Georgia Southern University Digital Commons@Georgia Southern Legacy ETDs Spring 1987 Spermatogenesis in the Mosquito Eretmapodites quinquevittatus Robert Daniel Hunter Jr. Follow this and additional works at: https://digitalcommons.georgiasouthern.edu/etd_legacy Part of the Biochemistry, Biophysics, and Structural Biology Commons, and the Biology Commons Recommended Citation Hunter, Robert Daniel Jr., "Spermatogenesis in the Mosquito Eretmapodites quinquevittatus" (1987). Legacy ETDs. 991. https://digitalcommons.georgiasouthern.edu/etd_legacy/991 This thesis (open access) is brought to you for free and open access by Digital Commons@Georgia Southern. It has been accepted for inclusion in Legacy ETDs by an authorized administrator of Digital Commons@Georgia Southern. For more information, please contact [email protected]. SPERMATOSENESiS- IN: THE MOSQUITO ERETMAI'ODSTES QLllNQUEV!TrATUS KSwi: DgrM H^ntsr, Jr. * flL *' * S3b * • HAS */ i(Se^ q Georgia Southern College ^ ^ Zach S. Henderson Library SPERMATOGENESIS IN THE MOSQUITO ERETMAPODITES QUINQUEVITTATUS by Robert Daniel Hunter, Jr. B.S., College of Charleston, 1984 A Thesis Submitted to the Graduate Faculty of Georgia Southern College in Partial Fulfillment of the Requirement for the Degree MASTER OF SCIENCE STATESBORO, GEORGIA 1987 SPERMATOGENESIS IN THE MOSQUITO ERETMAPODITES QUINQUEVITTATUS submitted by ROBERT DANIEL HUNTER, JR. Approved: r\ w DateU^^KV'T) Major Professor i ) ly '.if & & /"uib&ta '/asm Committee Member / Date Ik??? 7 %oved: i liiate Dean ACKNOWLEDGEMENTS I would like to take this opportunity to thank my major professor and advisor, Dr. Richard L. Osburn, whose moral support and encouraqement made this research possible. I am also grateful to committee members, Dr. Sara N. Bennett and Dr. Frank E. French, for their careful review of the manuscript. I am further indebted to Dr. W. Keith Hartberq for his continuous support of this project. I also thank Greg Vogel, Dr. Sturgis McKeever and Matt Stanley for invaluable assistance with photography. Dr. James B. Claiborne for use of the centrifuge, and Leslie Callaham for her dedicated work in the mosquito research laboratory. I am especially appreciative of Lillian Eatman, who not only typed the manuscript, but provided much encouraqement throughout this study. Additional gratitude is expressed to fellow graduate students, friends and faculty members of the Department of Biology. Finally, I am immensely thankful to my parents and brother for their enduring patience, support, love and encouragement. TABLE OF CONTENTS ABSTRACT 1 INTRODUCTION 2 MATERIALS AND METHODS 8 RESULTS 13 DISCUSSION 17 LITERATURE CITED 21 PLATES 27 TABLE 31 ABSTRACT Various stages of spermatogenesis in pupal testes of the mosquito Eretmapodites quinquevittatus (Theobald) were determined by 2% 1acto-aceto-orcein and silver nitrate staining techniques. Temporal relationships of stages were demonstrated and behavior and appearance of meiotic chromosomes were descri bed. Pupal testes were most active meiotically for the first 12-14 hours after onset of pupation. The prepachytene stage of leptotene and a nucleolus were observed with the use of silver nitrate staining. Experimental observations demonstrated the first spermatids and visible mature sperm at 6-8 and 18 hours, respectively, after onset on pupation. E. quinquevittatus mean sperm size was reported (head = 50 urn long; flagellum = 200 pm long). These measurements closely compared to dimensions reported for Aedes aegypti (head = 40 urn long; flagellum = 270 urn long). 1 INTRODUCTION The genus Eretmapodites (Theobald) of the family Culicidae contains approximately 44 species and 3 subspecies (Knight, 1977). Mosquitoes of this genus are diagnostically similar to the genus Aedes (Meigen). Both genera possess a dark proboscis, dark palps, dark-scaled wings, and long, mainly black, legs. A major distinguishing feature is that the abdomen of Aedes is more pointed than the abdomen of Eretmapodi tes, which is more laterally compressed. Developmental stages of mosquitoes include egg, larva, pupa and adult. Average developmental time of the genus Eretmapodi tes from hatching of egg to adults is 10-12 days, with the larval stage being 8-10 days, and a pupal stage of 2 days (Hartberg and Gerberg, 1971). Various studies have implicated the genus Eretmapodi tes as a vector of several viruses. Viruses isolated from Eretmapodi tes include Middleburg virus (Brottes et_ aj_., 1969) which causes fever in lambs and viremia in chickens; Rift Valley fever virus (Smithburn et_ al_., 1948) which can lead to deaths in pregnant and abortions in newborn goats, sheep, and cattle; Semiliki Forest virus (Macnamara, 1953) which is believed to cause encephalitis in mice, guinea pigs, rabbits, and