Análise morfométrica de larvas de Simulium pertinax (Kollar, 1932) e Simulium (inaequalium) sp. e sua relação como potencial bioindicador da qualidade da água no Parque Nacional da Tijuca e uma área adjacente

Abstract

Blackflies are dipteran insects that, in their immature life stages, colonize freshwater flowing aquatic environments. This study aims to compare the body size of simulid larvae of the species Simulium pertinax and Simulium (Inaequalium) sp. collected in water courses inside and outside of Sector A of the Tijuca National Park. Collections were made in the years 2019 and 2021. Abiotic variables were verified in situ by specific equipment and a protocol was also applied to each river to assess the integrity of the waters of the rivers. The water velocity was verified by the “head rod” method. The morphometric analysis was performed using the software Cmeias-IT. The calculation of the biodiversity index and statistical analysis were carried out. A total of 1,311 larvae were collected and the following species were seen: Simulium pertinax, Simulium (Inaequalium) sp., Simulium (Psaroniocompsa) Simulium (Psaroniocompsa) anamariae and S. (Psilopelmia) perflavum. There was a decrease in the relative abundance of S. pertinax, which in 2019 represented 59% of the individuals, and passes to 16% in 2021. The Tijuca River stretch 1 was the one with the lowest Simpson diversity index (0.0049). In the assessment of water integrity, the rivers located inside the conservation unit presented class II (very good), whereas the stretch of the Tijuca river outside was the only one to have class III (good). The averages of body size, cephalic region and propata of the larvae were larger in the stretch of the Tijuca River on the outside than in the stretch on the inside. The Wilcoxon Test found that there was a significant difference (p-value<0.05) for the body size of S.pertinax and S. (Inaequalium) sp. compared to the years 2019 and 2021; In the canonical correspondence analysis (CCA) as a function of S. anamariae species, there was a strong positive correlation with water conductivity. S.(Inaequalium) sp. was positively influenced by the significant variables of altitude and “middle” collection position. The CCA also showed that the measurements of body size, head and silver of the species S. pertinax were negatively influenced by the luminosity and altitude of the rivers. Correlations between abiotic variables and morphometric measurements were highly significant with a canonical R of 0.9601 and a p-value of 0.0001. Few studies correlate the morphometry of the body size of the simulid larvae with the water integrity indices of the rivers, so more studies are needed to confirm the relationship that both can present and if in fact they can be used as biological indicators.