Wing morphometrics of Aedes (Ochlerotatus) albifasciatus (Macquart, 1838) (Diptera: Culicidae) from different climatic regions of Argentina.

BACKGROUND: Gene flow restrictions between populations of Aedes albifasciatus, the vector of Western equine encephalitis and Dirophilaria immitis, have been described in the central region of Argentina. Genetic and eco-physiological variations usually result in local forms reflecting the climatic regions. Mosquito wings and their different parts have ecological functions in flight and communication. Therefore, wing shape could be considered an aspect of sexual dimorphism, and its eco-physiological responses can be expressed as morphological changes induced by the environment. METHODS: To compare the geographical and sexual variations with respect to wing shape and size in two Ae. albifasciatus populations from contrasting climates of Argentina (temperate: Buenos Aires, and the arid steppe of Patagonia: Sarmiento), the wings of adults reared in thermal trays at different constant temperatures (10-29 °C) were analyzed. RESULTS: The wing size of Ae. albifasciatus showed inverse linear relationships with the rearing thermal condition and higher slope for Buenos Aires. In the cool range (10-17 °C), geographical size variations responded to the converse Bergmann's rule, where Buenos Aires individuals were larger than those from Sarmiento. Sexual shape dimorphism occurred in both populations while geographical variation in shape was observed in both sexes. CONCLUSIONS: Buenos Aires individuals showed greater response sensitivity with respect to the size-temperature relation than those from Sarmiento. The converse Bergmann's rule in size variation could be due to a higher development rate in Sarmiento to produce more cohorts in the limited favorable season. The shape could be more relevant with respect to the size in the study of population structures due to the size being more liable to vary due to changes in the environment. The geographical variations with respect to morphology could be favored by the isolation between populations and adaptations to the environmental conditions. Our results demonstrate that the shape and size of wing provide useful phenotypic information for studies related to sexual and environmental adaptations.

High morphological and genetic variabilities of Ochlerotatus scapularis, a potential vector of filarias and arboviruses.

BACKGROUND: Ochlerotatus scapularis is a potential vector of filarias and arboviruses in the Neotropics. This species was once typically associated with sylvatic environments; however, cases of synanthropy and urbanization of this species have been increasingly reported in southeast Brazil. Despite the medical relevance of Oc. scapularis, its populational variability is not yet known. To our knowledge, this is the first report describing the morphological and genetic variabilities of this species. METHODS: Population samples were characterized using the cytochrome oxidase subunit I (COI) mitochondrial gene and wing geometrics. Adult mosquitoes were collected from five sampling sites from remnants of the Atlantic forest embedded in the urban or rural areas of southeast Brazil. RESULTS: In the 130 individuals analyzed, 46 COI haplotypes were detected. Haplotype diversity was high and ranged from 0.66 to 0.97. Six haplotypes were present in 61% of the individuals, whereas the remaining haplotypes were less frequent (39%). Wing shape was also highly polymorphic. Differentiation of populations across sampling sites according to genetic distances (Fst = -0.009 to 0.060) and morphological distances (Qst = 0.47) indicated that populations were not identical. No correlations were noted for phenetic and genetic diversities (p = 0.19) or for genetic or phenetic distances with geographical distances (p = 0.2 and p = 0.18, respectively). CONCLUSIONS: Our study results suggest that Oc. scapularis has a rich genetic patrimony, even though its habitat is fragmented. Implications of such genetic richness with respect to vectorial competence, plasticity, and ability to exploit urbanized areas need to be further investigated.

A pictorial key to the species of Aedes (Ochlerotatus and Coetzeemyia) in the Afrotropical Region (Diptera: Culicidae).

Six species of the subgenus Ochlerotatus and one species of the subgenus Coetzeemyia of the genus Aedes in the Afrotropical Region are treated in a pictorial key based on diagnostic morphological features. Brief remarks on the new reclassification of the genus Aedes are also included.

Description of Himalayan mosquito pupae III, Ochlerotatus albolateralis and Ochlerotatus deccanus.

The pupae of Ochlerotatus albolateralis and Oc. deccanus are described and illustrated for the first time from specimens collected in the Himalayan Mountains in Nepal, breeding in tree holes and bamboo stumps. Chaetotaxal tables and illustrations show the morphology of their setae. Characters to recognize each species are explained.

