Anal Gills Research Articles

Histological validation of in-vivo larvicidal efficacy of marine Streptomyces sp. RD06 secondary metabolites against filariasis causing Culex quinquefasciatus and statistical media optimization for larvicidal derivatives production

Mosquito-borne disease pandemics, such as the Zika virus and chikungunya, have escalated cognizance of how critical it is to implement proficient mosquito vector control measures. The prevention of Culicidae is becoming more difficult these days because of the expeditious imminence of synthetic pesticide resistance and the universal expansion of tremendously invasive mosquito vectors. The present study highlights the insecticidal and larvicidal efficacy of the prospective novel actinobacterium derived from the marine Streptomyces sp. RD06 secondary metabolites against Culex quinquefasciatus mosquito. The pupicidal activity of Streptomyces sp. RD06 showed LC50=199.22 ± 11.54 and LC90= 591.84 ± 55.41 against the pupa. The purified bioactive metabolites 1, 2-Benzenedicarboxylic acid, diheptyl ester from Streptomyces sp. RD06 exhibited an LC50 value of 154.13 ± 10.50 and an LC90 value of 642.84 ± 74.61 tested against Cx. quinquefasciatus larvae. The Streptomyces sp. RD06 secondary metabolites exhibited 100 % non-hatchability at 62.5 ppm, and 82 % of hatchability was observed at 250 ppm. In addition, media optimization showed that the highest biomass production was attained at a temperature of 41.44 °C, pH 9.23, nitrogen source 11.43 mg/ml, and carbon source 150 mg/ml. Compared to control larvae, the histology and confocal microscopy results showed destruction to the anal gill, lumen content, and epithelial layer residues in the treated larvae. Utilizing an eco-friendly method, these alternative inventive insecticidal derivatives from Streptomyces sp. RD06 eradicates Culex quinquefasciatus. This study highlights the promising potential of these Streptomyces sp. RD06 secondary metabolites to develop affordable and efficacious mosquito larvicides to replace synthetic insecticides in the future.

Casearia tomentosa fruit extracts exposed larvicidal activity and morphological alterations in Culex quinquefasciatus and Aedes albopictus under in vitro and semi field conditions

Mosquitoes are notorious insects that transmit a wide range of infectious diseases, including zika, malaria, chikungunya, filariasis, and dengue. The overuse and incorrect application of synthetic pesticides to control mosquitoes has resulted in resistance development and environmental contamination, both of which have had a negative impact on human health. To address this issue, the larvicidal and pupicidal potential of acetone extract from Casearia tomentosa fruits was investigated. The extract was evaluated in a lab setting against all larval instars and pupa of Culex quinquefasciatus and Aedes albopictus, as well as against third instar larvae in a semi-field condition. Purified compounds through TLC were also tested against 3rd instar larvae of both mosquito and non-target organisms. The FT-IR and GC-MS analyses were used to characterise the extract. Morphological aberration caused by the acetone extract was observed using FESEM. The anal gills and respiratory siphon of both mosquitoes showed significant deformation from their normal state. 100 ppm was found to cause 100% larval mortality at 24 h of exposure in case of Cx. quinquefasciatus and at 72 h of exposure in Ae. albopictus larvae. After 72 h of exposure under in vitro conditions, the extract demonstrated considerable larvicidal activity with LC50 values of 38.33 and 47.56 against 3rd instar larvae of Culex quinquefasciatus and Aedes albopictus, respectively. The acetone extract can be considered as a highly effective mosquito larvicidal agent that is safe for the environment.Graphical abstract

Larvicidal potential, toxicological assessment, and molecular docking studies of four Egyptian bacterial strains against Culex pipiens L. (Diptera: Culicidae)

