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John D. Pettigrew - One of the best experts on this subject based on the ideXlab platform.
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Electroreception in monotremes.
The Journal of Experimental Biology, 1999Co-Authors: John D. PettigrewAbstract:I will briefly review the history of the bill sense of the platypus, a sophisticated combination of Electroreception and mechanoreception that coordinates information about aquatic prey provided from the bill skin mechanoreceptors and electroreceptors, and provide an evolutionary account of Electroreception in the three extant species of monotreme (and what can be inferred of their ancestors). Electroreception in monotremes is compared and contrasted with the extensive body of work on electric fish, and an account of the central processing of mechanoreceptive and electroreceptive input in the somatosensory neocortex of the platypus, where sophisticated calculations seem to enable a complete three-dimensional fix on prey, is given.
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Histological observations on presumed electroreceptors and mechanoreceptors in the beak skin of the long-beaked echidna, Zaglossus bruijnii .
Proceedings of the Royal Society of London. Series B: Biological Sciences, 1997Co-Authors: Paul R. Manger, Rita Collins, John D. PettigrewAbstract:Sensory receptors in the rostral portion of the beak skin of a single specimen of the rare long–beaked echidna, Zaglossus bruijnii , are described. Mucous glands which have been modified to accommodate sensory innervation, similar to those seen in Ornithorhynchus , are found in the rostral 2 cm of the beak skin, anterior to the maxillofacial foramen, at a density of approximately 12/mm 2 . The papillary epidermal portion of the gland ducts are walled by concentric layers of keratinocytes, and each duct is innervated by 10–15 myelinated nerve terminals. The mucous gland receptors in Zaglossus are intermediate in structure between those of Ornithorhynchus and Tachyglossus , but are similar enough to the former to suggest that Electroreception may play a major role in the sensory experience of Zaglossus . Push–rod mechanoreceptors also occur throughout the same region of beak skin, and appear similar to those described for Tachyglossus .
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Electroreception and the feeding behaviour of platypus ornithorhynchus anatinus monotremata mammalia
Philosophical Transactions of the Royal Society B, 1995Co-Authors: Paul R. Manger, John D. PettigrewAbstract:It has previously been shown that platypus are sensitive to small electrical fields. It was predicted that platypus use their electrosensitivity to locate the source of foodstuffs on the bottom of the freshwater river systems in which they live, because the platypus are nocturnal, and close their eyes, ears and nostrils while underwater. In this paper we demonstrate for the first time that platypus are indeed sensitive to electrical waveforms that imitate the electromyogenic potential’s of fleeing prey, and following stimulation show interest in area surrounding the electrodes. We also show that platypus respond with a reflex after stimulation with a square wave, and show that this reflex is directionally tuned to the origin of the electrical pulse, with a preferential sensitivity axis 40 times more sensitive than non-preferred axes. The strong directional sensitivity explains previous discrepancies in the lowest threshold for platypus Electroreception, which we find to be 50 μV cm -1 . Platypus are also sensitive to galvanic fields. We present the data in the light of standardized feeding strategies of the platypus, and discuss the integration of the findings into these feeding strategies. We surrounded our platypus enclosure with a Faraday cage, thereby eliminating excess electrical noise, a suggested new addition to the husbandry regime of platypus.
Ken W.s. Ashwell - One of the best experts on this subject based on the ideXlab platform.
