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University Microfilms 300 North Zeeb Road Ann Arbor, Michigan 48106 A Xerox Education Company I I 72 - 30,009 MCGREGOR, Don L., 1936- THE OSTRACODA OF GULL LAKE, MICHIGAN: SELECTED ASPECTS OF THEIR ECOLOGY, Michigan State University, Ph.D. , 1972 Limnology University Microfilms, A XEROX Company , Ann Arbor, Michigan THE OSTRACODA OF GULL LAKE, MICHIGAN: SELECTED ASPECTS OF THEIR ECOLOGY By DON L. MCGREGOR A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Zoology 1972 PLEASE NOTE: Some pages may have indistinct print. Filmed as received. University Microfilms, A Xerox Education Company ABSTRACT THE OSTRACODA OF GULL LAKE, MICHIGAN: SELECTED ASPECTS OF THEIR ECOLOGY By Don L. McGregor This study presents both qualitative and quantitative description of selected aspects of the ecology of the free-living ostracods In­ habiting littoral and sublittoral areas of Gull Lake, Michigan. Most data reported were collected over a period of one year. Twenty-four species representing 10 genera of the superfamllles Cypridacea, Darwlnulacea and Cytheracea were identified from samples totalling nearly 33,000 ostracods. Twelve species are reported from Michigan, and one from North America, for the first time. Seventeen species are non-swimmers and seven are free-swlmmers; of the latter, all but one were restricted to the littoral region (0-9 m). Almost 98 percent of the ostracods collected from sediment cores were found in the top five cm sediment interval. Most species of ostracods from Gull Lake reproduce sexually, all are dioecious and all but two are oviparous. Cypridopsis vidua. Darwlnula stevensonl and I). pagliolii are known to be parthenogenetic and the last two species carry their young through embryologlcal development to the first, and occasionally second, instar. The maximum number of uterine eggs and/or young, recorded for different species from a sample of 7,533 females, ranged from three (Darwlnula pagliolii) to 69 (Candone crogmanlana). The maximum number of eggs and young Don L . McGregor reported for each species Is believed to be a more realistic estimate of the actual reproductive performance of most females than were the reported means. A majority of the free-swimming species reproduce during the summer months* but some have more than one generation per year. Cyprlnotus glaucus was found only from May to September. Many non-swlmmlng species, excepting those of Darwlnula and two species of Candona, re­ produce during the Fall, Winter and Spring. Most species of Candona had an annual reproductive cycle; Candona ohloensls had an annual reproductive cycle In the littoral areas and a biannual cycle In the sublittoral. The reproductive cycles of free- and non-swlmmlng species exhibited little overlap. Ostracod diversity, In number of species and Individuals was greatest In the littoral areas of Gull Lake. Candona was the dominant genus, In number of species, and undoubtedly accounted for most of the standing crop biomass of non-swimming species. Free- swlmming species appeared to account for most of the standing crop biomass in the littoral areas during the summer months, whereas, in the late Fall and Winter non-swlmmlng species presumably were dominant in biomass and number of species. Statements regarding ostracod biomass, based upon visual observation, are supported by information on species size, composition, and density. For those species of Candona whose life histories were studied In sufficient detail, the proportion of males always was greatest during the initial phase of the reproductive cycle* Most evidence indicated that males have a shorter life span than females. Greater mortality rates of males resulting from predation by fish was strongly indicated by analyses of stomach and gut contents of the yellow perch, Perea Don L . McGregor flavescens. Percentages of males of two species of Candona found In the stomach contents of perch were much higher than those ever en­ countered in sediment core or dredge samples. Ostracods representing 13 species and six genera, were found in three species of fish, P_. f laves cens (yellow perch) , Lepomis macro chi rus (blueglll) , and Osmerus mordax (smelt) from Gull Lake. Detailed Information is presented on the life history, reproductive performance and cycle(s), temporal and spatial distribution, population density, size and age structure, sex and juvenile-adult ratio, para­ sites, and predators of most species of the ostracod fauna of Gull Lake. Literature reviewed on the above topics focuses attention on our limited knowledge of the biology of freshwater Ostracoda. ACKNOWLEDGMENTS Acknowledgment Is made to the Department of Zoology and the W. K. Kellogg Biological Station of Michigan State University for providing laboratory facilities, equipment and financial assistance throughout most of this investigation. Most of this research was supported by a National Institutes of Health predoctoral fellowship, 1-F1-GM-22, 970-01 and 02, from the Institute of General Medical Sciences to which I owe my sincere thanks. Appreciation is expressed to members of my Doctoral committee, Drs. T. Wayne Porter (Chairman), Marvin M. Hensley, Robert C. Ball, and Jane E. Smith for their council, encouragement and constructive criticism. I thank Dr. T. W. Porter, in particular, for generous financial assistance. I thank Drs. J. Whitfield Gibbons, Donald C. McNaught, Messrs. Richard G. Burbidge, Peter H. Rich, John L. Hesse, Sigurd Nelson, Robert L. Llppson, and Arthur Wlest for assistance in the field sampling. Temperature data on Gull Lake were provided by Dr. D. C. McNaught, and Messrs. R. G. Burbidge and J. L. Hesse. Dr. J. W. Gibbons and Mr. R. L. Llppson, respectively, collected Darwlnula stevenson1 from Mississippi and Florida. 1 am grateful to the late Professor Edward Ferguson, Jr., Lincoln University of Missouri for verifying my identifications of certain free-swimming ostracods from Gull Lake. Additional pro­ fessional and technical assistance was provided by Drs. Robert V. ii Keeling and David G. Darby, University of Michigan; Dr. Vernon W. Proctor, Texas Tech University; Dr. Iraja D. Pinto, Unlversldade do Rio Grande Do Sul, Porto Alegre, Brazil; Messrs. Eugene Howell, Sr., Eugene Howell, Jr., and Alfred Pshea, formerly of the H. K. Kellogg Biological Station. A prototype of the Glamacher frozen core sampler was kindly loaned to me by Drs. Matthew Hohn and Laverne Curry of Central Michigan University. I owe a debt of gratitude to Dr. Richard G. Wiegert, University of Georgia, for providing laboratory facilities and financial assistance during the last phase of this work. Sincere thanks go to Dr. Wiegert for many hours of enjoyable, rewarding discussion and for his unselfish assistance and kindness during my stay at the University of Georgia. I thank the Department of Zoology and Biological Sclencas Division of the University of Georgia for many services. The assistance of Mrs. Virginia Mullen also is acknowledged. Special thanks are due the students and faculty of the W. K. Kellogg Biological Station of Michigan State University. Drs. Robert G. Wetzel and George H. Lauff contributed to many aspects of this work that cannot be summarized here. 1 acknowledge Dr. R. G. Wetzel and Mr. Harold L. Allen for their kindness in translating several manu­ scripts . Mr. H. L. Allen and Mt b . Dolores Johnson assisted, respectively, in the preparation of certain figures and tables and Mr. Arthur Wiest provided many services for which I am truly grateful. Thanks are extended to many of my colleagues for their stimulating ideas and helpful suggestions during the course of the investigation; I am especially grateful to Drs. J. Whitfield Gibbons, David R. Osborne, Ronald J. Pfohl, and Donald W. Tinkle. Mrs. Bernadette Henderson also H i deserves my warmest personal thanks for years of considerate and faith­ ful assistance. Finally, I thank my wife, Geraldine, for generous assistance and for her many contributions to this study. Through her efforts I have been afforded the opportunity to work toward professional goals that are not punctuated simply by Ri.D. iv TABLE OF CONTENTS Page INTRODUCTION .