(AGCTG) (AGCTG) (AGCTG) (GGGTG) as the primordial sequence of intergenic spacers: the role in immunoglobulin class switch

The means employed for immunoglobulin heavy chain class switch appears to be no different from that by which meiotic intergenic crossing-overs at accomplished. As with other intergenic spacers, the 5' noncoding sequence of each Ig CH (immunoglobulin heavy chain constant region) gene apparently undergoes unconstrained sequence changes due to randomly sustained base substitutions, deletions, and duplications. Yet, there remains sufficient regional sequence homology between the Ig Cmu 5' noncoding sequence and those of its somatic recombination partners, e.g., Ig C gamma 1, Ig C gamma 2b, Ig C alpha, because each of these 5' noncoding sequences is made of multiple copies in various stages of degeneracy of one primordial 20 base pair-long sequence: (AGCTG) (AGCTG) (AGCTG) (GGGTG).     

Ultrastructure of the intracellular melanization of Brugia malayi (Buckley) (Nematoda : Filarioidea) in the thoracic muscles of Anopheles quadrimaculatus (Say) (Diptera : Culicidae)

Ultrastructural details of the melanization of the filarial parasite Brugia malayi (Nematoda : Filarioidea) in the thoracic muscle cell of selected susceptible and refractory strains of Anopheles quadrimaculatus (Diptera : Culicidae) were examined. In both susceptible and refractory strains, following infection of the muscle cells, there is a dissolution of the sarcoplasmic cytoskeletal matrix surrounding the myofibrils, causing the myofibrils and mitochondria to drift apart and lose their regular spacing. This is coupled with a reorganization of the cytoplasm near the normally developing intracellular larva. Masses of vesicles and vesiculated cytoplasmic bodies accumulate near the larva. Eventually, these form a dense layer of cytoplasm around the parasite. Fine grains of melanin begin to appear in this dense cytoplasmic layer, increasing gradually until a nearly complete capsule of melanin surrounds the larva. The time course of melanization was found to be quite variable among and even within mosquitoes. Strains of A. quadrimaculatus selected to be refractory or susceptible to B. malayi, were found to vary substantially in the frequency of intracellular melanization, but not in the mechanism.     

Choriogenesis in the medfly Ceratitis capitata (Wiedermann) (Diptera : Tephritidae)

Four chorionic stages (11, 12, 13, 14) can be discerned in the medfly Ceratitis capitata (Diptera : Tephritidae) by light microscope. More detailed staging (stages 11A, 11B, 12A, 12B, 12C, 13A, 13B, 13C, 14A and 14B) is possible only by electron microscope. Throughout these stages, the first chorionic layer (wax layer) is formed at stage 11A, followed by the formation of the innermost chorionic layer (stage 12A), the inner endochorion, the pillars and the cavities of the first trabecular layer (stage 12), creation of the second trabecular layer and the chorionic network (stage 13), and finally the secretion of the exochorionic layers (stage 14). Pulse-chase autoradiography has revealed that the follicle cells are responsible for the synthesis of all proteinaceous layers. No extensive regional complexity is observed besides the existence of the micropylar apparatus and aeropyles in the anterior pole. Biochemical analysis has revealed several eggshell proteins and their stage-specific synthesis: two intermediate molecular-weight proteins are the major chorion proteins; in addition, there are 2 more groups comprising 6 proteins, which might be characteristic for the different chorion layers as can be deduced by their stage-electrophoretic pattern.     

Malformations of the genitalia in male Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae)

Phlebotomus papatasi ( Scopoli, 1786 ) (Diptera: Psychodidae) is a major vector of Leishmania major (Kinetoplastida: Trypanosomatidae), a causative agent of zoonotic cutaneous leishmaniasis. Morphological characters of sand fly genitalia are key indicators for species identification. Various anomalies affecting male genitalia have been previously described. We take advantage of a large sand flies survey conducted in 32 stations in Central and Southern Morocco to systematically quantify the prevalence and spatial distribution of malformations affecting the genitalia of P. papatasi. Among 597 examined males, 122 were abnormal (20.4%). Malformations were widespread and largely concerned the number of spines in the lateral lobes and in the styles. Asymmetrical anomalies in lateral lobes were common. Correspondence analysis of our results highlighted the symmetrical anomalies observed in the lateral lobes, and abnormal styles of the male genitalia were found to be associated with environmental disturbances since they were prevalent in sewage dumps.     

