The haemocytes of Calliphora erythrocephala (Meig.) (Diptera)

Summary The haemocytes of larvae and young pupae of Calliphora erythrocephala are studied by phase contrast and electron microscopy and three cell lineages are distinguished: plasmatocytes, thrombocytoids and oenocytoids. The plasmatocytes show important modifications during larval development and at the time of histolysis, which are described and discussed in relation to the function of these cells in the physiology of Calliphora. The thrombocytoids, haemocytes which had not been recorded so far, are characterized by a strong tendency to fragmentation, this process leading to the formation of the anucleated cytoplasmic fragments and the naked nuclei referred to by earlier authors. The ability of the cell fragments, which retain normal cytological characteristics, to agglutinate and form intricate networks, is discussed in relation to haemostasis in Calliphora.The ultrastructural study of the haemocyte accumulations in the vicinity of the posterior part of the dorsal vessel reveals the basic organization of haemocytopoetic tissue, as described recently in orthopteran insects. The functional importance of this tissue in the production of haemocytes is demonstrated by X-irradiation and ligation experiments in larvae of Calliphora.

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Résumé L'étude en microscopie en contraste de phase et au microscope électronique permet de distinguer dans le sang circulant de larves et de jeunes pupes de Calliphora erythrocephala trois lignées cellulaires: les plasmatocytes, les thrombocytoïdes et les oenocytoïdes. Les plasmatocytes, numériquement les plus importants, présentent au cours du développement larvaire et chez les pupes des modifications considérables, qui sont décrites et discutées en rapport avec la fonction évidente de ces hémocytes chez Calliphora. Les thrombocytoïdes, inconnus dans la littérature, se caractérisent par une forte tendance à la fragmentation, qui aboutit à la formation des «fragments cytoplasmiques anucléés» et des «noyaux nus» signalés par divers auteurs. Les phénomènes d'agglutination des «fragments cytoplasmiques anucléés», dont les caractères cytologiques restent normaux, sont discutés en rapport avec le problème de l'hémostase chez cet insecte.L'étude ultrastructurale des accumulations hémocytaires autour du vaisseau dorsal dans la partie postérieure de l'abdomen montre une organisation de base comparable à celle décrite dans les organes hématopoïétiques des Insectes Orthoptères. L'importance fonctionelle de ce tissu hématopoïétique de Calliphora dans la production des hémocytes au cours de la vie larvaire est démontrée par des irradiations de ce tissu et par des ligatures de la partie postérieure de l'abdomen.

     

The contribution of the fatbody to RNA and ribosomal changes during development of the blowfly Calliphora erythrocephala (Meig)

The initiation of blowfly metamorphosis is associated with a pronounced decrease in the number of larval ribosomes; this reduced number then remains constant throughout pharate adult development. Ribosomal RNA accounts for most of the total RNA in larvae shortly after the cessation of feeding and growth, but thereafter the amount of rRNA declines disproportionately to total RNA until early pharate adult development; thereafter, the ratio remains constant until adult emergence. Larval fatbody ribosomes, which constitute about half of the total in the entire organism, are destroyed in situ prior to pupariation. The progressive decrease in fatbody rRNA is accompanied by a corresponding increase in a degraded, relatively insoluble 4–7 S nucleic acid which, stored until adult emergence when it is discarded, accounts for the disparity between total RNA and rRNA. The extracellular ribosomes previously observed during pharate adult development are thus derived from dissolution of larval tissues other than fatbody.     

Structure and kinematics of the prosternal organs and their influence on head position in the blowfly Calliphora erythrocephala Meig.

Summary The blowfly Calliphora has a mobile head and various, presumably proprioceptive, sense organs in the neck region. The prosternal organs are a pair of mechanosensory hair fields, each comprising ca. 110 sensilla. We studied their structure (Figs. 2–4), kinematics (Figs. 5, 6) and, after surgery, their influence on head posture (Figs. 7–11) in order to reveal their specific function.The hair sensilla are structurally polarized, all in roughly the same direction, and are stimulated by dorsoventral bending of the hairs (Figs. 3, 4). This occurs indirectly by flap-movements of two contact sclerites (Figs. 3, 6); they move in the same direction during pitch turns of the head, in opposite directions during roll turns, and barely at all during yaw turns of the head (Fig. 5).Bending and arresting all hairs of one field elicits a head roll bias to the non-operated side (Fig. 7) during tethered flight in visually featureless surroundings. In contrast, shaving all hairs of one field elicits a head roll to the operated side (Figs. 8–10). The surgically induced bias of head posture is not compensated within three days (Fig. 10). Our results show that the prosternal organs of Calliphora sense pitch and roll turns of the fly's head, and control at least its roll position.Abbreviations HP° TP° angular positions of the sagittal planes of the fly's head and thorax, respectively, relative to an external reference - HR° = HP — TP head roll angle of the fly's head relative to its thorax, HR>0° for clockwise head roll, looking in flight direction - N number of flies - n number of measurements - PO prosternal organ - SD standard deviation - SEM standard error of the mean     

The fine structure of peritrophic membranes of the blowfly, Calliphora erythrocephala, grown in vitro under different conditions.