Mosquito control in Egypt depends on applying chemical synthetic pesticides that impact negatively on human health and the environment as well as the development of antibiotic and chemical resistance. This study aims to control the 3rd and 4th instars of Culex pipiens larvae using four bacterial strains. According to Phenotypic and molecular identification, the four isolates were identified as Bacillus subtilis MICUL D2023, Serratia marcescens MICUL A2023, Streptomyces albus LARVICID, and Pseudomonas fluorescens MICUL B2023. All strains were deposited in GenBank under accession numbers OQ764791, OQ729954, OQ726575, and OQ891356, respectively. Larvicidal activity of all microbial strain metabolites against a field strain of C. pipiens explored low LC50 results and reached its lowest values on the 3rd day with values of 6.40%, 38.4%, and 46.33% for P. fluorescens, S. albus, and S. marcescens, respectively. In addition, metabolites of P. fluorescence were more toxic than those of S. albus, followed by S. marcescens. B. subtilis shows no larvicidal effect on both field and lab mosquito strains. Microscopic alterations of 3rd and 4th instars showed toxic effects on different body parts (thorax, midgut, and anal gills), including losing external hairs, abdominal breakage, and larvae shrinkage, as well as different histological malformations in the digestive tract, midgut, and cortex. GC–MS analysis detected 51, 30, and 32 different active compounds from S. albus, S. marcescens, and P. fluorescens, respectively. GC detected 1, 2-BENZEA2:A52NEDICARBOXYLIC ACID, 2-Cyclohexene-1-carboxylic-acid-5-2-butenyl-methyl ester, and 3 octadecahydro2R3S4Z9Z-11R-12S from S. albus, S. marcesens, and P. fluorescens, respectively. Total protein, Total carbohydrate, and Acetylcholine esterase activity indicated significantly low levels on the 3rd day. All strain metabolites were safe against HSF cell lines. The docking results confirmed the role of the produced metabolites as larvicidal agents and Acetylcholine esterase inhibition. Such a problem need more studies on applying more and more natural pesticides.

PLANTS EXTRACTS AS AN EFFECTIVE CONTROLLING AGENT AGAINST MOSQUITO: A REVIEW

Different plant extracts and their oils can be used to jurisdiction different species of mosquitoes. Mosquitoes causes many life threatening disease like malaria, zika virus and dengue, so it is crucial to control it by using some biological ways instead of chemical ways. As there are many chemicals to control it but it’s better to use biologicals ways to control the pest as plant extract are ecofriendly to use so using plant extracts is safe to control the pest. Garlic (Allium sativum) , Momordica charantia, and Black pepper (Piper nigrum) was found to be effective against different mosquitoes. Allium sativum contain some compounds having ajoene, diallyl polysulfides, allicin, S-allylcysteine, and enzymes like saponins, flavonoids, and Maillard reaction products, These phytochemicals fabricated by garlic are the major contributors to the characteristic odor of garlic, has bactericidal properties, interfere and restrict the synthesis of parasite cell membranes and causes lysis, and helps in killing mosquitoes by blocking their respiratory system and even Momordica charantia leaves have flavonoids, alkaloids, saponins and terpenoids they will enter into the digestive tract of the mosquito larvae and then got absorbed by the intestinal wall of the tract and then after that will circulate all along the blood that will interfere with the metabolism of body of the mosquito and kills them. Piper nigrum also have compoundPiperine which is very pungent and a very strong alkaloid. It also contains some compound like sabinene, safrol, pinene, limonene, caryo-phyllene and linaonol. It exhibited good larvicidal and mortality activities and showed abnormal behavior and became restless in mosquitos then muscle contraction seize which lead to paralysis and eventually mosquito dies so the extract of these species basically attack on the neuromuscular system of the mosquito and the anal gill membrane also shrinks. So these can be used to kill mosquito using the biological ways.

Utilization of electrocoagulation for the isolation of alkaloids from the aerial parts of Stemona aphylla and their mosquitocidal activities against Aedes aegypti

The electrocoagulation (EC) technique is an alternative method of isolating natural products with the advantage of minimizing the amounts of organic solvents required for this process, which are often harmful to the environment. In this research, the EC and the conventional solvent extraction methods were used in the isolation of Stemona alkaloids from the aerial parts of Stemona aphylla. A comparison was made between the amounts of the isolated alkaloids and the solvents used. The isolated alkaloids were evaluated for their larvicidal, ovicidal and oviposition-deterrent activities against the dengue vector, Aedes aegypti. The morphology and histopatology of the alkaloid treated larvae were also investigated. Two Stemona alkaloids, (2′S)-hydroxystemofoline and stemofoline, were isolated from both the EC and the conventional method. The amounts of (2′S)-hydroxystemofoline from the EC method was about the same as that obtained from the conventional method. However, the amounts of stemofoline obtained from the EC method were about two times larger than those obtained from the conventional method. Importantly, the EC method required six times less total organic solvents. The larvicidal activity assays of (2′S)-hydroxystemofoline and stemofoline showed that these were highly effective against Aedes aegypti larvae with LC50 values of 3.91 μg/ml and 4.35 μg/ml, respectively. Whereas, the crude EC extract (LC50 = 11.86 μg/ml) showed greater larvicidal activity than the crude extract obtained from the conventional extraction method (LC50 = 53.40 μg/ml). The morphological observations of the (2′S)-hydroxystemofoline and the stemofoline treated larvae revealed that the anal gills were the sites of aberrations. A histopathological study showed that larvae treated with these alkaloids had cytopathological alterations to the epithelial cells of the midgut. At a concentration 40 μg/ml (2′S)-hydroxystemofoline showed 100% ovicidal activity on 24 h old eggs while stemofoline showed 97.2%. Furthermore, the oviposition-deterrent effects of (2′S)-hydroxystemofoline and stemofoline, at a concentration of 80 μg/ml were 99.5% and 97.2%, respectively.

