Abstract
This study observed the mosquito population in a rural eutrophised dam. Larvae of L3 and L4 stages and pupae were dipped out during twelve month collections and the reared to the adult stage for identification. The collections were done along nine metres from the edge of the dam divided in three parts (P1, P2 and P3), each part being 3 m long. P1 did not have vegetation (grass) along its edge,which would reach or sink into the water to promote some shade on the marginal water. A total of 217 adults of four species was identified with the following constancies and frequencies: Culex quinquefasciatus (Say, 1823) (83% and 40.6%), Anopheles (Nyssorhynchus) evansae (Brèthes, 1926) (92% and 26.7%), Anopheles (Nyssorhynchus) rangeli (Gabaldon, Cova Garcia and Lopez, 1940) (83% and 14.3%) and Culex nigripalpus (Theobald, 1901) (33% and 18.4%). C. quinquefasciatus, A. evansae, A. rangeli and C. nigripalpus were more frequent in the quarters Nov./Dec./Jan. (85.7%), May/June/July (75%), Aug./Sept./Oct. (29.4%) and Aug./Sept./Oct. (23.5%) particularly in the months of December (88.4%) Sept.tember (48.94), (38.3) and August (47.62) respectively. The presence of C. quinquefasciatus and the high incidence of Daphinia sp. and also the levels of Organic Nitrogen (0.28 mg/L) and of total Phosphorus (0.02 mg/L) are indications of the eutrophication of the dam. There was a difference regarding the total of Anopheles (A. avansae + A. rangeli) and Culex species (C. quinquefasciatus + C. nigripalpis) between P1 and P2 (χ(2) = 0.0097), P1 and P3 (χ(2) = 0.0005), but not between P2 and P3 (χ(2) = 0.2045).The high C. quinquefasciatus constancy and frequency were confirmed to be a good biological indicator for a eutrophised environment and A. evansae showed a good potential for this environment. Vegetation can be an important factor for anopheline population dynamic also in eutrophic breeding sites.
Highlights
Due to the importance of mosquitoes to public health, they have been much studied, and that is the case of vector species adapted to anthropic environments.These studies have privileged the adults, mainly females, for epidemiological purpose, to the detriment of studies on their immature aquatic stages
Knowledge of the mosquito capacity to exploit degraded environments is limited to the species which may occur in polluted breeding, such as the Culex quinquefasciatus (Say, 1823), Culex pipiens (Linnaeus, 1758), Culex nigripalpis (Theobald, 1901), Armigeres subalbatus (Coquillett, 1989), (Clements, 1999; Forattini, 2002) and Anopheles (Anopheles) quadrimaculatus (Say, 1824) (Reinert et al, 2003)
The C. quinquefasciatus, A. evansae, A. rangeli and C. nigripalpus were more frequent in the quarters Nov./Dec./Jan. (85.7%), May/
Summary
Due to the importance of mosquitoes to public health, they have been much studied, and that is the case of vector species adapted to anthropic environments.These studies have privileged the adults, mainly females, for epidemiological purpose, to the detriment of studies on their immature aquatic stages. Eutrophication is one of the most important humaninduced modifications affecting aquatic systems in the biosphere (Pinto-Coelho et al, 2005) and it is the enrichment by nutrients, especially nitrogen and phosphorus, leading to the imbalance of the aquatic ecosystem and degeneration of the water quality (Brito de Figueiredo et al, 2007). It may occur in lakes, dams, rivers and even on the marine coast and it may be natural or due to the human activities.
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