Larval Density Research Articles

Oviposition site selection and subsequent offspring performance of Aedes aegypti in short- and long-term detritus accumulation conditions

The “oviposition preference-offspring performance” hypothesis proposes that females lay their eggs in habitats that maximize the fitness of their offspring. The aim of this study was to assess the oviposition site selection by Aedes aegypti females and the success of their larvae in habitats with different detritus accumulation times, under conditions representative of the natural spatial variability of detritus quality and quantity in the Metropolitan Area of Buenos Aires, Argentina. Two experiments were performed, one assessing oviposition site selection and the other analyzing developmental success. In both experiments, two levels of detritus accumulation time were compared, one with short-time detritus accumulation (2 weeks), and the other with long-time detritus accumulation (8 weeks). Naturally fallen detritus was used in both experiments, collected in ten sites across the Metropolitan Area of Buenos Aires. In the oviposition experiment, two contiguous ovitraps corresponding to each accumulation time were placed at each of the ten sites and the number of eggs received for each accumulation time was compared. In the development experiment, always 19 larvae were raised in containers of both accumulation times and overall performance was compared using an integrated index that considers survival, development time and female size. A large variability in the amount of detritus collected at the different sites was observed. The number of eggs was significantly higher in the long-time than in the short-time detritus accumulation containers, and approximately proportional to the amount of detritus in each ovitrap. The performance was not affected by the detritus accumulation time, but a better performance was detected in containers that received a higher amount of organic detritus, regardless of the accumulation time. Leaves were on average the most abundant type of detritus, with an average of 53 % of the total detritus collected. The amount of leaves added 2 weeks before hatching showed a positive effect on larval performance. Our results do not support the “oviposition preference-offspring performance” hypothesis, since Ae. aegypti females laid eggs in containers where larvae did not show a better performance. Moreover, at larval densities related to the number of eggs actually laid in each of the accumulation times, it is expected that the performance would be even worse in the most selected containers, due to the density-dependent effects of crowding. Since the results obtained reflect the natural heterogeneity of the environmental conditions in the region studied, they might be a fairly good indicator of what occurs in natural larval habitats.

Loss of amphibian species alters periphyton communities in montane ponds

Amphibian larvae can affect the structure and functioning of freshwater ecosystems, but their effects have been little explored although amphibian biodiversity is rapidly declining. Given that larvae of different amphibian species belong to different trophic levels, their effects on freshwater communities and processes can be expected to differ, with herbivores likely having direct effects on algae and predators having indirect effects through trophic cascades. We explored this question through a mesocosm experiment conducted in montane ponds, using an anuran and a urodele species affected by emergent diseases. We used different scenarios of reduction and loss of one or both species, and compared them to a control scenario representing a typical amphibian community in the study area composed of four species, with total larval density held constant. Loss of the anuran resulted in lower chlorophyll concentration and algal density, likely due to replacement by more efficient grazers. Loss of the urodele produced similar trends but weaker, possibly due to an increase of invertebrate grazing activity in the absence of this predator. Our study shows how the loss of amphibian species can alter the structure of montane ponds, but also how the mechanisms involved and the intensity of effects differ for different species.

Density-dependent development in pest and domestic Drosophilidae species

The capacity to lay eggs inside healthy fruits rather than on decaying plant matter differentiates insect fruit pests from domestic species. This niche differentiation has been previously proposed to be an adaptation to avoid competition. We hypothesize that pest species will be more strongly affected by competition. We compare the impact of larvae density on fitness traits between Drosophila pests ( Drosophila suzukii (Matsumura, 1931); Zaprionus indianus Gupta, 1970) and domestic species ( Drosophila immigrans Sturtevant, 1921; Drosophila melanogaster Meigen, 1830). We assessed the effect of crowding on adult emergence and development time. Viability decreased gradually with density for D. immigrans and D. suzukii, while for D. melanogaster and Z. indianus it remained high. Development time increased with density; this was stronger on Z. indianus and D. immigrans than on D. suzukii, which had a moderate increase, and D. melanogaster, which did not change. Contrary to expectations, the distinct patterns observed were not related to each species' domestic or pest lifestyle. In fact, patterns consistent with either scramble or contest type of competition were observed on both pest and domestic species, respectively. These findings challenge prior beliefs regarding competition effects among Drosophila pest species and provide information relevant to integrated pest management.

