The morphology of suboesophageal ganglion cells innervating the nervus corporis cardiaci III of the locust

Summary The nervus corporis cardiaci III (NCC III) of the locust Locust migratoria was investigated with intracellular and extracellular cobalt staining techniques in order to elucidate the morphology of neurons within the suboesophageal ganglion, which send axons into this nerve. Six neurons have many features in common with the dorsal, unpaired, median (DUM) neurons of thoracic and abdominal ganglia. Three other cells have cell bodies contralateral to their axons (contralateral neuron 1–3; CN 1–3). Two of these neurons (CN2 and CN3) appear to degenerate after imaginal ecdysis. CN3 innervates pharyngeal dilator muscles via its anterior axon in the NCC III, and a neck muscle via an additional posterior axon within the intersegmental nerve between the suboesophageal and prothoracic ganglia. A large cell with a ventral posterior cell body is located close to the sagittal plane of the ganglion (ventral, posterior, median neuron; VPMN). Staining of the NCC III towards the periphery reveals that the branching pattern of this nerve is extremely variable. It innervates the retrocerebral glandular complex, the antennal heart and pharyngeal dilator muscles, and has a connection to the frontal ganglion.Abbreviations AH antennal heart - AN antennal nerves - AO aorta - AV antennal vessel - CA corpus allatum - CC corpus cardiacum - CN1, CN2, CN3 contralateral neuron 1–3 - DIT dorsal intermediate tract - DMT dorsal median tract - DUM dorsal, unpaired, median - FC frontal connective - FG frontal ganglion - HG hypocerebral ganglion - LDT lateral dorsal tract - LMN, LSN labral motor and sensory nerves - LN+FC common root of labral nerves and frontal connective - LO lateral ocellus - MDT median dorsal tract - MDVR ventral root of mandibular nerve - MVT median ventral tract - NCA I, II nervus corporis allati I, II - NCC I, II, III nervus corporis cardiaci I, III - NR nervus recurrens - NTD nervus tegumentarius dorsalis - N8 nerve 8 of SOG - OE oesophagus - OEN oesophageal nerve - PH pharynx - SOG suboesophageal ganglion - T tentorium - TVN tritocerebral ventral nerve - VLT ventral lateral tract - VIT ventral intermediate tract - VMT ventral median tract - VPMN ventral, posterior, median neuron - 1–7 peripheral nerves of the SOG - 36, 37, 40–45 pharyngeal dilator muscles     

Moulting hormone,juvenile hormone and the ultrastructure of the fat body of adult Sarcophaga bullata (Diptera)

Summary In the ovoviviparous fly, Sarcophaga bullata, vitellogenesis is cyclic; a process reflected in ultrastructural changes in the fat body cells and oenocytes. At eclosion the larval fat body has not yet completely disappeared. During vitellogenesis the fat body cells are specialized for intensive protein synthesis showing a very extensive RER and numerous invaginations of the plasma membrane. These features disappear when the eggs descend into the oviducts to complete embryogenesis. The predominant feature of the oenocytes is their very prominent SER. The fat body cells of the males are never as specialized for protein synthesis as those of the females. Feeding of ecdysterone to males for 3 or more days induces a rather extensive subcellular apparatus for protein synthesis, i.e., invaginations of the plasma membrane and an extensive RER. Juvenile hormone is completely ineffective in this respect. Both ecdysterone and juvenile hormone have pronounced but different effects on the oenocytes of males.     

Variations in ecdysteroid levels in 5th instar larvae of Schistocerca gregaria in gregarious and solitary phases

Moulting hormone levels in whole bodies of 5th instar S. gregaria were determined throughout the 5th larval instar using gas chromatography with electron capture detection of the derivatized hormone. No differences were found between hormone levels in insects in the gregarious and solitary phase. No evidence for the existence of polar ecdysteroid conjugates used for storage or transport of these hormones was found. Approximately one tenth of the 20-hydroxyecdysone observed in the gregarious insects was detected in the faeces, almost equally divided between free hormone and polar conjugates of it.     

