scholarly journals Larvicidal Effect of Vorticella microstoma (Ehrenberg, 1830) on Mosquito Larvae, and Morphological Changes under Induced Environmental Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Achini Koshila Ranasinghe ◽  
L. D. Amarasinghe
Keyword(s):  
Environmental Conditions ◽  
Biocontrol Agent ◽  
Morphological Changes ◽  
Weather Conditions ◽  
Mosquito Larvae ◽  
Larvicidal Effect ◽  
Breeding Habitats ◽  
Mosquito Breeding ◽  
Tropical Weather ◽  
A Current

Development of microbiota assemblage usually occurs in all most all domestic and peridomestic mosquito breeding habitats. There may be parasitic, epibiont, pathogenic, or even predatory species among this biota, and to investigate their potential against the mosquito population is worth studying. This may contribute to formulating environmentally agreeable approaches in controlling mosquitoes which is a current need. Vorticella spp. is a peritrich ciliate, and its trophont stage has become epibiont to certain biota. Further, their existence in seasonal water bodies that dry off during drought in tropical weather conditions is not known. Therefore, the potential of the larvicidal effect of Vorticella microstoma on different species of mosquito larvae was studied. We found that V. microstoma causes the 100% death of the third instar larvae of Culex tritaeniorhynchus (Giles, 1901) within 48 h of exposure. In contrast to that, this species did not cause any mortality to Aedes albopictus (Skuse, 1894) and Aedes aegypti (Linnaeus in Hasselquist, 1762) mosquito larvae in repeated trials. The dynamics of polymorphism of V. microstoma was studied under induced environmental conditions. V. microstoma remained as trophont stage throughout at room temperature (25±2°C). When the temperature was reduced to 6°C, V. microstoma settled in the cyst stage. Evidently, V. microstoma is a good biocontrol agent of Culex species mosquito larvae, and they able to overcome drought periods in cyst forms. The findings of this study would be considered as the first step for a new avenue to work on environmentally agreeable manner in reducing the Culex spp. mosquito populations.

scholarly journals Naturally Occurring Microbiota Associated with Mosquito Breeding Habitats and Their Effects on Mosquito Larvae

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
H. A. K. Ranasinghe ◽  
L. D. Amarasinghe
Keyword(s):  
Abiotic Factors ◽  
Mosquito Species ◽  
Breeding Habitat ◽  
Larval Abundance ◽  
Mosquito Larvae ◽  
Natural Habitats ◽  
Individual Fitness ◽  
Naturally Occurring ◽  
Breeding Habitats ◽  
Mosquito Breeding

Immature mosquitoes are aquatic, and their distribution, abundance, and individual fitness in a particular breeding habitat are known to be dependent on mainly three factors: biotic factors, abiotic factors, and their interaction between each other and with other associated taxa. Mosquito breeding habitats harbor a diversified naturally occurring microbiota assemblage, and the biota have different types of interactions with mosquito larvae in those habitats. Those interactions may include parasitism, pathogenism, predation, and competition which cause the mortality of larvae, natural reduction of larval abundance, or alterations in their growth. Many microbiota species serve as food items for mosquito larvae, and there are also some indigestible or toxic phytoplanktons to larvae. However, when there is coexistence or mutualism of different mosquito species along with associated microbiota, they form a community sharing the habitat requirements. With the available literature, it is evident that the abundance of mosquito larvae is related to the densities of associated microbiota and their composition in that particular breeding habitat. Potential antagonist microbiota which are naturally occurring in mosquito breeding habitats could be used in integrated vector control approaches, and this method rises as an ecofriendly approach in controlling larvae in natural habitats themselves. To date, this aspect has received less attention; only a limited number of species of microbiota inhabiting mosquito breeding habitats have been recorded, and detailed studies on microbiota assemblage in relation to diverse vector mosquito breeding habitats and their association with mosquito larvae are few. Therefore, future studies on this important ecological aspect are encouraged. Such studies may help to identify field characteristic agents that can serve as mosquito controlling candidates in their natural habitats themselves.

