Effect of entomopathogenic fungus, Beauveria bassiana on larvae of three species of mosquitoes

Beauveria bassiana, an entomopathogenic fungus, was evaluated for its potential against second and third instar larvae of Culex quinquefasciatus, Anopheles stephensi and Aedes aegypti. Conidiospores of this fungus were effective in causing infection leading to mortality of different larval instars. Larvae of Cx. quinquefasciatus were more susceptible to infection than An. stephensi and the second instar larvae of these two species were more susceptible than third instar larvae. Larvae of Ae. aegypti were resistant to infection by B. bassiana.     

Understanding the mechanism of Chikungunya virus vector competence in three species of mosquitoes

Chikungunya virus (CHIKV) is primarily transmitted by Aedes spp. mosquitoes. The present study investigated vector competence for CHIKV in Aedes aegypti and Aedes albopictus mosquitoes found in Madurai, South India. The role of receptor proteins on midguts contributing to permissiveness of CHIKV to Aedes spp. mosquitoes was also undertaken. Mosquitoes were orally infected with CHIKV DRDE‐06. Infection of midguts and dissemination to heads was confirmed by immunofluorescence assay at different time points. A plaque assay was performed from mosquito homogenates at different time points to study CHIKV replication. Presence of putative CHIKV receptor proteins on mosquito midgut epithelial cells was detected by virus overlay protein binding assay (VOPBA). The identity of these proteins was established using mass spectrometry. CHIKV infection of Ae. aegypti and Ae. albopictus midguts and dissemination to heads was observed to be similar. A plaque assay performed with infected mosquito homogenates revealed that CHIKV replication dynamics was similar in Aedes sp. mosquitoes until 28 days post infection. VOPBA performed with mosquito midgut membrane proteins revealed that prohibitin could serve as a putative CHIKV receptor on Aedes mosquito midguts, whereas an absence of CHIKV binding protein/s on Culex quinquefasciatus midguts can partially explain the non‐permissiveness of these mosquitoes to infection.     

Larval feeding behavior of three co-occurring species of container mosquitoes.

Interspecific differences in foraging behavior may help to determine whether the outcome of interspecific competition is coexistence or exclusion. Mosquitoes in the genus Culex are commonly described as foraging primarily by filtering the water column. This behavior contrasts with that of other container-dwelling genera, such as Aedes and Ochlerotatus, that are thought to forage primarily by browsing on container and detritus surfaces. We compared the feeding behavior of Cx. pipiens, Ae. albopictus, and Oc. triseriatus in a laboratory experiment in which we monitored behavior of individual mosquitoes in two different food environment treatments: food suspended in the water column only and food attached to leaf surfaces only. For each mosquito in each food environment, we quantified the time allocated by larvae to one of four positions and to one of three activities. The effect of treatment was significant, with individuals in Fluid Only environments spending more time resting-filtering at the surface, and individuals in Leaf Only environments spending more time browsing on walls. There were significant differences among species, with Cx. pipiens spending more time at the surface than the other species, which spent more time thrashing below the surface. There was no significant interaction of species and treatment, indicating that all three species modify their behavior in similar ways in these environments. Contrary to current understanding, our data suggest that Cx. pipiens browse as frequently as do these potential competitors but show a greater concentration of foraging effort at the top of a container.     

The major sterols from three species of polyporaceae

The free sterols of the fungi Ganoderma applanatum, Ganoderma lucidum and Polyporus sulfureus were isolated and characterized by means of GC and GC/MS techniques. 24-Methylcholesta-7,22-dien-3β-ol was the main component of the sterol mixtures while 24-methylcholesta-5,7,22-trien-3β-ol ergosterol) and 24-methylcholest-7-en-3β-ol were also present although in lower amounts. P. sulfureus, besides the mentioned sterols, also contained 24 ethylcholestan-3β-ol.     

Conversion of ecdysone and 20-Hydroxyecdysone into 26-OIC derivatives is a major pathway in larvae and pupae of species from three insect orders

Insects convert ecdysone and 20-hydroxyecdysone into their corresponding 26-oic derivatives, named ecdysonoic acid and 20-hydroxyecdysonoic acid respectively. The conversion takes piace in several tissues and can either be the only pathway for converting ecdysone into highly polar ecdysteroids, or coexist with various conjugating mechanisms. 20-Hydroxyecdysonoic acid was isolated from Pieris brassicae pupae as its methyl ester derivative. Its chemical structure was identified by Cl/D mass spectrometry and compared with a synthetic compound (20-hydroxy-25-deoxyecdysonoic acid) chemically prepared by oxidation of inokosterone (20,26-dihydroxy-25-deoxyecdysone). Natural ecdysonoic acids appear to exist as a mixture of 25R and 25S isomers. The significance of this pathway is discussed in comparison with similar reactions occuring in the metabolism of steroid hormones in vertebrates.     