Ultrastructural development of the neurohemal organ joined to the ecdysial gland after imaginal moulting in the male isopod Sphaeroma serratum fab. (Crustacea Flabellifera)

Summary The present ultrastructural study deals with the lateral cephalic nerve plexus of Sphaeroma serratum, a neurohemal organ joined to the Y organ (ecdysial gland). This plexus acts as a storage centre for neurosecretory products from two sources: the two autochtonous cells (plexus cells) within the plexus itself, and the neurosecretory cells in various parts of the central nervous system, particulary the mandibular ganglion (A-cells).In prepuberal animals, plexus cells and subesophageal A-cells produce neurosecretory granules of two types measuring 1550±50Å and 1570±40Å respectively. Five categories of axon terminals were distinguished in the plexus. The granules found in two of these terminal types are believed to come from the plexus cells and from the mandibular ganglion A-cells.Cessation of production of neurosecretory granules in these A cells and plexus cells was observed in puberal animals, in the plexus with concomitant depletion and disappearance of different granule categories. The first axon terminals affected by this process are the two categories containing granules originating in the plexus and mandibular ganglion A-cells. Degeneration of the ecdysial gland in male Sphaeroma serratum might be connected with the cessation of granule formation in these two types of cell.

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Résumé Chez Sphaeroma serratum, la mue de puberté est suivie d'une dégénérescence de l'organe Y (glands de mue). Le plexus nerveux céphalique latéral, organe neurohémal accolé à cette glande a été l'objet de la présente étude ultrastructurale. Cet organe représente un centre de stockage de neurosécrétions qui proviennent d'une part, de deux cellules autochtones (cellules plexales) situées au sein même de ce plexus, d'autre part, de cellules neurosécrétrices situées dans le ganglion mandibulaire (cellules de type A).Chez les individus pubères, les cellules plexales et les cellules A du ganglion sous-oesophagien synthétisent des granules de neurosécrétion dont la taille est respectivement 1550±50Å et 1570±40Å. Il a été reconnu au sein du plexus 5 catégories de terminaisons dont les granules proviendraient pour deux d'entre elles des cellules plexales et des cellules A du ganglion mandibulaire. Chez les animaux pubères on observe un arrêt de la synthèse des granules de neurosécrétion au sein des cellules plexales et des cellules A du ganglion mandibulaire. Simultanément on enregistre dans le plexus la raréfaction puis la disparition des divers types de granules. Ce processus atteint en premier les terminaisons correspondant aux cellules plexales et aux cellules A du ganglion mandibulaire. La dégénérescence de la glande de mue chez les mâles pourrait être en relation avec l'arrêt de synthèse de ces cellules.

     

Ultrastructure of the Y-organ of Astacus astacus (L.) (Crustacea) in relation to the moult cycle

Summary The electron microscopical investigation of Y-organs of Astacus astacus revealed that during intermoult (stage C) the cytoplasm is poorly developed and that it increases at premoult (stage D). It then shows the typical signs of steroid production, namely agranular endoplasmic reticulum and mitochondria of the tubular type. Furthermore, a larger type of mitochondria with a regular pattern of internal structure is described.Supported by Sächsische Akademie der Wissenschaften zu LeipzigWe are grateful for technical assistance to Mrs. B. Cosack und Mrs. A. Schmidt     

Mitochondrial-driven sustained active water vapour absorption (WVA) in the firebrat, Thermobia domestica (Packard), during development and the moulting cycle