scholarly journals Naturally Occurring Microbiota in Dengue Vector Mosquito Breeding Habitats and Their Use as Diet Organisms by Developing Larvae in the Kandy District, Sri Lanka

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
H. A. K. Ranasinghe ◽  
L. D. Amarasinghe
Keyword(s):  
Sri Lanka ◽  
Food Limitation ◽  
Mosquito Larvae ◽  
Dengue Vector ◽  
Additional Tool ◽  
Food Items ◽  
Naturally Occurring ◽  
Breeding Habitats ◽  
Vector Mosquito ◽  
Mosquito Breeding

Naturally occurring microbiota in mosquito larval habitats are among biotic factors which affect the population dynamics of developing larvae. Many microbiota species serve as food items for vector mosquito larvae, and food limitations within habitats adversely affect larval survival, developmental rate, adult fitness, and thereby vector competence. Therefore, identification of microbiota as associates with larvae reveals their relationship between each other as parasites, pathogens, epibionts, or diet organisms. Analysis of associated microbiota species in the dengue vector larval breeding habitats ( n = 40 ) and the mosquito larval gut content were conducted in Kandy District in Sri Lanka. Study revealed that a total of 22 microbiota species belong to nine phyla (Amoebozoa, Bacillariophyta, Ciliophora, Chlorophyta, Sarcodina, Cyanobacteria/Cyanophyta, Euglenozoa, Ochrophyta/Heterokontophyta, and Rotifera) were encountered from different Ae. aegypti mosquito breeding habitats while 26 microbiota species that belonged to ten phyla were recorded from Ae. albopictus mosquito breeding habitats with one additional phylum Arthropoda. Considering Ae. aegypti breeding habitats, only Philodina citrina in low roof gutters existed as constant species. Considering Aedes albopictus breeding habitats, Volvox aureus in plastic containers, Lecane luna in coconut shells, Phacus pleuronectes in concrete slabs, and Pinnularia sp. in tree holes existed as constant species. The rest of the microbiota existed as common or accidental/rare species in a variety of habitat types. The Shannon-Weiner diversity (21.01 and 19.36) and gamma diversity (eight and eight) of the microbiota associated with Ae. aegypti and Ae. albopictus larvae, respectively, in ponds were found to be higher than other types of breeding habitats recorded during the study. Twelve microbiota species were recorded from larval gut analysis as food organisms of both species of mosquito larvae. However, the distribution of gut microbiota species differed between Ae. aegypti and Ae. albopictus ( Chi − square = 21.294 , P = 0.002 ). Identification of microbiota as food items of vector mosquito larvae led to a focus on larval food limitation by introducing food competitors, which could be a potential additional tool for integrated vector control approaches within the country.

scholarly journals Diversity and Species Composition of Microbiota Associated with Mosquito Breeding Habitats: A Study from Kurunegala District in Sri Lanka

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
L. D. Amarasinghe ◽  
H. A. K. Ranasinghe
Keyword(s):  
Sri Lanka ◽  
Habitat Type ◽  
Lethal Effect ◽  
Common Species ◽  
Breeding Habitat ◽  
Mosquito Larvae ◽  
Breeding Habitats ◽  
Mosquito Breeding ◽  
Characteristic Features ◽  
The Relationship