The formation of peritrophic membranes (PM) in vitro was studied in a flow chamber in order to avoid the accumulation of metabolic substances during prolonged incubation. During the first 8 to 10 hr of incubation the production of PM was nearly constant—3·5 ± 1·4 mm PM/hr. After about 10 hr it decreased and stopped after about 35 hr. Between 1 and 8 hr after the beginning of incubation the width of the periodic crossband pattern reached or nearly reached the values found in PM which had formed in vivo; afterwards it decreased more and more. During the first 20 min of incubation a ‘disturbed zone’ of PM without any regular crossband pattern is formed.In the cardia of adult Calliphora erythrocephala there are three formation zones forming three PM of different fine structures. The fine structure of PM 1 to 3 formed in vitro during the first 6 to 8 hr of incubation in Leloup's medium 1, with an osmolarity of 340 mOsmol, a pH of 6·8, and a temperature of 27°C, does not differ from the PM grown in vivo. PM 1–3 grown in vitro in Tyrode's solution with added glutamine or in Leloup's medium with added β-ecdysone show a considerable increase in thickness and a disturbed formation of the electron dense layer of PM 1.     

Cholinergic neurons in the lamina ganglionaris of the blowfly Calliphora erythrocephala

Summary The distribution of putative cholinergic neurons in the lamina of the blowfly Calliphora erythrocephala was studied by immunocytochemical and histochemical methods. Three different antibodies directed against the AChsynthesizing enzyme, choline acetyltransferase (ChAT), revealed a cholinergic population of fibres running parallel to the laminar cartridges, which have branch-like structures at the distal lamina border. Cell bodies in the chiasma next to the lamina border were also labelled by the anti-ChAT antibodies. Monopolar cell bodies in the nuclear layer were faintly labelled. The distribution of the acetylcholine hydrolyzing enzyme, acetylcholine esterase (AChE), was revealed by histochemical staining and was similar to the ChAT immunocytochemistry. The arrangement of ChAT positive fibres in transverse and longitudinal sections and the distribution of AChE stained fibres indicate that the amacrine cells of the lamina are cholinergic cells.We dedicate this work to Prof. F. Zettler who passed away in fall 1988: K.-H. Datum, I. Rambold     

Hormonal control of resilin deposition in the blowfly, Calliphora erythrocephala

The deposition of the resilin tendon in the blowfly Calliphora erythrocephala was investigated in normal and in various experimental conditions. The results showed that the weight of the protein resilin that is deposited is controlled by diet as well as by the hormone secreted by the medial neurosecretory cells.Endocrinologically abnormal Calliphora adults deposited a tendon with normal ultrastructure but showed signs of premature ageing while Calliphora fed on a sugar diet deposited a tendon with abnormal ultrastructure.     

Fine structural organization of the rectum in the blowfly, Calliphora erythrocephala (Meig.) with special reference to connective tissue, tracheae and neurosecretory innervation in the rectal papillae

The rectal epithelium of Calliphora is made up of three quite distinct cell types: rectal, cortical and junctional cells. The thin wall of the rectal pouch is made up of rectal cells which are relatively simple and unspecialized; their general structure does not suggest any direct participation in ion transport. A function of ion and water transport can probably be ascribed to the cortical cells, which are arranged in the form of four cones which project into the rectal lumen. The cavity of each cone is filled up with tracheae, nerve and neurosecretory terminals, and connective tissue to form medulla. The medulla and cortex are separated from each other by deeply staining bridges or trabeculae to form an infundibular space. The most conspicuous feature of the cortex is the presence of an extensive intercellular sinus formed by complex infoldings of the lateral plasma-membranes. It is postulated that fluid, which is absorbed from the rectal lumen, is transported into the intercellular sinus and finally reaches the haemolymph via the infundibular space. The actual site of ion transport is probably the stacks of lateral plasma-membrane which are closely associated with mitochondria. The junctional cells, which are packed with microtubules, form a collar around the base of the papillae at the point of their insertion into the rectal wall. It is suggested that the neurosecretory terminals present in the medulla might release a hormone which controls rate of ion and water reabsorption by the papillae cells.     

Antennal receptors in the blowfly Calliphora erythrocephala: II. Fine structure of the large pedicellar campaniform sensillum

A large mechanosensory campaniform sensillum (LCS) is found close to the flagellum/pedicellus joint in the antennae of the blowfly Calliphora erythrocephala. The LCS possesses a single sensory cell, enveloping cells and a cuticular stimulus-conducting structure. The distal part of the sensory process is developed as a tubular body and is connected to the two parts of the stimulusconducting apparatus. The sensory cell is characterized by the complete absence of ciliary structures in the transition zone between dendrite and sensory process.