The effect of white grub (Maladera Verticalis) larvae feeding on rhizosphere microbial characterization of aerobic rice (Oryza sativa L.) in Puer City, Yunnan Province, China

BackgroundRhizosphere microorganisms are vital in plants’ growth and development and these beneficial microbes are recruited to the root-zone soil when experiencing various environmental stresses. However, the effect of white grub (Maladera verticalis) larvae feeding on the structure and function of rhizosphere microbial communities of aerobic rice (Oryza sativa L.) is unclear.ResultsIn this study, we compared physicochemical properties, enzyme activities, and microbial communities using 18 samples under healthy and M. verticalis larvae-feeding aerobic rice rhizosphere soils at the Yunnan of China. 16 S rRNA and ITS amplicons were sequenced using Illumina high throughput sequencing. M. verticalis larvae feeding on aerobic rice can influence rhizosphere soil physicochemical properties and enzyme activities, which also change rhizosphere microbial communities. The healthy and M. verticalis larvae-feeding aerobic rice rhizosphere soil microorganisms had distinct genus signatures, such as possible_genus_04 and Knoellia genera in healthy aerobic rice rhizosphere soils and norank_f__SC − I−84 and norank_f__Roseiflexaceae genera in M. verticalis larvae-feeding aerobic rice rhizosphere soils. The pathway of the metabolism of terpenoids and polyketides and carbohydrate metabolism in rhizosphere bacteria were significantly decreased after M. verticalis larvae feeding. Fungal parasite–wood saprotroph and fungal parasites were significantly decreased after M. verticalis larvae feeding, and plant pathogen–wood saprotroph and animal pathogen–undefined saprotroph were increased after larvae feeding. Additionally, the relative abundance of Bradyrhizobium and Talaromyces genera gradually increased with the elevation of the larvae density. Bacterial and fungal communities significantly correlated with soil physicochemical properties and enzyme activities, respectively.ConclusionsBased on the results we provide new insight for understanding the adaptation of aerobic rice to M. verticalis larvae feeding via regulating the rhizosphere environment, which would allow us to facilitate translation to more effective measures.

Exposure to entomopathogenic fungus and high larval density induce a strong immune response and life‐history costs in black soldier fly, a commercially important insect

AbstractPathogen infection and conspecific density may considerably affect key life‐history traits of organisms. For naturally aggregating species, even low concentrations of pathogens or high larval densities may have detrimental effects. However, the detailed influence of these factors, particularly their interaction effect, is often overlooked in ecological and life‐history studies. To investigate the effects of conspecific density and pathogen infection on life‐history traits, we explored the influence of larval density (1 and 5 larvae cm−2, i.e., low and high density, respectively) on phenoloxidase (PO) activity, body mass, and development time of Hermetia illucens L. (Diptera: Stratiomyidae) larvae in the presence of two strains of the entomopathogenic fungus (EPF) Beauveria bassiana (Bals.‐Criv.) Vuill. We observed higher PO activity in EPF‐treated larvae than in the untreated control and a pronounced difference in PO activity between the two EPF‐strain treatments. Larvae reared at high density and treated with EPF showed higher PO activity than untreated larvae at low density. The EPF‐treated larvae and larvae reared at high density had longer larval periods than untreated larvae and larvae reared at low density, respectively. Larvae reared at high density also achieved reduced prepupal and pupal masses compared to conspecifics at low density. Interestingly, untreated larvae only achieved higher prepupal and pupal masses at low density, whereas at high density, the pattern was reversed (treated individuals had higher pupal masses). Overall, our results demonstrate that high density and fungal pathogens both induce a higher immune response compared to low density and pathogen‐free environments, but this comes with a cost of a longer larval period and reduced body mass.

Evaluation of light traps for sampling lobster larvae in the German Bight, North Sea

Biological monitoring of planktonic animals is greatly dependent on the deployment of traps. A variety of specialized traps have been designed for surface plankton and vertebrates. However, certain groups, such as planktonic larvae of benthic marine invertebrates remain underrepresented in sampling efforts. Catching them has proven to be more challenging because of their size, swimming ability, location, and abundance. In the present study a successful light trap for sampling American lobster larvae in New Brunswick, Canada, is evaluated on the island of Helgoland (German Bight, North Sea). Our results showed the traps were successful in catching larvae in laboratory experiments but were unable to catch European lobster larvae in the field. Traps deployed in the field were successful in capturing other benthic and pelagic zooplankton predominantly consisting of crustaceans from the orders: Cumacea, Amphipoda, Mysida and Isopoda. The low density of lobster larvae, the island's topography, and their unique photactic response possibly limited the success rate of the light traps. Future research is needed to construct a specialized trap to sample Helgoland's lobster larvae and provide information on the current larval fitness and population numbers.

