Aedes albopictus life table: environment, food, and age dependence survivorship and reproduction in a tropical area

Background Environmental conditions affect the biology of mosquito vectors. Aedes albopictus is a major vector of many important diseases including dengue, Zika, and chikungunya in China. Understanding the development, fecundity, and survivorship of Ae. albopictus mosquitoes in different environmental conditions is beneficial for the implementation of effective vector control measures. Methods Aedes albopictus larval and adult life-table experiments were conducted under natural conditions in indoor, half-shaded, and fully shaded settings, simulating the three major habitat types in Hainan Province, a tropical island in the South China Sea. Temperature, humidity, and light intensity were recorded daily. Larval rearing used habitat water and tap water, with and without additional artificial food. Development time, survivorship, pupation rate, and adult emergence rates were monitored. Adult mosquito survivorship and fecundity were monitored daily and reproductive rates were determined, and age-dependent survivorship and reproduction were analyzed. Results The pupation time and male and female emergence times were significantly shorter in indoor conditions than in shaded and half-shaded conditions for both tap water with added food and habitat water with added food groups. For habitat water with added food, the shaded environment had the lowest pupation rate among the settings. For tap water with added food group, the shaded environment had the lowest pupation rate. The mean survival time of females was 27.3 ± 0.8 days in the indoor condition, which was significantly longer than that in the half-shaded (18.4 ± 0.6 days) and shaded (13.8 ± 1.2 days) conditions. Adult mortality was age-dependent, and the rate of change in mortality with age was not significantly different among different environmental conditions. The mean net replacement rate (R0) of female mosquitoes showed no significant difference among the three conditions, whereas the per capita intrinsic growth rate (r) in the shaded condition was 42.0% and 20.4% higher than that in the indoor and half-shaded conditions, respectively. Female daily egg mass was also age-dependent in all the settings, decaying exponentially with age. Conclusions Our results imply that half-shaded conditions are likely the best natural condition for adult emergence and female reproduction, and food supply is crucial for larval development and pupation. The results provide new avenues for integrated mosquito management in indoor and outdoor areas, especially in half-shaded areas. Graphical Abstract

Survivorship of Anopheles gambiae sensu lato in irrigated sugarcane plantation scheme in Ethiopia

Background To ensure food security, sub-Saharan Africa has initiated massive water resource development projects, such as irrigated agriculture, in recent years. However, such environmental modifications affect the survivorship and development of mosquitoes, which are vectors of different diseases. This study aimed at determining the effects of irrigation practices on development and survivorship of Anopheles gambiae s.l. in Ethiopia. Methods A life table experiment was conducted to examine the effect of environmental modification on survivorship of both immature and adult An. gambiae s.l. in irrigated and non-irrigated areas. The pupation rate and development time of the immatures and adult longevity and fecundity were compared between the two settings. Results The estimated mean survival time of female An. gambiae s.l. in the irrigated and non-irrigated areas was 37.9 and 31.3 days, respectively. A survival analysis showed that adult females of An. gambiae s.l. placed in an irrigated area lived significantly longer than those in a non-irrigated area (χ2 = 18.3, df = 1, P <0.001), and An. gambiae s.l. females lived significantly longer than males in both areas (P < 0.001). Conclusions Adult An. gambiae s.l. survivorship was found to be enhanced in the irrigated area compared to non-irrigated area. Longer survival of adult mosquitoes in irrigated areas could have important implications for vectorial capacity and hence malaria transmission.

Survivorship of Anopheles gambiae sensu lato in irrigated sugarcane plantation scheme in Ethiopia

Background: To ensure food security, the sub-Saharan Africa has initiated massive water resource development projects, like irrigated agriculture, in recent years. However, such environmental modifications affect the survivorship and development of mosquitoes that are vectors of different diseases. This study aimed at determining the effects of irrigation practices on development and survivorship of Anopheles gambiae s.l in Ethiopia. Methods: Life-table experiment was conducted to examine the effect of environmental modification on survivorship of both immature and adults An. gambiae s.l. in irrigated and non-irrigated areas. The pupation rate and development time of the immatures and adult longevity and fecundity were compared between the two settings.Results: The estimated mean survival time of female An. gambiae s.l. in irrigated and non-irrigated area was 37.9 and 31.3 days, respectively. A survival analysis showed that adult females of An. gambiae s.l. placed in irrigated area lived significantly longer than those at the non-irrigated area (χ2 = 18.3, df = 1, p <0.001) and An. gambiae s.l. females lived significantly longer than males in both areas (p < 0.001). Conclusions: Adult An. gambiae s.l. survivorship was found to be enhanced in irrigated area compared to non-irrigated area. Longer survival of adult mosquito in irrigated area could have important implications in vectorial capacity and hence malaria transmission.

