Ecology of Aedes vittatus (Diptera: Culicidae) in rock pools across agroecosystem in Northern Savanna, Nigeria

BACKGROUND & OBJECTIVES

This study focuses on modulating dexterity of some ecological variables of Aedes vittatus classically breeding in rocky habitats. The study provides a useful insight into ecological variables that underpin or hinder profuse breeding of Ae. vittatus in rock pools and its probable role in disease transmission.

METHODS

HANNA HI98129 pH/EC/TDS/TEMP meter was used in situ while standard protocols were used to determine other hydro-chemical variables. Aedes vittatus larvae were obtained with soup ladle and modified ladle dippers. D-frame net was used to capture macroinvertebrates while plankton net was used to obtain samples of microalgae. Tadpoles and water turtles were collected with fine mesh invertebrate net. Macrophytes were uprooted and identified at the Herbarium Unit, Department of Botany, Ahmadu Bello University, Zaria. The influence of physicochemical variables was correlated with distribution of Ae. vittatus using Principal Component Analysis. Regression and ANOVA were used to test for association between predictor variables and mosquito abundance and for the difference amongst inselbergs.

RESULTS

Linear larval density of Ae. vittatus in rock pools which tapered across Guinea savanna were obtained from twenty-one sites with average density of 139.6 in Sudan savanna. Guinea savanna had an average larval density of 75.5 with lower subsets of moving average densities compared to Sudan savanna. One hundred and sixty-one aquatic insects belonging to four insect orders cohabited rock pools with Ae. vittatus. Toads and frogs' tadpoles were of Bufonidae and Pyxicephalidae families while water turtles belong to Emydidae. pH, TDS (ppm), EC (μs/cm) and alkalinity (mg/l) differed significantly (p<0.05) with the abundance of Ae. vittatus in rock pools. Temperature, depth, water hardness and total suspended solid had direct influence on the distribution of Ae. vittatus in rock pools across sites. Significant positive correlation exists between aquatic insects and abundance of Ae. vittatus. Hydroperiod length, concentration of nitrate and pH were determinants that leverage profuse breeding of Ae. vittatus and survival of rock pool biota.

INTERPRETATION & CONCLUSION

Results revealed that the bearing influence of rock pool variables is inevitable for breeding of Ae. vittatus. A well defined measure of efficacy incorporating indigenous communities for sustained vector control on inselbergs will go a long way in decimating population of Ae. vittatus and limit the risk of spread of yellow fever hitherto areas not thriving.

Effects of Environmental Variables and Habitat Integrity on the Structure of the Aquatic Insect Communities of Streams in the Cerrado-Caatinga Ecotone in Northeastern Brazil

Alterations in the environmental gradients of streams have a direct influence on the structure of the insect communities of the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT), which are extremely sensitive to changes in habitat. The present study evaluated how habitat integrity in streams influence the composition of EPT genera, by testing three hypotheses: (i) the composition of the EPT genera is modified along the gradient of environmental disturbance; (ii) the composition of the EPT genera is more homogeneous in gradients with a higher degree of anthropogenic disturbance, and (iii) the greatest degree of environmental disturbance along the gradient results in the reduction of the richness and abundance of EPT genera. The study focused on 14 tributaries of the middle Itapecuru River, within an area of ecotone between the Brazilian Cerrado and Caatinga biomes. Data on the structure and physicochemical traits of the streams were collected between September 2014 and July 2015, a period that covers both the dry and rainy seasons in the study region. The results of the present study indicate that the composition of the EPT genera is modified in accordance with the variation in the habitat integrity, although, in contrast with expectations, more impacted areas had a more heterogeneous composition than undisturbed ones. The areas with more integrated landscapes contribute positively to the richness and abundance of EPT genera of the streams of the Cerrado-Caatinga ecotone. Given this, habitat integrity provide an important predictor of EPT diversity in the streams of the Cerrado-Caatinga ecotone.