Ecosystem effects of intraspecific variation in a colour polymorphic amphibian.

An emerging consensus suggests that evolved intraspecific variation can be ecologically important. However, evidence that evolved trait variation within vertebrates can influence fundamental ecosystem-level processes remains sparse. In this study, we sought to assess the potential for evolved variation in the spotted salamander (Ambystoma maculatum) to affect aquatic ecosystem properties. Spotted salamanders exhibit a conspicuous polymorphism in the colour of jelly encasing their eggs-some females produce clear jelly, while others produce white jelly. Although the functional significance of jelly colour variation remains largely speculative, evidence for differences in fecundity and the morphology of larvae suggests that the colour morphs might differ in the strength or identity of ecological effects. Here, we assessed the potential for frequency variation in spotted salamander colour morphs to influence fundamental physiochemical and ecosystem properties-dissolved organic carbon, conductivity, acidity and primary production-with a mesocosm experiment. By manipulating colour morph frequency across a range of larval densities, we were able to demonstrate that larva density and colour morph variation were ecologically relevant: population density reduced dissolved organic carbon and increased primary production while mesocosms stocked with white morph larvae tended to have higher dissolved organic carbon and conductivity. Thus, while an adaptive significance of jelly coloration remains hypothetical, our results show that colour morphs differentially influence key ecosystem properties-dissolved organic carbon and conductivity.

Larval competition between three endemic fruit flies (Diptera: Tephritidae) of differing phylogenetic relatedness

AbstractWithin a fruit, fruit fly larvae can be subject to scramble competition, in which density‐dependent effects can influence the fitness of subsequent adults. While there is significant research on tephritid interspecific larval competition, it has been conducted in invasive situations where the species are evolutionarily novel to each other. There has been no published research investigating larval competitive interactions between naturally coexisting, endemic species. We ran laboratory‐based, intraspecific and interspecific larval competition trials involving three co‐occurring Bactrocera species of differing genetic relatedness and also measured aspects of juvenile development rate to test possible mechanisms of competitive difference. Larval density had an influence on intraspecific competition in Bactrocera tryoni, Bactrocera neohumeralis and Bactrocera jarvisi, with a decreasing percentage of pupation with increasing larval density. Interspecific competition between B. tryoni and B. neohumeralis, and between B. tryoni and B. jarvisi was influenced by the interaction between species and density. The intensity of competition between B. tryoni and B. neohumeralis was minimal but high between B. tryoni and B. jarvisi. B. jarvisi produced larger eggs and had faster initial larval growth rates than the other two species, but it took the longest time for pupation to occur. Our results conflict with theory, as the greatest competition was observed between the two more distantly related species (B. tryoni and B. jarvisi) rather than between the two most closely related species (B. tryoni and B. neohumeralis). Further, and contrary to other studies, egg size, hatch rate and larval growth rate did not provide B. jarvisi with a competitive advantage; thus, larval size does not appear to be a mechanism of larval competition between B. tryoni and B. jarvisi.

Development and field evaluation of a novel sugar bait device for controlling residential vector mosquitoes in Zhejiang Province, China.

