Different responses of two floodwater mosquito species, Aedes vexans and Ochlerotatus sticticus (Diptera: Culicidae), to larval habitat drying.

Insect larvae that live in temporary ponds must cope with a rapidly diminishing resource. We tested the hypothesis that floodwater mosquitoes would react to diminishing water levels by accelerating larval development time and emerging as smaller adults. Since a reduction in habitat size leads to increased larval densities, we also included two larval densities. Newly-hatched floodwater mosquito larvae, Aedes vexans (87.9% of emerged adults) and Ochlerotatus sticticus (12.0% of emerged adults), were taken from the field and randomly assigned to one of three water level schedules. Survival to adult emergence was significantly affected by the water level schedule. Ae. vexans adults emerged later in the decreasing schedule than the constant water schedule, but time to emergence was not affected by larval density. In the drying water schedule, Ae. vexans adults emerged 6 to 14 days after complete water removal. Adult size was significantly affected by both water level schedule and larval density. Adults of Oc. sticticus emerged earlier in the decreasing than the constant water schedule which was in accordance with our hypothesis, but size was not affected. Our results indicate two different responses of two floodwater mosquito species to diminishing larval habitat. Oc. sticticus accelerated larval development while Ae. vexans larvae showed remarkable survival in humid soil. Both species are often numerous in inundation areas of large rivers, and climatic conditions after a flood might influence which species dominates the adult mosquito fauna.     

Morphology, biology and geographical distribution of the mosquito Aedes (Ochlerotatus) sergievi (Diptera, Culicidae)

New data on morphology and differential diagnosis of adults (variability of the pattern of mesonotum and wings, difference from all other species of the cantans group of the Palaearctic fauna by the spot of the scales on the mesepimeron reaching its lower edge, difference of its male genitalia from those of Ae. montchadskyi Dub.), biology (period of activity and predomination indices of the females attacking man, breeding places and period of occurrence of preimaginal phases in the south of the East Transbaikalia and Krasnoyarsk Region), and geographical distribution (from the Tuva ASSR and south of Krasnoyarsk Region in the west to the south of the Chita Region in the east, misidentification in East Kazakhstan, confinement of the range to the Mongolian district of the Kazakhstan-Mongolian province of the Central Asian subregion of the Holarctic that suggests that the main part of its distribution range is situated in Mongolia) are given for the recently described species of mosquitoes, Aedes sergievi Danilov, Markovich et Proskuryakova, 1978 from the south of East Siberia.     

Genetic distance between two sibling species of the Aedes mariae complex (Diptera, Culicidae)

Two sibling species of the mariae complex of the Aedes genus have been studied: Ae. mariae and Ae. zammitii. Thee mosquitoes are allopatric and show similar adaptations to rocky mediterranean coasts. The isolating mechanisms between the two species are well studied. A partial sterility of hybrid F1, limited to males, has been found with laboratory cross experiments. Strong pre-mating isolating mechanisms were shown in nature by means of release experiments, the frequency of hybrids never exceeding 2% without evidence of introgression. We analyzed genetic variation at 26 enzyme loci in a population of each species: 35% of loci were polymorphic, with an observed mean heterozygosity of 0.07 in Ae. mariae and 0.06 in Ae. zammitii; 6 loci allow discrimination between the two species at a probability of at least .99. Nei's measures of genetic identity and genetic distance are respectively I = 0.6096 and D = 0.2828. The distribution of genetic identities relative to loci is strongly bimodal, reflecting a different contribution of highly variable and fast evolving loci on one side and conservative and slowly evolving loci on the other. We consider, on the base of various experimental data (see Powell, 1975), in the first class ("fast evolving" loci) both variable substrate and regulatory enzymes, in the second ("slow evolving" loci) non regulatory enzymes. Values of genetic distance calculated separately for the "fast" (54% of the loci studied) and "slow" (46%) evolving loci are respectively Df = 0.41 and Ds = 0.03, showing that the main contribution to genetic distance in the first period of divergence is due to fast evolving loci, whose rate of evolution is about ten times more rapid with respect to slow evolving loci.     