Toxicity and possible mechanisms of action of honokiol from Magnolia denudata seeds against four mosquito species

This study was performed to determine the toxicity and possible mechanism of the larvicidal action of honokiol, extracted from Magnolia denudata seeds, and its 10 related compounds against third-instar larvae of insecticide-susceptible Culex pipiens pallens, Aedes aegypti, and Aedes albopictus and Anopheles sinensis resistant to deltamethrin and temephos. Honokiol (LC50, 6.13–7.37 mg/L) was highly effective against larvae of all of the four mosquito species, although the toxicity of the compound was lower than that of the synthetic larvicide temephos. Structure–activity relationship analyses indicated that electron donor and/or bulky groups at the ortho or para positions of the phenol were required for toxicity. Honokiol moderately inhibited acetylcholinesterase and caused a considerable increase in cyclic AMP levels, indicating that it might act on both acetylcholinesterase and octopaminergic receptors. Microscopy analysis clearly indicated that honokiol was mainly targeted to the midgut epithelium and anal gills, resulting in variably dramatic degenerative responses of the midgut through sequential epithelial disorganization. Honokiol did not affect the AeCS1 mRNA expression level in Ae. aegypti larvae, but did enhance expression of the genes encoding vacuolar-type H+-ATPase and aquaporin 4, indicating that it may disturb the Na+, Cl− and K+ co-transport systems. These results demonstrate that honokiol merits further study as a potential larvicide, with a specific target site, and as a lead molecule for the control of mosquito populations.

Identification key to the mosquito (Diptera: Culicidae) larvae of the Tongatapu Island group, Kingdom of Tonga

ABSTRACTAn illustrated key is provided for the identification of third and fourth instar larvae of the nine mosquito species known to occur in the Tongatapu island group, Kingdom of Tonga. This includes five Aedes species: Ae. aegypti (Linnaeus, 1762), Ae. albopictus (Skuse, 1895), Ae. horrescens Edwards, 1935, Ae. tongae Edwards, 1926, and Ae. vexans nocturnus (Theobald, 1903) and four Culex species: Cx. quinquefasciatus Say, 1823, Cx. annulirostris Skuse, 1889, Cx. albinervis Edwards, 1929, and Cx. sitiens Wiedemann, 1828. The key includes illustrations of diagnostic features of both the third and fourth instar larvae (siphon, tufts, saddle, comb scales and anal gills). This will help workers correctly identify mosquito larvae in the Tongatapu island group, of which several species (Ae. aegypti, Ae. albopictus, Cx. quinquefasciatus, Cx. annulirostris) are medically important vectors of disease.

Variation in morphometric and meristic traits of Aspidoparia morar from Brahmaputra and Barak Rivers of Assam, India

The minor carp, Aspidoparia morar is a benthopelagic fish belonging to the sub-family Danioninae under the family Cyprinidae. It has emerged as the single most dominant species in the river Brahmaputra in Assam. In the present study, 240 specimens were collected from Guwahati and Tezpur in the Brahmaputra River and Silchar in the Barak River to investigate the morphometric and meristic variation among the populations. For this a total of 20 morphometric traits and 11 meristic traits were studied. The mean lengths for most of the morphometric traits were higher for the Barak River except eye diameter, inter orbital length and anal fin length which were significantly higher on the Brahmaputra River, while the post orbital length and pelvic fin length were found to be almost equal. The regressions of standard length with all the morphometric traits except pelvic fin length, pelvic fin base, pectoral fin length, dorsal fin length, anal fin length, pre orbital length, post orbital length, inter orbital length and eye diameter showed significant variation between the rivers. Two meristic traits viz. branched rays in anal fin and gill rakers on the first gill arch also showed significant variation in the samples of the rivers.

