Effects of 17α-Methyltestosterone on Sexually Dimorphic Characters in the Weakly Discharging Electric Fish,Brienomyrus niger(Günther, 1866) (Mormyridae): Electric Organ Discharge, Ventral Body Wall Indentation, and Anal-Fin Ray Bone Expansion

1998 ◽  
Vol 34 (3) ◽  
pp. 303-319 ◽  
Author(s):  
Sonja Herfeld ◽  
Peter Moller
Keyword(s):  
Electric Fish ◽  
Body Wall ◽  
Electric Organ Discharge ◽  
Electric Organ ◽  
Sexually Dimorphic ◽  
Fin Ray ◽  
Bone Expansion ◽  
Brienomyrus Niger

scholarly journals Arginine Vasotocin Modulates a Sexually Dimorphic Communication Behavior in the Weakly Electric fish APTERONOTUS LEPTORHYNCHUS

2001 ◽  
Vol 204 (11) ◽  
pp. 1909-1923 ◽  
Author(s):  
Joseph Bastian ◽  
Stephanie Schniederjan ◽  
Jerry Nguyenkim
Keyword(s):  
Electric Fish ◽  
Electric Organ Discharge ◽  
Electric Organ ◽  
Arginine Vasotocin ◽  
Weakly Electric Fish ◽  
Type I ◽  
Sexually Dimorphic ◽  
Type Ii ◽  
Apteronotus Leptorhynchus ◽  
Weakly Electric

SUMMARY South American weakly electric fish produce a variety of electric organ discharge (EOD) amplitude and frequency modulations including chirps or rapid increases in EOD frequency that function as agonistic and courtship and mating displays. In Apteronotus leptorhynchus, chirps are readily evoked by the presence of the EOD of a conspecific or a sinusoidal signal designed to mimic another EOD, and we found that the frequency difference between the discharge of a given animal and that of an EOD mimic is important in determining which of two categories of chirp an animal will produce. Type-I chirps (EOD frequency increases averaging 650Hz and lasting approximately 25ms) are preferentially produced by males in response to EOD mimics with a frequency of 50–200Hz higher or lower than that of their own. The EOD frequency of Apteronotus leptorhynchus is sexually dimorphic: female EODs range from 600 to 800Hz and male EODs range from 800 to 1000Hz. Hence, EOD frequency differences effective in evoking type-I chirps are most likely to occur during male/female interactions. This result supports previous observations that type-I chirps are emitted most often during courtship and mating. Type-II chirps, which consist of shorter-duration frequency increases of approximately 100Hz, occur preferentially in response to EOD mimics that differ from the EOD of the animal by 10–15Hz. Hence these are preferentially evoked when animals of the same sex interact and, as previously suggested, probably represent agonistic displays. Females typically produced only type-II chirps. We also investigated the effects of arginine vasotocin on chirping. This peptide is known to modulate communication and other types of behavior in many species, and we found that arginine vasotocin decreased the production of type-II chirps by males and also increased the production of type-I chirps in a subset of males. The chirping of most females was not significantly affected by arginine vasotocin.

scholarly journals A sodium-activated potassium channel supports high-frequency firing and reduces energetic costs during rapid modulations of action potential amplitude

2013 ◽  
Vol 109 (7) ◽  
pp. 1713-1723 ◽  
Author(s):  
Michael R. Markham ◽  
Leonard K. Kaczmarek ◽  
Harold H. Zakon
Keyword(s):  
Action Potential ◽  
High Frequency ◽  
Electric Fish ◽  
Electric Organ Discharge ◽  
Electric Organ ◽  
Weakly Electric Fish ◽  
Energetic Costs ◽  
Dynamic Regulation ◽  
Voltage Gated

We investigated the ionic mechanisms that allow dynamic regulation of action potential (AP) amplitude as a means of regulating energetic costs of AP signaling. Weakly electric fish generate an electric organ discharge (EOD) by summing the APs of their electric organ cells (electrocytes). Some electric fish increase AP amplitude during active periods or social interactions and decrease AP amplitude when inactive, regulated by melanocortin peptide hormones. This modulates signal amplitude and conserves energy. The gymnotiform Eigenmannia virescens generates EODs at frequencies that can exceed 500 Hz, which is energetically challenging. We examined how E. virescens meets that challenge. E. virescens electrocytes exhibit a voltage-gated Na+current ( INa) with extremely rapid recovery from inactivation (τrecov= 0.3 ms) allowing complete recovery of Na+current between APs even in fish with the highest EOD frequencies. Electrocytes also possess an inwardly rectifying K+current and a Na+-activated K+current ( IKNa), the latter not yet identified in any gymnotiform species. In vitro application of melanocortins increases electrocyte AP amplitude and the magnitudes of all three currents, but increased IKNais a function of enhanced Na+influx. Numerical simulations suggest that changing INamagnitude produces corresponding changes in AP amplitude and that KNachannels increase AP energy efficiency (10–30% less Na+influx/AP) over model cells with only voltage-gated K+channels. These findings suggest the possibility that E. virescens reduces the energetic demands of high-frequency APs through rapidly recovering Na+channels and the novel use of KNachannels to maximize AP amplitude at a given Na+conductance.

Sensory coding and corollary discharge effects in mormyrid electric fish

1989 ◽  
Vol 146 (1) ◽  
pp. 229-253 ◽  
Author(s):  
C. C. Bell
Keyword(s):  
Electric Fish ◽  
Spatial Information ◽  
Electric Organ Discharge ◽  
Low Frequency ◽  
Electric Organ ◽  
Motor Command ◽  
Corollary Discharge ◽  
Weakly Electric Fish ◽  
Central Projection ◽  
Sensory Coding

Weakly electric fish use their electrosensory systems for electrocommunication, active electrolocation and low-frequency passive electrolocation. In electric fish of the family Mormyridae, these three purposes are mediated by separate classes of electroreceptors: electrocommunication by Knollenorgan electroreceptors, active electrolocation by Mormyromast electroreceptors and low-frequency passive electrolocation by ampullary electroreceptors. The primary afferent fibres from each class of electroreceptors terminate in a separate central region. Thus, the mormyrid electrosensory system has three anatomically and functionally distinct subsystems. This review describes the sensory coding and initial processing in each of the three subsystems, with an emphasis on the Knollenorgan and Mormyromast subsystems. The Knollenorgan subsystem is specialized for the measurement of temporal information but appears to ignore both intensity and spatial information. In contrast, the Mormyromast subsystem is specialized for the measurement of both intensity and spatial information. The morphological and physiological characteristics of the primary afferents and their central projection regions are quite different for the two subsystems and reflect the type of information which the subsystems preserve. This review also describes the electric organ corollary discharge (EOCD) effects which are present in the central projection regions of each of the three electrosensory subsystems. These EOCD effects are driven by the motor command that drives the electric organ to discharge. The EOCD effects are different in each of the three subsystems and these differences reflect differences in both the pattern and significance of the sensory information that is evoked by the fish's own electric organ discharge. Some of the EOCD effects are invariant, whereas others are plastic and depend on previous afferent input. The mormyrid work is placed within two general contexts: (a) the measurement of time and intensity in sensory systems, and (b) the various roles of motor command (efferent) signals and self-induced sensory (reafferent) signals in sensorimotor systems.

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