monkeys; and Spondweni virus (Brottes et_ aK, 1969; Worth, Patterson, and deMeillon, 1961) known to infect man, possibly with hepatitis. Mosquitoes of this genus are also good laboratory vectors of yellow fever (Bauer, 1928), a viral disease in man characterized by high fever, jaundice, 2 black vomit, and even death, and chickungunya (Gilotra and Shah, 1967), also a viral disease in which man is the only known vertebrate host. Victims of chickungunya suffer extreme pain in the spine and joints. According to Hartberg and Gerberg (1971), Eretmapodites qui nquevi ttatus might serve as a vector for PIasmodi urn gal 1inaceum, a malarial parasite of domestic hens. E. qui nquevi ttatus is most widely distributed throughout Madagascar and the Ethiopian region of Africa (Gillett, 1971). Descriptions of mitotic chromosomes in E. quinquevittatus (Hartberg and Faircloth, 1983) and the chromosome complement of E. chrysogaster (Graham) (Rai, 1966) account for the only known cytogenetic work in the genus Eretmapodi tes. Additional investigation into the cytogenetics of E. quinquevittatus can not only provide more knowledge on reproductive development through the information gained, but may also improve current understanding of speciation within the Culicidae. Spermatogenesis has been studied in various culicid species through the last eighty to one hundred years. Most studies on spermatogenesis have been with the Culex pipiens L. complex (Callan and Montalenti, 1947; Grell, 1946; Jost, 1971; Lomen, 1914; Moffett, 1936; Patau, 1941; Stevens, 1910; Taylor, 1914; Whiting, 1917). Other species which have provided data on spermatogenesis include Aedes aeqypti (L.) (Akstein, 1962; Bhalla, 1971; Krafsur, 1964; Mescher and Rai, 1966; Motara et_ al., 1985), Aedes albopictus (Skuse) (Jost, 1971; Smith and Hartberg, 1974), Anopheles maculipennis (Meigen) (DeBuck and Swellengrebel , 1935), Anopheles punctipennis (Say) (Stevens, 3 1911), Anopheles stephensi (Listen) (Rishikesh, 1959), Corethra piumicornis (F.) (Frolowa, 1929), Culex tarsalis (Coquillett) (Stevens, 1911), Culiseta incidens (Thomson) (Stevens, 1911), Culiseta inornata (Williston) (Breland et a]_., 1964), Theobaldia incidens (Thomson) (Callan and Montalenti, 1947), Theobaldia 1 ongiareolata (Macquart) (Callan and Montalenti, 1947). Though spermatoqenesis is a continuous process, for descriptive purposes, it may be considered in three distinct stages: (1) spermatogonial divisions, (2) meiosis, and (3) spermiogenesis. Spermatogonial divisions occur prior to meiosis and involve gonadal cells (spermatogonia) actively undergoing mitosis to form primary spermatocytes. The diploid spermatocyte then undergoes the first of two meiotic divisions to form two secondary spermatocytes, each of which divides, and this results in a total of four haploid spermatids. Transformation of spermatids into functional sperm (spermatozoa) is defined as spermiogenesis (Wilson, 1925). All phases of spermatogenic development occur in testes, which in mosquitoes are paired ellipsoidal structures located in the dorsolateral region of the sixth abdominal segment. Although the testes in mosquitoes are generally colorless, clear organs surrounded by a brownish layer of fat cells (Mescher and Rai, 1966; Smith and Hartberg, 1974), some differences in their appearance have been observed. Testes of Aedes dorsalis (Meigen) were not clear but were characterized as white or yellowish organs (Mukherjee and Rees, 1970). Rishikesh (1959) reported the testes of Anopheles stephensi as 4 pale, yellowish translucent bodies. Testes have also been described as dark spots" (Akstein, 1962). These observations demonstrate possible variations in reproductive development amonq genera and/or species. Testes are usually of unequal size and vary in the stage of physiological development (Mescher and Rai , 1966). Each testis is divided into cysts partitioned by septa (Asman, 1974; Breland et al_., 1964; Smith and Hartberg, 1974; Mescher and Rai, 1966; Rishikesh, 1959; Wandall, 1986; Warren and Breland, 1963; Whiting, 1917). Christophers (1960) described a striated appearance in testes of Aedes aegypti and attributed this to be the result of considerable packing of spermatogonia and spermatocytes into the cysts. Onset of spermatogenesis varies among species. Rishikesh (1959) found primary spermatocytes in Anopheles stephensi as early as the fourth instar larval stage of development. He noted that gonial divisions were quite rare in testes of pupae. More recent cytological descriptions of spermatogenesis in the genus Aedes have demonstrated the presence of primary spermatocytes in early pupal life (Mescher and Rai, 1966; Mukherjee and Rees, 1970; Smith and Hartberg, 1974). In Aedes dorsalis actively dividing spermatogonia occurred