Study on effect of microfauna and some abiotic parameters for the prevalence of mosquito larvae inhabiting marshlands

Abstract

This study was carried out in selected marshlands of Kelaniya in Sri Lanka to determine the prevalence of various mosquito species larvae and their association with biotic and abiotic parameters of the habitat. Larval sampling, recording of physico chemical parameters and microfauna identification were done at monthly interval from March 2015 to August 2015. The study was carried out in eight marshlands with varying Biochemical Oxygen Demand (BOD) levels and total number of 893 mosquito larvae were collected (n=144). Culex gelidus, Cx. whitmorei, Cx. tritaeniorhynchus, Cx. quinquefasciatus, Cx. fuscocephala and Anopheles sp. 1 were the species/taxa identified. Cx. gelidus, Cx. whitmorei, Cx. quinquefasciatus were found in mashes with BOD level ranging from 1.5-2 mg/L and Cx. fuscocephala with 1-1.5 mg/L. Anopheles sp. 1 was found in significantly low level. pH levels in these habitats did not vary significantly and lied between 6.5-7.0. When Cx. whitmorei and Cx. gelidus co-existed in one habitat, it was found a significant negative correlation between the populations of two species. Similar results were found when Cx. quinquefasciatus with Cx. gelidus present together in same habitat. However, Cx. fuscocephala and Cx. gelidus when present together in same habitat, it was shown a positive correlation. In marshlands, 14 genera of microfauna were identified (n=144). Among them Zoothamnium sp 1 was most common and found higher densities and followed by Difflugia sp 1, Nauplius larva, Cyclops sp 1, and Daphnia sp 1. Pearson correlation showed that there was a correlation between the density of mosquito larvae and associated microfauna. Zoothamnium sp. 1 was given negative correlation with the Cx. gelidus when they present in higher density. A significant positive correlation was obtained between Daphnia sp. 1, Difflugia sp. 1, Nauplius larva and Keratella sp. 1 with mosquito larvae. Hence, there is no relationship between microfauna and mosquito populations. However, this may depend on the BOD of the habitat.