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Journal ArticleDOI

‘Communication’ in weakly electric fish, Gnathonemus niger (Mormyridae) I. Variation of electric organ discharge (EOD) frequency elicited by controlled electric stimuli

01 Nov 1970-Animal Behaviour (Academic Press)-Vol. 18, pp 768-786
TL;DR: The regularisation of the discharge activity is thought to be involved in the fish's electrolocating system whereas frequency variations are considered as being involved in both the locating system and as communication signals among weakly electric fish.
About: This article is published in Animal Behaviour.The article was published on 1970-11-01. It has received 97 citations till now. The article focuses on the topics: Electric fish.
Citations
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Journal ArticleDOI
03 Apr 1981-Science
TL;DR: An electric fish in the African family Mormyridae recognizes members of its own species by "listening" to electric organ discharges, which are species-specific signatures.
Abstract: An electric fish in the African family Mormyridae recognizes members of its own species by "listening" to electric organ discharges, which are species-specific signatures. Reactions of fish in the field and of individual electroreceptors to both normal and modified computer-synthesized discharges emphasize the importance of the waveform (time-domain cues) in species recognition.

236 citations

Journal ArticleDOI
TL;DR: The role of electrical signals in agonistic behavior of Eigenmannia virescens was studied by as discussed by the authors, who found that at least three classes of electric signals are important in communication among Eigenmania: the normal discharge, interruptions, and rises.
Abstract: Eigenmannia virescens was observed in aquaria in Guyana, South America, during the non-breeding and breeding seasons. Agonistic behavior was described and correlated with electrical activity. Variations in the electric discharges play important roles in agonistic behavior as displays given during attack and retreat. Although descriptions of sexual behavior are not complete, certain electrical signals also appear to be used in courtship. The role of electrical signals in agonistic behavior of Eigemnannia were studied by (1) an analysis of the behavior of fish in dominant and subordinate roles, (2) an analysis of the simultaneous occurrence of electrical displays and motor actions, (3) an analysis of preceding actions of one fish and following actions of the other fish, and (4) analysis of responses to artificial electrical stimuli. These studies indicate that at least three classes of electric signals are important in communication among Eigenmannia: the normal discharge, Interruptions, and Rises. The normal discharge. The normal discharge of Eigenmannia virescens is species-distinctive in the area where this study was conducted. Playback of recorded signals and presentation of sinusoidal electrical stimuli, indicates that the normal discharge particularly the fundamental frequency of the normal discharge (240 to 600 Hz)- is used in species recognition. Males and females overlap extensively in their discharge frequency, and males do not appear to distinguish the electric discharges of males from those of females. Interruptions. Interruptions are brief cessations of the electric discharge. They are most often 20 to 40 msec in duration during agonistic interactions whereas they are often 60 to 80 msec when given by males during interactions with females during the breeding season. Interruptions are usually given in bouts where a bout is any group of Interruptions separated by less than 1.5 seconds. Interruptions are given almost exclusively by dominant fish. They are given at the same time as Attacks, Threats, and No Action, but rarely during Retreat. Bouts with many Interruptions are more likely to be associated with Attacks, and less likely with No Action, than are bouts containing only a few Interruptions. Interruptions correlate with motivation to Attack, and the number of Interruptions in a bout correlates with the probability of attack. Interruptions in one fish are followed by Retreat and No Action in the other fish, thus they appear to be an effective threat display. Interruptions with long durations are given at high repetition rates by male Eigenmannia in the presence of females during the breeding season, thus they may play a role in courtship. Rises. A Rise is an increase in discharge frequency followed by a decrease to the resting frequency. Rises lasting less than two seconds (Short Rises) are often given by dominant fish in agonistic interactions, most often at the same time as Attacks or Threats. They are given rarely. Long Rises (longer than two seconds) are given predominantly by subordinate fish in agonistic interactions. They are given simultaneous with Retreat and No Action and are thus an indicator of submissive behavior. Long Rises in one fish are followed by Attacks, Threats, Approaches, and by No Action in the other. During the breeding season, females, in the presence of males, often give long series of frequency modulations of unknown significance.

206 citations

Journal ArticleDOI
02 Jun 1972-Science
TL;DR: Playback experiments demonstrate that species and sex differences in electric discharges have communicative significance in Sternopygus macrurus.
Abstract: The electric discharge of Sternopygus macrurus is distinctly different from the discharges of ten sympatric species of electric fish in Guyana, South America. Sternopygus is the first known example of a fish with sexually different electric discharges. Males and females differ in the steady-state frequency of their discharges, and males produce variations in their discharge during courtship. Playback experiments demonstrate that species and sex differences in electric discharges have communicative significance.