Rapid pre-functional mitochondrial biogenesis in the short-lived first-instar nymph occurs in the cells of the developing posterior rectal sacs which when mature are the organs believed to be responsible for sustained active water vapour absorption (WVA) in the firebrat Thermobia domestica (Packard). During the second instar, the mitochondria migrate apically and begin to associate with deep portasome-studded infolds of the apical plasma membrane (apm), just as WVA starts sporadically. By mid to late in the third instar the mature mitochondria-apm apical complex is fully developed, with elongated tubular mitochondria vertically packed hexagonally in transverse section and adpressed to the deeply pleated infolds of the apm, giving the greatest known concentration of mitochondria. This coincides with peak mass-specific WVA. During moults, WVA temporarily ceases as the sac cells secrete a new cuticle overlying the sac epithelium. Their apical complex fully regresses. Mitochondria migrate perinuclearly. The apm is pinched-off into numerous small portasome-studded pouches which remain sequestered within the cytoplasm. Towards the end of the moult the apm pouches reassemble into deeply pleated infolds into which the mitochondria migrate and elongate, rapidly re-establishing the hexagonal array of the apical complex. This coincides with the recommencement of WVA.     

Prothoracic gland involution related to moulting hormone levels during the metamorphosis of Tenebrio molitor L.

Prothoracic gland (PG) of Tenebrio shows ultrastructural changes which can be correlated with ecdysteroid levels (measured by radioimmunoassay) during larval-pupal development. However, the gland cells begin to degenerate before pupal-adult ecdysis: the PG involution is completed before the moulting hormone peak which triggers pupal-adult development. These facts strongly suggest that another endocrine organ produces moulting hormone needed for adult development.     

Ecdysteroid levels throughout the life cycle of the desert locust, Schistocerca gregaria

Moulting hormone levels for all stages of the life cycle of the desert locust, Schistocerca gregaria, have been determined using gas chromatography with electron capture detection of the trimethylsilylated hormones. During larval development, the major hormone detected is 20-hydroxyecdysone with smaller quantities of ecdysone present. In mature adult females the major ecdysteroid observed is a polar conjugate of ecdysone, with smaller quantities of conjugated 20-hydroxyecdysone also present. During embryonic development the pattern changes from a high proportion of conjugated ecdysone in the early stages to give more free hormone and a higher proportion of 20-hydroxyecdysone in later stages. The highest titre of 20-hydroxyecdysone found in this insect is during the 5th larval instar. Maximal levels of ecdysteroid per insect are found in mature females just before oviposition, while the highest level of ecdysteroid per g of tissue is found in the eggs.     

Maternal death relaxes developmental inhibition in nymphal aphid defenders

In certain aphids, first-instar nymphs defend their gall by attacking intruding arthropod predators. One correlate of such defensive behaviour is a lengthened duration of the first nymphal stadium during the galling phase of the life cycle. A prolonged first stadium allows a large army of first-instar defenders to accumulate, which may be advantageous for gall defence. The factors determining developmental delay have been unclear, however. Our field experiment with Pemphigus obesinymphae, a North American gall-forming aphid with defensive first-instar nymphs, tests whether first-stadium duration is influenced by the death of the colony''s fundatrix (mother). We killed fundatrices in certain galls, left those in control galls alive, and counted aphids in each stadium in each gall. Galls in which fundatrices were killed contained a lower proportion of first-instar defenders and more late-instar nymphs than did galls with living fundatrices, indicating that maternal death dramatically increased developmental rate of nymphs. Possibly nymphal aphids respond adaptively to environmental cues that signal a threat to the colony''s welfare. Alternatively, the fundatrix actively suppresses offspring development in order to maintain a large army of soldiers to protect her gall. The results add a new layer of complexity to our understanding of social aphid systems.     

In vitro stimulation of cell death in the moulting glands of Oncopeltus fasciatus by 20-hydroxyecdysone

The moulting glands of the milkweed bug, Oncopeltus fasciatus, normally degenerate just before the time of ecdysis to an adult (day 7 of the fifth instar). Morphologically normal cell death can be prematurely stimulated in vitro by 20-hydroxyecdysone. Breakdown is triggered by a 24-hr period of exposure to 20-hydroxyecdysone, but an additional incubation period is required before clear signs of degeneration are manifested. Glands removed after the onset of endogenous ecdysteroid secretion degenerate in vitro in the absence of added hormones. Thus, in the moulting glands of Oncopeltus, ecdysteroids appear to act as an important trigger for metamorphic cell death.