Mosquito-borne diseases pose serious public health threats in Zhejiang Province, China, and vector control is believed to be the primary method for reducing transmission. Due to severe resistance problems, effective and sustainable methods without chemical insecticides are urgently required to control mosquito vectors. Attractive toxic sugar baits (ATSB) are newly developed methods to control mosquitoes in recent decades with the core element sugar bait, which was invented according to the sugar-feeding behavior of mosquitoes. In this study, we developed a Novel Sugar Bait Device (NSBD) trap by combining sugar bait and physical adhesive capture technology. The study aimed to evaluate the effect of the NSBD trap on controlling mosquitoes in residential environments and to identify the optimal sugar solution concentration in the sugar bait of the NSBD for real use. Four residential villages in Ningbo City with similar geographic environments and mosquito densities were selected for field trials in 2022. One village (site 1) was designated as the control group, and three villages (sites 2-4) served as the test groups to assess the effectiveness of NSBD traps with different sugar solution concentrations (6, 8, and 10%) in the sugar bait. Larval and adult mosquito densities were monitored monthly before and semi-monthly after the trials using the CDC light trap and larval pipette method. Before the trials, we monitored mosquito density for 3 months to confirm the baseline mosquito density among the four sites, and no statistical differences in adult and larval mosquitoes were found (adult, F = 3.047, p > 0.05; larvae, F = 0.436, p > 0.05). After the trials, all NCBD traps effectively controlled larval and adult mosquito densities, with the highest standard decrease rates of larval and adult mosquito densities at 57.80 and 86.31%, respectively, observed in site 4. The most suitable sugar solution concentration in the sugar bait was 10%. NSBD traps effectively controlled mosquitoes in residential environments during field trials. Without the use of insecticides, this may be a promising choice for mosquito vector control to prevent mosquito-borne diseases.

Evaluating entomological measures and cypermethrin use in pest control

Purpose: This study aims to analyze entomological indicators and the susceptibility status of the Aedes aegypti mosquito to cypermethrin in the Tanjung Balai Karimun Port Health Office area. Methods: This type of study is observational, using a cross-sectional design approach. Entomology indicator data collection is carried out routinely every month by observing containers in each building both inside and outside. The vulnerability test uses the WHO susceptibility test method. Results: The results of entomological indicators in the perimeter area showed no density of Aedes aegypti mosquito larvae. In contrast, the density of larvae in the buffer area was low to moderate. A susceptibility test showed that 0.05% cypermethrin was still susceptible to Aedes aegypti mosquitoes. Conclusion: These findings underscore the efficacy of the current control measures implemented in the study area and emphasize the critical need for continuous monitoring and surveillance. Maintaining such efforts is paramount for sustaining effective mosquito control initiatives and mitigating the potential risks posed by Aedes aegypti mosquitoes, thereby reducing the threat of vector-borne disease.

Research and development of a predictive system for fall armyworm early warning on maize crop

The rapid increase in fall armyworms (FAW, Spodoptera frugiperda) in recent years has posed major challenges to maize growers around the globe. To keep larval density below the economic threshold, we need interdisciplinary agricultural solutions like plant protection epidemiology, the Internet of Things, and scientific data techniques for early detection, monitoring, forecasting, and making informed decisions. Pest control should be planned ahead of time to prevent indiscriminate pesticide spraying, waste, and a negative effect on the environment. In this study, the authors plan to create a comprehensive iFAWcast software system that will automatically predict, alert, and gather research data on fall armyworms on maize crops in Vietnam. The system is comprised of three major components: (i) An automatic forecasting and alerting tool for fall armyworm outbreaks on the web platform; (ii) An agriculture reporting, forecasting, alerting, and user management tool on the web platform; and (iii) A mobile app that provides forecasting and alerting services on fall armyworms to farmers based on their geographical location. The iFAWcast system includes a central computation that dynamically updates weather forecasts from the Visual Crossing API and the OpenWeatherMap API, as well as a formula for the effective cumulative temperature based on the characteristics of fall armyworms on maize crops in Vietnam. The developed system was tested using data collected straight from the field, yielding extremely accurate and dependable results.

Environmental dynamics and seasonal wing physiological changes of coastal mosquito vectors (Diptera: Culicidae) in Central Thailand