147 citations

Journal ArticleDOI
26 Apr 2010-Ethology
TL;DR: Zusammenfassung Sternopygus macrurus, eine der dreizehn im Rupununi Distrikt von Guyana beheimateten Messeraal-Arten benutzt elektrische Signale im Fortpflanzungsverhalten, das die Individuen typische Entladungs-Frequenzen haben.
Abstract: Zusammenfassung Sternopygus macrurus, eine der dreizehn im Rupununi Distrikt von Guyana beheimateten Messeraal-Arten benutzt elektrische Signale im Fortpflanzungsverhalten. Sternopygus leben in steinigen und sandigen Bachen und kommen nachts aus ihren Verstecken. Ihre Laichzeit beginnt vor Eintritt der Regenzeit Ende April. Sternopygus hat langdauernde Entladungen mit kurzen Pausen, die im Lautsprecher einen summenden Ton ergeben (im Unterschied zu Arten mit kurzen Entladungen und langen Pausen, die “knattern”). Von den vier summenden Fischarten hat S. macrurus eine eigene Tonlage und Tonstarke. Ausgewachsene ♂♂ und ♀♀ erzeugen verschiedene Ruhe-Entladungen. In der Laichzeit reagieren ♂♂ auf Annaherung eines ♀ mit veranderten Entladungen. Diese scheinen ♀♀ anzulocken. Auch ♀♀ konnen ihre Entladungen variieren. Kunstlich uber Elektroden ins Wasser gespielte Sinus-Schwingungen mit ♀-Frequenz wurden von ♂♂ richtig beantwortet; auf ♂-Frequenz oder Frequenzen anderer Arten gab es keine Reaktion. Beobachtungen an zwei Sternopygus-Paaren ergaben, das die Individuen typische Entladungs-Frequenzen haben. Paarpartner konnen Frequenzen annehmen, die genau eine Oktave auseinander liegen.

145 citations

References
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Journal ArticleDOI
TL;DR: A theory has been proposed which suggests that these fish, by means of their electric pulses, can locate objects if their electrical conductivity differs from that of water, and show striking features of convergent evolution.
Abstract: 1. The electric discharges of Gymnarchus niloticus and of representative species of seven genera of the Mormyridae have been examined in their natural habitat in Africa and in the laboratory. 2. Comparable investigations of the South American Gymnotidae have shown the existence of two discharge types in both these unrelated fish families. 3. The first type of electric discharge consists of very regular sequences of continuously emitted, monophasic pulses, varying from species to species in frequency, and within narrower limits from individual to individual. 4. Fish emitting this first type of pulses include Gymnarchus , Hypopomus and Eigenmannia . The frequency range for these fish lies between 60 and 400 discharges/sec. 5. The frequency does not alter with the state of excitation of the fish. The duration of individual pulses is relatively long, i.e. 2-10 msec. 6. The second type of discharge is less regular in frequency, the pulse duration much shorter and the pulse shape more complex. The individual discharge from the whole electric organ lasts about 0.2 msec, in Petrocephalus . 7. This type of discharge is found in all the examined species of the Mormyridae and in such forms as Gymnotus carapo and Staetogenes elegans . 8. The basic discharge rate of a resting mormyrid is somewhat variable and not strictly rhythmical. It usually lies between 1 and 6 pulses/sec. 9. Stimuli which excite the mormyrids cause an increase in the discharge frequency. The recorded maximum is about 130 pulses/sec. 10. Suitable stimuli can inhibit the discharges of the Mormyridae for prolonged periods. 11. In Gymnotus carapo and Staetogenes elegans the basic discharge rate is higher and of regular rhythmicity. Depending on temperature the frequencies lie between 30 and 87 pulses/sec. When these fish are excited the frequencies are increased up to 200 pulses/sec, for a short time. 12. The shape of the electric field, which is set up with each pulse around the fish, has been examined. 13. A theory has been proposed which suggests that these fish, by means of their electric pulses, can locate objects if their electrical conductivity differs from that of water. 14. These fish have shown themselves extremely sensitive to influences affecting the electric field. This has been studied by applying artificial electric stimuli, by studying the effects of conductors and non-conductors introduced into the field, and the reactions towards magnetic fields and electrostatic charges. 15. Conditioned reflex experiments with Gymnarchus niloticus and Gymnotus carapo have shown that these fish can detect the presence of a stationary magnet, and that they can discriminate between conductors and non-conductors. 16. The prey of these fish does not appear to be affected by the discharges. Inter alia , the electric pulses have a social significance. 17. This locating mechanism may be considered as an adaptation to life in turbid water. 18. Gymnotidae and Mormyridae (taken to include Gymnarchus ) show striking features of convergent evolution. 19. Unusual locomotory adaptations such as swimming by means of the dorsal fin ( Gymnarchus ), the anal fin (Gymnotidae) and ‘Gemminger9s bones’ (Mormyridae) may be considered as a means which tends to make the axis of symmetry of the fish and of its electric field coincide during active movements. 20. A new theory for the evolution of electric organs has been suggested. A major prerequisite appears to be a receptor sensitive to electrical stimulation. 21. It is suggested that special sensory and nervous differentiations of the lateralis system (‘mormyromasts’, valvulae cerebelli) are concerned with the perception and integration of electric stimuli. 22. Muscular action potentials have been recorded in the water at some distance from non-electric fish. 23. The easiest explanation for the evolution of strong electric organs would appear to start from such muscular action potentials, and proceed via weak electric organs used for orientation, to the powerful offensive and defensive electric organs.

