João Ânderson Fulan

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.

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.