Novel Histopathological and Molecular Effects of Natural Compound Pellitorine on Larval Midgut Epithelium and Anal Gills of Aedes aegypti

The yellow fever mosquito, Aedes aegypti, is a vector for transmitting dengue fever and yellow fever. In this study, we assessed the histopathological and molecular effects of pellitorine, an isobutylamide alkaloid, on the third instar of Ae. aegypti larvae. At 5 mg/l concentration of pellitorine, the whole body of the treated larvae became dark in color, particularly damaged thorax and abdominal regions. Pellitorine was targeted mainly on midgut epithelium and anal gills, indicating variably dramatic degenerative responses of the midgut through a sequential epithelial disorganization. The anterior and posterior midgut was entirely necrosed, bearing only gut lumen residues inside the peritrophic membranes. Pellitorine caused comprehensive damage of anal gill cells and branches of tracheole and debris was found in hemolymph of the anal gills. RT-PCR analysis indicates that the compound inhibited gene expression encoding V-type H+-ATPase and aquaporine 4 after treatment with 2.21 mg/l pellitorine. These results verify that pellitorine merits further study as a potential larvicide with a specific target site and a lead molecule for the control of mosquito populations.

Comparison of Biological Attributes ofCulex quinquefasciatus(Diptera: Culicidae) Populations from India

Understanding the population dynamics of mosquito populations through life table analysis and insecticide susceptibility is important to assess the likely impact of vector control strategies as well as to aid the design of novel interventions. Variation in the life tables and other biological data was compared for two populations ofCulex quinquefasciatusSay 1823 from geographically isolated regions, Gorakhpur and Pune from India. Under a standardized rearing regime and constant laboratory conditions, mosquitoes were reared and biological attributes of these populations were compared. Development and survival of immature and adult stages ofCulex quinquefasciatuswere found significantly different in Gorakhpur and Pune populations. Principal component analysis of morphological data revealed that the two populations form significantly different clusters which can be differentiated from each other based on siphon, saddle, anal gills, and pecten teeth related variables. Insecticide susceptibility results suggest that the larvae from both areas were more susceptible to deltamethrin as compared to DDT and malathion. The current study provides baseline information on survivorship, morphological variation and insecticide susceptibility ofCulex quinquefasciatus. The results obtained in this study suggest that different geographical areas with contrasting habitats have significant influence on survival and reproductive strategies ofCulex quinquefasciatus.

<p class="SP180260"><strong>Utilization of alien freshwater fishes by the parasitic copepod <em>Neoergasilus japonicus </em>(Ergasilidae) on Okinawa-jima Island, Japan, with a list of its known hosts</strong></p>

Currently, many fish parasites have been dispersed worldwide via the movement of fishes for food, sport, or the aquarium trade. The freshwater parasitic copepod Neoergasilus japonicus (Harada, 1930) is such an example: it is native to eastern Asia, but has been introduced to southern Asia, Europe, and North America. Since N. japonicus has been regarded as an important alien parasite in such regions, more information is needed on the ecology and host-parasite relationships of this species. In this study, specimens of N. japonicus were collected from the following seven alien freshwater fishes on Okinawa-jima Island, southern Japan: redbelly tilapia (Tilapia zillii), Mozambique tilapia (Oreochromis mossambicus), and Nile tilapia (O. niloticus niloticus) (Perciformes: Cichlidae); bluegill (Lepomis macrochirus) (Perciformes: Centrarchidae); Indian glassy fish (Pseudambassis ranga) (Perciformes: Ambassidae); mosquitofish (Gambusia affinis) (Cyprinodontiformes: Poeciliidae); and vermiculated sailfin catfish (Pterygoplichthys disjunctivus) (Siluriformes: Loricariidae). Copepods occurred on alien fishes taken from reservoirs, but were absent on those from rivers. The dorsal fin was most heavily infected, followed by the anal fin, gills, and body surface. The native freshwater fishes in our sampling locations have been replaced by alien fishes that were introduced from various regions of the world. Our results therefore showed that this low host-specific species can persist by utilizing alien fishes as hosts even after the native fishes have either disappeared or greatly decreased in abundance. A list is also given of fishes (88 species and 3 subspecies in 7 orders and 16 families) reported as hosts of N. japonicus.

