Ecology of Preimaginal Culicine Mosquitoes in Rock Pools on Inselbergs Within Kaduna State, Nigeria

Abstract

Ecological investigations were conducted between June and October 2013 on the species composition of culicine mosquitoes breeding in discrete rock pool habitats and chemistry of their microhabitats on inselbergs within Kaduna State, Nigeria. Standard soup ladle dipper (0.105L capacity) was used to obtain representative samples of preimaginal stages of mosquito into plastic bowls. HANNA HI98129 pH/EC/TDS/TEMP meter was used to determine habitats' physicochemical parameters in situ. Habitats' turbidity, alkalinity, total suspended solids, total hardness, Chemical oxygen demand, phosphate and nitrate levels were determined following standard laboratory protocols. Fully developed (4th instar) larvae were preserved with 70% ethanol in labelled specimen bottles while larvae in their lower instars were nurtured on baker's yeast diet in the laboratory, prior to preservation. Mosquitoes were identified microscopically to species by means of pictorial morphological keys. Data were analysed by ANOVA, Pearson correlation and principal component analyses. A total of 269(69.69%) of the 386 rock pools examined were positive with culicine mosquitoes, yielding 31691 larvae belonging to seven species. These included 30366(95.97%) Aedes vittatus, 266(0.84%) Culex albiventris, 105(0.33%) Culex horridus, 241(0.76%) Culex macfiei, 139(0.44%) Culex pipiens pipiens, 523(1.65%) Culex perfidiosus, 1(0.003%) Culex simpsoni and 1(0.003%) Culex tigripes. The mosquitoes bred as sole, double, triple and quadruple conspecific, heterospecific, congeneric and heterogeneric combinations. Specific ranges of breeding habitats' parameters were depths (0.4~65cm), surface areas (1.5~1970m2), temperatures (22.8°C~36.5°C), pH (7.05~12.69), TDS (0~276ppm), EC (0~572μs/cm), TSS (10~150mg/L), turbidity (1.97~178NTU), hardness (30.3~545.4 mg/L), COD (80~480mg/L), PO4 3- (mg/L), NO3 - (8.5~109.4 mg/L) and alkalinity (2~111mg/L). Water temperature and hardness were determinants of spatial distribution of mosquitoes in the rock pools. TDS, EC and akalinity significantly correlate with mosquito larval abundance in rock pools (p<0.001). The study observed widespread breeding of noxious mosquito vectors of diseases in rock pools throughout the State and recommends their targeted control in situ. Key words: Preimaginal culicines; Rock pools; Inselbergs; Physicochemical parameters