70-26,330 MEOLA, Shirlee May, 1935- A HISTOPHYSIOLOGICAL AND ULTRASTRUCTURAL STUDY OF THE CORPUS CARDIACUM OF THE MOSQUITO. The Ohio State University, Ph.D., 1970 Zoology I University Microfilms, A XERO\Company, Ann Arbor, Michigan THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED A HISTOPHY3IOIOG1CAL AND ULTRASTRUCTURAL STUDY OF THE CORPUS CARDIACUM OF THE MOSQUITO DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of the Ohio State University By Shirlee May Heola, B.Sc., M.Sc. * * a* * * * The Ohio State University 1970 Approved by Adviser Zoology Department ACKNOWLEDGMENTS The assistance and advice of my adviser Dp . Wayne Parrish in the use of the electron microscope is gratefully acknowledged, as well as the advice and encouragement of Dr. Willard Myser. I wish to thank Mr. Joe ONeal and Mr. William Janse of the Entomological Research Center, Vero Beach, Florida, for their assistance in preparation of the illustrations. My gratitude is extended to Dr. Carl Venard for his critical reading of the dissertation and suggestions for its improvement. I am especially indebted to Dr. Arden 0. Lea for his suggestion of the problem and under whose direction this research was carried out. Financial support was received from the U.S. Public Health Service through Research Grant No AI-06587 to Dr. Lea. To my husband, Dr. Roger Meola, who has endured this effort with infinite patience, I extend my gratitude for rearing the mosquitoes and performing the operations. ii VITA December 7, 1935 .... Born - Canton, Ohio 1 9 5 3 ................... B.Sc., The Ohio State University, Columbus, Ohio 1957“I960 ............. Research Assistant, Department of Anatomy, The Ohio State University, Columbus, Ohio 1 9 6 1 ..... ........ M.Sc., The Ohio State University, Columbus, Ohio I96O-I963 ...... Research Assistant, Department of Physiological Chemistry and Pharmacology The Ohio State University, Columbus, Ohio 1964-1969 ...... Biologist, Florida State Board of Health, Vero Beach, Florida 1970-present ............ Research Associate, Department of Entomology, The University of Georgia, Athens, Georgia PUBLICATIONS "Sensitive Paraldehyde-fuchsin Technique for the Neurosecretory System of Mosquitoes." Trans. Am. Microscop. Soc. 89(1):66-71. 1970. "Histological Changes in the Corpus Cardiacum of Adult Mosquitoes." Trans. Am. Microscop. Soc. (in press) FIELDS OF STUDY Major Fields Zoology Vertebrate Zoology: Chromatography of the Free Amino Acids in the Serum of Different Genera of Pheasants." Professors Eugene Good and Carl Reese. Cytology and Pathology: Professors Willard Myser, Wayne Parrish and Dante Scarepelli Neurosecretion: Professor Arden Lea (Supervisor of off-campus research at the Entomological Research Center, Florida State Board of Health and at The University of Georgia). iii TABLE OF CONTENTS Page ACKNOWLEDGMENTS.................. ,....................... ii VITA ..................................................... iii INTRODUCTION............... ............................... 1 METHODS AND MATERIALS .................... 5 RESULTS I. The Anatomy of the Cephalic Aorta . 9 II. The Anatomy of the Cerebral Neurosecretory System A. The Neurosecretory Cells of the Br ain........ 13 B. The Structure ofthe Corpus Cardiacum........... 15 1. The Neurohemal Sites of the Cardiacum ....... 17 2. The Neuroglial Cells of the Cardiacum...... 19 3. The Elementary Neurosecretory Granules of the Cardiacum ........ 20 C. The Nervi Corporis Allati and Nervi Oesophagei .... 22 D. The Neurosecretory Cells of the Cardiacum” Allatum Complex ...... 22 III. The Anatomy of the Stomodeal System .... 23 IV. A Comparative Study on the Corpus Cardiacum of Unoperated and Operated Mosquitoes ............ 25 A. Paraldehyde-fuchsin Stainable Material in the Cardiacum of Unoperated Mosquitoes ..... 25 B. Paraldehyde-fuchsin Stainable Material in the Cardiacum of Operated (MNC-Ablated) Mosquitoes .... 26 iv Pag© DISCUSSION .............................................. 28 I, The Corpus Cardiacum 29 II. Similarities Between the Neurosecretory Systems of Mosquitoes and Vertebrates 33 III. Musculature of the Aorta Associated with the Corpus Cardiacum ..... 34 IV. The Recurrent Nerve ..... 36 V. Histological Changes in the Corpus Cardiacum.......... 36 ABBREVIATIONS USED IN FIGURES............................. 39 LIST OF FIGURES .......................................... 41 FIGURES ................................................. 45 APPENDIX................................................ 81 LITERATURE CITED......................................... 