© 2021. Published by The Company of Biologists Ltd | Journal of Experimental Biology (2021) 224, jeb242965. doi:10.1242/jeb.242965 INSIDE JEB Brachyhypopomus bennetti are simplifying their bolts of electricity B. brevirostris are produced by sodium ion channels located on opposite faces of the electric cells – triggering electric currents flowing in opposite directions within 0.5 ms of each other to produce the distinctive voltage traces – Saenz and Markham reasoned that B. bennetti must have lost the sodium channels from the front side of the electric cells, resulting in their single-peaked discharge pattern. However, when Tingting Gu (University of Oklahoma) and Yue Ban (University of California, San Diego, USA) helped Saenz reveal where sodium ion channels occur in the electricity generating cells, they were surprised to find that B. bennetti still retained the front side sodium ion channels. And, when A preserved Brachyhypopomus bennetti. Photo credit: David Saenz. Saenz measured the electric currents produced by both faces of the cells, he was Zapping opponents with bolts of B. bennetti, which produces a simpler, surprised to see that the B. bennetti cells electricity is a staple of the superhero single-peaked discharge pattern. were still generating oppositely directed magazines, but the reality for most currents, but the discharges were electric fish is far more benign. ‘Fish Unfortunately, only B. gauderio can simultaneous, partially cancelling out generate electric signals to communicate currently be bred in captivity, so Saenz the larger current generated by the rear side with each other and to explore and joined José Alves-Gomes from the of the cells, to produce what appeared to be navigate their environment’,says Instituto Nacional de Pesquisas da a single-peaked discharge voltage. David Saenz from Texas A&M Amazônia, Brazil, to collect eight wild University, USA. ‘Most only generate a B. bennetti and one B. brevirostris from the Brachyhypopomus bennetti seem to be in few millivolts of electricity, so you can’t Amazon River. Joining Markham in the process of losing the complex and feel it’, he adds. Explaining that some Oklahoma, Saenz began the painstaking variable electrical signals generated by electric fish modulate their electric signals task of measuring how adrenocorticotropic other members of the Brachyhypopomus through the day with hormones – hormone affected the discharge patterns family, and Saenz admits that it isn’tclear producing higher voltage discharges at produced by the three fish. ‘We removed why B. bennetti have reverted to their night, while crackling more softly when a piece of the tail, which fully regenerates simpler discharge signature, which could inactive during the day – Saenz describes in 2–3weeks… and manoeuvred four inadvertently reveal them to hungry how many electric fish produce glass electrodes into and around a single catfish. He suggests that B. bennetti may be complicated discharge patterns by closely electric cell’, Saenz says, adding that the trying to pass themselves off as terrifying synchronising two or several electrical process was particularly nerve-racking, electric eels, which also produce a single- discharges. Knowing that given his shaky hands. As Saenz applied peaked discharge or simply attempting to adrenocorticotropic hormone regulates the hormone, the voltage of B. brevirostris’ stand out from the knifefish crowd to catch the strength of the mild electric discharges multipeaked discharge became 20–35% the attention of mates. produced by one family of bluntnose stronger. However, the voltage of the knifefish, Brachyhypopomus, Saenz, Kirk single-peaked B. bennetti discharge pattern 10.1242/jeb.242965 Winemiller (Texas A&M University) and barely increased (∼5%). Unlike their Michael Markham, at the University of Saenz, D. E., Gu, T., Ban, Y., Winemiller, K. O. and knifefish cousins, B. bennetti are unable to Markham, M. R. (2021). Derived loss of signal Oklahoma, USA, decided to find out how vary the strength of their crackling electric complexity and plasticity in a genus of weakly the hormone affects the electric crackles calls through the day. electric fish. J. Exp. Biol. 224, jeb242400. doi:10. of two members of the family – 1242/jeb.242400 B. gauderio and B. brevirostris – that Knowing that the more sophisticated Kathryn Knight produce complex discharges, and discharge patterns of B. gauderio and [email protected] Inside JEB highlights the key developments in Journal of Experimental Biology. Written by science journalists, each short report gives the inside view of the science in JEB. Journal of Experimental Biology 1.