Diets and resource partitioning between larvae of three anisopteran species

Analysis of resource partitioning between larvae of three Anisopteran species showed that Aeshna cyanea and Anax imperator (both Aeshnidae) tended to occupy similar ecological niches which were not shared by Libellula depressa (Libellulidae).The diets of these predators and comparisons between trophic availability and diets indicated that prey species eaten varied according to season and predator species, and that some selection of prey species occurred.     

Involvement of male accessory gland substance in the fertility of mosquitoes.

The male accessory gland substance is shown to be involved in the fertility of eggs for the first time in Aedes aegypti and Culex pipiens fatigans. Surgical removal of the paired accessory glands of males did not impair their mating ability. However, the eggs laid by the females after mating with operated males were found to be sterile. This condition could be reversed if the accessory gland substance was later received by the females. Evidence suggests that the accessory gland substance is essential for fertilization.     

Identification of 3,4-didehydrorhodopin as major carotenoid in Rhodopseudomonas species.

Recently we isolated the purple photosynthetic bacterium, Rhodopseudomonas sp. Rits, which was phylogenetically related to Rhodopseudomonas (Rps.) palustris. In this study, the light-dependent and time-dependent changes in the carotenoid composition were investigated by HPLC analysis of extracts from the cultures. All seven carotenoids in the biosynthetic pathway from lycopene to spirilloxanthin were detected. Especially, 3,4-didehydrorhodopin, having twelve conjugated double bonds as well as one terminal hydroxy group, was isolated in a remarkably large amount and fully characterized for the first time. The biosynthetic intermediate was commonly found in the Rps. palustris strains (CGA009, Morita and NBRC100419).     

Variation in the hormonal stress response among larvae of three amphibian species

In a series of studies, we examined how larval corticosterone treatment for several species of amphibians can impact fitness parameters both during exposure and after metamorphosis. We completed confinement stress series on larvae of three species in natural/semi-natural conditions: wood frogs (Rana sylvatica), Jefferson salamanders (Ambystoma jeffersonianum), and Eastern spadefoot toads (Scaphiopus holbrooki). Two of the species had a typical vertebrate response of increasing corticosterone with confinement. However, Eastern spadefoot toads, which have a very short developmental period before metamorphosis, did not show any increase in corticosterone in response to confinement. In a second study, we treated the three species with a low and a high concentration of corticosterone (0.001 and 0.01?μM dissolved in tank water) in the laboratory and examined effects on growth. Although we were successful in raising baseline corticosterone levels with our high corticosterone concentrations, this did not translate into changes in mean larval growth for any of the three species. The larval treatments also did not appear to translate into differences in the juvenile response to confinement stress after metamorphosis. Although juvenile wood frogs did respond to confinement with increasing corticosterone, there was no variation based on larval treatment. As with the larval responses, the juvenile Eastern spadefoot toads did not have a hormonal response to confinement. In summary, while our larval corticosterone exposures did elevate baseline corticosterone levels, we did not see effects of exposure on growth or any latent effects of larval exposure on juvenile responses to confinement.     

Hemolymph pH of the larvae of three species of mosquitoes,and the effect of Romanomermis culicivorax parasitism on the blood pH of Culex pipiens

The hemolymph pHs of late fourth-instar Culex pipiens, Aedes taeniorhynchus, and Toxorhynchites amboinensis were measured with pH-sensitive glass microelectrodes and were slightly alkaline; pH 7.51, 7.62, and 7.37, respectively. The hemolymph pH remained relatively constant during the development of C. pipiens larvae through the third and early and late fourth instars. The hemolymph pH in C. pipiens larvae parasitized with the mermithid nematode Romanomermis culicivorax was unaltered. These measurements provide an approximate pH (ca 7.4) which is normal for the hemolymph of larval mosquitoes, and should be useful for further development of a culture medium for R. culicivorax.     

Molecular cloning of three major sequence species from Rainbow trout protamine mRNA.

Double stranded cDNA molecules complementary to purified Rainbow trout protamine mRNA have been cloned in the bacterial plasmid pBR322. In order to circumvent the problems associated with a heterogeneous cDNA probe when identifying recombinants, a comparative hybridisation technique was used which can resolve between closely related cloned sequences. Using this technique, selected recombinants were shown to carry sequences corresponding to separate major fractions of protamine mRNA. Partial nucleotide sequences of the inserts in two clones confirms this conclusion.     

Demonstration of three major species of pseudorabies virus glycoproteins and identification of a disulfide-linked glycoprotein complex.

The glycoproteins of pseudorabies virus (PRV) Phylaxia were characterized with monoclonal antibodies as specific reagents. Three major structural glycoproteins with molecular weights of 155,000 (155K) (gC), 122K (gA), and 90K (gB) could be identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing conditions. We investigated the processing of glycoproteins gA, gB, and gC by in vitro translation, pulse-chase experiments, and in the presence of the ionophore monensin which inhibits glycosylation. gA and gB were found to compose a single polypeptide, whereas gC was found to be a disulfide-linked glycoprotein complex. Immunoprecipitates formed with the aid of anti-gC monoclonal antibodies gave rise to three glycoprotein bands (gC0 [120K], gC1 [67K], and gC2 [58K]) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. Limited proteolysis of gC0, gC1, and gC2 resulted in peptide maps of gC0 related to those of both gC1 and gC2. No common peptide bands between gC1 and gC2, however, were seen. We suggest that (i) gC1 and gC2 arise by proteolytic cleavage from the same precursor molecule and stay joined via disulfide bridges and (ii) gC0 is an uncleaved precursor.     