Insecticidal activity against Aedes aegypti of m‐pentadecadienyl‐phenol isolated from Myracrodruon urundeuva seeds

Myracrodruon urundeuva Fr. Allemao is a common tree in the Caatinga that has been widely used for various medical purposes. Previous studies showed that the ethanol seed extract of M. urundeuva has potent activity against the larval stage of the dengue vector Aedes aegypti. Given this potential insecticidal activity, bioguided separation steps were performed in order to isolate the active compound(s). The isolation process resulted in only one active chemical compound, identified by infrared spectroscopy and mass spectrometry as m-pentadecadienyl-phenol. This compound presented potent larvicidal and pupicidal activity (LC50 10.16 and 99.06 µg mL(-1) respectively) and great egg hatching inhibitory activity (IC50 49.79 µg mL(-1)). The mode of action was investigated through observations of behavioural and morphological changes performed in third-instar larvae treated with m-pentadecadienyl-phenol solution after 1, 6, 12, 16 and 20 h of exposure. Some changes were observed as flooding of the tracheal system, alterations in siphonal valves and anal gills and lethargy, probably caused by the strong anticholinesterasic activity reported previously. The compound isolated from M. urundeuva seeds, m-pentadecadienyl-phenol, showed potent activity against immature stages of dengue vector, Ae. aegypti, being considered the main larvicidal principle.

Growth and morphological characteristics comparison of northern large-mouth bass, Florida largemouth bass and their reciprocal hybrids

Based on northern largemouth bass and florida largemouth bass, four populations including selfing of N(Micropterus salmoides salmoides ♀×M. s. salmoides♂) and F(M. s. floridanus ♀×M. s. flori-danus♂), direct cross NF(M. s. salmoides♀×M. s. floridanus♂) and FN(M. s. floridanus♀×M. s. sal-moides♂) were established. Further comparative analysis of growth and morphological characteristics were carried out between parents and their reciprocal hybrids. The results were as follows. The growth rates had no difference between N, NF and FN on 152nd day. After 152 days the northern largemouth bass grew more rapidly than two hybrids. As meristic characters, the numbers of soft ray of pelvic, spine of anal fin, gill raker and vertebra were consistent in these four populations, and the chi-square analysis of meristic characters showed highly significant differences between parents and hybrids in soft ray of dorsal, soft ray of pectoral, soft ray of anal fin, soft ray of tail fin, scales above lateral line and scales below lateral line. The results of cluster analysis have revealed that the morph metric characters of N and F were much closer, the same to the reciprocal hybrids groups. Three principal components with accumulative variance per-centage 71.44% were summarized in principal component analysis. The principal components 1, 2 and 3 reflected the morphological variations of frame, head and caudal peduncle, with the variance percentage being 54.90%, 11.20% and 5.33%. In discriminant analysis, 11 parameters were selected from 35 measured parameters to establish discriminant functioned of the populations. Discriminant accuracy was 83.90%—100.00%. This study would be beneficial to the identification, breeding and aquaculture of largemouth bass.

Occurrence ofMegaselia imitatrixBorgmeier andMegaselia hansonixDisney in Florida (Diptera: Phoridae)