Mosquitoes (Diptera: Culicidae) are small hematophagous insects that serve as disease vectors by transmitting pathogens to humans and animals. This study was conducted on the coastline of Samut Songkhram Province in Thailand's central region to evaluate the impact of environmental factors on coastal mosquitoes, namely Anopheles epiroticus and Culex sitiens. A zero-inflated negative binomial (ZINB) regression was employed to assess the relationship between the density of larval mosquitoes and water quality factors. Spearman's rank correlation was used to examine the relationship between the number of adult mosquitoes and meteorological factors, and the geometric morphometric (GM) technique was used to study the wing size and shape of adult mosquitoes throughout different seasons. The ZINB analysis revealed a significant negative relationship (p < 0.05) between dissolved oxygen, high-range phosphate, and the number of An. epiroticus larvae. Conversely, in the case of Cx. sitiens, there was a significant positive relationship between nitrate-nitrogen and larval density (p < 0.01), while dissolved oxygen exhibited a significant negative relationship (p < 0.05). Regarding adult mosquitoes, relative humidity was positively correlated with the abundance of adult Cx. sitiens (r = 0.85, p < 0.01), whereas each meteorological parameter—temperature, relative humidity, rainfall, wind speed, and atmospheric pressure—was negatively correlated with adult An. epiroticus abundance (p < 0.05 for each). The GM analysis revealed statistically significant seasonal variations in wing shapes for both species (p < 0.05 for all seasonal comparisons), underscoring their adaptation to seasonal environmental conditions in coastal habitats.

Analysis of Aedes Aegypti Larval Density on The Potential Transmission of Dengue Fever

Dengue hemorrhagic fever (DHF) is caused by the dengue virus transmitted through the Aedes aegypti mosquito. DHF remains a health problem in Indonesia. Based on data from the Ministry of Health, there were 184 cases of the disease in 2022, an increase of 94.8% compared to 2021, which had 73,518 cases. According to the Central Statistics Agency of South Sumatra Province, the number of DHF cases in South Sumatra was 2,854 cases, with the highest number in the city of Palembang at 908 cases. This condition requires serious attention. The aim of this study is to analyze the potential transmission of DHF based on entomological evidence in the Sukarami district of Palembang. The method used in the research is a cross-sectional study conducted in December 2023, involving 92 households in the Sukarami sub-district, with a total of 552 containers. The survey results of larval identification under a microscope showed a Larval Free Index of 45.7%, a Container Index of Aedes aegypti larvae of 56.0%, a house index of 73.9%, and a Breteau index of 152.2%. The results of entomological indices indicate a high density of DHF vector mosquitoes Aedes aegypti, which means that this area has a high risk of DHF transmission, thus requiring the control of Aedes aegypti larvae and the eradication of DHF. breeding sites for the vector.

Economic supply chain modelling of industrial insect production in the Netherlands

Abstract Defatted larvae meal (dLM), specifically from black soldier flies, could help overcome the animal protein gap. As insect production is an emerging sector, current economic research is scarce and very diverse. Thus, the aim of this research was to develop a simulation model that enables the analysis of full industrial scale costs of producing dLM and to provide insight in the distribution of these costs in the insect supply chain. The deterministic supply chain model is built on three modules, technical, transition and economic module, which all follow a previously defined supply chain structure and allow to extract quantity and price information for intermediate or final products. The model was parameterized and checked for plausibility in multiple consultation rounds with the INSECTFEED consortium and business partners. Additionally, model behaviour was checked with scenario, sensitivity, and break-even price analyses. In the default situation 5.57 tDM raw substrate and 26.7 million neonates are required to produce 1 tDM dLM for a price of €5,116/tDM. Most costs are added in the raw substrate delivery (€1,952/tDM) and production and collection (€821/tDM) step. Important cost factors are the raw substrate (€1,939/tDM) and building and inventory (€1,459/tDM). Parameters with high relative response rate towards the price of dLM are the feed conversion rate, dry matter percentage of larvae, raw substrate price, larvae density, labour wage and growth rate. To reach break-even prices for substituting fish meal with alive grown larvae (AGL) (€1,318/tDM AGL), improving production parameters is not sufficient. Just changing prices of raw substrate to −€78/tDM or frass to €1,175/tDM would enable a profitable operation. However, these are not deemed as realistic in mass production. Although there is some insecurity in data, the model results are the most realistic representation of industrial scale production amounts and costs.