Segregation of autosomes during spermatogenesis in the peach-potato aphid (Myzus persicae) (Sulzer) (Hemiptera: Aphididae)

Most aphids are cyclic parthenogens, so are ideal models in studies of the mechanisms and consequences of sex and recombination. However, owing to a shortage of physical and genetic markers, there have been few studies of the most fundamental genetic processes in these organisms. For example, it is not known whether autosomal segregation during male spermatogenesis is in Mendelian proportions: we address that question here. The aphid Myzus persicae has a typical karyotype of 2n = 12 in females (XX), while males are XO (2n = 11). During male meiosis, only the spermatocytes with an X chromosome are viable. We hypothesized that assortment of autosomes might be non-random because chromosomal imprinting leading to elimination of the paternal autosomes is seen in the closely related coccoids. In other aphid models, we have observed segregation distortions at single microsatellite loci (Wilson, 2000). Such distortions may have nothing to do with 'selfish' behaviour, but may be caused by mutation accumulation causing fitness differentials. Thus single-locus distortions might be predicted to be more likely to be detected via the male lines of clones that have lost the ability to reproduce sexually (male-producing obligate parthenogenesis (androcyclic)). Using microsatellites we show that genetic imprinting or selfish autosome behaviour does not occur in male M. persicae. Generally, loci segregated in Mendelian proportions in both sexes of cyclically parthenogenetic (holocyclic) clones. However, in androcyclic clones, segregation distortions consistently involved the same two autosomes. This is consistent with linkage of markers to deleterious mutations associated with a loss of sexual reproduction.     

Phylogenetic systematics of the Empis (Coptophlebia) hyalea-group (Insecta: Diptera: Empididae)

Six clades are inferred from a phylogenetic analysis including 42 species belonging to the Empis (Coptophlebia) hyalea‐group. These clades are named as follows: E. (C.) acris, E. (C.) aspina, E. (C.) atratata, E. (C.) hyalea, E. (C.) jacobsoni and E. (C.) nahaeoensis. The presence of two dorsal more or less developed epandrial projections is considered autapomorphic for the E. (C.) hyalea‐group in addition to two characters previously found to support the monophyly of this group (presence of an unsclerotized zone in the middle of labella and epandrium unpaired). Amongst the cladistically analysed species, 24 are newly described [ E. ( C. ) acris , E. ( C. ) aspina , E. ( C. ) cameronensis , E. ( C. ) duplex , E. ( C. ) incurva , E. ( C. ) inferiseta , E. ( C. ) kuaensis , E. ( C. ) lachaisei , E. ( C. ) lamellalta , E. ( C. ) lata , E. ( C. ) loici , E. ( C. ) longiseta , E. ( C. ) mengyangensis , E. ( C. ) menglunensis , E. ( C. ) missai , E. ( C. ) nimbaensis , E. ( C. ) padangensis , E. ( C. ) parvula , E. ( C. ) projecta , E. ( C. ) pseudonahaeoensis , E. ( C. ) submetallica , E. ( C. ) urumae , E. ( C. ) vitisalutatoris and E. ( C. ) woitapensis ], five are reviewed [E. (C.) hyalea Melander, E. (C.) jacobsoni De Meijere, E. (C.) ostentator Melander, E. (C.) sinensis Melander and E. (C.) thiasotes Melander] and 13 were recently described in two previous papers. Two additional species, E. (C.) abbrevinervis De Meijere and E. (C.) multipennata Melander, are also reviewed but not included in the cladistic analysis since they are only known from the female. A lectotype is designated for E. (C.) jacobsoni. A key is provided to the six clades of the E. (C.) hyalea‐group as well as to species of each clade. A catalogue of the E. (C.) hyalea‐group, including 72 species, is given. The taxonomic status of 25 additional species mainly described by Bezzi and Brunetti, from the Oriental and Australasian regions, is discussed. The E. (C.) hyalea‐group is firstly recorded from the Palaearctic Region and Australia. Finally, the distribution and the habitats of the species compared with their phylogeny suggest a possible relationship between the diversification of the group and forest fragmentations during the Quaternary. © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society, 2005, 145 , 339–391.     

(AGCTG) (AGCTG) (AGCTG) (GGGTG) as the Primordial Sequence of Intergenic Spacers: The Role in Immunoglobulin Class Switch

The means employed for immunoglobulin heavy chain class switch appears to be no different from that by which meiotic intergenic crossing-overs are accomplished. As with other intergenic spacers, the 5' noncoding sequence of each Ig C_H (immunoglobulin heavy chain constant region) gene apparently undergoes unconstrained sequence changes due to randomly sustained base substitutions, deletions, and duplications. Yet, there remains sufficient regional sequence homology between the Ig C_μ 5' noncoding sequence and those of its somatic recombination partners, e.g., Ig C_γ1, Ig C_γ2b, Ig C_α, because each of these 5' noncoding sequences is made of multiple copies in various stages of degeneracy of one primordial 20 base pair-long sequence: (AGCTG) (AGCTG) (AGCTG) (GGGTG).     

