Hopkins Lab, Department of Neurobiology & Behavior, Cornell University
Electric fish speak out
A video showing acoustic communication in the mormyrid, Pollimyrus isidori, recorded in Mali on the Niger River in 1994.
Electrical Communication: Sequences of Pulse Intervals in Mormyridae. The following are flash video clips of electrical and motor activities of the electric fish, Brienomyrus brachyistius, recorded and analyzed in the Hopkins Lab by Kevin Gardner, Brian Isett, Tom Kraft Garry Harned.
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Each of these examples was recorded using infrared light only. The visible light was completely absent during these observations. The electric discharges were recorded on two audio channels and synchronized with a single audio track from the video recorder. After recording the signals the two fish were separated using the Matlab program GPRIME written by Gus Lott. The dominant and subordinate and the male and female fish used in these studies differed in the peak spectral frequency of their EODs. To avoid changes in amplitude and polarity of the signal, a single period sine wave was substituted for each recorded EOD; the spectral peak of the sine wave was matched to the spectral peak of the recorded EOD.
Example 1: courtship and spawning.
This clip is of the spawning behavior between a male and female Brienomyrus brachyistius. The clip begins with the male located in the upper right netting of the tank and the female in the center of the tank. The female proceeds to gain the male’s attention and then return to the bottom center of the tank. Spawning then ensues, after which the female exhibits a “prodding” behavior, looking for eggs for approximately three seconds after spawning. Electrically, the male discharges the stereotypical Rasp both before and after spawning. During actual spawning, the male discharges an SPI known as a Creak. Immediately prior to, and during spawning the female discharges the Long Repeated Acceleration Deceleration (LRAD).
Example 2: long silence
This clip shows the end of a fight settling a dominance dispute between two male Brienomyrus brachyistius. Prior to the behavior seen in the clip, the two males had been fighting with characteristic head butts and anti-parallel displays for approximately ten minutes. In the clip both males can be seen attacking using head butts; no anti-parallel displays are visible due to the fact that at the end of a fight fewer anti-parallel displays are used while more head butts are used. At approximately 15 seconds into the clip the fight ends with the fish labeled “subordinate” losing. Electrically, both fish emit the stereotypical Rasp SPI which is seen during both agonistic and courtship interactions. Upon losing the fight, the subordinate immediately falls silent and displays the long cessation characteristic of subordinates. The dominant, having won the fight, continues to discharge continuously.
Example 3: LRAD:
This clip shows the Long Repeated Acceleration–Deceleration and the associated motor behavior. The clip begins with the dominant located on the right side of the tank and the subordinate in the center. The dominant approaches the subordinate and begins chasing. Upon beginning to flee, the subordinate immediately begins discharging the LRAD. The subordinate continues to discharge the LRAD for the duration of the chasing, halting the display only when chasing ends. The duration of the LRAD is approximately 20 seconds, during which time the dominant discharges a continuous but low frequency discharge.
Example 4: Pulse Pairs:
This clip shows Pulse Pairing and the associated motor behavior. Clip begins with the dominant located in the center tubing and the subordinate to the left of the tubing. The dominant then exits the tube and proceeds to attack the subordinate. Upon attacking the subordinate, the dominant begins pulse pairing for approximately 2 seconds. The dominant then returns to the center tubing, after which he approaches the subordinate located in the upper net. Upon approaching the subordinate, the dominant begins pulse pairing and then attacks with the pulse pairs lasting 2 seconds.
Example 5: Long Cessation/Patrolling:
This clip shows both the patrolling behavior of dominants and the long cessations of subordinates. The dominant begins the clip swimming actively around section A, occasionally attacking the subordinates. The dominant then enters sections B and C and finally returns shortly thereafter to section A. Upon returning to section A the dominant rasps and attacks subordinate 2. Both subordinates exhibit long cessations and are silent for the duration of the clip.
Sound Production in Mormyrid Fish
We discovered sound production in mormyrid fish in 1984 and published a series of papers on the use of sounds in courtship and mating. JD Crawford published a series of papers on sound production and sound reception in mormyrids between 1986 and 2002. Below are two video examples of sounds produced by two species: Pollimyrus adspersus and Pollimyrus isidori. This work was done by Crawford et al. (1986) and by Crawford et al 1999 (see Crawford Publications)
Courtship Song in a Gymnotid Fish (Sternopygus macrurus)
Courtship singing in Sternopygus macrurus