-Hour Exposure of Control #2 37 3.13 Tritium Concentrations from Beetle Body after 48-Hour Exposure of Control #3 38 3.14 Frequency Distribufion of Trifium Concentration in Beefie's Bodies after 48-Hour Exposure of Control #3 39 viii 3.15 Tritium Concentrations from Beetle Elytra after 48-Hour Exposure of Control #3 40 3.16 Frequency Distribution of Tritium Concentration in Beetle" s Elytra after 48-Hour Exposure of Control #3 41 3.17 Correlation Between Number of Deutonymphs Attached to a Beetle and the Tritium Concentration from that Beetle's Body after the 48-Hour Exposure Period in the Treatment 42 3.18 Correlation Between Number of Deutonymphs Attached to a Beetle and the Tritium Concentration from that Beetle's Elytra after the 48-Hour Exposure Period in the Treatment 43 3.19 Correlation Between Number of Deutonymphs Attached to a Beetle and the Tritium Concentration from that Beetle's Body after the 48-Hour Exposure Period in Control #1 44 3.20 Correlation Between Number of Deutonymphs Attached to a Beetle and the Tritium Concentration from that Beetle's Elytra after the 48-Hour Exposure Period in Control #1 45 3.21 Summary Boxplots and Median Tritium Concentrations from the Beetle's Bodies for the Treatment and All Controls 46 3.22 Summary Boxplots and Median Tritium Concentrations from the Beetle's Elytra for the Treatment and All Controls 47 IX ^... < a»« V'J*^-J^^^•S•^' Ji' ^>*•• ••-!' CHAPTER I INTRODUCTION Coevolution has played a significant role in the adaptation of organisms to their environments. Coevolufion, reciprocal changes caused in interacting organisms over time (Brooks and McLennan, 1993), can be seen in many different types of interactions including phoresy, parasifism and mutualism. Phoresy can be defined as an interspecific relationship in which one organism attaches to another for the sole purpose of transportafion (Houck and OConnor, 1991). Phoretic relafionships can be ancient and can involve major morphological adaptations for attachment, including grasping appendages and sucker plates (Houck and OConnor, 1991; Houck, 1993). Although the goal of phoresy is simply dispersal, the relationships between the organisms involved can be complex (Krombein, 1962; Fain and Ide, 1976; Crawford, 1984; Houck and OConnor, 1991). Parasitism requires that nutritional benefit be obtained from the host, during association, without killing it (Vinson, 1974). The parasite typically adapts to the host's natural defenses while the host is selected to maintain strategies that limit the extent of the parasitic infection (Esch and Fernandez, 1993).