scholarly journals Electroreception in the obligate freshwater stingray, Potamotrygon motoro

2015 ◽  
Vol 66 (11) ◽  
pp. 1027 ◽  
Author(s):  
Lindsay L. Harris ◽  
Christine N. Bedore ◽  
Stephen M. Kajiura
Keyword(s):  
Electric Fields ◽  
Sensory System ◽  
Voltage Gradient ◽  
Single Family ◽  
Potential Prey ◽  
Freshwater Environment ◽  
Electrosensory System ◽  
High Impedance ◽  
Morphological Adaptations ◽  
Elasmobranch Fishes

Elasmobranch fishes use electroreception to detect electric fields in the environment, particularly minute bioelectric fields of potential prey. A single family of obligate freshwater stingrays, Potamotrygonidae, endemic to the Amazon River, demonstrates morphological adaptations of their electrosensory system due to characteristics of a high impedance freshwater environment. Little work has investigated whether the reduced morphology translates to reduced sensitivity because of the electrical properties of freshwater, or because of a marine-tuned sensory system attempting to function in freshwater. The objective of the present study was to measure electric potential from prey of Potamotrygon motoro and replicate the measurements in a behavioural assay to quantify P. motoro electrosensitivity. Median orientation distance to prey-simulating electric fields was 2.73cm, and the median voltage gradient detected was 0.20mVcm–1. This sensitivity is greatly reduced compared with marine batoids. A euryhaline species with marine-type ampullary morphology was previously tested in freshwater and demonstrated reduced sensitivity compared with when it was tested in seawater (0.2μVcm–1 v. 0.6nVcm–1). When the data were adjusted with a modified ideal dipole equation, sensitivity was comparable to P. motoro. This suggests that the conductivity of the medium, more so than ampullary morphology, dictates the sensitivity of elasmobranch electroreception.

Electrosensory-driven feeding behaviours of the Port Jackson shark (Heterodontus portusjacksoni) and western shovelnose ray (Aptychotrema vincentiana)

2016 ◽  
Vol 67 (2) ◽  
pp. 187 ◽  
Author(s):  
R. M. Kempster ◽  
C. A. Egeberg ◽  
N. S. Hart ◽  
S. P. Collin
Keyword(s):  
Electric Fields ◽  
Interspecific Variation ◽  
Electrosensory System ◽  
Field Gradients ◽  
Highly Sensitive ◽  
Elasmobranch Species ◽  
Elasmobranch Fishes ◽  
Species Specific ◽  
Port Jackson ◽  
Abundance And Distribution

Elasmobranch fishes (sharks, skates and rays) possess a highly sensitive electrosensory system that enables them to detect weak electric fields, such as those produced by potential prey organisms. Despite several comparative anatomical studies, the functional significance of interspecific variation in electrosensory system morphology remains poorly understood. In the present study, we directly tested the electrosensitivity of two benthic elasmobranchs that share a similar habitat and feed on similarly sized prey items (Port Jackson sharks, Heterodontus portusjacksoni, and western shovelnose rays, Aptychotrema vincentiana), but differ significantly in their electrosensory system morphology. Aptychotrema vincentiana possesses almost five times the number of electrosensory pores of H. portusjacksoni (~1190 and ~239 respectively), yet both species are able to initiate feeding responses to electric-field gradients below 1 nV cm–1, similar to other elasmobranch species tested. However, A. vincentiana showed a greater ability to resolve the specific location of electrosensory stimuli, because H. portusjacksoni would more often overshoot the target and have to turn around to locate it. These results suggested that differences in abundance and distribution of electrosensory pores have little to no effect on the absolute electrical sensitivity in elasmobranchs, and instead, may reflect species-specific differences in the spatial resolution and directionality of electroreception.

Electric Fields Generated by Monotreme Prey Species.

1998 ◽  
Vol 20 (2) ◽  
pp. 171
Author(s):  
J.E. Gregory
Keyword(s):  
Electric Fields ◽  
Muscle Activity ◽  
Prey Species ◽  
Tap Water ◽  
Prey Detection ◽  
Potential Prey ◽  
Electrosensory System ◽  
Invertebrate Species ◽  
Close Range ◽  
Prey Items

The electric sense of the platypus may be used for the detection of prey, as may the similar but less elaborate electrosensory system in the echidna. However, for neither animal has this been shown directly. In this study, further support for the feasibility of an electrosensory role in prey detection was sought by determining whether potential prey items of either animal generate electric fields with appropriate characteristics. Prey items were placed in tap water and recordings made with a pair of electrodes placed near the specimen. Movement-related electric fields of a few to a few hundred µVcm-1 in amplitude were generated by a number of items including shrimps, fish, earthworms, mealworms and cockchafer larvae. Some recorded potentials were at a frequency consistent with an electromyogenic origin, while others were at a lower frequency and seemed more related to the movements of the animal itself than to the underlying muscle activity. No electric fields could be recorded from several other small invertebrate species tested. It is concluded that the platypus would be able to detect some prey items at close range by sensing the electric fields they generate, but this has not been demonstrated for the echidna.

