Weakly electric fish 1

One important use of electrocommunication in weakly electric fish species is conspecific and heterospecific recognition. The use of electric signals for this purpose has been demonstrated in both wave-type and pulse-type fish (Fugère & Krahe 2010, 213; Dunlap et al. 2010, 213; Worm et al. 2018, 1). Counterintuitively, some weakly electric fish preferentially avoid conspecific signals, and this has been attributed to differences in their jamming avoidance response (JAR) (Stamper et al. 2010, 368). Interestingly, it has been hypothesized that JAR doesn’t just serve to avoid interference among fish living in a group, but also as a means of intragroup communication (Stamper et al. 2010, 376; Petzold et al. 2018, 1). 

Species recognition has been demonstrated in the wave-type brown ghost knifefish, Apteronotus leptorhynchus (Fugère & Krahe 2010, 213; Dunlap et al. 2010, 2234). Like other wave-type fish, A. leptorhynchus modulates the frequency and amplitude of its EOD, to produce communication signals generally referred to as “chirps”, “rises”, and “interruptions” (Fugère & Krahe 2010, 213). It has been shown that the waveform of the electrical stimuli A. leptorhynchus encounters does not affect its chirping or approach behaviour whereas frequency changes have a strong effect on chirping and approach behaviour (Fugère & Krahe 2010, 231). This has been corroborated by another study, whose findings show that A. leptorhynchus chirp rate changes when the fish is presented with electrical stimuli that have different frequencies (Dunlap et al. 2010, 2234). Thus, current findings suggest that A. leptorhynchus uses changes in frequency and not waveform to recognise conspecifics (Fugère & Krahe 2010, 234). It has also been shown that A. leptorhynchus can distinguish between conspecifics and heterospecifics, chirping at higher rates in response to conspecifics and at lower rates in response to heterospecifics (Dunlap et al. 2010, 2241). However, there lacks research into whether or not heterospecific type chirp response has any communicative value in A. leptorhynchus (Dunlap et al. 2010, 2241). In addition, the evolutionary origins and adaptive value of this type of electrocommunication in A. leptorhynchus have yet to be discovered.

Only relatively recently, it was shown that a pulse-type fish, Mormyrus rume proboscirostris (M. rume), also uses electrical signaling for species recognition (Worm et al. 2018, 1). In the absence of both vision and the lateral line system, M. rume can rely solely on its electrocommunication system to track and match a source of conspecific electrical signals (Worm et al. 2018, 1). M. rume recognise each other via stereotyped inter-discharge intervals (IDIs) that consist of a short sequence of double-pulses, synchronized at approximately the same frequency as the conspecific signal they receive (Worm et al. 2018, 4). Additionally, and as opposed to A. leptorhynchus behaviour, it was shown that M. rume uses conspecific electrical signals to orient itself spatially, as observed by its following behaviour when presented with a moving source of conspecific signals (Worm et al. 2018, 10).