505 citations

Journal ArticleDOI
TL;DR: In this article, the effect on the receptors of the perturbing field due to an object depends on the electrical properties of the receptors: in the extreme cases the stimulation of the receptor is proportional either to the potential or to its second derivative.
Abstract: 1. Experiments with moving electrostatic and magnetic fields show that Gymnarchus niloticus is sensitive to a potential gradient of about 0.03 µ V./cm. 2. Alternative explanations of some previous experiments are given in terms of this high d.c. sensitivity. 3. An explanation in similar terms is given of experiments in which Gymnotus carapo is trained to detect a stationary magnet. 4. The mechanisms available for the location of objects by electric fish are reviewed. It is concluded from the results of a critical experiment (described in a succeeding section) that Gymnarchus niloticus can detect objects by the disturbance of its own electric field in the water. 5. The approximate theory of this method of object location is derived. The effect on the receptors of the perturbing field due to an object depends on the electrical properties of the receptors: in the extreme cases the stimulation of the receptors is proportional either to the potential or to its second derivative. Graphs are given showing the effect of an object on the potential and on its second derivative around the surface of the fish. 6. Experiments are described using Gymnarchus niloticus which ( a ) confirm that the mechanism of object location employs electric field distortion; ( b ) indicate the limits of the sensitivity of the fish. 7. The second derivative mode appears to be the most probable one operating in Gymnarchus . The experimentally determined limits of detection are discussed in relation to the random noise in the receptor circuit: it is concluded that both spatial and temporal integration are likely to be employed. 8. The thresholds for object location and for response to direct currents are compared: it is concluded that the same receptors are probably operating in both cases.

444 citations

Journal ArticleDOI
TL;DR: A South American gymnotid Eigenmannia, changes the discharge frequency of its electric organ when a weak electric signal is applied to it with a frequency very close to that of its own discharge.
Abstract: 1. A South American gymnotid Eigenmannia , changes the discharge frequency of its electric organ when a weak electric signal is applied to it with a frequency very close to that of its own discharge. Otherwise, the discharge frequency is extremely constant at a fixed temperature. 2. When the frequency of the applied signal is higher or lower than that of the fish discharge, the response is a decrease or increase of the discharge frequency, respectively. When the two frequencies are exactly the same, the response fails to occur. 3. The threshold of this response is very low. In one fish it was about 3 µ V./cm.

182 citations

Journal ArticleDOI
TL;DR: Morphological aspects of lateral line system of Gymnotidae, Mormyridae and Gymnarchidae were studied and one of the specialized sense organs was identified as a newly recognized sense organ, the electroreceptor.
Abstract: Morphological aspects of lateral line system of Gymnotidae, Mormyridae and Gymnarchidae were studied: “Ordinary” and specialized sense organs were identified and their somatic distribution and their relation to the lateral line nerves established. An attempt was made to classify the specialized sense organs of the lateral line system in these families. The morphological results are discussed in relation to recent physiological data permitting identification of one of the specialized sense organs as a newly recognized sense organ, the electroreceptor.

170 citations