ELECTROSENSORY BRAIN STEM NEURONS COMPUTE THE TIME DERIVATIVE OF ELECTRIC FIELDS IN THE PADDLEFISH

2004 ◽  
Vol 04 (01) ◽  
pp. L129-L138 ◽  
Author(s):  
MICHAEL H. HOFMANN ◽  
MARIANNE FALK ◽  
LON A. WILKENS
Keyword(s):  
Brain Stem ◽  
Electric Fields ◽  
Time Derivative ◽  
Sensory System ◽  
Rate Of Change ◽  
Electrosensory System ◽  
First Derivative ◽  
Medium Range ◽  
Electrophysiological Studies ◽  
New Interpretation

For many aquatic animals, the electrosense is an important sensory system used to detect prey or conspecifics at short to medium range and for long-range orientation. Passive electroreceptive animals sense the minute electric fields of animate and inanimate sources and it has been thought that they are most sensitive to sources that modulate the field around a few Hertz. Our data on the properties of the electrosensory system in the paddlefish reveal that the firing rate of electrosensory brain stem neurons represents the first derivative of the stimulus, i.e. the rate of change in intensity of an electric field. Furthermore, the responses to several non-periodic stimuli suggest that the electrosensory system monitors changes in field intensity caused by the relative movement between source and receiver and converts spatial field structure into its time derivative form. This new interpretation solves a number of contradictions between behavioural observations and electrophysiological studies on the electrosensory system of vertebrates.

Human keratinocytes migrate to the negative pole in direct current electric fields comparable to those measured in mammalian wounds

1996 ◽  
Vol 109 (1) ◽  
pp. 199-207 ◽  
Author(s):  
K.Y. Nishimura ◽  
R.R. Isseroff ◽  
R. Nuccitelli
Keyword(s):  
Electric Fields ◽  
Human Keratinocytes ◽  
Voltage Gradient ◽  
Primary Human Keratinocytes ◽  
Directed Movement ◽  
Average Cell ◽  
Negative Pole ◽  
Mammalian Skin ◽  
Dc Electric Fields

Previous measurements of the lateral electric fields near skin wounds in guinea pigs have detected DC fields between 100–200 mV/mm near the edge of the wound. We have studied the translocation response of motile primary human keratinocytes migrating on a collagen substrate while exposed to similar physiological DC electric fields. We find that keratinocytes migrate randomly on collagen in fields of 5 mV/mm or less, but in larger fields they migrate towards the negative pole of the field, exhibiting galvanotaxis. Since these cells have an average cell length of 50 microns, this implies that they are able to detect a voltage gradient as low as 0.5 mV along their length. This cath-odally-directed movement exhibits increased directedness with increasing field strengths between 10 and 100 mV/mm. We observe a maximally directed response at 100 mV/mm with half of the cells responding to the field within 14 minutes. The average speed of migration tended to be greater in fields above 50 mV/mm than in smaller fields. We conclude that human keratinocytes migrate towards the negative pole in DC electric fields that are of the same magnitude as measured in vivo near wounds in mammalian skin.

scholarly journals Detection and processing of electromagnetic and near–field acoustic signals in elasmobranch fishes

2000 ◽  
Vol 355 (1401) ◽  
pp. 1135-1141 ◽  
Author(s):  
Ad. J. Kalmijn
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Cell Membranes ◽  
Near Field ◽  
Feedback Mechanism ◽  
Earth’S Magnetic Field ◽  
Earth's Magnetic Field ◽  
Positive Feedback Mechanism ◽  
Elasmobranch Fishes ◽  
Physical Features

The acoustic near field of quietly moving underwater objects and the bio–electric field of aquatic animals exhibit great similarity, as both are predominantly governed by Laplace's equation. The acoustic and electrical sensory modalities thus may, in directing fishes to their prey, employ analogous processing algorithms, suggesting a common evolutionary design, founded on the salient physical features shared by the respective stimulus fields. Sharks and rays are capable of orientating to the earth's magnetic field and, hence, have a magnetic sense. The electromagnetic theory of orientation offers strong arguments for the animals using the electric fields induced by ocean currents and by their own motions in the earth's magnetic field. In the animal's frame of reference, in which the sense organs are at rest, the classical concept of motional electricity must be interpreted in relativistic terms. In the ampullae of Lorenzini, weak electric fields cause the ciliated apical receptor–cell membranes to produce graded, negative receptor currents opposite in direction to the fields applied. The observed currents form part of a positive–feedback mechanism, supporting the generation of receptor potentials much larger than the input signal. Acting across the basal cell membranes, the receptor potentials control the process of synaptic transmission.