The pool of microbiota associated with mosquito breeding habitats varies with the habitat type and its characteristic features. The pool of microbiota in a given mosquito breeding habitat can include free living, symbiotic, noncompetitive, parasitic, predatory, and toxin producing species. However, in Sri Lanka the studies on the microbiota associated with mosquito breeding habitats are scarce. The present study was conducted to identify microbiota species/taxa associated with a variety of mosquito breeding habitats in selected areas of the Kurunegala district in Sri Lanka to determine the relationship, if any, the microbiota has with mosquito larvae breeding. A total of 44 microbiota species/taxa belonging to 10 phyla, namely, Bacillariophyta, Charophyta, Chlorophyta, Cyanobacteria/Cyanophyta, Ochrophyta/Heterokontophyta, Amoebozoa, Euglenozoa, Ciliophora, Arthropoda, and Rotifera were identified. Vorticella microstoma (Ciliophora) showed a constant occurrence frequency in rice field habitats occupied mainly by Culex tritaeniorhynchus while the rest of the species had an accidental or rare frequency of occurrence. Nineteen species/taxa were identified as common species. Trophont stages of Vorticella microstoma and Zoothamnium spp. were found attached to the cuticle of mosquito larvae but only V. microstoma caused a lethal effect. The autotrophic protist, Euglena geniculate, Closterium spp., and Pinnularia spp. served as the diet items to mosquito larvae. The majority of the microbiota identified had no observable effect on mosquito larvae breeding.

PATHOGENICITY OF METARHIZIUM ANISOPLIAE VAR. ANISOPLIAE1 TO MOSQUITO LARVAE

1985 ◽  
Vol 20 (4) ◽  
pp. 398-404 ◽  
Author(s):  
Abdul K. A. Mohamed ◽  
Fred R. S. Nelson
Keyword(s):  
Laboratory Test ◽  
Field Test ◽  
Metarhizium Anisopliae ◽  
Rice Field ◽  
Mosquito Larvae ◽  
Breeding Habitats ◽  
Highly Sensitive ◽  
Significant Difference ◽  
Percent Mortality ◽  
Mosquito Breeding

Water samples from various mosquito breeding habitats did not have an effect on the efficacy of Metarhizium anisopliae var. anisopliae isolate E9 when treated in the laboratory against 3rd instar of Culex quinquefasciatus. At the highest dosage rate (5.0 mg), the percent mortality varied from 89.1 ± 4.8 in rice field water to 94.4 ± 4.1 in sewer drainage and open ditch water. In another laboratory test, all field collected instars (89.25% Culex, 8.50% Aedes and 2.25% Psorophora) were found to be highly sensitive to isolate E9. At the 5.0 mg rate the percent mortality ranged from 91.2 ± 2.9 in the 2nd instars to 100.0 in the 3rd instars. There was no significant difference (P = 0.05) in mortality between instars except at the lowest dosage (1.25 mg) where the 4th instar mortality (28.6 ±8.5%) was significantly lower than those of other instars. The LT50 values for the 1st through the 4th instar increased with age and ranged from 1.1 to 1.8, 1.7 to 2.7, and 2.0 to 4.3 days at the 5.0, 2.5 and 1.25 mg dosages, respectively. In a preliminary field test to determine the susceptibility of field collected 3rd instar, up to 97.9 ± 1.8% mortality was recorded at the 800 mg rate.

scholarly journals Naturally Occurring Microbiota Associated with Mosquito Breeding Habitats and Potential Parasitic Species against Mosquito Larvae: A Study from Gampaha District, Sri Lanka

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
H. A. K. Ranasinghe ◽  
L. D. Amarasinghe
Keyword(s):  
Species Richness ◽  
Sri Lanka ◽  
Habitat Type ◽  
Lethal Effect ◽  
Breeding Habitat ◽  
Paddy Fields ◽  
Mosquito Larvae ◽  
Naturally Occurring ◽  
Breeding Habitats ◽  
Mosquito Breeding