Ultrastructure of the lateral organs in larvalArgas (Persicargas) arboreus (Ixodoidea: Argasidae)

The ultrastructure of lateral organs (LO) in the larval tickArgas (Persicargas) arboreus is described before and after feeding and up to the 1st day of moulting. Three pairs of LO are associated with three pedal nerves arising from the synganglion. In unfed ticks, each LO is ensheathed by a neural lamella and consists of 6–7 neuronal cell bodies; their cytoplasm is mostly occupied by cisternae of rough endoplasmic reticulm (RER). In fully engorged ticks, the enlarged neuronal cells contain vacuolar cisternae of smooth endoplasmic reticulum (SER), coated vesicles and mitochondria. Golgi bodies are involved in the formation of neurosecretory granules which dominate, with the SER vacuoles, the cell cytoplasm before moulting. The vacuoles, coated vesicles and neurosecretory granules are similar to those found in the vertebrate steroid-secreting cells. Condensing vacuoles may fuse with lysosome-like bodies to form larger ones; these are possibly responsible for the cell breakdown when secretory products are no longer required. Ultrastructural observations of LO suggest that they are neuroendocrine glands and that, in engorged larvae, they may secrete a hormone involved in the control of moulting.     

Species in the genus Rhytidelasma Gaud (Acarina: Pterolichidae) from the Green Conure,Aratinga holochlora (Sclater) (Aves: Psittacidae)

Three species in the genus Rhytidelasma Gaud (Pterolichoidea: Pterolichidae) are known from the Green Conure, Aratinga holochlora (Sclater): R. cornigera n. sp., R. urophila n. sp. and R. mesomexicana Atyeo et al. The new species are described, and the microhabitat(s) for each species discussed.     

Fine structure of muscles in the tickHyalomma (Hyalomma) dromedarii (Ixodoidea: Ixodidae)

Skeletal and visceral muscles are distinguished in the unfed nymphHyalomma (Hyalomma) dromedarii according to position, structure and function. The skeletal muscles include the capitulum, dorsoventral and leg oblique muscles. Their muscle fibres have the striated pattern of successive sarcomeres whose thick myosin filaments are surrounded by orbitals of up to 12 thin actin filaments. The cell membrane invaginates into tubular system (T) extending deeply into the sarcoplasm and closely associated to cisternae of sarcoplasmic reticulum (SR). The T and SR forming two-membered dyads are considered to be the main route of calcium ions whose movements are synchronized with the motor impulse to control contraction and relaxation in most muscles. Two types of skeletal muscle fibres are recognized, and are suggested as representing different physiological phases.In the visceral-muscle fibres investing tick internal organs, the actin and myosin filaments are slightly interrupted, and the T and SR are well demonstrated. Both skeletal and visceral muscles are invaginated by tracheoles and innervated by nerve-axons containing synaptic vesicles.     

Small-scale elevational variation in the abundance of Eufriesea violacea (Blanchard) (Hymenoptera: Apidae)

Eufriesea violacea (Blanchard) males were sampled in a small-scale elevational gradient in Southeastern Brazil and showed sequential peaks of abundance from lowest (700 m) to highest (1,100 m) altitudes during the sampling period. The influence of the temperature on the length of the egg-to-adult period and flowering dates of plants producing food (nectar) suggests that it may be one of the factors determining the distribution of male abundance along the altitudinal gradient. The results emphasize the importance of obtaining altitudinal stratified samples when studying Euglossini populations, especially when the studies are done at sites with marked topographical variation.     

