Active electrolocation of objects in weakly electric fish

1999 ◽  
Vol 202 (10) ◽  
pp. 1205-1215 ◽  
Author(s):  
G. von der Emde
Keyword(s):  
Electric Fish ◽  
Electric Organ ◽  
Weakly Electric Fish ◽  
Entire Body ◽  
Body Parts ◽  
Surrounding Water ◽  
Two Parameters ◽  
Electric Organ Discharges ◽  
Electric Signals ◽  
Weakly Electric

Weakly electric fish produce electric signals (electric organ discharges, EODs) with a specialised electric organ creating an electric field around their body. Objects within this field alter the EOD-induced current at epidermal electroreceptor organs, which are distributed over almost the entire body surface. The detection, localisation and analysis of objects performed by monitoring self-produced electric signals is called active electrolocation. Electric fish employ active electrolocation to detect objects that are less than 12 cm away and have electric properties that are different from those of the surrounding water. Within this range, the mormyrid Gnathonemus petersii can also perceive the distance of objects. Depth perception is independent of object parameters such as size, shape and material. The mechanism for distance determination through electrolocation involves calculating the ratio between two parameters of the electric image that the object projects onto the fish's skin. Electric fish can not only locate objects but can also analyse their electrical properties. Fish are informed about object impedance by measuring local amplitude changes at their receptor organs evoked by an object. In addition, all electric fish studied so far can independently determine the capacitative and resistive components of objects that possess complex impedances. This ability allows the fish to discriminate between living and non-living matter, because capacitance is a property of living organisms. African mormyrids and South American gymnotiforms use different mechanisms for capacitance detection. Mormyrids detect capacitance-evoked EOD waveform distortions, whereas gymnotiforms perform time measurements. Gymnotiforms measure the temporal phase shift of their EODs induced at body parts close to the object relative to unaffected body parts further away.

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.

scholarly journals Count and spark? The echo response of the weakly electric fish Gnathonemus petersii to series of pulses

2001 ◽  
Vol 204 (8) ◽  
pp. 1401-1412
Author(s):  
S. Schuster
Keyword(s):  
Electric Fish ◽  
Electric Organ ◽  
Weakly Electric Fish ◽  
Simple Strategy ◽  
Mormyrid Fish ◽  
Pulse Type ◽  
After Effect ◽  
Electric Organ Discharges ◽  
Weakly Electric ◽  
Gnathonemus Petersii

Weakly electric fish of the pulse type electrolocate objects in the dark by emitting discrete electric organ discharges (EODs) separated by intervals of silence. Two neighbouring pulse-type fish often reduce the risk of discharging simultaneously by means of an ‘echo response’: one fish will respond to a neighbour's EOD with a discharge of its own following at a fixed short latency so that its EOD will occur long before the next EOD of its neighbour. Although working elegantly for two partners, this simple strategy should fail in larger groups because two fish could discharge in response to the same EOD of a third fish. Here, I show that the mormyrid fish Gnathonemus petersii could use a simple mechanism to reduce this problem. Individuals were stimulated with two closely spaced pulses, the second following so as to coincide with an echo given in response to the first. All the fish examined were able to respond more to the second pulse so that most of their echoes did not collide with the second pulse. An analysis was made of how echoing more to the second pulse depends on (i) the delay at which the stimulus followed the last spontaneous EOD, (ii) the spontaneous firing rate, (iii) the intensity of the stimulus, (iv) the number of stimulus pulses, (v) the interval between stimulus pulses, and (vi) the level of previous stimulation with double pulses. The results suggest that echoing more in response to the second pulse is probably because the first pulse causes an after-effect whose inferred properties would be compatible with the properties of the mormyromast afferences thought to be involved in the echo response.

scholarly journals Evidence for mutual allocation of social attention through interactive signaling in a mormyrid weakly electric fish

2018 ◽  
Vol 115 (26) ◽  
pp. 6852-6857 ◽  
Author(s):  
Martin Worm ◽  
Tim Landgraf ◽  
Julia Prume ◽  
Hai Nguyen ◽  
Frank Kirschbaum ◽  
...  
Keyword(s):  
Cognitive Abilities ◽  
Electric Fish ◽  
Electric Organ ◽  
Social Attention ◽  
Weakly Electric Fish ◽  
Vertebrate Lineage ◽  
Discharge Patterns ◽  
Species Specific ◽  
Electric Organ Discharges ◽  
Weakly Electric

Mormyrid weakly electric fish produce electric organ discharges (EODs) for active electrolocation and electrocommunication. These pulses are emitted with variable interdischarge intervals (IDIs) resulting in temporal discharge patterns and interactive signaling episodes with nearby conspecifics. However, unequivocal assignment of interactive signaling to a specific behavioral context has proven to be challenging. Using an ethorobotical approach, we confronted single individuals of weakly electricMormyrus rume proboscirostriswith a mobile fish robot capable of interacting both physically, on arbitrary trajectories, as well as electrically, by generating echo responses through playback of species-specific EODs, thus synchronizing signals with the fish. Interactive signaling by the fish was more pronounced in response to a dynamic echo playback generated by the robot than in response to playback of static random IDI sequences. Such synchronizations were particularly strong at a distance corresponding to the outer limit of active electrolocation, and when fish oriented toward the fish replica. We therefore argue that interactive signaling through echoing of a conspecific’s EODs provides a simple mechanism by which weakly electric fish can specifically address nearby individuals during electrocommunication. Echoing may thus enable mormyrids to mutually allocate social attention and constitute a foundation for complex social behavior and relatively advanced cognitive abilities in a basal vertebrate lineage.

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.

Sign in / Sign up

Export Citation Format

Share Document