The hemodynamic activity of Melipona flavolineata workers was evaluated during restraint stress for a period of 30 min. The observed parameters were power variation in the elapsed time, and subsequently, six periods of one second were divided and called A, B, C, D, E and F; in each period, the electrocardiographic parameters were evaluated: spike frequency, amplitude, spike intervals and spike duration. The experiment was carried out with eight worker bees of M. flavolineata, for which electrodes of a nickel–chromium alloy were made. The bees were previously anesthetized with isoflurane and properly contained and fixed in a base for stereotaxis in which the electrode was implanted. All these procedures were performed inside a Faraday cage. The results showed power oscillations during the recording, with the highest energy level being between 300 and 600 s. Spike frequency, spike amplitude, interval between spikes and spike duration parameters underwent changes during the restraint stress period. Thus, the cardiac activity of M. flavolineata can be used as a biomarker and can be used to clarify physiological issues or alterations caused by toxic agents and indicate risk factors for these animals.

A mortality of bees (Apis mellifera) caused by fipronil intoxication, due to its indiscriminate use in crops, has long been attracting the scientific community’s attention, either due to its acute or residual effects. In this study, we assessed the cardiac activity as a biomarker of fipronil intoxication through electrophysiological recordings of bees. Eighteen foragers, from the apiary of EMBRAPA—Eastern Amazon (Belém-Pará), bees were previously anesthetized at low temperature (− 10 °C) for 5 min and properly restrained and fixed on a stereotaxic base, where electrodes were implanted. All these procedures were carried out within a Faraday cage. Eighteen bees were used in the study. Worker bees engaged in foraging activities were selected. The bees were divided into a control group and a group treated with fipronil at 0.025 mg/bee (n = 9). The recordings lasted for 4 min and were evaluated at 1-s intervals represented by the following letters: A = (2–3 s), B = (59–60 s), C = (119–120 s), D = (179–180 s), and E = (239–240 s). The results showed that fipronil reduced the frequency and intensity of cardiac activity, exhibiting rapidly evolving effects, and promoting a disruption of homeostasis in bee hemodynamics. Through the obtained data, it was observed variation in spike amplitude, with a loss of cardiac strength and magnitude of the electrical impulse in the bee’s heart during exposure to fipronil.