rp EMBRYOLOGY OF CHROTOGONUS TRACHYPTERUS BLAWCHARDrA PEST OF COTTOl^-SEEBUNGS. (ORTHOPTEPiA: ACRIOIOAE) ABSTRACT THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN ZOOLOGY By MANZOOR A. SIDDIQUI DEPARTMENT OF ZOOLOGY AUGARH MUSLIM UNIVERSITY. ALIGARH 1978 ff^f'^ ice \o. >,^\ Freshly laid egg of CJir'(rto)2:6r[crs trachyi)terus Blanchard. is a typically cuirved and elongated structure with the posterior end a little more "bluntly rounded than the anterior. The dorsal surface is convex while the ventral one is concave. The entire egg is covered with a raucous membrane under which lies the chorion. The chorion is soft and thin in a newly laid egg hut gets hardened later, causing fractures at different places at the time of emergence. In section it appears to consists of three layers starting from outside, the extrachoriqn the exo-chorion and the eado-choilon. The exo-and endo-choilon show uniformity of thickness all over the surface of the egg. Below the endo- chorion lies a thin structureless membrane - the vitelline membrane which encloses the entire yolk mass, Ohsearvations on the living egg show that the posterior end of the egg is characterized by the presence of micropylar canals and hydropylar pores. Sections of freshly laid eggs show a definite chromosomal arrangement in the posterior pole which is probably a metaphase stage of maturation division. After maturation and subsequent fertilization the nucleus undergoes mitotic division with the result that a few large cleavage cells are formed. Six such cleavage cells are present at 10 hours incubation which lie in the posterior extremity of the egg. The cleavage cells divide to produce a large number of cells and later begin to migrate - ? - anteriad. Peripheral cells tend to airange themselves in a row to form primaiy epithelium. Towards the posterior pole a certain number of cells stand out distinctly by their larger size, rounded form and close spacing. This part constitutes the embryonic blastoderm. The rest of the cells of primary epithelium are held at a distance from each other and form the extra­ embryonic blastoderm. The embryonic part or the germ band then undergoes rapid division resulting in the formation of a it)und concave disc lying in the posterior end of the egg. Soon after the differentiation of the germ band embryonic envelops (the amnion and serosa) develop and the serosal cells start secreting the white and yellow cuticle. The thickness of these two cuticles varies in different parts of the egg being much thicker in the posterior region than the anterior. The white cuticle thickens further and finally disappears leaving only the yellow cuticle at the time of emergence, A third cuticular,, layer appears a day after blastokinesis and persists till hatching occurs. The morphogenesis of the embryo has been described under three main headss pre-blastokinetic, blastokinetic and post- blastokinetic phase. In all twenty three stages have been made out during the entire embryonic development which lasts for about 14 days starti23g from the germ-disc formation upto hatching. During pre-blastokinetic phase the embTjo undergoes a remarkable increase both in length and width. Segmentation of the body follows soon after. In the blastokinetic phase the embryo - 3 - moves along the posterior pole of the egg and begins to rotate on its own axis. At the close of the blastokinesis the embryo shortens with its head end pointing anteriorly and tixil in the opposite direction. In the post-blastokinetic phase the e^ubryo again starts growing anteriad and extends upto the whole length of the egg. Details of blastokinetic movements and the course of revolution have been described. Observations were made on the oilgin of the mesoderm and the fate of the coelomic sacs. In all nineteen pairs of coeloraic sacs were formed in the body segments. No trace of either pre- antennary or pre-mandibular sac could be seen. Soon after the establishment of these sacs the cardioblasts and germ cells make their appearance. The cardioblasts are formed from the mesoderm of the dorso-lateral regions of the coelomic sacs. Those of the opposite sides move towards mid-dorsal region of the embryo along with the body-wall and finally unite to form the heart enclosing raid-dorsal sinus. With the separation of the provisional dorsal closure from the somatic mesoderm a pair of lateral blood sinus is formed. Later these move towards the mid-dorsal region and unite with each other to form the dorsal sinus. The heart runs from the second maxillary to the tenth abdominal segment. In the head region it is connected with the posterior aorta. The two parts of the cephalic aorta-anteilor and posterior are derived from the dorso-rostral and dorso-anal pouches of the antennary coelom respectively which supply blood to the head. - 4 - The pericardial cells and the peilcardial septums take their origin from the somatic mesoderm. The former lie on the ventro­ lateral side of the heart as