scholarly journals Energetic constraints on electric signalling in wave-type weakly electric fishes

2011 ◽  
Vol 214 (24) ◽  
pp. 4141-4150 ◽  
Author(s):  
E. E. Reardon ◽  
A. Parisi ◽  
R. Krahe ◽  
L. J. Chapman
Keyword(s):  
Wave Type ◽  
Energetic Constraints ◽  
Electric Fishes ◽  
Weakly Electric

scholarly journals Convergent mosaic brain evolution is associated with the evolution of novel electrosensory systems in teleost fishes

2021 ◽  
Author(s):  
Erika L. Schumacher ◽  
Bruce A. Carlson
Keyword(s):  
Brain Region ◽  
Brain Size ◽  
Brain Evolution ◽  
Brain Regions ◽  
Torus Semicircularis ◽  
Micro Computed Tomography ◽  
Electrosensory System ◽  
Electric Fishes ◽  
Weakly Electric ◽  
Region Size

AbstractBrain region size generally scales allometrically with total brain size, but mosaic shifts in brain region size independent of brain size have been found in several lineages and may be related to the evolution of behavioral novelty. African weakly electric fishes (Mormyroidea) evolved a mosaically enlarged cerebellum and hindbrain, yet the relationship to their behaviorally novel electrosensory system remains unclear. We addressed this by studying South American weakly electric fishes (Gymnotiformes) and weakly electric catfishes (Synodontis spp.), which evolved varying aspects of electrosensory systems, independent of mormyroids. If the mormyroid mosaic increases are related to evolving an electrosensory system, we should find similar mosaic shifts in gymnotiforms and Synodontis. Using micro-computed tomography scans, we quantified brain region scaling for multiple electrogenic, electroreceptive, and non-electrosensing species. We found mosaic increases in cerebellum in all three electrogenic lineages relative to non-electric lineages and mosaic increases in torus semicircularis and hindbrain associated with the evolution of electrogenesis and electroreceptor type. These results show that evolving novel electrosensory systems is repeatedly and independently associated with changes in the sizes of individual brain regions independent of brain size, which suggests that selection can impact structural brain composition to favor specific regions involved in novel behaviors.

Coding of Stimuli by Ampullary Afferents in Gnathonemus petersii

2010 ◽  
Vol 104 (4) ◽  
pp. 1955-1968 ◽  
Author(s):  
J. Engelmann ◽  
S. Gertz ◽  
J. Goulet ◽  
A. Schuh ◽  
G. von der Emde
Keyword(s):  
Frequency Tuning ◽  
Low Frequency ◽  
Weakly Electric Fish ◽  
Behavioral Experiments ◽  
Low Frequencies ◽  
Similar Frequency ◽  
Linear Feature ◽  
Reconstruction Methods ◽  
Electric Fishes ◽  
Weakly Electric

Weakly electric fish use electroreception for both active and passive electrolocation and for electrocommunication. While both active and passive electrolocation systems are prominent in weakly electric Mormyriform fishes, knowledge of their passive electrolocation ability is still scarce. To better estimate the contribution of passive electric sensing to the orientation toward electric stimuli in weakly electric fishes, we investigated frequency tuning applying classical input-output characterization and stimulus reconstruction methods to reveal the encoding capabilities of ampullary receptor afferents. Ampullary receptor afferents were most sensitive (threshold: 40 μV/cm) at low frequencies (<10 Hz) and appear to be tuned to a mix of amplitude and slope of the input signals. The low-frequency tuning was corroborated by behavioral experiments, but behavioral thresholds were one order of magnitude higher. The integration of simultaneously recorded afferents of similar frequency-tuning resulted in strongly enhanced signal-to-noise ratios and increased mutual information rates but did not increase the range of frequencies detectable by the system. Theoretically the neuronal integration of input from receptors experiencing opposite polarities of a stimulus (left and right side of the fish) was shown to enhance encoding of such stimuli, including an increase of bandwidth. Covariance and coherence analysis showed that spiking of ampullary afferents is sufficiently explained by the spike-triggered average, i.e., receptors respond to a single linear feature of the stimulus. Our data support the notion of a division of labor of the active and passive electrosensory systems in weakly electric fishes based on frequency tuning. Future experiments will address the role of central convergence of ampullary input that we expect to lead to higher sensitivity and encoding power of the system.

scholarly journals Spooky interaction at a distance in cave and surface dwelling electric fishes

2019 ◽  
Author(s):  
Eric S. Fortune ◽  
Nicole Andanar ◽  
Manu Madhav ◽  
Ravi Jayakumar ◽  
Noah J. Cowan ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Amazon Basin ◽  
Electric Discharges ◽  
Social Signals ◽  
Natural Habitats ◽  
Surface Population ◽  
Show Evidence ◽  
Electric Fishes ◽  
Weakly Electric

ABSTRACTGlass knifefish (Eigenmannia) are a group of weakly electric fishes found throughout the Amazon basin. We made recordings of the electric fields of two populations of freely behaving Eigenmannia in their natural habitats: a troglobitic population of blind cavefish (Eigenmannia vicentespelaea) and a nearby epigean (surface) population (Eigenmannia trilineata). These recordings were made using a grid of electrodes to determine the movements of individual fish in relation to their electrosensory behaviors. The strengths of electric discharges in cavefish were larger than in surface fish, which may be a correlate of increased reliance on electrosensory perception and larger size. Both movement and social signals were found to affect the electrosensory signaling of individual Eigenmannia. Surface fish were recorded while feeding at night and did not show evidence of territoriality. In contrast, cavefish appeared to maintain territories. Surprisingly, we routinely found both surface and cavefish with sustained differences in electric field frequencies that were below 10 Hz despite being within close proximity of less than one meter. A half century of analysis of electrosocial interactions in laboratory tanks suggest that these small differences in electric field frequencies should have triggered the jamming avoidance response. Fish also showed significant interactions between their electric field frequencies and relative movements at large distances, over 1.5 meters, and at high differences in frequencies, often greater than 50 Hz. These interactions are likely envelope responses in which fish alter their EOD frequency in relation to changes in the depth of modulation of electrosocial signals.

scholarly journals Spatial and temporal distribution of Gymnorhamphichthys rondoni (Gymnotiformes: Rhamphichthyidae) in a long-term study of an Amazonian terra firme stream, Leticia - Colombia

2019 ◽  
Vol 17 (3) ◽  
Author(s):  
Carolina Escamilla-Pinilla ◽  
José Iván Mojica ◽  
Jorge Molina
Keyword(s):  
Site Fidelity ◽  
Nearest Neighbor ◽  
Electric Organ ◽  
Temporal Distribution ◽  
Terra Firme ◽  
Water Conductivity ◽  
Long Term Study ◽  
Electric Fishes ◽  
Electric Organ Discharges ◽  
Weakly Electric

ABSTRACT Weakly electric fishes continually emit electric organ discharges (EOD) as a means of communication and localization of objects in their surroundings. Depending on water conductivity, the amplitude of the electric field generated is known to increase with decreases in electrical conductivity of the water. In Amazonian terra firme streams, water conductivity is extremely low and fluctuates constantly due to local and regional rains. In this context, the space between freely moving weakly electric fishes may be expected to decrease, on average, with an increase in water conductivity. To test this hypothesis, we recorded the positions at rest of the sand-dwelling fish Gymnorhamphichthys rondoni in a terra firme stream for several days in alternating months, over two years. Based on daily nearest neighbor distances among individual fish in a grid, we found a uniform temporal distribution pattern (which was not affected by water conductivity) indicative of site fidelity. Here we highlight the role of other factors that could influence resting site fidelity.

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