Suppression of Ventilatory Reafference in the Elasmobranch Electrosensory System: Medullary Neuron Receptive Fields Support a Common Mode Ejection Mechanism

1992 ◽  
Vol 171 (1) ◽  
pp. 127-137 ◽  
Author(s):  
DAVID BODZNICK ◽  
JOHN C. MONTGOMERY
Keyword(s):  
Receptive Fields ◽  
Strong Support ◽  
Projection Neurons ◽  
Common Mode ◽  
Electrosensory System ◽  
Ejection Mechanism ◽  
Inhibitory Components ◽  
Field Organization ◽  
Elasmobranch Fishes ◽  
Receptive Field Organization

Elasmobranch fishes have an electroreceptive system which they use for prey detection and orientation. Sensory inputs in this system are corrupted by a form of reafference generated by the animal's own ventilation. However, we show here that in the carpet shark, Cephaloscylium isabella, as in two previously studied batoid species, this ventilatory ‘noise’ is reduced by sensory processing within the medullary nucleus of the electrosensory system. It has been proposed that the noise cancellation is achieved by a common mode rejection mechanism. One prediction of this hypothesis is that secondary neurons within the medullary nucleus should have both excitatory and inhibitory components to their receptive fields. This prediction is experimentally verified here. Projection neurons of the medullary nucleus in the carpet shark typically have a focal excitatory, and a diffuse inhibitory, receptive field organization including a component of contralateral inhibition. This result provides strong support for the hypothesis that ventilatory suppression in the elasmobranch electrosensory system is achieved by a common mode mechanism. Note: Department of Biology, Wesleyan University, Middletown, CT 06457, USA. Present address: Department of Zoology, University of Auckland, Auckland, New Zealand.

Palaeobiogeographic relationships and palaeoenvironmental implications of an earliest Oligocene Tethyan ichthyofauna from Egypt

2014 ◽  
Vol 51 (10) ◽  
pp. 909-918 ◽  
Author(s):  
Alison M. Murray ◽  
Thodoris Argyriou ◽  
Todd D. Cook
Keyword(s):  
Protected Area ◽  
Freshwater Fishes ◽  
Seasonal Influence ◽  
Freshwater Environment ◽  
Fresh Waters ◽  
Early Oligocene ◽  
Fossil Material ◽  
Complex Picture ◽  
Marine Influence ◽  
Elasmobranch Fishes

The Fayum Depression of Egypt has produced a great diversity of fossil material, including marine and freshwater fishes. In contrast to the Eocene formations of the Fayum, the Oligocene Jbel Qatrani Formation has been more or less consistently considered to be deposited in a freshwater environment; however, the ichthyofauna indicates a more complex picture. Cenozoic fishes have been convincingly used to interpret the palaeoenvironment in which sediments were deposited. Based on the elasmobranch and osteichthyan faunas of the Jbel Qatrani Formation, we interpret that this formation was not deposited entirely in fresh waters, but had some marine influence, particularly in the lower part of the formation. The mixture of freshwater elements, such as polypterids and alestids, with brackish and marine elements, including myliobatid stingrays, in the Quarry E site suggests a local palaeoenvironment that was very close to the shoreline, in a less protected area, or under more seasonal influence than the rest of the sites in the formation. Additionally, the early Oligocene elasmobranch fishes from Quarry E have a strong biogeographic relationship with sites in Oman and Pakistan, in the eastern Tethys, representing a restricted fauna possibly limited in distribution by cooling global temperatures.

scholarly journals Navigation by Induction-Based Magnetoreception in Elasmobranch Fishes

2009 ◽  
Vol 2009 ◽  
pp. 1-6 ◽  
Author(s):  
T. C. A. Molteno ◽  
W. L. Kennedy
Keyword(s):  
Frequency Domain ◽  
Geomagnetic Field ◽  
Domain Model ◽  
Relative Movement ◽  
Behavioral Experiments ◽  
Synchronous Detection ◽  
Electrosensory System ◽  
Elasmobranch Fishes

A quantitative frequency-domain model of induction-based magnetoreception is presented for elasmobranch fishes. We show that orientation with respect to the geomagnetic field can be determined by synchronous detection of electrosensory signals at harmonics of the vestibular frequency. The sensitivity required for this compass-sense mechanism is shown to be less than that known from behavioral experiments. Recent attached-magnet experiments have called into doubt the induction-based mechanism for magnetoreception. We show that the use of attached magnets would interfere with an induction-based mechanism unless relative movement between the electrosensory system and the attached magnet is less than 100 m. This suggests that further experiments may be required to eliminate induction as a basis for magnetoreception.

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