The influence of head position on the flight behaviour of the fly. Calliphora erythrocephala

The heads of flies were passively turned during fixed flight (open loop conditions). The turning stimuli had ramp-shaped onsets. The resulting torque produced by the thorax was plotted as a function of the degree of head-turn.Directional, passive turns of the head evoke active turning tendencies (yawing forces) of the same sign from the thorax. The strength of these tendencies is dependent on the size of the given angle through which the head was turned. The cushion of sensory hairs on the neck (prosternal organ) is very important in the elicitation of the turning tendencies. The results which have been obtained indicate that the position of the fly's head has a substantial influence on the magnitude of the turning tendencies elicited by visual stimuli.     

Serotonin and gastrin/cholecystokinin-like immunorcactive neurons in the larval retrocerebral complex of the blowfly Calliphora erythrocephala

Summary The presence and distribution of neurons immunoreactive against antibodies to serotonin (5-HT) and gastrin/cholecystokinin (gastrin/CCK) has been studied in the larval retrocerebral complex of the blowfly Calliphora erythrocephala, a composite structure which consists of the corpus cardiacum, the corpus allatum, the thoracic gland and a portion of the cephalic aorta. Immunoreactive material was found in all these elements except in the corpus allatum. Six to eight cell bodies in the corpus cardiacum and four to eight cell bodies in the thoracic gland were 5-HT immunoreactive (5-HTi). These 5-HTi cell bodies send processes to the neuropil of the corpus cardiacum and to neurohemal sites in the cephalic aorta, corpus cardiacum and ventral part of the thoracic gland. Six to eight cell bodies in the corpus cardiacum and four to six cell bodies in the thoracic gland reacted with antibodies against gastrin/CCK. These cell bodies send processes to the neuropil of the corpus cardiacum and to neurohemal sites in the corpus cardiacum and the cephalic aorta in a pattern resembling that of the 5-HTi fibers. Additional gastrin/CCK-like immunoreactive fibers were shown to come from the central nervous system via the two nervi corporis cardiaci. An electron-microscopical analysis was performed to analyze further the morphological features revealed by the light-microscopic immunocytochemical technique. This confirmed the existence of neurosecretory-like terminals among the gland cells of the thoracic glands and the existence of neurohemal sites in several regions of the larval retrocerebral complex. Some functional aspects of the retrocerebral complex are discussed on the basis of the presented data.     

The fine structure of haltere sensilla in the blowfly Calliphora erythrocephala (Meig.), with scanning electron microscopic observations on the haltere surface

The dipteran haltere incorporates large numbers of regularly disposed mechanoreceptors providing the sensory input enabling the vibrating haltere to function as a gyroscopic organ of equilibrium. Campaniform sensilla of the basal and scapal regions have been investigated by light and transmission electron microscopy, and these observations are augmented by scanning electron studies of the cuticle overlying the groups of sensilla. Each sensillum possesses a specialized fan-shaped terminal containing a complex and ordered association of microtubules and filaments. The transmission of stress to this region via the cuticle, and its possible role in transduction is considered. The fine structure of apical and basal sections of the distal sensory process and associated sheath cells is described; the functional significance of the distribution of mitochondria and other components is discussed. The organization of haltere chordotonal sensilla is described briefly, and compared with other mechanoreceptors with particular reference to microtubules and scolopale structures.     

Synthesis and turnover of hdRNA and mRNA in the salivary gland of the blowfly Calliphora erythrocephala.

