Evoked chirping in the weakly electric fish Apteronotus leptorhynchus: a quantitative biophysical analysis

1993 ◽  
Vol 71 (11) ◽  
pp. 2301-2310 ◽  
Author(s):  
Günther K. H. Zupanc ◽  
Leonard Maler
Keyword(s):  
Electric Organ Discharge ◽  
Electric Organ ◽  
Stimulus Onset ◽  
Weakly Electric Fish ◽  
Apteronotus Leptorhynchus ◽  
Biophysical Analysis ◽  
Absolute Amplitude ◽  
Electric Organ Discharges ◽  
Gymnotiform Fish ◽  
Weakly Electric

Apteronotus leptorhynchus, a gymnotiform fish, produces highly regular electric organ discharges of 600–1000 Hz. Short-term modulations of the electric organ discharge ("chirps") were elicited by imitating the discharges of neighboring fish. Chirps displayed an increase in frequency of approximately 100 Hz, a duration of about 15 ms, and an absolute amplitude of 0.5–2 mV. Since, similar to natural conditions, chirps summated with the beat caused by interference of the fish's own electric organ discharge and the imitating discharge, the size and shape of the chirp's amplitude envelope varied greatly according to its phase relative to the beat cycle; however, the frequency of the chirp amplitude modulation was always 50–100 Hz. All 21 males examined chirped, but their rate of chirping varied considerably (range 2–59 chirps/30 s; mean 22 chirps/30 s). In contrast, only one out of nine females chirped (mean 0.25 chirps/30 s). The latency between stimulus onset and first chirp was variable and often long (range 1.0–25.0 s; median 3.3 s). We propose that chirps are not a sensory reflex but a communicatory behavior regulated by hypothalamic peptidergic input.

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.

Echo response to chirping in the weakly electric brown ghost knifefish (Apteronotus leptorhynchus): role of frequency and amplitude modulations

2011 ◽  
Vol 89 (6) ◽  
pp. 498-508 ◽  
Author(s):  
José Antonio Gama Salgado ◽  
Günther K.H. Zupanc
Keyword(s):  
Electric Organ Discharge ◽  
Electric Organ ◽  
The Other ◽  
Electric Discharges ◽  
Apteronotus Leptorhynchus ◽  
Electric Organ Discharges ◽  
Frequency Modulations ◽  
Brown Ghost Knifefish ◽  
Weakly Electric

Teleost fish of the order Gymnotiformes are distinguished by their ability to produce electric discharges by means of specialized organs. These electric organ discharges serve various behavioral functions, including communication. During such electric interactions, male brown ghost knifefish ( Apteronotus leptorhynchus (Ellis in Eigenmann, 1912)) generate several types of transient frequency and amplitude modulations (“chirps”) of the otherwise nearly constant discharges. Previous studies have shown that the chirps generated by one individual follow those of the other with a preferred latency of approximately 500–1000 ms. As demonstrated in the present study, signals consisting of either frequency modulations or amplitude modulations are able to trigger this echo response. Signals composed of just amplitude modulations are effective in triggering an echo response only if the reduction in amplitude is large (approximately 40%, relative to baseline of the electric organ discharge of the emitting fish). By contrast, in frequency-modulated signals, a maximum frequency increase as small as 1.2% relative to baseline frequency is sufficient to trigger an echo response. This remarkable sensitivity might be an adaptation for the detection of so-called type-2 chirps, as chirps of this type are composed of rather small frequency increases and negligible amplitude modulations. In line with this hypothesis is the observation that during electric interactions of two fish, the generation of these chirps dominates the production of any of the other five chirp types known.

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 The weakly electric fish, Apteronotus albifrons, avoids hypoxia before it reaches critical levels

2020 ◽  
Author(s):  
Stefan Mucha ◽  
Lauren J. Chapman ◽  
Rüdiger Krahe
Keyword(s):  
Electric Fish ◽  
Electric Organ Discharge ◽  
Electric Organ ◽  
Swimming Activity ◽  
Weakly Electric Fish ◽  
Dissolved Oxygen Concentration ◽  
Freshwater Habitats ◽  
Electric Organ Discharges ◽  
Weakly Electric ◽  
Electric Organ Discharge Frequency

