Marcelo Rodrigues dos Anjos

Predation by Erythemis nymphs (Odonata) on Chironomidae (Diptera) and Elmidae (Coleoptera) in different conditions of habitat complexity

Aim: The goal of this study was to analyze the effects of predation by nymphs of Erythemis Hagen, 1861 on Elmidae and Chironomidae and to check if the presence and the architecture of aquatic macrophytes may mediate this interaction. Methods: All prey as well as nymphs were captured near macrophytes in a small lagoon alongside a highway near Humaita, Amazonas, Brazil. Twelve buckets were used in three different treatments: with Pistia stratiotes Linnaeus, 1753, with Salvinia auriculata Aublet and without macrophytes. Results: We found a mortality rate of 100% of Chironomidae and Elmidae larvae in the treatment without macrophytes. There was a greater survival of Elmidae compared to Chironomidae in the treatments with P. stratiotes and S. auriculata; however, there was a greater survival of both preys on treatment with P. stratiotes. Conclusions: We conclude that the presence of macrophytes decreased the efficiency of predation of Erythemis nymphs under experimental conditions. The architecture of macrophytes affected predation as macrophytes with longer roots and with greater habitat complexity promoted a greater survival of prey.

Mercury in fish from the Madeira River and health risk to Amazonian and riverine populations

The objective of this study was to quantify total mercury in highly popular Amazonian fish pacu, curimatã, jaraqui, and sardinha from the Madeira River and to estimate the exposure to methylmercury from fish consumption. The samples were obtained from two locations - Puruzinho Igarapé and Santa Rosa - near Humaitá, Amazonia, Brazil in two seasons of 2015 (high and low waters). The fish were identified, weighed and measured, and lipids were quantified. Total mercury was determined by gold amalgamation-atomic absorption spectrometry. Mean levels were used to calculate exposure of Amazonian and riverine populations. There was significant correlation (p < 0.05) between length × weight for all fish; length × lipid and weight × lipid were significant only for pacu. Total mercury levels varied along muscle tissue for the fish, except for sardinha; therefore muscle from the dorsal area along the fish were sampled, homogenized and used for analysis. The levels of total mercury varied from 0.01 to 0.46 mg/kg, with higher median levels in sardinha (0.24 mg/kg), followed by curimatã (0.16 mg/kg), jaraqui (0.13 mg/kg) and pacu (0.04 mg/kg), corresponding with the respective feeding habits along the trophic chain. Total mercury levels were not affected by the location of fish capture and by high and low waters seasons. Total mercury correlated significantly with length and weight for jaraqui and with length for sardinha (negative correlation). Total mercury levels in fish complied with legislation; however, exposures to methylmercury from fish consumption overpassed the safe intake reference dose for sardinha for Amazonians; however, for the riverine communities, all of the fish would cause potential health risk, mainly for children and women of childbearing age.

ASSEMBLEIAS DE PEIXES EM IGARAPÉS DE TERRA FIRME EM DUAS SUB-BACIAS DO MÉDIO RIO MADEIRA, BRASIL

A bacia Amazonica abriga a maior diversidade de peixes de agua doce do mundo. O objetivo deste estudo foi analisar as assembleias de peixes em igarapes de terra firme em duas sub-bacias do Medio Rio Madeira. O estudo foi realizado em duas sub-bacias no Medio Rio Madeira localizadas em terras indigenas. Foram coletados 475 individuos, distribuidos em 55 especies. As curvas do coletor e de rarefacao indicam esforco amostral satisfatorio. A ordem Characiformes foi a mais abundante. A especie mais abundante foi Potamorhina latior e a mais amplamente distribuida foi Crenicichla lenticulata . A cor da agua estruturou a assembleia de peixes em igarapes na area de estudo com maior diversidade de especies em igarapes de agua preta. Diferencas entre aguas pretas, brancas e claras sao obvias, mas mais estudos sobre assembleias de peixes nestes ambientes da bacia Amazonica sao necessarios.

Effect of temperature on the life cycle of Acanthagrion Selys, 1876 (Insecta: Coenagrionidae) under artificial conditions

The goal of this study was to investigate the effect of temperature on the life cycle of Acanthagrion nymphs sampled in a stream in the southern state of Amazonas. Altogether, 50 nymphs (10 in each of the five treatments) with ambient temperatures of 16, 20, 24, 28 and 32°C and water temperatures of 18, 22, 26, 30 and 34oC, respectively, were used. The only treatment that had a hatching adult was at a temperature of 28oC, identified in a single species, Acanthagrion apicale. In all other treatments (16, 20, 24 and 32oC), all nymphs died, respectively 1, 1, 3 and 2 days. We conclude from the results of this study that controlling water temperature near 28°C was the most efficient for obtaining adult A. apicale, and that this temperature was close to the average temperature where the nymphs were sampled, indicating that the control of this variable in artificial conditions is extremely important to obtain adults from nymphs.