Development of Amblyospora campbelli (Microsporida: Amblyosporidae) in the mosquito Culiseta incidens (Thomson)

The complete life cycle of Amblyospora campbelli (Kellen and Wills, 1962) (Microsporida: Amblyosporidae) requires a two-host system involving the mosquito host, Culiseta incidens (Thomson), and an obligatory intermediate copepod host. The parasite has dimorphic spore development producing meiospores (haploid condition) and binucleated spores (diploid condition), either as an exclusive infection or simultaneously (within females only). This is the 1st known report of concurrent spore development within an adult mosquito host, and, therefore, shows the Amblyospora campbelli system to be uniquely different from other Amblyospora spp. cycles previously described. The significance of dimorphic spore development is discussed. In females, diplokaryotic meronts may invade oenocytes, causing a benign-type of infection. A blood-meal is required to initiate sporulation of the binucleate spore. The binucleate spore contains the sporoplasm involved in transovarial transmission. A 2nd sporulation sequence, primarily in adipose tissue, may involve both males and females. In this sequence, repeated merogonic division greatly increased the density of diplokaryotic meronts and generally involved most of the body of the host. Production of meiospores, unlike that for the binucleate spore, appeared to be spontaneous (i.e. no obligatory blood meal). Survivorship of male and female larval mosquitoes was nearly equal. Adult females spread the parasite in three ways: transovarial, transovum, and by meiospore deposition.     

d(CGGTGGT) forms an octameric parallel G-quadruplex via stacking of unusual G(:C):G(:C):G(:C):G(:C) octads

Among non-canonical DNA secondary structures, G-quadruplexes are currently widely studied because of their probable involvement in many pivotal biological roles, and for their potential use in nanotechnology. The overall quadruplex scaffold can exhibit several morphologies through intramolecular or intermolecular organization of G-rich oligodeoxyribonucleic acid strands. In particular, several G-rich strands can form higher order assemblies by multimerization between several G-quadruplex units. Here, we report on the identification of a novel dimerization pathway. Our Nuclear magnetic resonance, circular dichroism, UV, gel electrophoresis and mass spectrometry studies on the DNA sequence dCGGTGGT demonstrate that this sequence forms an octamer when annealed in presence of K(+) or NH(4)(+) ions, through the 5'-5' stacking of two tetramolecular G-quadruplex subunits via unusual G(:C):G(:C):G(:C):G(:C) octads.     

Development of Amblyospora campbelli (Microsporida: Amblyosporidae) in the Mosquito Culiseta incidens (Thomson)

The complete life cycle of Amblyospora campbelli (Kellen and Wills, 1962) (Microsporida: Amblyosporidae) requires a two-host system involving the mosquito host, Culiseta incidens (Thomson), and an obligatory intermediate copepod host. The parasite has dimorphic spore development producing meiospores (haploid condition) and binucleated spores (diploid condition), either as an exclusive infection or simultaneously (within females only). This is the 1st known report of concurrent spore development within an adult mosquito host, and, therefore, shows the Amblyospora campbelli system to be uniquely different from other Amblyospora spp. cycles previously described. The significance of dimorphic spore development is discussed. In females, diplokaryotic meronts may invade oenocytes, causing a benign-type of infection. A blood-meal is required to initiate sporulation of the binucleate spore. The binucleate spore contains the sporoplasm involved in transovarial transmission. A 2nd sporulation sequence, primarily in adipose tissue, may involve both males and females. In this sequence, repeated merogonic division greatly increased the density of diplokaryotic meronts and generally involved most of the body of the host. Production of meiospores, unlike that for the binucleate spore, appeared to be spontaneous (i.e. no obligatory blood meal). Survivorship of male and female larval mosquitoes was nearly equal. Adult females spread the parasite in three ways: transovarial, transovum, and by meiospore deposition.     

On the respiratory quotient (RQ) of termites (Insecta: Isoptera)

The respiratory quotient (RQ) at 28 degrees C was determined by Warburg manometry in 23 species of termites from the Mbalmayo Forest Reserve (Cameroon) and three sub-tropical species cultured under laboratory conditions in the U.K. or freshly collected in Australia. The data are tabulated with other recently reported RQs (determined by manometry or GC) and with measured CH(4) emission rates to provide a survey of 29 species covering both lower and higher termites in all major trophic (functional) categories. In all species, except the wood-feeding Coptotermes acinaciformis and the soil-feeding Cubitermes fungifaber, the observed mean values (with manometry corrected for known fluxes of H(2) and CH(4)) were at or well above 1.00. Soil-feeding forms (except C. fungifaber) generally showed a high apparent RQ (not corrected for H(2)), with nine species (out of 13) above 1.20 and six species above 1.30. Well-replicated laboratory experiments with Reticulitermes lucifugus showed that there was a tendency for RQ to fall with time over a 4-h incubation, although remaining greater than 1.00.The observed RQs are consistent with carbohydrate being the principal substrate supporting respiration in all trophic and taxonomic categories, with little or no contribution from the degradation of lignin or other polyaromatic materials. However, in many species (especially soil-feeders), the observed RQ is greater than that expected from known fluxes of O(2), CO(2) and CH(4) on the assumption that carbohydrate is the respiratory substrate. This presupposes that there is a large hydrogen sink (additional to CH(4) production), possibly the emission of H(2) gas, and/or the existence of unresolved digestive mechanisms or electron routings. Uncertainties in the use of manometry with termites are discussed.     

