Diel oxygen uptake in Chaoborus punctipennis (diptera : culicidae)

Oxygen consumption (µl/ mg dry wt. · hr^–1 corrected to STP) in Chaoborus punctipennis was measured in a Gilson differential respirometer at two-hour intervals during 24-hour periods. Animals were held at controlled conditions similar to those at the time of collection. Respiration was measured under controlled temperatures and natural photoperiod. Measurements were begun about 36 hours after collection.Winter-collected animals showed a lower and more stable respiration than summer and fall-collected animals which did not differ from one another. Respiration increased with temperature becoming quite variable at 30°C where mortality was highest. Animals collected at different seasons and subjected to a variety of temperatures did not show a predictable pattern of respiration during the daily cycle under any condition tested.Since the 36-hour delay in respiration measurements could have dampened a diel cycle, oxygen consumption was determined within an hour of collection and followed for 24 hours. For this experiment animals were collected at six-hour intervals over a 24-hour period. Respiration did not show a predictable pattern of variation during the day-night cycle.This work was supported in part by a grant from Department of Interior, Office of Water Resources Research. All correspondence should be addressed to A.S. Tombes.     

On the contribution of Prof. Yu. S. Balashov to fundamental parasitology

A brief review of the original concepts of Yu.S. Balashov in the field of fundamental parasitology devoted to the types of parasitism, origin and evolution of parasitism in arthropods, transmissible infections, and the structure of parasite populations, the ecological niches and communities of parasites is presented.     

Comparative dehydrogenase activity during the ontogenesis of the yellow fever mosquito Aedes (Stegomyia) aegypti L. (diptera:culicidae)

• 1.1. α-GPDH in most active in adults, LDH in third instar larvae, and MDH in third instar larvac.
• 2.2. During pre-pupal growth, LDH is the most active enzyme, followed by MDH and α-GPDH; while during post-pupal growth, MDH is most active followed by α-GPDH and LDH.
• 3.3. Increased enzyme activity is in response to changing physiological and physical environments, and is due to temporal activation of new gene loci indicated by the production of new α-GPDH and MDH isozymes. LDH activity is probably controlled by the temporal action of regulatory gene(s).
• 4.4. Dehydrogenase activity profiles during ontogenesis are probably species-specific.

     

Genetics of glucose phosphate isomerase and phosphoglucomutase in Aedes albopictus (diptera: culicidae)

Summary Glucose phosphate isomerase (E.C. 5.3.1.9) and phosphoglucomutase (E.C. 2.7.5.1) were found to be polymorphic in a laboratory colony of Aedes albopictus. The glucose phosphate isomerase locus is represented by two alleles resulting in three genotypes, while the phosphoglucomutase locus is represented by at least five alleles giving rise to a total of 15 genotypes. The inheritance of these two enzymes is of the Mendelian type with codominant alleles. Present data indicate that these genes are not linked.Of 105 mosquitoes analysed for these two gene-enzyme systems, the frequencies for glucose phosphate isomerase alleles are Gpi ^S=0.68 and Gpi ^F=0.32, while the frequencies for phosphoglucomutase alleles are Pgm ^A=0.16, Pgm ^B=0.11, Pgm ^C=0.19, Pgm ^D=0.30 and Pgm ^F= 0.24. The frequencies of the three glucose phosphate isomerase genotypes are in accord with Hardy-Weinberg expectations (X ₁ ² =2.74). Similarly, the frequencies of the 15 phosphoglucomutase genotypes probably do not differ significantly from Hardy-Weinberg expectations (X ₁₀ ² = 18.45).     