Descriptions of the pupae of Ochlerotatus aloponotum and Ochlerotatus campestris.

Pupae of 2 western species, Ochlerotatus aloponotum and Oc. campestris, are described and illustrated. Sources of the original descriptions and known stages are given. The relation of Oc. aloponotum to Oc. excrucians and characters to separate them are discussed.

Description of the pupae of Ochlerotatus flavescens and Ochlerotatus melanimon.

The previously unknown pupae of Ochlerotatus flavescens and Oc. melanimon are described and illustrated. They will both be included in a forthcoming key to known pupae of genera Aedes and Ochlerotatus in the Nearctic Region. Characters to recognize each are explained.

Redescription of the pupae of Ochlerotatus dorsalis and Ochlerotatus squamiger.

The pupae of Ochlerotatus dorsalis and Oc. squamiger are completely described and illustrated for the first time. Considering the entire pupal morphology, characters to separate the 2 pupae are discussed.

On the evolution of saline tolerance in the larvae of mosquitoes in the genus Ochlerotatus.

We examined physiological and morphological parameters associated with saline tolerance in the larvae of 11 species of mosquito in the genus Ochlerotatus that were collected from the wild in a variety of sites around North America. Saline tolerance was assayed, and all of the species were osmoregulators. Six of the species examined were found to be physiologically restricted to freshwater habitats, while the other five could successfully osmoregulate in both freshwater and saline water, including seawater. All larvae that were obligate freshwater forms had only one rectal segment, while all of the euryhaline osmoregulators had two. We were interested in the evolutionary pathway by which saline tolerance arose in this lineage. DNA sequence data were obtained by polymerase chain reaction amplification and sequencing of the D2 region of the 28s rDNA gene in all of the freshwater and saline-tolerant Ochlerotatus species we studied. When the morphological and physiological characters were mapped on the resultant cladogram, they revealed a complex pattern, with freshwater and saline-water forms being adjacent and interspersed through the tree. The data also demonstrate that saline tolerance has been gained and then lost at least once in this lineage. Two possible evolutionary scenarios are presented, but the one we favor is that saline tolerance arose one time in this lineage and repeated reversions to the freshwater condition have occurred.

Description of Himalayan mosquito pupae III. Ochlerotatus gubernatoris and Ochlerotatus unicinctus.

The pupae of Ochlerotatus gubernatoris and Oc. unicinctus are described and illustrated for the first time. They were collected in the Himalaya Mountains of Nepal during field trips to the region. Both breed in natural and artificial containers.

Description of Himalayan mosquito pupae II. Ochlerotatus shortti and Oc. elsiae.

The pupae of Ochlerotatus shortti and Oc. elsiae are described and illustrated. These species occur in the Himalaya Mountains at middle range altitudes. Characters to recognize each are explained.

Description of the pupa of the Himalayan mosquito, Ochlerotatus pulchriventer.

The pupa of Ochlerotatus pulchriventer (=Aedes pulchriventer) is described and illustrated for the first time. It was collected at midrange altitudes in the Himalaya Mountains of Nepal. A subspecies from Taiwan is discussed.

First description of the pupa of Ochlerotatus gilcolladoi.

The pupa of Ochlerotatus gilcolladoi is described and illustrated for the first time. Specimens were caught near Madrid. A table lists the range and mode of the branches of each pupal seta.

[Parity of Ochlerotatus scapularis in laboratory and field conditions]. / Paridade de Ochlerotatus scapularis em condições de laboratório e campo.

OBJECTIVE: To identify the parity status of Ochlerotatus scapularis females in laboratory and field conditions. METHODS: Field collections were carried out fortnightly using a hand-held aspirator in Vale do Ribeira, Southeastern Brazil, from April 2003 to March 2004. In laboratory, 100 Ochlerotatus scapularis F1 females were obtained and followed up individually, reporting the number of blood meals, the length of gonotrophic cycle, survival and number of eggs laid. The parity status and ovarian development were observed through ovarian dissection of 90 field females for each collection and all females reared in laboratory. RESULTS: The parity status diagnoses of the 100 females reared in laboratory and dissected agreed with 55% of the oviposition data, and it was underestimated in 37% and overestimated in 2%. Also in the laboratory, 106 gonotrophic cycles were completed, around 55% of females needed more than one blood meal before laying eggs. In laboratory conditions the species survival was 26 days. A total of 1,180 field females of Ochlerotatus scapularis were dissected: 418 (35.4%) nulliparous, 655 (55.5%) uniparous, 46 (3.9%) biparous and 61 (5.2%) could not be evaluated. Ninety field females were found in Christophers and Mer's phase III-V. CONCLUSIONS: The gonotrophic discordance hypothesis could be confirmed based on field and laboratory observations of Ochlerotarus scapularis females.

