Weakly electric fish conclusion

 In summary, although the last decade has produced many studies on social electrocommunication in weakly electric fish, they have been biased towards proximate research and to some extent wave-type species. Species recognition in the wave-type fish A. leptorhynchus is mediated by stereotyped EOD frequencies and in the pulse-type fish. M. rume it is determined by a species-specific IDI (Fugère & Krahe 2010, 213; Dunlap et al. 2010, 2234; Worm et al. 2018, 1). JAR seems to be unique to wave-type species and has been hypothesized to have an intrasocial function in Apteronidae, Eigenmannia, and Dystocyclus, but seems absent from Sternopygus (Worm et al. 2018, 1; Stamper et al. 2010, 368). Ritualised aggression in weakly electric fish is often negotiated via modulated EOD frequencies, EOD lengths, and IDI patterns that signal the dominance of one fish over another, and in the males of some species, dominance strongly correlates with levels of 11-ketotestosterone (Gebhardt et al. 2012, 623; Fugère et al. 2011, 197; Salazar & Stoddard 2009, 399; Cuddy et al. 2012, 4; Raab et al. 2019, 1). Sexual dimorphism of EODs is evolutionarily labile, as A. leptorhynchus shows sexual dimorphism in EOD frequency and chirping while many other wave-type genera are sexually monomorphic (Smith 2013, 2428; Batista et al. 2012, 398). S. nattereri is a unique case where electrocommunication is sexually monomorphic but different male morphs vary in their EOD frequencies (Ho et al. 2013,337; Fernandes et al. 2010, 660). Lastly, pulse-type fish of the Marcusenius genus also show differences in sexual dimorphism, as M. pongolensis males show a life-long increase in their EOD length while male M. altisambesi only show increased EOD length during the breeding season (Machnik et al. 2010, 699). Overall, these studies show that weakly electric fish use electrocommunication in a variety of contexts and explore how electrocommunication takes place but explanations for its evolution remain largely in the hypothetical realm. Answering ultimate questions about electrocommunication would be facilitated by studies into: (1) how differences in selection pressures have affected species differences in electrocommunication, (2) the evolutionary history of electrocommunication in Gymnotiformes and Mormyriformes to understand how these groups diverged and became segregated to South America and Africa respectively, (3) the environmental and evolutionary factors that contribute to sexually dimorphic electrocommunication.