Ecology and epizootology of Microsporidia in malarial mosquitoes (diptera: culicidae) from the south of Western Siberia

The ecology and epizootology of Microsporidia were studied in the natural population of malarial mosquitoes from Western Siberia over a 30-year period. Symptoms of the disease, host specificity and character of parasite localization in host tissues were investigated. Microsporidia of 9 species from 4 genera, namely Amblyospora, Crepidulospora, Senoma, and Parathelohania, were found in the malarial mosquito larvae from the territory examined. The mosquito species Anopheles messeae was infested by larger number of the microsporidian species, than A. beklemishevi. Spores and active stages of the microsporidian Senoma sp. from mosquito larvae are localized in epithelial cells of the host's intestine. There are no external signs of the infestation. The infested larvae do not die, and the infection proceeds to the pupal stage. Microsporidians of the genus Parathelohania infest larvae of both male and female mosquitoes. The parasites localized in the fat body cells. Body of the infested host gets an opaque white color in the period of spore maturation. The infested larvae perish at 4th stage. Microsporidian spores are formed in the mosquito larvae of both sexes. However, infection rate is much higher in the male larvae (77.8%), than that in the female larvae (22.2%). Symptoms of the disease under the infestation by the genera Crepidulospora and Amblyospora are similar to those under the infestation by Parathelohania sp. There are no external signs of the infestation in the adult mosquito females. In these hosts microsporidians form large two-nuclear spores with a thin capsule accounted for transovarial transmission. An about two times decrease of fertility in the Anopheles messeae females infested by the Parathelohania microsporidians is revealed. Mean number of eggs laid by the infested females was 121, while that of the noninfested ones was 232. Thus, the cause of the decrease in the mosquito abundance is both the elimination of male larvae and the decrease of fertility in females. In Siberia malarial mosquitoes yield 2 or 3 generations per year. Infested larvae are rarely occurred in the beginning of summer. Maximal extensiveness of the invasion may be observed in the end of summer, because of the accumulation of the infection in water bodies. Number of the peaks of infestation coincides with the peaks of abundance of mosquito larvae of 4th stage. Peaks of infestation are delayed as compared with the peaks of mosquito abundance. It is an evidence of the development delay in the infested larvae. Long-term dynamics of the infestation by microsporidians is studied. The epizooty caused by Parathelohania was observed in the malarial mosquitoes in the eighties (with the infestation rate up to 62 %). In the last ten years the infestation rate was low (from 0.1 to 2.6%).     

Organization of motor neurons innervating the proboscis musculature in Drosophila melanogaster meigen (diptera : Drosophilidae)

The present study addresses the question as to how the motor neurons involved in feeding in Drosophila melanogaster Meigen (Diptera : Drosophilidae) are organized. The motor neurons have been visualized both by Golgi-silver impregnation and by intramuscular injection of horseradish peroxidase, and analyzed in light of the existing information on taste sensory system and the feeding behaviour. The motor neurons have been broadly classified into the following types: labial nerve motor neurons, pharyngeal nerve motor neurons, and accessory pharyngeal nerve motor neurons, depending on the nerve through which their axons exit. The arborization of all the motor neurons is confined to the suboesophageal ganglion (SOG). All of them have predominantly ipsilateral and some contralateral arborizations. Their dendrites predominantly occupy the ventral region of the neuropil of the SOG and partially overlap the taste sensory projections, thereby providing an opportunity for interaction with the taste sensory input. The pharyngeal motor neurons arborize more extensively in the ventral tritocerebram, anteroventral. and mid-ventral neuropil, whereas the dendritic fields of labial motor neurons are confined to the mid-ventral neuropil. There is a functional segregation in motor neuron organization: cibarial muscles involved in sucking are innervated by pharyngeal motor neurons, while the proboscis muscles involved in positioning, of the proboscis are innervated by labial motor neurons. We have also observed projections of the stomodaeal nerve in the tritocerebrum.     

Plant-feeding dipterans (Diptera,Chloropidae, Agromyzidae) from Wrangel Island (the Chukchi Sea)

Flies of the family Chloropidae were found in the arctic tundra for the first time. Oscinella frit L. was collected in several areas of the mountainous part of Wrangel Island, occurring mainly in the ground layer. Among three species of Agromyzidae, Napomyza mimula Spencer was the most numerous; it was found both in the mountains and on the coastal plain. Two other species, Phytomyza cineracea Hendel and Chromatomyia sp., were rare. The only biotope where all the four species were collected simultaneously was a zoogenic forb-grass meadow patch which developed around the arctic fox burrow.     