Biological cycle of Aedes albopictus (Diptera, Culicidae), in the laboratory]

Twelve colonies of Aedes albopictus were maintained at laboratory conditions, with the following results: Insectary conditions--Air humidity: 90-95%; Temperature: 25 degrees C; Blood source: human; Breeding places: Plastic glass or bamboo; Number eggs per female: 36.37; Incubation time: 1 to 6 days; Larval period: 4 to 9 days; Pupal period: 1 to 5 days; Adults life span: females--30.8 days and males--26.6 days.     

Molecular and ultrastructural characterization of Andreanna caspii n. gen., n. sp. (Microsporida: Amblyosporidae), a parasite of Ochlerotatus caspius (Diptera: Culicidae)

A new genus and species of microsporidia, Andreanna caspii n. gen., n. sp. is described from the mosquito, Ochlerotatus caspius (Pallas) based on ultrastructural morphology, developmental characteristics, and comparative sequence analyses of the small subunit (SSU) ribosomal DNA (rDNA). Parasite development is confined to fat body tissue and infected larvae appear swollen with dull white masses within the thorax and abdomen. Meronts have diplokaryotic nuclei and are delineated by a simple plasmalemma contiguous with the host cell cytoplasm. Merogony occurs by synchronous binary division followed by cytokinesis. Diplokaryotic sporonts undergo meiosis and synchronous nuclear division forming sporogonial plasmodia with two, four and eight nuclei enclosed within a persistent sporophorous vesicle. Cytokinesis of sporogonial plasmodia results in the formation of eight uninucleate spores. The episporontal space of early sporonts is filled with a homogeneous accumulation of electron dense granular inclusions and ovoid vesicles of various dimensions, transforming into an interwoven matrix during the initial phase of sporogenesis. Spores are oval, uninucleate and measure 4.8 ± 0.3 × 3.1 ± 0.4 μm (fixed). The spore wall is 260 μm thick with an irregular exospore consisting of two layers (150-170 μm) and a thinner endospore (90-100 μm). The anchoring disk is well developed and is contiguous with a lamellar polaroplast that occupies the anterior third of the spore and possess more narrow lamellae on the posterior end. The polar filament is gradually tapered and arranged in a single row consisting of six coils ranging from 180 to 150 μm in diameter. The posterior vacuole (posterosome) is moderately sized and filled with a matrix of moderate electron density. Phylogenetic analysis of SSU rDNA from A. caspii and 30 other species of microsporidia including 11 genera parasitic in mosquitoes using maximum parsimony, neighbor joining and maximum likelihood methods showed A. caspii to be a sister group to the clade containing all of the Amblyospora species, including Culicospora, Edhazardia and Intrapredatorus, as well as Culicosporella and Hyalinocysta thus providing strong support for establishment of Andreanna as a separate genus.     

A new species of blackflies--Simulium (Argentisimulium) dolini sp. n. (Diptera, Simuliidae)

Female, male and larva of the new species of black flies, Simulium (Argentisimulium) dolini sp. n. are described. By its morphology the species occupies an "intermediate position" between S. nolleri and S. palustre. In the USSR the species was found in wooded and forest-steppe zones of West Ukraine.     

Comparison of ribosomal dna nucleotide sequences of the mosquito genera Aedes and Ochlerotatus (Diptera: Culicidae: Aedini)

Nucleotide rDNA sequences of 9 species of the mosquito genus Ochlerotatus and 2 species of the genus Aedes were obtained and compared. Variation both within and between these genera was characterized. The phylogenetic relationships among the studied species of Ochlerotatus generally correspond to the grouping of species based on morphological characters.     

Long-term storage and viability of Ochlerotatus albifasciatus (Diptera: Culicidae)

The viability of Ochlerotatus albifasciatus (Macquart) eggs stored at room temperature and at 5 degrees C was studied over 31 months. After 12, 18 and 31 months of storage, eggs were acclimatized at 22 degrees C for ten days, and then inundated twice every seven days. The effect of the storage period on the percentage of hatching was analyzed by one way ANOVA. Differences on the hatching response between the first and second flooding were analyzed by paired t-test. Differences on the hatching response between the two storage conditions were analyzed by Mann-Whitney rank test. Results showed that (1) Oc. albifasciatus eggs were able to survive and hatch over 31 months; (2) the percent hatching of eggs stored at 5 degrees C was higher than that of eggs stored at room temperature; and (3) low temperatures and long periods without water favor installment hatching.     