Number of primary spermatocytes in the Drosophila immigrans (Sturtevant) group (Diptera : Drosophilidae)

Nine species of the Drosophila immigrans (Sturtevant) group (Diptera Drosophilidae) were examined for the number of primary spermatocytes per cyst. Seven species (D. formosana, D. immigrans, D. kohkoa, D. nasuta, D. neohypocausta, D. quadrilineata and D. sulfurigaster albostrigata) showed nearly 16 primary spermatocytes per cyst, but 2 species (D. annulipes and D. curviceps) had mean numbers of 20.41 and 24.02 primary spermatocytes per cyst, respectively. The frequency distribution patterns of the numbers of primary spermatocytes suggest that the multiplication divisions do not occur synchronously in these species. The systematic positions of D. annulipes and D. curviceps are also discussed.     

Serotonin-immunoreactive neurons in the retrocerebral neuroendocrine complex of the cricket Teleogryllus commodus (Walker) (Orthoptera : Gryllidae) and cockroach Periplaneta americana (L.) (Dictyoptera : Blattidae)

Retrocerebral glandular complexes of Teleogryllus commodus (Orthoptera : Gryllidae) and Periplaneta americana (Dictyoptera : Blattidae) were examined for 5-hydroxytryptamine (serotonin)-immunoreactive (5-HTi) neurons. In Teleogryllus, a prominent tract of 5-HTi axons crosses the ventral surface of the corpus allatum (CA) from nervus corporis allati 1 (NCA 1), and seems to end at varicosities in NCA 2. Serotoninergic axons within this tract pass cephalad to the corpus cardiacum (CC), which also contains numerous, fine 5-HTi branches. 5-HTi axons originate anteriorly, presumably from the pars intercerebralis (PI) and pars lateralis (PL) of the brain. This is suggested by absence of immunoreactivity at the NCA 2-subesophageal ganglion junction, by intense immunofluorescence of the nervi corporis cardiaci (NCC) 1 and 2, by the presence of 5-HTi perikarya in PI and PL, and by previous data obtained by backfilling NCA 1 and 2. In Periplaneta, 5-HTi varicosities are rare in the CA, but abound in the NCA 2, and in NCC 1, 2, and 3. A few 5-HTi fibers project anteriorly from NCA 2 into the cap-like junction of CA and CC, and some traverse the CA to enter the postallatal nerves. Large, 5-HTi axons of NCC 3 ramify within the CC, while others contribute to an anterior branch of NCA 2. As in Teleogryllus, it is unlikely that 5-HTi fibers in NCA 2 originate from somata in the subesophageal ganglion. When cobalt staining and serotonin immunocytochemistry were combined to stain subesophageal neurons of Periplaneta, 5-HTi somata could not be paired with those back-filled via NCA 2. Conspicuous 5-HTi tracts between NCA 2 and the CC of Teleogryllus have no counterpart in Periplaneta.     

Efficacy of the parasitoid,Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae) against Myzus persicae (Sulzer) (Hemiptera: Aphididae) infesting rapeseed-mustard

Efficacy of Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae) was determined by studying its biological and behavioural attributes on the aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae). Total developmental duration of the parasitoid was longer in younger instars compared to that in older instars of aphid. Host age negatively affected the oviposition period and fecundity of the ovipositing parasitoid. Survival of the immatures was higher in older than the younger instars of the aphid. Sex ratio for the parasitoid was female-biased. Longevity of female parasitoid was higher while parasitizing aphid nymphs of younger age groups (1–2 days old) compared to that of older age groups (4–5 days old). Parasitoid showed a higher preference towards second instar of M. persicae both in choice and no-choice tests. Results on mutual interference revealed that per capita searching efficiency decreased from 0.91 to 0.07 as parasitoid densities increased from 1 to 8. Logistic regression exhibited a type II functional response for D. rapae. The estimated values of search-efficiency (a) and handling time (T_h) were 0.038 h⁻¹ and 1.59 h, respectively. The maximum parasitization rate was 15.08. This investigation suggests that D. rapae could be an effective candidate for augmentative biological control of M. persicae which infests several plant species of economic importance.