During a study of container-inhabiting mosquitoes in the Florida Keys, Hribar et al. (2004) reported finding larvae of a phorid fly, Megaselia scalaris (Loew), in some aquatic habitats. Identification was made on the basis of reared adults. Since that time, aquatic phorid larvae occasionally have been collected during routine mosquito surveillance. Examination of those larvae revealed that their general habitus did not conform to that of descriptions of the larva of M. scalaris. Particularly notable were the caudal spiracles being located on an extensible tube, similar to beach fly larvae (Diptera: Canacidae), and large bulbous anal gills, typical of aquatic Phoridae (Disney 1991). Some specimens were cleared and slidemounted and the cephalopharyngeal skeleton compared to illustrations of that of M. scalaris (Liu & Greenberg 1989). Cephalopharyngeal morphology was not consistent with M. scalaris; instead, larval morphology was consistent with Megaselia imitatrix Borgmeier and M. hansonix Disney (Hanson & Disney 2008; Disney et al. 2009). Attempts to rear additional larvae to the adult stage were unsuccessful. However, adult phorids were seen occasionally in traps set for adult mosquito surveillance. The Florida Keys Mosquito Control District deploys several different mosquito traps for adults. Phorids were collected in dry-ice-baited ABC light traps (Clarke Mosquito Control, Roselle, Illinois, USA) and BG Sentinel traps (Biogents, Regensburg, Germany) baited with octenol and lactic acid. Adult Phoridae were cleared and mounted on microscope slides according to the protocol of Wirth & Marston (1968). Adult males were compared with the figures and description provided by Disney et al. (2009). Four species were identified: Megaselia hansonix Disney, M. imitatrix Borgmeier, M. scalaris (Loew), and an apparently undescribed species of Megaselia. Voucher specimens of adult flies have been deposited in the Los Angeles County Museum of Natural History, California, and the Cambridge University Museum of Zoology, UK.

Phylogeny and evolution of corambid nudibranchs (Mollusca: Gastropoda)

Organismic diversity, as well as distributional and ecological patterns, can be fully understood in an evolutionary framework only. Reliable phylogenetic trees are required to ‘read history’, but are not yet available for most marine invertebrate groups. Molecular systematics offers an enormous potential, but still fails for ‘all-species approaches’ on groups with species that are rare or occur in remote areas only, simply because there is no easily collectable material available for sequence analyses. Exploring morphologically aberrant corambid nudibranch gastropods as a case study, we assess whether or not morphology-based phylogenetic analyses can fill this gap and produce a tree that allows a detailed view on evolutionary history. Morphology-based parsimony analysis of corambids and potential relatives resulted in a well-resolved and remarkably robust topology. As an offshoot of kelp-associated onchidoridid ancestors, and obviously driven by the heterochronic shortening of life cycles and morphological juvenilization in an ephemeral habitat, the ancestor of corambids originated in cool northern Pacific coastal waters. A basal clade (the genus Loy) diverged there, adapting to live on soft bottoms under successive reversals of paedomorphic traits. The more speciose Corambe lineage radiated preying upon short-lived encrusting bryozoa in a high-energy kelp environment. Selection favoured transformation of the mantle into a cuticle-covered shield, and successive paedomorphic translocations of dorid anal gills to the protected ventral side of the body, where compensatory, multiple gills evolved. Corambe species probably first colonized tropical American seas, and then radiated in worldwide temperate waters: this is explained by the excellent long-distance dispersal abilities afforded by rafting on kelp, with the subsequent divergence of colonizers in allopatry. The competitive coexistence of Corambe pacifica MacFarland & O'Donoghue, 1929 and Corambe steinbergae (Lance, 1962) off California is the result of independent colonization events. The closing of the Isthmus of Panama separated the latter species from a flock that have radiated within warm Atlantic waters since then. Our case study shows that morphological structures, if investigated in depth, bear the potential for an efficient phylogenetic analysis of groups that are still elusive to molecular analyses. Tracing character evolution and integrating a wide range of geographic, biological, and ecological background information allowed us to reconstruct an evolutionary scenario for corambids that is detailed and plausible, and can be tested by future molecular approaches. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, 585–604.

3D-anatomy of a new tropical Peruvian nudibranch gastropod species, Corambe mancorensis, and novel hypotheses on dorid gill ontogeny and evolution

Nudibranch molluscs of the genus Corambe differ from most other Doridoidea by having ventral rather than dorsal anus and gills. Because of these and other features, such as separate cerebral and pleural ganglia, corambids have been considered as an archaic or enigmatic group. The first tropical eastern Pacific Corambe species is described in morphological and some histological detail. Selected organs such as circulatory and central nervous features are reconstructed from serial semithin histological slides and visualized in three dimensions using Amira software. Anatomical findings include two separate ganglia on the visceral loop and an additional ganglion on the right side of the body that is connected to the pedal ganglion. Corambe mancorensis n. sp. is dorsoventrally depressed, has an oval, fleshy notum covered with a cuticle, and has a wide posterior medial notch that can be closed completely by unique lobules. Gills are arranged in an unusual horseshoe-like manner including both phanerobranch anal (=medial) gills and corambid lateroventral gill rows, and are connected to the atrium by a complex vessel system. The three medial gills arise from a posterodorsal gill cavity within the notal notch, similar to the case in Corambe evelinae Marcus, 1958. By scanning electron microscopy a vestigial gill cavity is also detectable in C. pacifica MacFarland & O'Donoghue, 1929, but here it is situated ventrally. Our new information on adult corambids is compared with new and published ontogenetic data on phanerobranch and cryptobranch dorids, to contribute to a novel interpretation of the ontogeny of dorid mantle and gill complexes. The progenetic evolution of corambids ‘recapitulates’ early juvenile dorid stages – turning Haeckel's Law upside down.