Comparison of nucleotide sequences of ribosomal DNA of the mosquito genera Aedes and Ochlerotatus (Diptera: Culicidae: Aedini)

Morphological study allowed identifying 9 species of mosquitoes of the genus Ochlerotatus and 2 species of the genus Aedes. Sequencing of the rDNA region was performed for all these speciemens. The sequences of rDNA were the following: A. cinereus -868 bp, A. vexans--889 bp, Och. cantans--803 bp, O. excrucians--801 bp, O. euedes--794 bp, Och. cyprius--777 bp, O. diantaeus--758 bp, O. intrudens--817 bp, Och. punctor--783 bp, O. dorsalis--748 bp, O. species--767 bp. On average, the size of Aedes rDNA fragments exceeds rDNA of Ochlerotatus by 90-100 bp. The sequences are characterized by a high number of insertions and deletions, and also by point substitutions of nucleotides. It is important to notice that interspecific differences include not only different regions of the internal transcribed spacers, but also the conservative site which is represented by the 5.8S gene. Among four substitutions in this gene, one (C/A) represents the difference between Aedes and Ochlerotatus, the next (T/A) distinguishes A. cinereus from Ochlerotatus speciment and A. vexans, and two substitutions (A/C, T/G) testify the similarity between O. dorsalis and O. species and specimens of Aedes. Besides, two more deletions are typical for O. dorsalis and O. species. One deletion is com- mon, it distinguishes them from the other examined species, and another one is typical only for O. dorsalis. When analyzing morphological characteristics and comparing nucleotide rDNA sequences of O. species with the database, the similarity to O. caspius has been revealed. On the whole, phylogenetic relationships among Ochlerotatus species correspond to subdivision into groups based on morphological characters. Probably, examination of the larger number of specimens will change the morphological division into groups.     

Description of Crassolabium persicum sp. n. (Nematoda, Dorylaimida, Qudsianematidae), an interesting species from Iran

A new species of the genus Crassolabium, Crassolabium persicumsp. n., collected from Arasbaran rangelands of Iran, is described and illustrated. It is characterized by its body 1.92-2.40 mm long, lip region offset by constriction and 17-19 μm wide, odontostyle 16-19 μm long with aperture occupying less than one-third (27-30%) its length, neck 428-690 μm long, pharyngeal expansion 369-390 μm long or occupying 54-56% of total neck length, female genital system amphidelphic, uterus bipartite and 162-218 μm long or 2.3-3.5 times as long as body diameter, pars refringens vaginae well developed, V = 54-57.5, vulva longitudinal, prerectum bearing a blind sac, tail conical with rounded tip to conoid (25-36 μm, c=60-69, c'=0.5-0.9), spicules 68-72 μm long, precloacal pair of supplements far (22-27 μm) from cloacal aperture, and 13-17 shortly spaced ventromedian supplements with hiatus. The new taxon is compared in depth to its relatives in Crassolabium as well as other similar species of Aporcelaimellus and Amblydorylaimus.     

Observations on subgenus Aedes (genus Aedes, Diptera, Culicidae) in northeast Italy and first italian report of Aedes geminus Peus]

The paper reports some observations on the subgenus Aedes (genus Aedes, Diptera, Culicidae) in northeast Italy. Two species were collected: Ae. cinereus and Ae. geminus, the latter recorded for the first time in Italy. Morphological, ecological and biological data of the two species are presented. The identification is possible only on the male hypopigium; larvae, pupae and adult females show no differential characters. For both species, the larval breeding sites were fresh water marshes mainly within woods; preimaginal development took place twice a year, in Spring and Autumn. The females were strongly anthropophilic. No biological differences between the two species were noticed, but more data are needed to ascertain their relationships and the presence of subtle biological divergences.