First Records of Heartbeats via ECG in a Stingless Bee, Melipona flavolineata (Apidae, Meliponini), during Contention Stress Using Isoflurane as an Anesthetic

SIMPLE SUMMARY: Changes in the heart activity of bees have been correlated with several stressors. However, this has been studied in just a few species within Apoidea. The purpose of our study was to evaluate several parameters of heart activity in a stingless bee species from the Amazon region, Melipona flavolineata, during a 30 min stress period. Workers of the species were restrained and anesthetized using isoflurane. The basal heartbeat at the first five minutes of the records was about 600 beats per minute, which generally increased over the restraining period. The contention stress also changed other parameters of heart activity in the species. Our study was the first to evaluate the cardiac activity in a stingless bee, an important group of tropical pollinators, and showed that heart activity was altered by stress. Thus, heart monitoring using ECG is a feasible technique to show some of the effects of different stressors, such as pesticides, in the physiology of worker bees. We also showed that isoflurane can be used as an anesthetic, an alternative to narcosis induced by CO(2) and cold, although its effects must still be studied. ABSTRACT: 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.