Density-dependent development of the yellow mealworm Tenebrio molitor (Coleoptera: Tenebrionidae)

Abstract The increasing global population has led to high food demand and the interest for alternative resources is highly topical. The interest in utilizing insects as a source of food and feed has been rapidly increasing, as the on-growing population has made the need for protein even more demanding. Insect rearing is economically viable, since they can be fed with organic waste and agricultural by-products. The inclusion of bioactive compounds and active ingredients in insect diets has been identified as a potential key factor for enhancing their growth and performance. The aim of this study was to evaluate the effect of a diet enriched with functional ingredients of medicinal and aromatic plants and agricultural by-products of the Greek flora on the growth, survival and development of larvae of the yellow mealworm, Tenebrio molitor (Coleoptera: Tenebrionidae), in the context of larval density-induced stress. Wheat bran enriched with 5%, 10% or 20% of a prepared mixture containing post-distillation residues of medicinal and aromatic plants of the Greek flora (oregano, thyme, sage and rosemary, linseed oil, rock-samphire, industrial cannabis, and olive paste by-product) was evaluated as insect feeding substrate, whereas wheat bran alone (0% enrichment) served as control. Groups of 25, 50, 75 and 100 first instar larvae were separately collected, weighed, and put in cylindrical plastic cups to test if larval density had any effect on survival and development. According to our results, the final larval weight of T. molitor is significantly affected by the density of larvae but not by the rearing substrate. The highest individual weight among all tested substrates was achieved at the density of 25 larvae. Individual weights were highest when larvae were reared on 5% mixture. The weight of those reared on the control substrate was slightly lower, followed by the 10% and 20% mixtures. Larvae fed with 10% enriched substrate showed the highest survival rate, followed closely by those fed with the control and 5% substrates. Our results clearly demonstrate that larval survival is not density dependent, but density is important in the case of individual larval weight.

Competition, cooperation, and parental effects in larval aggregations formed on carrion by communally breeding beetles Necrodes littoralis (Staphylinidae: Silphinae).

Aggregations of juveniles are dominant forms of social life in some insect groups. Larval societies are shaped by competitive and cooperative interactions of the larvae, in parallel with parental effects. Colonies of necrophagous larvae are excellent systems to study these relationships. Necrodes littoralis (Staphylinidae: Silphinae), a carrion beetle that colonizes cadavers of large vertebrates, forms massive juvenile aggregations. By spreading over carrion anal and oral exudates, the beetles form the feeding matrix, in which the heat is produced and by which adults presumably affect the fitness of the larvae. We predict that exploitative competition shapes the behavior of N. littoralis larvae in their aggregations. However, cooperative interactions may also operate in these systems due mainly to the benefits of collective exodigestion. Moreover, indirect parental effects (i.e., formation of the feeding matrix) probably modulate larval interactions within the aggregations. By manipulating parental effects (present/absent) and larval density (0.02-1.9 larvae/g of meat), we found a strong negative group-size effect on fitness components of N. littoralis, in colonies with parental effects over almost the entire density range, and in colonies without parental effects for densities larger than 0.5 larva/g. This was accompanied by positive group-size effects in terms of development time (it shortened with larval density) and thermogenesis (it increased with larval density). A pronounced positive group-size effect on juvenile fitness was found only in colonies without parental effects and only in the low-density range. These results support the hypothesis that larval societies of N. littoralis are shaped by exploitation competition.

Immunological regulation by Toll-1 and Spätzle-4 in larval density-dependent prophylaxis of the oriental armyworm, Mythimna separata

High population density has been shown to alter insect prophylactic immunity. Toll-Spätzle pathway performs a key function in insect innate immune response. To determine the role of Toll and Spätzle, two main components of Toll-Spätzle pathway, in the density-dependent prophylaxis of Mythimna separata. We identified full-length cDNA encoding the Toll-1 and Spätzle-4 genes in M. separata (designed MsToll-1 and Ms Spätzle-4). Both MsToll-1 and MsSpätzle-4 were expressed throughout all developmental stages. MsToll-1 expression was highly in fat body and brain and MsSpätzle-4 was highly expressed in brain and Malpighian tubule. With increased larval density, MsToll-1 expression was markedly up-regulated. MsSpätzle-4 expression was found to be raised in larvae that were fed in high density (5 and 10 larvae per jar). Co-immunoprecipitation assays demonstrated that MsToll-1 interacted with MsSpätzle-4. Immune-related genes transcriptions were considerably reduced in high-density larvae MsToll-1 (or MsSpätzle-4) was silenced by dsRNA injection. Meanwhile, a discernible reduction in the survival rate of the larvae exposed to Bacillus thuringiensis infection with silence of MsToll-1 (or MsSpätzle-4) was observed. This study implies that prophylactic immunity was influenced by crowded larvae via modulating the Toll-Spätzle pathway in M. separata and allow for a new understanding of into density-dependent prophylaxis in insects.

