Androgen Correlates of Socially Induced Changes in the Electric Organ Discharge Waveform of a Mormyrid Fish

2000 ◽  
Vol 38 (3) ◽  
pp. 177-186 ◽  
Author(s):  
Bruce A. Carlson ◽  
Carl D. Hopkins ◽  
Peter Thomas
Keyword(s):  
Electric Organ Discharge ◽  
Electric Organ ◽  
Mormyrid Fish ◽  
Induced Changes

Categorisation of Interpulse Intervals and Stochastic Analysis of Discharge Patterns in Resting Weak-Electric Mormyrid Fish (Gnathonemus Petersii)

Behaviour ◽  
1987 ◽  
Vol 102 (3-4) ◽  
pp. 264-282 ◽  
Author(s):  
Claudine TEYSSÈDRE ◽  
Michel Boudinot ◽  
Catherine Minisclou
Keyword(s):  
Individual Differences ◽  
Stochastic Analysis ◽  
Electric Organ Discharge ◽  
Electric Organ ◽  
Electric Pulses ◽  
Oscillating Systems ◽  
Mormyrid Fish ◽  
Discharge Patterns ◽  
Gnathonemus Petersii ◽  
Criterion Method

AbstractInter-individual similarities in the electric organ discharge activity of immobile, isolated and undisturbed mormyrid fish were investigated. Two types of analysis were performed on the discharge patterns of 10 Gnathonemus petersii: (1) The Bout Interval Criterion method was used to categorise the intervals between consecutive electric pulses; (2) an analysis of sequences of acts was performed to study the serial ordering of the interpulse intervals. Interpulse intervals were demonstrated to belong to distinct classes, having similar limits for most animals. Most fish show five classes of interpulse intervals (23 to 68 ms; 69 to 108 ms; 109 to 170 ms; 171 to 212 ms; >212 ms), to which a sixth class (<23 ms) is added in some cases. Each class contains a similar number of intervals in all individuals. Particular associations were found between the occurrences of interpulse intervals belonging to different classes. Some of these associations (for example BB and EC) are displayed by most fish, whereas others express individual differences in the patterns of discharge. The discharge of immobile, undisturbed, isolated mormyrid fish is thus shown to present many similarities among individuals. Inter-individual differences exist only in the serial ordering of the intervals, where they arc best regarded as variations around a same theme. The absence of overlapping between the two main categories of interpulse intervals (category I: 69 to 108 ms; category II: 171 to 212 ms), as well as the constancy of their baselines, suggest that two oscillating systems participate to the electromotor command. The stochastic analysis of the serial ordering of the interpulse intervals suggest in addition that these two oscillators do not function independently. Momentaneous modifications of the activity of these two oscillators would provide an economical explanation for the various changes in the types of interpulse intervals associated with behavioural state or social interactions.

scholarly journals Electric organ discharge patterns during group hunting by a mormyrid fish

2005 ◽  
Vol 272 (1570) ◽  
pp. 1305-1314 ◽  
Author(s):  
Matthew E Arnegard ◽  
Bruce A Carlson
Keyword(s):  
Low Voltage ◽  
Electric Organ Discharge ◽  
Electric Organ ◽  
Lake Malawi ◽  
Weakly Electric Fish ◽  
Species Flock ◽  
Unexpected Finding ◽  
Size Estimation ◽  
Vertebrate Lineage ◽  
Mormyrid Fish

Weakly electric fish emit and receive low-voltage electric organ discharges (EODs) for electrolocation and communication. Since the discovery of the electric sense, their behaviours in the wild have remained elusive owing to their nocturnal habits and the inaccessible environments in which they live. The transparency of Lake Malawi provided the first opportunity to simultaneously observe freely behaving mormyrid fish and record their EODs. We observed a piscivorous mormyrid, Mormyrops anguilloides , hunting in small groups in Lake Malawi while feeding on rock-frequenting cichlids of the largest known vertebrate species flock. Video recordings yielded the novel and unexpected finding that these groups resembled hunting packs by being largely composed of the same individuals across days. We show that EOD accelerations accompany prey probing and size estimation by M. anguilloides . In addition, group members occasionally synchronize bursts of EODs with an extraordinary degree of precision afforded by the mormyrid echo response. The characteristics and context of burst synchronization suggest that it may function as a pack cohesion signal. Our observations highlight the potential richness of social behaviours in a basal vertebrate lineage, and provide a framework for future investigations of the neural mechanisms, behavioural rules and ecological significance of social predation in M. anguilloides .

Changes in electric organ discharge after pausing the electromotor system of Gymnotus carapo

2000 ◽  
Vol 203 (9) ◽  
pp. 1433-1446 ◽  
Author(s):  
S. Schuster
Keyword(s):  
Electric Organ Discharge ◽  
Amplitude Ratio ◽  
Electric Organ ◽  
Recovery Phase ◽  
Weakly Electric Fish ◽  
Electromotor System ◽  
Phase Amplitude ◽  
Electric Organ Discharges ◽  
Induced Changes ◽  
Weakly Electric

During their entire lives, weakly electric fish produce an uninterrupted train of discharges to electrolocate objects and to communicate. In an attempt to learn about activity-dependent processes that might be involved in this ability, the continuous train of discharges of intact Gymnotus carapo was experimentally interrupted to investigate how this pausing affects post-pause electric organ discharges. In particular, an analysis was conducted of how the amplitude and relative timing of the three major deflections of the complex discharge change over the course of the first 1000 post-pause discharges. The dependence of these variables on the duration of the preceding pause and on water temperature is analysed. In addition, pause-induced small reverberations at the end of the discharge are described. Common to all amplitude changes is a fast initial decrease in amplitude with a slow recovery phase; amplitude changes scale with the duration of the preceding pause and are independent of the interdischarge interval. The absence of changes in the postsynaptic-potential-derived first phase of the discharge together with changes in the amplitude ratio of the third and fourth deflections suggest that the amplitude changes are mainly due to pause-induced changes in the inner resistance of the electric organ. A model is formulated that approximates the pattern of amplitude changes. The post-pause changes described here may provide a new way to test current models of complex discharge generation in Gymnotus carapo and illustrate the speed at which changes of an electric organ discharge can take place.

Neuronal responses to electrosensory input in mormyrid valvula cerebelli

1978 ◽  
Vol 41 (6) ◽  
pp. 1495-1510 ◽  
Author(s):  
C. J. Russell ◽  
C. C. Bell
Keyword(s):  
Single Unit ◽  
Evoked Potential ◽  
Electric Organ Discharge ◽  
Electric Organ ◽  
Neuronal Responses ◽  
Sensory Stimuli ◽  
Separate Area ◽  
Mormyrid Fish ◽  
Electrosensory Processing ◽  
Gnathonemus Petersii

1. We have examined a large portion of the valvula cerebelli of the mormyrid fish Gnathonemus petersii for responses related to the three known classes of electroreceptors. Evoked potential and extracellular single-unit records from curarized and non-curarized preparations show that a separate area of the valvula is related to each of the different electrosensory modalities. 2. The area related to ampullary receptors is also strongly affected by mechanical stimulation to the skin. In the mormyromast and Knollenorgan regions, responses to sensory stimuli depend on when they are given in relation to the command to fire the electric organ. In the Knollenorgan region the interaction is quite simple. Responses are completely blocked if the stimulus is given during a brief period when the electric organ discharge occurs. A greater variety of interactions is seen in the mormyromast region. 3. Large areas of the valvula do not appear to be clearly and strongly retated to any of the three electrosensory modalities, suggesting the possibility that much of the structure is not devoted to electrosensory processing.

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