Performance of Some Bivoltine Silkworm,Bombyx mori L. Hybrids during Summer

Aim: The present study was aimed to find out the robust hybrid during summer season under temperate climatic conditions. Study Design: Completely Randomized Design (CRD). Place and Duration of Study: College of Temperate Sericulture (CoTS) Mirgund, Sher-e-Kashmir University of Agricultural Sciences and Technology, of Kashmir (SKUAST-K), in the year 2014. Methodology: The disease free layings (dfl’s) of the selected hybrids viz., SK31× SK13, SK6 × SK13 and CSR18× CSR19 were obtained from the Germplasm Bank maintained at College of Temperate Sericulture (CoTS) Mirgund, Sher-e-Kashmir University of Agricultural Sciences and Technology, of Kashmir (SKUAST-K). Thesedfl’s were incubated, brushed and reared up to 3rd instar en masse following the standard rearing procedure. Just after 3rdmoult, 3 replications of 100 larvae in each treatment were maintained. Cocoon and post cocoon parameters viz, pupation rate, single cocoon weight, single shell weight, shell ratio, raw silk, denier and leaf cocoon ratio were calculated and recorded during the course of experimentation. Results: No significant difference was recorded in pupation rate among the hybrids. H1 hybrid was found significantly superior over H2 and H3 for single cocoon and shell weight with mean value as 1.957 and 0.406 respectively. On the other hand influence of hybrids over shell ratio remained non significant. The performance of silkworm hybrids with respect to raw silk was recorded higher in H1 (17.98%) followed by H2 (17.96%) and H3 (17.93%), while the fine denier of 2.86 d was reported in H3 followed by H1 (2.94d) and H2 (3.01d). Leaf cocoon ratio was recorded lower in H1with mean value as 15.16 /100 dfl’s. Conclusion: Significant differences among the hybrids were observed, but no hybrid performed better in all traits studied, however in maximum traits SK31× SK13, seems to be superior to the other two studied hybrids.

Performance of Double Hybrid of Silkworm (Bombyx mori L.) Fed on Leaf Raised under Different Fertilizer Schedules

Aim: The present study was aimed to see the performance of silk worm (Bombyx mori L.) double hybrid fed on leaf raised through splitting the recommended dose of chemical fertilizers. Study Design: Completely Randomized Design (CRD). Place and Duration of Study: College of Temperate Sericulture (CoTS) Mirgund, Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir (SKUAST-K), during 2017 and 2018. Methodology: The present investigation was carried out at the experimental farm of College of Temperate Sericulture-Mirgund. Goshoerami a popular variety of mulberry in the region was used for the study. Disease free layings (dfl’s) of the popular double hybrid were obtained from the Germplasm Bank maintained at College of Temperate Sericulture (CoTS) Mirgund. These dfl’s were incubated, brushed and reared up to 3rd instar en masse following the standard rearing procedure. After 3rd moult, 3 replications of 100 larvae in each treatment were maintained. Different larval and Cocoon parameters were recorded during the course of experimentation. Standard procedure was followed to record observations. The data was compiled and analyzed. Results: T11 recorded the shortest values for total larval and fifth instar larval duration being statistically at par with treatments/ fertilizer schedules T12, T9, T10, T3, T4, T1, T2 and T7. Weight of ten mature larvae was recorded higher in treatment T14 being statistically at par with treatments T13, T16 and T15 respectively. Cocoon yield per 10,000 larvae by number was recorded highest In T14 treatment, which was recorded statistically at par with treatments T13 and T16 respectively. Cocoon yield by weight was more in treatment T14 being at par with treatments T13 and T16. Pupation rate was found higher in treatment T14 being at par treatment T13. Conclusion: Double hybrid performed better under parameters like- total as well as fifth instar larval duration in case of fertilizer schedule - T11 (N3P2K1), while as in case of larval weight, cocoon yield by number and by weight and pupation rate, the hybrid performed better under T14 (N4P1K2) fertilizer Schedule.

Malaria Vector Survivorship Linked to Irrigated Sugarcane Plantation Scheme in Ethiopia

Background: To ensure food security, the sub-Saharan Africa has initiated massive water resource development projects in recent years. However, such environmental modifications affect the survivorship and development of mosquitoes that are vectors of different diseases. This study aimed at determining the effects of irrigation practices on development and survivorship of Anopheles gambiae s.l in Ethiopia. Methods: Life-table experiment was conducted to examine the effect of environmental modification on survivorship of both immature and adults An. gambiae s.l. in irrigated and non-irrigated areas. The pupation rate and development time of the immatures and adult longevity and fecundity were compared between the two settings.Results: The estimated mean survival time of female An. gambiae s.l. in irrigated and non-irrigated area was 37.9 and 31.3 days, respectively. A survival analysis showed that adult females of An. gambiae s.l. placed in irrigated area lived significantly longer than those at the non-irrigated area (χ2 = 18.3, df = 1, p <0.001) and An. gambiae s.l. females lived significantly longer than males in both areas (p < 0.05). Conclusions: Adult An. gambiae s.l. survivorship was found to be enhanced in irrigated area compared to non-irrigated area. Longer survival of adult mosquito in irrigated area could have important implications in vectorial capacity and hence malaria transmission.