List of species described in the egg stage of tribe Aedini (Diptera: Culicidae) with their literature citations.

Species of Aedini with published morphological descriptions and/or illustrations of eggs are listed with their literature citations. Each species has a notation indicating descriptions are written, illustrated or both. Only approximately 16% of aedine species currently have morphological descriptions published for the egg stage. The new classification of tribe Aedini proposed by Reinert et al. (2004) is utilized.

Descriptions of Finlaya Theobald, a genus in tribe Aedini (Diptera: Culicidae), and its type species Fl. kochi (Dönitz).

Genus Finlaya Theobald is characterized based on the morphology of females, female genitalia, males, male genitalia, pupae, and 4th-stage larvae. Distinctive characters of the genus are discussed and included species are listed. Finlaya kochi, the type species, is described in detail and a syntype female is selected as neotype. An extensive list of previous literature pertaining to the genus is provided.

Fecundity of naturally blood-fed Ochlerotatus japonicus.

Ochlerotatus japonicus (Theobald) collected in gravid traps were held individually in modified BioQuip breeders in a darkened room under ambient conditions and readily oviposited on Styrofoam blocks. Counts were made of eggs laid on Styrofoam blocks, container sides, and water surface, and dissections allowed for counts of retained eggs to determine the fecundity of this species. In total, 32,970 eggs were oviposited by 289 females with a range of 3-249 eggs per female. The mean +/- SD number of eggs oviposited per female, 114.08 +/- 51.08, was significantly less than the mean number of eggs produced per female, 125.85 +/- 47.89. Wing lengths ranged from 2.8 to 4.7 mm with a mean of 3.81 +/- 0.38 mm. Wing length was positively correlated with total eggs formed (r2 = 0.3481); wing = 3.22054 + 0.0047 total eggs formed. There was no monthly size difference although females collected during October produced significantly fewer eggs than females collected from June to September. A low egg viability of 40% was attributed to improper storage of the Styrofoam blocks on which eggs were oviposited.

Quantitative genetics of vector competence for La Crosse virus and body size in Ochlerotatus hendersoni and Ochlerotatus triseriatus interspecific hybrids.

La Crosse virus is a leading cause of pediatric encephalitis in the United States. The mosquito Ochlerotatus triseriatus is an efficient vector for La Crosse virus, whereas the closely related O. hendersoni transmits only at very low rates. Quantitative trait loci (QTL) affecting the ability to orally transmit this virus and adult body size were identified in 164 F(2) female individuals from interspecific crosses of O. hendersoni females and O. triseriatus males using a combination of composite interval mapping (CIM), interval mapping (IM) for binary traits, and single-marker mapping. For oral transmission (OT), no genome locations exceeded the 95% experimentwise threshold for declaring a QTL using IM, but single-marker analysis identified four independent regions significantly associated with OT that we considered as tentative QTL. With two QTL, an increase in OT was associated with alleles from the refractory vector, O. hendersoni, and likely reflect epistatic interactions between genes that were uncovered by our interspecific crosses. For body size, two QTL were identified using CIM and a third tentative QTL was identified using single-marker analysis. The genome regions associated with body size also contain three QTL controlling OT, suggesting that these regions contain either single genes with pleiotropic effects or multiple linked genes independently determining each trait.

Description of Bruceharrisonius, a new subgenus of Ochlerotatus, and a redescription of its type species Oc. (Brh.) greenii.

The new subgenus Bruceharrisonius is described and principal features of all known stages are provided for separating it from other subgenera of genus Ochlerotatus. The female, male, female and male genitalia, pupa, and 4th-stage larva of the type species, Oc. greenii, are described in detail. Eight species (Oc. alektorovi, Oc. aureostriatus, Oc. doonii, Oc. christophersi, Oc. greenii, Oc. hurlbuti, Oc. okinawanus, and Oc. taiwanus) currently are recognized in the subgenus.