We have measured the absolute molar rates of synthesis, accumulation, and turnover of blowfly salivary gland heterodisperse RNA. Twelve- and 84-hr-stage third-instar Calliphora erythrocephala larvae were injected with [³H]adenosine, and its flow into glandular ATP, heterodisperse RNA, and polyadenylated RNA was each quantitated over a 360-min time course. The results of these experiments indicate that at least 80% of the newly synthesized heterodisperse RNA mass is a >28 S nuclear species whose average first-order half-life is approximately 20 min. The remaining 20% of the heterodisperse RNA has a 6–28 S size distribution, accumulates in the cytoplasm, and is associated with functional polysomes. The average first-order half-life of this more stable species is 20–25 hr. In addition, we have independently quantitated by optical methods the developmental change in the content of polysome-associated mRNA. The mRNA in these studies also has an average first-order half-life of 25 hr and accounts for 25–55% of the mRNA mass predicted by the incorporation-kinetic analysis of the pulse-labeled heterodisperse RNA. Despite the increased polyteny of the older stage glands, the rates of synthesis and accumulation of each of the individual heterodisperse RNA classes are the same at the 12- and 84-hr stages. Collectively, these results demonstrate that salivary gland functional specialization results from the accumulation of long-lived mRNA and not from changes in the overall rate of mRNA synthesis.     

Functional-morphological investigations on the flight muscles and their insertion points in the blowfly Calliphora erythrocephala (Insecta,Diptera)

Summary In flies, for example the blowfly Calliphora erythrocephala, the thorax has fused to form a chitinous capsule. In it we find three functional types of flight muscles, the indirect flight muscles, the direct, and the tension muscles. The indirect or wing beat muscles transfer their power to the capsule which is capable of oscillating. They are suspended nearly horizontally and vertically. The direct muscles used for steering insert laterally on the capsule and go to the wing joint. The third functional type of flight muscle serves to put the lateral walls of the thorax under tension. The site and morphology of the flight muscles are described in detail, making use of 3-dimensional drawings. The flight muscles of Calliphora erythrocephala (Heide 1968) and their functions are compared with those of other dipterans described by different authors.With support of the Deutsche Forschungsgemeinschaft to Professor Nachtigall     

Ultrastructural immunocytochemical localization of vitellogenin in the fat body of the blowfly,Calliphora vicina Rob.-Desv. (erythrocephala Meig.) by use of the unlabeled antibody-enzyme method

Summary The unlabeled antibody-enzyme method was used to demonstrate ultrastructurally the specific localization of vitellogenin in the fat body of Calliphora. In control flies the binding sites to vitellogenin were localized in secretory granules situated in the Golgi complex, and in larger bodies named composite secretory granules. These composite granules appear to be formed when a part of a Golgi complex containing secretory granules and a number of small vesicles become surrounded by a common membrane. Ovariectomized flies, which apparently do not produce secretory granules, exhibited no immunocytochemical staining. Ovariectomized flies in which the administration of ecdysterone induced formation of secretory granules, also revealed specific staining on these granules. This is the first ultrastructural evidence of: (a) the specific localization of vitellogenin in secretory granules of the fat body of an insect; (b) the relationship between the presence of the ovary, and of ecdysterone, and the synthesis of vitellogenin by the fat body.     

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.     

Lyriform slit sense organs on the pedipalps and spinnerets of spiders

Lyriform slits sense organs (LSSO) are a precise assembly of stress detecting cuticular slit sensilla found on the appendages of arachnids. While these structures on the legs of the wandering spiderCupennius salei are well studied in terms of morphology, function and contribution to behaviour, their distribution on pedipalps and spinnerets of spiders is not well explored. A study was therefore carried out to observe the distribution of LSSO on pedipalps and spinnerets of some spider species. Haplogyne spiders belonging to familyPholcidae have a simple complement of LSSOs represented by one or two LSSOs on their femur. The entelegyne spiders possess a complex assembly of LSSOs on the distal segments of their pedipalps. Various types of LSSOs are found on the pedipalps indicating a capacity for analysis of complex cuticular stress. It is suggested that the complexity of LSSOs on pedipalps of entelegyne spiders relates to courtship and spermatophore transfer and may help in reproductive isolation. Lack of LSSOs on the distal segments of pedipalps leads us to infer that unlike legs, pedipalps are less likely to receive vibratory input through their distal segments. Spinnerets have a relatively simple complement of LSSOs. One LSSO is found only on anterior spinnerets and it is a common feature observed among spiders, irrespective of the variations in web building behaviour. The orb-weaving araneidArgiope pulchella, however, has two LSSOs on the anterior spinneret. As non-web builders and orb weavers do not differ markedly in terms of LSSOs on the spinnerets and LSSOs are simple in nature (type A), it is likely that spinning and weaving are not largely regulated by sensory input from LSSOs on the spinnerets.     