Morphometric and Allozyme Variation inCulex tritaeniorhynchusMosquito Populations from India

Four populations of Culex tritaeniorhynchus (Giles) (Diptera: Culicidae), collected from Bellary, Cuddalore, Pune, and the Microbial Containment Complex laboratory culture in India were analyzed for morphological and allozyme variation. Multivariate analysis based on eight morphological characteristics and three morphometric indices was used to investigate the morphological variations among the four populations. Principal component analysis of the data suggested that siphon, saddle, and anal gills related variables were most important. Discriminant factor analysis of morphological data revealed that the four populations form significantly different clusters which can be differentiated from each other based on siphon, saddle, and pectin teeth related variables. Allozyme electrophoresis of the four populations revealed that the mean heterozygosity per locus value had high variation, ranging from 0.0879 to 1.794. Fst values between 0 and 0.519 suggested genetic differentiation within these populations. Fis values ranged from 0 to 1 with most of the values closer to 1. The allelic frequencies and Nei's genetic identity values showed that genetic differences between populations were small, but significant. Some of the morphological and allozyme variations in the Cx. tritaeniorhynchus populations could be partly attributed to the environmental conditions. The findings suggested that transition of morphological characters and allozyme variations in Cx. tritaeniorhynchus populations seem to be consequences of influence and selection by the environmental conditions. These results indicated that populations of Cx. tritaeniorhynchus in non-endemic areas of Japanese encephalitis (JE) virus infection have higher adaptability as compared to endemic areas of JE infection.

Mosquito-killing water molds isolated from soil samples collected in Taiwan

Mosquito-killing water molds were isolated from soils collected from various parts in Taiwan. The first-instar larvae of Aedes aegypti and Aedes albopictus were used as baits. A total of 453 soil samples were collected from Taipei, Ilan, Hualien, Taoyuan, Hsinchu, Miaoli, Taichung, Tainan, Nantou, Chiayi, Yunlin and Pintung. Four mosquito-killing Pythium spp. and one Saprolegnia sp. were isolated from the soil samples. Using zoospores of the Pythium spp. as inoculum to infect the first-instar larvae, scanning electron micrographs showed that most zoospores attached in the anal gill and a few attached between head and thorax. Thus, Pythium spp. is a potential biocontrol agent against first-instar larvae of A. aegypti and A. albopictus .

Effect of ultraviolet activated alfa-terthienyl upon anal gill membrane of mosquito larvae: a spin label study

The mode of interaction of the plant-derived phototoxic insecticide alfa-terthienyl was examined in larvae of the mosquito Aedes aegypti, using spin-labelling and electron paramagnetic resonance (EPR) spectral techniques. Spin-labels 16-doxyl stearate and TEMPO were used to probe the lipid and aqueous fractions of the gill membrane. Exposure of mosquito larvae to alfa-terthienyl and ultraviolet light resulted in loss of membrane integrity, damaging the lipid and aqueous components of the gill membrane. The potential role of singlet oxygen in mediating this alfa-terthienyl phototoxicity is discussed.

Generation of superoxide anion radical by alpha-terthienyl in the anal gills of mosquito larvae Aedes aegypti: a new aspect in alpha-terthienyl phototoxicity.

The present study documents that the secondary plant metabolites, especially alpha-terthienyl, exert phototoxic action through inhibition of certain enzymes and generation of singlet oxygen. Some of the reports have emerged exhibiting involvement of free radical generation in vitro by alpha-terthienyl. We provide evidence for the generation of a free radical viz., superoxide anion radical, by alpha-terthienyl employing spin-trapping techniques, probably due to the extension of the latter reaction. On the basis of this observation the phototoxic action of alpha-terthienyl on Aedes aegypti larvae is explained.