AbstractAnthropogenic environmental degradation has led to an increase in the frequency and prevalence of aquatic hypoxia (low dissolved-oxygen concentration, DO), which may affect habitat quality for water-breathing fishes. The weakly electric black ghost knifefish, Apteronotus albifrons, is typically found in well-oxygenated freshwater habitats in South America. Using a shuttle-box design, we exposed juvenile A. albifrons to a stepwise decline in DO from normoxia (>95% air saturation) to extreme hypoxia (10% air saturation) in one compartment and chronic normoxia in the other. Below 22% air saturation, A. albifrons actively avoided the hypoxic compartment. Hypoxia avoidance was correlated with upregulated swimming activity. Following avoidance, fish regularly ventured back briefly into deep hypoxia. Hypoxia did not affect the frequency of their electric organ discharges. Our results show that A. albifrons is able to sense hypoxia at non-lethal levels and uses active avoidance to mitigate its adverse effects.SummaryThe weakly electric knifefish, Apteronotus albifrons, avoids hypoxia below 22% air saturation. Avoidance correlates with increased swimming activity, but not with a change in electric organ discharge frequency.

scholarly journals The weakly electric fish, Apteronotus albifrons, actively avoids experimentally induced hypoxia

2021 ◽  
Author(s):  
Stefan Mucha ◽  
Lauren J. Chapman ◽  
Rüdiger Krahe
Keyword(s):  
Active Avoidance ◽  
Electric Fish ◽  
Electric Organ ◽  
The Other ◽  
Weakly Electric Fish ◽  
Dissolved Oxygen Concentration ◽  
Shuttle Box ◽  
Freshwater Habitats ◽  
Electric Organ Discharges ◽  
Weakly Electric

AbstractAnthropogenic environmental degradation has led to an increase in the frequency and prevalence of aquatic hypoxia (low dissolved oxygen concentration, DO), which may affect habitat quality for water-breathing fishes. The weakly electric black ghost knifefish, Apteronotus albifrons, is typically found in well-oxygenated freshwater habitats in South America. Using a shuttle-box design, we exposed juvenile A. albifrons to a stepwise decline in DO from normoxia (> 95% air saturation) to extreme hypoxia (10% air saturation) in one compartment and chronic normoxia in the other. On average, A. albifrons actively avoided the hypoxic compartment below 22% air saturation. Hypoxia avoidance was correlated with upregulated swimming activity. Following avoidance, fish regularly ventured back briefly into deep hypoxia. Hypoxia did not affect the frequency of their electric organ discharges. Our results show that A. albifrons is able to sense hypoxia at non-lethal levels and uses active avoidance to mitigate its adverse effects.

The electric image in weakly electric fish: perception of objects of complex impedance

2000 ◽  
Vol 203 (3) ◽  
pp. 481-492 ◽  
Author(s):  
R. Budelli ◽  
A.A. Caputi
Keyword(s):  
Linear Function ◽  
Electric Organ Discharge ◽  
Amplitude Ratio ◽  
Complex Impedance ◽  
Electric Organ ◽  
Weakly Electric Fish ◽  
Peak Amplitude ◽  
Electrical Characteristics ◽  
Electric Image ◽  
Weakly Electric

Weakly electric fish explore the environment using electrolocation. They produce an electric field that is detected by cutaneous electroreceptors; external objects distort the field, thus generating an electric image. The electric image of objects of complex impedance was investigated using a realistic model, which was able to reproduce previous experimental data. The transcutaneous voltage in the presence of an elementary object is modulated in amplitude and waveform on the skin. Amplitude modulation (measured as the relative change in the local peak-to-peak amplitude) consists of a ‘Mexican hat’ profile whose maximum relative slope depends on the distance of the fish from the object. Waveform modulation depends on both the distance and the electrical characteristics of the object. Changes in waveform are indicated by the amplitude ratio of the larger positive and negative phases of the local electric organ discharge on the skin. Using the peak-to-peak amplitude and the positive-to-negative amplitude ratio of this discharge, a perceptual space can be defined and correlated with the capacitance and resistance of the object. When the object is moved away, the perceptual space is reduced but keeps the same proportions (homothetically): for a given object, the positive-to-negative amplitude ratio is a linear function of the peak-to-peak amplitude. This linear function depends on the electrical characteristics of the object. However, there are ‘families’ of objects with different electrical characteristics that produce changes in the parameters of the local electric organ discharge that are related by the same linear function. We propose that these functions code the perceptual properties of an object related to its impedance.

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