The effect of chromosomal polytenization on the rates of RNA synthesis and decay in the salivary glands of the blowfly, Calliphora erythrocephala

The rates of total RNA synthesis and accumulation have been measured in the polytenic salivary gland cells of the blowfly, Calliphora erythrocephala, by three methods: (1) injecting larvae with [2-³H]adenosine and determining its flow into the cellular ATP pool and RNA, (2) measuring the increase in glandular RNA optically, and (3) measuring the rate of flow of ATP out of the cellular pool. The size of the steady-state pool of rapidly turning over RNA and its half-life, were calculated from these kinetic data and, also, by an independent measurement of the steady-state content of nuclear RNA. These parameters were compared at a number of developmental stages which differed in degree of chromosomal polytenization. The results indicate that these polytenic cells synthesize RNA at a rate approximately 10³ times those of other diploid eukaryotic cells. This rate is independent of the increase in chromosomal polyteny that accompanies larval development. Approximately 67% of the newly synthesized salivary gland RNA is an unstable component with an average first-order half-life of 20–25 min. The remainder is a long-lived species with an estimated average first-order half-life of about 30 hr.     

Optical properties of the ocelli of Calliphora erythrocephala and their role in the dorsal light response

The 3 ocelli of the blowfly Calliphora erythrocephala, grouped close together on the top of the head (Fig. 1), have large, extensively overlapping visual fields. Together they view the entire upper hemisphere of the surroundings plus part of the lower hemisphere (Figs. 5, 7). It is shown for the lateral ocelli that despite the underfocussing of the ocellar lens large patterns are imaged on the receptor mosaic. Because of the astigmatism of the lens, patterns in longitudinal orientations are more accurately represented than in others (Fig. 3). Nevertheless, an artifical horizon rotated around the long axis of the animal does not elicit head roll. Likewise, changes of overall brightness in the visual field of the median and one lateral ocellus elicit only weak phasic-tonic dorsal light responses of the animal which supplement the tonic dorsal light responses mediated by the compound eyes (Figs. 9, 10). Our results show that, in Calliphora, the ocelli have little influence on head orientation during flight, and must be assumed to serve other functions.Abbreviations body pitch angle - head-tilt angle - DNOVS descending neuron of the ocellar and vertical cell systems - HR head roll - spatial wavelength - R roll angle - SD standard deviation     

The organization of giant horizontal-motion-sensitive neurons and their synaptic relationships in the lateral deutocerebrum of Calliphora erythrocephala and Musca domestica

Summary Three giant horizontal-motion-sensitive (HS) neurons arise in the lobula plate. Their axons terminate ipsilaterally in the medial deutocerebrum and suboesophageal ganglion. Both Golgi impregnations and cobalt fills demonstrate that endings of the two HS cells, representing the upper and middle third of the retina, differ in shape and location from that of the HS cell subtending the lower third of the eye. This dichotomy is reflected by the terminals of a pair of centrifugal horizontal cells (CH), one of which invades lobula plate neuropil subtending the upper two-thirds of the retina. The other overlaps the dendrites of the HS cell subtending the lower one-third of the retina.The HS cells are cobalt-coupled to a variety of complexly arborizing descending neurons. In Musca domestica, gap-junction-like apposition areas have been observed between HS axon collaterals and descending neuron dendrites. The three HS cells also share conventional chemical synapses with postsynaptic elements, which include the dendritic spines of descending neurons. Unlike the giant vertical-motion-sensitive neurons of the lobula plate, whose relationships with descending neurons appear to be relatively simple, the horizontal cells end on a large number of descending neurons where they comprise one of several different populations of terminals. These descending neurons terminate within various centres of the thoracic ganglia, including neuropil supplying leg, neck, and flight muscle.     