A comparison of swimming structures and kinematics in three species of crustacean larvae

Crustacean larvae swim with paired rowing appendages that rotate around the body of the animal. The number of paired rowing appendages varies from one species of larvae to another. In addition, the size of the crustacean larvae is different between species and increases as they grow. The nature of the fluid forces changes as size increases, so the morphology and mechanics of swimming in these animals will change during increases in size. This article demonstrates the changing kinematics of locomotion between three species of crustacean larvae, which swim with one (Artemia franciscana), two (Carcinus maenas) or five (Homarus americanus) pairs of propulsive limbs. The relative change in the surface area and volume ratios of the locomotor structures are also demonstrated.     

A comparison of swimming structures and kinematics in three species of crustacean larvae

Crustacean larvae swim with paired rowing appendages that rotate around the body of the animal. The number of paired rowing appendages varies from one species of larvae to another. In addition, the size of the crustacean larvae is different between species and increases as they grow. The nature of the fluid forces changes as size increases, so the morphology and mechanics of swimming in these animals will change during increases in size. This article demonstrates the changing kinematics of locomotion between three species of crustacean larvae, which swim with one (Artemia franciscana), two (Carcinus maenas) or five (Homarus americanus) pairs of propulsive limbs. The relative change in the surface area and volume ratios of the locomotor structures are also demonstrated.     

Introgressive hybridization as a mechanism for species rescue

Rapid evolution on ecological time scales can play a key role in species responses to environmental change. One dynamic that has the potential to generate the diversity necessary for evolution rapid enough to allow response to sudden environmental shifts is introgressive hybridization. However, if distinct sub-species exist before an environmental shift, mechanisms that impede hybridization, such as assortative mating and hybrid inferiority, are likely to be present. Here we explore the theoretical potential for introgressive hybridization to play a role in response to environmental change. In particular, we incorporate assortative mating, hybrid inferiority, and demographic stochasticity into a two-locus, two-allele population genetic model of two interacting species where one locus identifies the species and the other determines how fitness depends on the changing environment. Simulation results indicate that moderately high values for the strength of assortative mating will allow enough hybridization events to outweigh demographic stochasticity but not so many that continued hybridization outweighs backcrossing and introgression. Successful introgressive hybridization also requires intermediate relative fitness at the allele negatively affected by environmental change such that hybrid survivorship outweighs demographic stochasticity but selection remains strong enough to affect the genetic dynamics. The potential for successful introgression instead of extinction with greater environmental change is larger with monogamous rather than promiscuous mating due to lower stochasticity in mating events. These results suggest species characteristics (e.g., intermediate assortative mating and mating systems with low variation in mating likelihood) which indicate a potential for rapid evolution in response to environmental change via introgressive hybridization.     

三种萤火虫幼虫臀足的形态与功能

本文利用显微拍照和电镜扫描技术,以黄缘窗萤(Pyrocoelia analis)、穹宇萤(Pygoluciola qingyu)和雷氏黄萤(Aquatica leii)为例,对四川峨眉山较为常见的三种萤火虫幼虫臀足的形态结构及功能进行了研究。研究表明,三种萤火虫幼虫臀足的相似特征为:腹内侧均有趾钩,趾钩的排布规律基本相同;均为左右对称的两部分,背外侧的臀足较长,腹内侧的臀足较短;基本都为白色透明。不同特征为:黄缘窗萤幼虫的臀足数量最多,穹宇萤次之,雷氏黄萤最少;黄缘窗萤幼虫的臀足存在一级或两级的分叉现象,而另外两种则无此现象;臀足基部的斑纹和刚毛的情况各有不同,差异较大。三种萤火虫幼虫臀足都有着相似的功能:吸附功能,将身体吸附在物体上;作为清理工具,清理体表黏着的泥土等脏物;辅助爬行。此外,穹宇萤幼虫还可利用臀足筑巢化蛹。     

Food selection in adults and larvae of three species of Lepidoptera: a behavioural and electrophysiological study

Adults and larvae of Spodoptera littoralis, Heliothis virescens and Heliothis armigera were tested with a range of sugars, amino acids, sugar alcohols and allelochemics. Feeding behaviour was correlated with the electrophysiological responses of maxillary styloconic sensilla in the larvae and proboscis styloconic sensilla in the adult. The neural response was more vigorous in larvae than in adults but otherwise the spectra of responses were similar in the two life stages. Phagostimulants and antifeedants stimulated maximally different sensilla in larvae but not in adults. The responses of adult sensilla to sugars and amino acids were significantly correlated to behaviour in all three species, but only in H. armigera was there a similar correlation with the sugar alcohols and allelochemics.