Seasonal Diversity in Mosquito Larval Ecology and Its Public Health Implications in Urban Slums of Lagos, Nigeria.

Mosquito-borne diseases (MBDs) are major public health burdens in tropical nations, including Nigeria. This study assessed mosquito larval species composition, abundance, and abiotic factors influencing mosquito breeding in slum communities of Lagos with the goal of informing MBD control measures. Three slum communities-Bariga, Makoko, and Ajegunle-were selected along with the nonslum community of Ikeja, which served as a control site. Larval sampling was done using the standard dipping technique between December 2021 and July 2022 across the dry and wet seasons. Mosquito larvae were raised to adults and identified using morphological keys and molecular assays. A total of 57,753 immature mosquitoes were collected from all study sites, with a significantly (P < 0.05) greater abundance in the dry season than the wet season. The majority (98.1%) of the mosquitoes collected belonged to Culex pipiens s.l., the only species found during the dry season in almost all locations. In the wet season, species identified from all sites combined were Anopheles gambiae ss., Anopheles arabiensis, Aedes aegypti, Aedes albopictus, Cx. pipiens s.l., and Lutzia tigripes, with Ajegunle having the greatest species diversity (H = 0.593). Among physicochemical parameters measured, only water temperature had a significant positive correlation (r = 0.934, P = 0.020) with larval densities in Ajegunle only. Permanent mosquito-breeding habitats had significantly greater larval densities than temporary habitats within the slum communities. These findings could inform the development of integrated vector control strategies that address the different species of mosquitoes in the fight against MBDs in urban slums.

CHARACTERISTICS OF ANOPHELES BREEDING PLACES IN DAHIAN TAMBUK VILLAGE, GUNUNG MAS DISTRICT, CENTRAL KALIMANTAN

Background: Malaria cases in Dahian Tambuk Village have been ranked first for four consecutive years in Gunung Mas District. Purpose: This study aims to describe the physical and chemical characteristics of Anopheles breeding places in Dahian Tambuk Village, Gunung Mas District. Method: It is a descriptive study using a survey method. The characteristics studied were Anopheles species, number, temperature, salinity, breeding sites, and density of larvae found in each breeding site. Result: Seven breeding places were found positive to contain Anopheles larvae, consisting of puddles, fish ponds, and sewers. The sewer was predominantly found. Physical characteristics of water showed a temperature ranging from 29.9 0C - 35 0C, pH levels between 5.35 - 6, and a salinity of 0 ppt, with a density level of 9 larvae/2 dippers. The species of Anopheles larvae found in all breeding sites was identified as Anopheles kochi. Conclusion: Seven breeding sites found in the studied area consisted of puddles, fish ponds, and sewers, with physical characteristics that qualify for Anopheles larvae in general An. kochi was the only species of larvae found in all breeding sites.

Insecticidal Effects of Transgenic Maize Bt-Cry1Ab, Bt-Vip3Aa, and Bt-Cry1Ab+Vip3Aa against the Oriental Armyworm, Mythimna separata (Walker) in Southwest China.

The oriental armyworm, Mythimna separata (Walker), an important migratory pest of maize and wheat, is posing a severe threat to maize production in Asian countries. As source areas of spring-summer emigratory populations, the control of M. separata in southwestern China is of great significance for East Asian maize production. To assess the toxicity of Bt maize against the pest, bioassays of Bt-(Cry1Ab+Vip3Aa) maize (event DBN3601T), Bt-Cry1Ab maize (event DBN9936), and Bt-Vip3Aa maize (event DBN9501) were conducted in Yunnan province of southwest China. There were significant differences in insecticidal activity between the three Bt maize events, and DBN3601T presented the highest insecticidal role. The results also indicated that the insecticidal effect of various Bt maize tissues took an order in leaf > kernel > silk, which is highly consistent with the expression amounts of Bt insecticidal protein in leaf (69.69 ± 1.18 μg/g), kernel (11.69 ± 0.75 μg/g), and silk (7.32 ± 0.31 μg/g). In field trials, all larval population densities, plant damage rates, and leaf damage levels of DBN3601T maize were significantly lower than the conventional maize. This research indicated that the DBN3601T event had a high control efficiency against M. separata and could be deployed in southwest China for the management of M. separata.