The influence of forskolin on the metabolism of ecdysone and 20-hydroxyecdysone in isolated fat body of the blowfly, Calliphora vicina

Rates of ecdysone and 20-hydroxyecdysone metabolism were measured by radio-assay in an in vitro system containing fat body isolated from blowfly larvae. The addition of forskolin which is known to stimulate artificially the intracellular adenylate cyclase system led to decreased rates of conversion of ecdysone into 20-hydroxyecdysone (= hormone activation) and of 20-hydroxyecdysone further to other metabolites (= hormone inactivation). The effect of forskolin was dose-dependent and reversible. Extracts prepared from larval brains were also tested. Some of them had the same effect as forskolin. It is concluded that the reactions leading from ecdysone to 20-hydroxyecdysone and further to hormonally inactive ecdysteroids are modulated by the intracellular level of cyclic nucleotides. We propose that a neurohormone is involved in the control of the reactions of the ecdysone metabolism. The observed new principle may contribute to the control of the titer of moulting hormone.     

Comparison of lymphocyte production in lymphoid organs and their compartments using the metaphase-arrest technique

Summary Lymphocyte proliferation was studied in normal young anesthetized pigs by the metaphase-arrest technique using vincristine (VCR). In each animal biopsies were taken simultaneously from the thymus, mesenteric lymph nodes, spleen, palatine tonsil and Peyer's patches from the ileum and jejunum. After taking the first samples, 0.25 mg VCR/ kg body weight was injected i.v. and then four more biopsies were excised for up to 3.5 h after VCR. Imprints of the lymphoid organs were evaluated as an overall index for each organ, and histological sections were used to determine the mitotic index in typical B-and T-lymphocyte areas in these organs. In follicles of mesenteric lymph nodes, tonsils and the two types of Peyer's patches a comparable increase in the mitotic index was found, 3.62% per hour. In the corona the increase was also comparable but much lower, 0.43% per hour and in the interfollicular area similarly 0.38% per hour. In the spleen the mitotic rate was 0.69% for the white pulp and 0.42% per hour for the red pulp. In the thymic cortex the mitotic index increased by 0.49% and in the medulla by a surprisingly high value of 0.32% per hour. The metaphase-arrest technique in larger animals enables a comparison of lymphocyte production among organs and their different compartments, and demonstrates the important contribution of peripheral lymphoid organs to the renewal of the lymphocyte pools.List of Abbreviations DNA deoxyribonucleic acid - ¹⁴C-TdR thymidine labelled with ¹⁴C - ³H-TdR tritiated thymidine - r_m rate of entry of cells in mitosis per hour - VCR vincristine sulphatePartly presented at the XII Int. Anat. Congress in London, August 1985     

The effect of larval temperature and photoperiod on the incidence of larval diapause in the blowfly, Calliphora vicina

ABSTRACT. The blowfly, Calliphora vicina Meigen (Diptera: Calliphoridae), displays a maternally induced larval diapause. Progeny of adults exposed to short days enter diapause if the larval temperature is 15C or below; exposing adults to long days, or larvae to temperatures above 15C, results in non-diapause. By keeping progeny from short-day parents at the parental temperature of 23.5C for various lengths of time before transfer to 11C, it could be shown that the diapause-averting effect of high temperature operates in the late wandering stage of larva, possibly at the moment of the decision for the brain-ring gland complex to release PTTH/ecdysone at the diapause/non-diapause stage.
Although photoperiodic induction in the blowfly is maternal, previous work had shown that the larvae were also slightly sensitive to photoperiod. From the present study it is evident that also the eggs are photo-sensitive.