Bloodsucking dipterans (Diptera: Ceratopogonidae,Culicidae, Simuliidae,Tabanidae) of the Kurgala Peninsula,Leningrad Province

The fauna of bloodsucking dipterans of the Kurgala Peninsula comprises 73 species, 34 of which belong to mosquitoes (Culicidae), 18 to blackflies (Simuliidae), 5 to biting midges (Ceratopogonidae, genus Culicoides), and 16 species to horseflies (Tabanidae). Nine species of the bloodsucking dipterans found on the Kurgala Peninsula are new to Leningrad Province, 6 of them being also recorded for the first time for the neighboring territories of Estonia and southern Finland.     

Morphological variation among members of theStellaria longipes complex:S. longipes,S. longifolia,andS. porsildii (Caryophyllaceae)

Morphological relationships were investigated among diploidStellaria porsildii, polyploidS. longipes, and diploidS. longifolia. Canonical discriminant analysis, based on a priori assumptions to maximize differences among groups, showed thatS. longipes clusters equally distant between the two diploid species along an axis connecting the diploids' centroids, but it differs along an axis perpendicular to this axis. The intermediacy along the former axis is evidence thatS. longipes is an amphiploid derived fromS. longifolia andS. porsildii. The divergence along the latter axis may be attributable to adaptively valuable heterotic traits which were retained following amphidiploidization. The only morphological discontinuity occurred between the two diploids, whereas the morphological range ofS. longipes overlapped the range of both diploids forming a continuum. The lack of discrete clusters is likely due to hybridization and introgression withS. longifolia on one hand, and convergence of traits betweenS. longipes var.monantha andS. porsildii on the other. High a posteriori assignments in classificatory discriminant analysis supports the separation ofS. longipes var.monantha from otherS. longipes specimens. AlthoughS. longipes var.monantha grouped close toS. porsildii, the two groups separate based on leaf shape traits. Overall results support, firstly, the hypothesis thatS. porsildii is a diploid parent species which by hybridizing withS. longifolia gave rise to polyploidS. longipes. Secondly, results suggest thatS. longipes var.monantha converged morphologically towardsS. porsildii relatively recently due to ecological specialization, and merits distinction at least as a variety ofS. longipes.     

Computational studies on the backbone-dependent side-chain orientation induced by the (S,S)-CXC motif

Disulfide cyclization is a well-known procedure to impose conformational restriction to peptides undergoing backbone flexibility. Rigid conformations are induced only for small rings with a specific combination of amino acids. In this work, we present a computational search of the backbone and backbone-dependent side-chain orientation of two series of linear and cyclic peptide analogs. The -C[XY]C- scaffold (where X,Y is arginine, aspartic acid or alanine residue) in its open and (S,S) cyclic form was used for the design of the studied analogs. Thirty-six compounds, resulting from the extension with one residue at either the N- or the C-terminus were studied with classical MD. The local backbone conformation and the relative orientation of the X and Y side chains induced by either cyclization and/or the presence of the charged residues are discussed. From the present study it is concluded that cyclization has a great impact on the synplanar orientation of the X and Y side chains in the (S,S)Ac-XCYC-NH2 series of compounds while charge-charge interaction has only a weak synergic effect. On the contrary, the antiplanar orientation is favored in the case of (S,S)Ac-CXCY-NH2.     

Yu.S. Balashov, <Emphasis Type="Italic">Parazitism kleshchei i nasekomykh na nazemnykh pozvonochnykh</Emphasis> (Parasitism of Ticks and Insects on Terrestrial Vertebrates), St Petersburg: Nauka, 2009, 357 p.

Consideration is given to basic concepts of natural focality that remain debatable (natural focus, epizootic and epidemic processes) and to the most relevant problems that largely determine the pathways of further research in this field, such as application of molecular biological methods to the study of natural foci, modes and forms of pathogen existence at the reservation phase, ways of emergence of “new” diseases with natural focality, and current strategy in disease prevention.