Suppression of Transferrin Expression Enhances the Susceptibility of Plutella xylostella to Isaria cicadae

Transferrins (Trfs) are multifunctional proteins with key functions in iron transport. In the present study, a Trf (PxTrf) from Plutella xylostella was identified and characterized. The PxTrf consisted of a 2046-bp open reading frame, which encoded a 681 amino acid protein with a molecular weight of 73.43 kDa and had an isoelectric point of 7.18. Only a single iron domain was predicted in the N-lobe of PxTrf. Although PxTrf was expressed ubiquitously, the highest levels of expression were observed in the fourth instar larvae. PxTrf transcript level was highest in fat bodies among various tissues. The PxTrf transcript levels increased significantly after the stimulation of pathogens. A decrease in PxTrf expression via RNA interference enhanced the susceptibility of P. xylostella to the Isaria cicadae fungus and inhibited hemocyte nodulation in response to the fungal challenge. In addition, a considerable increase in the pupation rate was observed in larvae treated with double-stranded PxTrf (dsPxTrf). Overall, according to the results, PxTrf may participate in P. xylostella immunity against fungal infection and insect development.

Stability and path analysis for yield and related traits in silkworm, (Bombyx mori L.) reared under stress conditions

The silkworm, Bombyx mori L. is a poikilothermic organism whose growth and development is adversely affected by high temperatures. Rearing of silkworm at high temperature conditions of tropical countries like India causes extensive crop loss by reducing cocoon yield. Breeding new silkworm breeds tolerant to high temperatures is the most effective and economical method to increase cocoon yield. Introduction of stable genotypes in such breeding programs and knowledge on the relationships between cocoon yield and other traits would be more advantageous in increasing cocoon yield at high temperatures. Therefore, in this study twenty silkworm genotypes were reared in five artificially simulated environments with different temperatures ranging from 25?C to 38?C. Based on coefficient of variation (%) values, the traits cocoon yield / 10,000 larvae by weight (CY) and cocoon weight showed maximum and minimal variation among the traits in all the five environments. Analysis of variance revealed a substantial genetic variability among the genotypes for most of the traits studied. The results of combined analysis of variance showed significant differences over traits indicating that the traits are influenced by genotype ? environment interactions. Stability analysis with respect to CY showed higher mean value compared to grand mean, regression coefficient equal to unity and less deviation from regression in ATR16, CSR17, BHR2, S-5 and D13 genotypes, suggesting that they are consistent with the CY over the different environments. Clustering based on the stability parameters resulted in separation of twenty silkworm genotypes into 5 clusters based on their ability to tolerate high temperatures. Correlation studies demonstrated positive and significant (P < 0.05) correlations between CY and other traits. Pupation rate was most positively associated with CY followed by larval weight, cocoon weight, cocoon shell weight and cocoon shell percent. Path coefficient analysis also revealed that the pupation rate had the maximum direct effect on CY followed by cocoon shell weight and larval weight. Cocoon shell percent and cocoon weight exhibited negative direct path effect on cocoon yield / 10,000 larvae by weight. Therefore, the selection based on pupation rate, larval weight and cocoon shell weight can be effective in improving cocoon yield in silkworm at different environments with varying temperature.

Effects of sodium chloride on oviposition and development of blowfly, Lucilia cuprina, (Wiedmann) (Diptera : Calliphoridae)

Effects of five different concentrations of sodium chloride (5 to 25%) treated fish flesh was tested on oviposition, growth and developmental parameters of blowfly, Lucilia cuprina (Wiedemann). The salt worked as an oviposition deterrent in the female flies. The highest amount of eggs (0.247 ± 0.0464 g) was oviposited on lowest salt concentration (5%) and the minimum amount (0.0003 ± 0.0004 g) of eggs was laid on the highest salt concentration (25%). The eggs laid on 20 and 25% salt treated fishes were not hatched. The larval periods were significantly affected by 10 and 15% salt treated fish while the pupal periods were prolonged at 15% of salt treated fish (p < 0.05). Average larval and pupal durations in control were 4.543 ± 0.18 and 4.833 ± 0.753 days, respectively, whereas at 15% salt average larval and pupal durations were 5.937 ± 0.133 and 5.5 ± 0.548 days, respectively. The average weight of the larvae and pupae were also reduced with the high concentrations of salt. Pupation rate also significantly reduced at higher concentrations of salt. These results suggest that application of 15% salt in raw fish can effectively protect sun?drying fish from blowfly infestation. DOI: http://dx.doi.org/10.3329/dujbs.v23i1.19825 Dhaka Univ. J. Biol. Sci. 23(1): 47-51, 2014