84 v INTRODUCTION Groups of cells that have the structure of a neuron but the function of an endocrine gland have been found in the central nervous system of both vertebrates and invertebrates. These neurosecretory cells have been studied in annelids (Oosaki, 1966} Hagadorn, 1958), molluscs (Gabe, 1965), crustacea (Knowles, 1962), fish (Palay, I96I), amphibia (Dawson, 1953} Smoller, 1966), reptiles (Scharrer, 195*0* birds (Nishioka, 196*0 and mammals (Bodian, 1963} 1966} Sloper, 195^; Barer, 1966), as well as in many orders of insects. The perikarya and axons of some neurosecretory cells contain material that stains with paraldehyde-fuchsin and in this manner these neurons can be detected and their tracts traced. The axons of neuro­ secretory cells terminate adjacent to vascular or hemocoel spaces into which they release their products. These areas of storage and release are termed neurohemal organs. The major neurosecretory system in the brain of vertebrates is the hypothalamo-neurohypophyseal system. In this system the neurosecretory perikarya are in the hypothalamus and the neurohemal sites are in the pars nervosa and the median eminence. In insects the corpus cardiacum is the major neurohemal organ of the neurosecretory cells of the protocerebrum. Hanstrom (19hl) suggested that the hypothalamo-neuropophyseal system of vertebrates might be analogous to the intercerebralis-corpus cardiacum system of insects. In insects several groups of neurosecretory cells synthesize tropic hormones that are essential for metamorphosis, tanning, and digestion (review by Wigglesworth, 1964). The medial neurosecretory cells appear to be the major source of these hormones. In some species medial neurosecretory cell perikarya also produce a hormone essential for egg maturation (Thomsen, 1952; Highnam, 1962; Girardie, 1966; Lea, 1967} Wilkens, 1968). The hormone apparently moves through the axons of these cells by axoplasmic flow and accumulates in the corpus cardiacum, because transplanted corpora cardiaca, as well as transplanted medial neurosecretory cells, will restore egg maturation which has been arrested by ablation of the medial neuro­ secretory cell perikarya (Thomsen, 1952; Lea, 1970). Several investigators (Highnam, 1962; Delphin, 1965; Strong, 1965; Girardie, 1966; Thomsen, 1969) have reported that the cytoplasmic inclusions which stain with paraldehyde-fuchsin, move through the axons of the medial neurosecretory cells to the corpus cardiacum. In aphids and cockroaches paraldehyde-fuchsin stainable material has been traced through the corpus cardiacum to organs in the thorax and ab­ domen (Johnson and Bowers, 1963)* However, in most insects this material accumulates either in the cardiacum or in the wall of the aorta (Nayar, 1956; Johansson, 1958; Strong, 1965). Considerable variation in the gross structure of the cardiacum has been reported in different species of insects (review by Bern and Hagadorn, 1965). In contrast, the ultrastructure of the cardiacum has been remarkably consistent (Bowers and Johnson, 1966; King, et al., 1966; Norman, 1965; Scharrer, 1963: Smith, 1966), In general micro­ graphs published thus far, depict a ganglion that contains a single neurohemal site consisting of terminals of intrinsic and extrinsic cells# These terminals appear to release their neurosecretory products into the hemocoel surrounding the cardiacum# Variations at the ultrastructural level consist mainly of differences in the size and electron density of the elementary neurosecretory granules in the neurons# The present report describes the histology of the cerebral neuro- secretory system of the mosquito# Its major contribution is a descrip­ tion of the ultrastructure of the corpus cardiacum and of the neuro­ secretory cells of the cardiacum-allatum complex# Surprisingly, the ultrastructure of the cardiacum of mosquitoes has not been previously examined for neurosecretory terminals, although more is known about the synthesis, storage, and release of the egg development neuro­ secretory hormone in this species than in any other insect. The cerebral neurosecretory system was also examined for histo­ logical changes during egg maturation. Other investigators have ob­ served fluctuations in the paraldehyde-fuchsin stainable material in the cardiacum of insects other than mosquitoes (Highnam, 1962; Mordue, 1967). However, as yet, there is no experimental evidence that a hormone is stored or released from the cardiacum in these species. In Aedes sollicitans. a blood meal is essential for egg matura­ tion, because the ingestion of blood acts as a stimulus causing the release of the egg development neurosecretory hormone from the cardi­ acum (Lea, 1970), The blood also supplies protein for egg maturation# But if, instead of blood, the mosquitoes are fed sugar, the hormone accumulates in the cardiacum. The release of the hormone can only be detected when the medial neurosecretory