rounded loose cells while the later are seen as thin delicate membranes. One of these called dorsal diaphragm lies below the dorsal sinus and the other between the nerve cord and the developing mid-gut. This is known as ventral septum. The blood cells oilginate from the median mesodermal cells which lie over the developing ganglia of the ventral nerve cord. These cells are liberated in the epineural sinus, peri­ cardial chamber, circum-intestinal blood sinus and also in other places of the body cavity. The oenocytes which are ectoderne-l in origin first appear before blastokinesis and are arranged in the form of groups near each abdominal spiracle. In the post- blastokinetic phase their regular arrangement is lost and they are distributed as free cells in all abdominal segments. Halevent information regarding the development of alimentary canal has been provided in the text. The stomodaeum and proctodaeum appear as invaginations of ectodermal cells. These later acquire a blind tvibular form. The blind ends of stomodaeum and proctodaeum are important regions as the midgut cells proliferate from these parts and are therefore considered here as originating from ectoderm. The hepatic caecae and six malpighian tubules arise from the stomodaeum and proctodaeum respectively before they develop free communication with the - 5 - midgut. The provisional dorsal closure and the splanchnic mesoderm are formed prior to the differentiation of mid-gut region althou^ the development of its functional epithelium is delayed considerably. A freshly hatched hopper does not resort to feeding till about 18-20 hours after hatching. The nervous system includes the development of nerve cord, the median cord, the brain and the stomatogastric ganglia. The neuroblasts repeatedly divide but no division of the ganglion cells have been observed. The nerve cord develops both the neurilemraal layers-an outer and an inner one as against a single one reported by Hoonwal and Baden. The median cord persists till hatching occurs. The component lobes of the brain develop from three paired ganglion. The stomatogastric nervous system comprising the three unpaired frontal, occipital and ventricular ganglia develops from three distinct rudiments from the dorsal v/all of the stomodaeum. Besides these a paired pharyngeal ganglion also appears in the same way. All these ganglia are connected together by a recurrent nerve which taJcesits origin from the tri to cerebrum. The text has been illustrated by suitable microphotographs and hand drawings. THE EMBRYOLOGY OF CHROTOGOMUS TRACHYPTERUS BLANCHARDr-A PEST OF COTTOi\!-SEEDLINGS. (ORTHOPTERA: ACRIDIDAE) THESIS SUBIViiTTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN ZOOLOGY By MANZOOR A. SIDDIQUi DEPARTMENT OF ZOOLOGY AUGARH MUSLIM UNIVERSITY. ALIGARH 1978 19^m w«o T1884 CEiffl^IPICATE This is to certify that the thesis entitled "The embryology of Chrotogonus trachyDterus Blanchard. (Orthoptera: Acrididae)'• which is being submitted by Mr, Manzoor A. Siddiqui, embodies original work done by the candidate himself. The entire wo'rk'.was'carried out under my supervision and that I allow'him to submit the same in fulfilment of the requirements for .the degree of Doctor of Philosophy In Zoology p.f .this University, (Dr. ^, MOIN PAEOOQUI) Reader, Department of Zoology, Aligarh Muslim University, Aligarh. CONTENTS Page I. ACKNOWLEDGEMENT 1 II. INTRODUCTION 2 III. KBVIEW OP LITESATURS 5 lY. MlTEittAL AND METHODS 1? V. 0BSEH7ATI0N3 ON PRS3HLY LAID EGG 16 VI, MORPHOGENESIS OP THE EMBRYO AND BLASTOKINETIC MOVaiSNTS 22 (1) Pre-Blastokinetic phase 24 (2) Blastokinetic phase 31 (3) Post-blastokinetic phase 3? VII. STRUCTURE OP THE PIZSD EGG 40 (1) The chorion and related structures 40 (?) The deutoplasm and the egg nucleus 44 VIII. CLEAVAGE, FORMATION OP BLASTODERM AND GERM BAiro 48 IX. EMBRYONIC MEMBRANES 5? (1) The amnion ,., 52 (?) The serosa and its secretion 53 X. THE DIPPERE1^[TIATI0N OP THE MESODERfl 57 (1) The origin of coelomic cavities 59 (?) Morphological differentiation of the coelomic sacs 62 XI. THE ALIMENTARY CANAL 67 (1) The development of the stomodaeum and hepatic caecae ... , 67 (2) The development of the proctodaeun and malpighian tubules ... ... ... 71 (3) The development of the mesenteron ... T5 (i) The provisional dorsal closure ... 74 XII. THE CIECTJllTOBI SYSTEM 85 (1) The dorsal vessel ... 83 (2) The cephalic aorta ,. 85 (i) The anterior aorta ... 86 (ii) The posterior aorta 87 (3) The pericardial cells and the pericardial septum ... ... ... 88 (4-) The blood cells and blood sinuses ... 90 XIII, THE OENOGYTSS 94 XIV. THE NERVOUS SYSTEM 96 (1) The nerve cord 97 (i) The Neurilemma ... ... ... 100 (ii) The median cord ... 101 (2) The Brain 103 (i) The development of the Protocerebrum 103 (a) The optic lobes 104 (b) The middle and the inner lobe of the protocerebrum ... ... 106 (ii) The deuto - and tritocerebrum ... 108 (3) The stomatogastric nervous system ... 109 XV. THE GONiPS 112 XVI.