A mosquito species has its own favourable requirements of abiotic and biotic characteristics including microbiota, in a breeding habitat. Some of the microbiota may cause parasitic or pathogenic effects to mosquito larvae such as species of viruses, parasitic bacteria, fungi, protists, entomopathogenic nematodes, and filamentous fungi. In Sri Lanka, there is a scarcity of information on microbiota associated with mosquito breeding habitats and their effect on mosquito larvae. Hence, the present study was conducted to determine microbiota species/taxa associated with a variety of mosquito breeding habitats in selected areas of the Gampaha District in Sri Lanka and the relationship, if any, the microbiota has with mosquito larva survival and breeding. Forty-five microbiota species belonging to 11 phyla were found from different mosquito breeding habitats with the highest percentage belonging to phylum Euglenozoa (27.89%). Species that belonged to the phylum Amoebozoa (1.22%) and Sarcodina (1.17%) had the lowest abundance, and each of its species richness was recorded as one. Philodina citrina followed by Monostyla bulla comprised 30.8% and 16.59%, respectively, of the total rotifer population. From the total microbiota, 25-50% existed as accidental while less than 25% rare, in the habitat type according to their abundance. Paddy fields had the highest species richness (17), evenness (23.52), Shannon-Weiner (66.64), and beta diversity (0.65) over 50% indicating high heterogeneity in microbiota composition among the habitats. Ciliated protists, namely, Vorticella microstoma, Zoothamnium spp., and Chilodinella sp., were identified as naturally occurring microbiota associated with Culex mosquito larvae that inhabited in paddy fields and associated irrigation canals. Only Vorticella microstoma caused a significant lethal effect on mosquito larvae. This study revealed that species of Cx. gelidus, Cx. pseudovishnui, Cx. tritaeniorhynchus, Cx. quinquefasciatus, and Cx. whitmorei served as hosts for V. microstoma where infectivity rate in Cx. tritaeniorhynchus reached 73.22. Chilodinella sp. selectively served as endoparasitic to Cx. gelidus larvae causing only 4.58% mortality, and invasive cysts of the pathogen were observed in the subcuticular layer of the host body. Even though Zoothamnium spp. were found on Cx. tritaeniorhynchus larvae, there was no lethal effect due to the attachment of the parasitic agent. The potential of these microbiotas in integrated vector controlling approaches in future perspectives is recommended.

Riser Fatigue Due to Currents and Waves

2002 ◽  
Author(s):  
C. Le Cunff ◽  
E. Fontaine ◽  
F. Biolley
Keyword(s):  
Modal Analysis ◽  
Environmental Conditions ◽  
Navier Stokes ◽  
Vortex Induced Vibrations ◽  
Two Factors ◽  
Shedding Frequency ◽  
The Waves ◽  
Structural Mode ◽  
A Current

Fatigue due to environmental conditions is studied on a top-tensioned riser. The fatigue is due to two factors. First, the waves produce a displacement of the top of the riser, which excites the structure. Secondly, currents create vortices behind the structures. The phenomenon is then referred to as vortex-induced vibrations (VIV), whereby the vortices can lock onto a structural mode through the shedding frequency. In the present paper, we have two objectives. The first is to compare the fatigue estimates given either by a modal analysis or by Navier-Stokes calculations for a riser in a current. The second is to determine if studying the wave and current effects separately produces conservative results or if they must be studied together.

scholarly journals Impacts of urbanisation level and distance from potential natural mosquito breeding habitats on the abundance of canine dirofilariosis

2016 ◽  
Vol 64 (3) ◽  
pp. 340-359 ◽  
Author(s):  
Attila Trájer ◽  
Antal Rengei ◽  
Kinga Farkas-Iványi ◽  
Ákos Bede-Fazekas
Keyword(s):  
Medical Problem ◽  
Urban Environments ◽  
Breeding Habitats ◽  
Mosquito Breeding ◽  
Fluvial Habitat ◽  
Occurrence Patterns ◽  
The City ◽  
Knott’S Test ◽  
Natural Water Bodies

Dirofilariosis is an emerging mosquito-borne veterinary and medical problem in the Northern hemisphere. The ecological investigation of 56 canine dirofilariosis cases in new endemic locations was performed in Szeged, Hungary. The aim was to analyse the influence of the spatial patterns of dog abundance and the potential mosquito breeding habitats on the spatial occurrence patterns of dirofilariosis in the city of Szeged. The limnoecological characterisation was based on the fluvial habitat classification of Amoros of natural water bodies; the built environment was evaluated using the UrbanisationScore urbanisation intensity measuring software. Dirofilaria immitis accounted for 51% and D. repens for 34.3% of the dirofilariosis cases, and in 20% of the cases only the Knott’s test was positive. It was concluded that most of the cases were related to locations with a medium to high urbanisation index, although the proximity of mosquito-bearing waters also played an important role in the observed spatial infection patterns. We found that the distance from potential mosquito habitats and the urbanisation intensity determine the abundance of dirofilariosis in urban environments.

scholarly journals Identification of Primary Container of Aedes Mosquitoes Breeding Site in Urban Region of Dengue Endemic Area, Purwokerto Indonesia

2020 ◽  
pp. 181-188
Author(s):  
Siwi Pramatama Mars Wijayanti ◽  
Devi Octaviana ◽  
Sri Nurlaela
Keyword(s):  
Urban Areas ◽  
Endemic Area ◽  
Breeding Site ◽  
Cross Sectional Study ◽  
Urban Region ◽  
Adult Mosquito ◽  
Mosquito Larvae ◽  
Cross Sectional ◽  
Mosquito Breeding ◽  
Dengue Prevention

Dengue prevention and control more reliant on reducing its vector,  Aedes sp. mosquitoes by mosquito breeding nest eradication method. Therefore, identification of the primary container of the Aedes sp. breeding site particularly in the urban region of dengue-endemic area is a crucial effort to conduct an effective dengue prevention program. This research aimed to identify the primary container of the Aedes sp. breeding site in the urban region of the dengue-endemic area. This is a descriptive cross-sectional study, located in an urban region of dengue-endemic area within Banyumas Regency of Central Java Indonesia. A total of 300 houses in three urban areas were observed in urban areas of Purwokerto namely Arcawinangun, Purwanegara, and Karangpucung (100 houses each area). A total of 1504 water-holding containers were observed. All container was observed and recorded the type, color, lid condition, position, and the presence of mosquito larvae. The analysis was conducted by calculating the percentage of types, color, lid condition, and position of the container also the presence of mosquito larvae. The result of this study highlighted that flower pots and bathtubs were the primary types of containers with Aedes sp. larvae in the urban area. The characteristics of larvae-positive containers mostly open, bright, and located indoor position. Dengue prevention efforts by targeting the primary types of containers for mosquito breeding are expected to reduce the adult mosquito population.

scholarly journals Ice fog monitoring near Fairbanks, AK

2021 ◽  
Author(s):  
Dragos Vas ◽  
Steven Peckham ◽  
Carl Schmitt ◽  
Martin Stuefer ◽  
Ross Burgener ◽  
...  
Keyword(s):  
Power Generation ◽  
Environmental Conditions ◽  
Weather Conditions ◽  
Cold Weather ◽  
The Arctic ◽  
Local Power ◽  
Environmental Complexity ◽  
Ice Fog ◽  
Innovative Methods ◽  
Generation Facility

Ice fog events, which occur during the Arctic winter, result in greatly decreased visibility and can lead to an increase of ice on roadways, aircraft, and airfields. The Fairbanks area is known for ice fog conditions, and previous studies have shown these events to be associated with moisture released from local power generation. Despite the identified originating mechanism of ice fog, there remains a need to quantify the environmental conditions controlling its origination, intensity, and spatial extent. This investigation focused on developing innovative methods of identifying and characterizing the environmental conditions that lead to ice fog formation near Fort Wainwright, Alaska. Preliminary data collected from December 2019 to March 2020 suggest that ice fog events occurred with temperatures below −34°C, up to 74% of the time ice fog emanated from the power generation facility, and at least 95% of ice particles during ice fog events were solid droxtals with diameters ranging from 7 to 50 μm. This report documents the need for frequent and detailed observations of the meteorological conditions in combination with photographic and ice particle observations. Datasets from these observations capture the environmental complexity and the impacts from energy generation in extremely cold weather conditions.

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