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Development of the dorsal and ventral thalamus in platypus (Ornithorhynchus anatinus) and short-beaked echidna (Tachyglossus aculeatus)
Brain Structure and Function, 2012Co-Authors: Ken W.s. AshwellAbstract:The living monotremes (platypus and echidnas) are distinguished from therians as well as each other in part by the unusual structure of the thalamus in each. In particular, the platypus has an enlarged ventral posterior (VP) nucleus reflecting the great behavioural importance of trigeminosensation and Electroreception. The embryological collections of the Museum für Naturkunde in Berlin were used to analyse the development of the dorsal thalamus and ventral thalamus (prethalamus) in both species. Prosomeric organization of the forebrain emerged at 6 mm crown-rump length (CRL), but thalamic neurogenesis did not commence until about 8–9 mm CRL. Distinctive features of the dorsal thalamus in the two species began to emerge after hatching (about 14–15 mm CRL). During the first post-hatching week, dense clusters of granular cells aggregated to form the VP of the platypus, whereas the VP complex of the echidna remained smaller and divided into distinct medial and lateral divisions. At the end of the first post-hatching week, the thalamocortical tract was much larger in the platypus than the echidna. The dorsal thalamus of the platypus is essentially adult-like by the sixth week of post-hatching life. The similar appearance of the dorsal thalamus in the two species until the time of hatching, followed by the rapid expansion of the VP in the platypus, is most consistent with ancestral platypuses having undergone changes in the genetic control of thalamic neurogenesis to produce a large VP for trigeminal Electroreception after the divergence of the two lineages of monotreme.
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distinct development of peripheral trigeminal pathways in the platypus ornithorhynchus anatinus and short beaked echidna tachyglossus aculeatus
Brain Behavior and Evolution, 2012Co-Authors: Ken W.s. Ashwell, Craig D. Hardman, Peter GiereAbstract:The extant monotremes (platypus and echidnas) are believed to all be capable of Electroreception in the trigeminal pathways, although they differ significantly in the number and distribution of electroreceptors. It has been argued by some authors that Electroreception was first developed in an aquatic environment and that echidnas are descended from a platypus-like ancestor that invaded an available terrestrial habitat. If this were the case, one would expect the developmental trajectories of the trigeminal pathways to be similar in the early stages of platypus and short-beaked echidna development, with structural divergence occurring later. We examined the development of the peripheral trigeminal pathway from snout skin to trigeminal ganglion in sectioned material in the Hill and Hubrecht collections to test for similarities and differences between the two during the development from egg to adulthood. Each monotreme showed a characteristic and different pattern of distribution of developing epidermal sensory gland specializations (electroreceptor primordia) from the time of hatching. The cross-sectional areas of the trigeminal divisions and the volume of the trigeminal ganglion itself were also very different between the two species at embryonic ages, and remained consistently different throughout post-hatching development. Our findings indicate that the trigeminal pathways in the short-beaked echidna and the platypus follow very different developmental trajectories from the earliest ages. These findings are more consistent with the notion that the platypus and echidna have both diverged from an ancestor with rudimentary Electroreception and/or trigeminal specialization, rather than the contention that the echidna is derived from a platypus-like ancestor.
Paul R. Manger - One of the best experts on this subject based on the ideXlab platform.
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Histological observations on presumed electroreceptors and mechanoreceptors in the beak skin of the long-beaked echidna, Zaglossus bruijnii .
Proceedings of the Royal Society of London. Series B: Biological Sciences, 1997Co-Authors: Paul R. Manger, Rita Collins, John D. PettigrewAbstract:Sensory receptors in the rostral portion of the beak skin of a single specimen of the rare long–beaked echidna, Zaglossus bruijnii , are described. Mucous glands which have been modified to accommodate sensory innervation, similar to those seen in Ornithorhynchus , are found in the rostral 2 cm of the beak skin, anterior to the maxillofacial foramen, at a density of approximately 12/mm 2 . The papillary epidermal portion of the gland ducts are walled by concentric layers of keratinocytes, and each duct is innervated by 10–15 myelinated nerve terminals. The mucous gland receptors in Zaglossus are intermediate in structure between those of Ornithorhynchus and Tachyglossus , but are similar enough to the former to suggest that Electroreception may play a major role in the sensory experience of Zaglossus . Push–rod mechanoreceptors also occur throughout the same region of beak skin, and appear similar to those described for Tachyglossus .
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Electroreception and the feeding behaviour of platypus ornithorhynchus anatinus monotremata mammalia
Philosophical Transactions of the Royal Society B, 1995Co-Authors: Paul R. Manger, John D. PettigrewAbstract:It has previously been shown that platypus are sensitive to small electrical fields. It was predicted that platypus use their electrosensitivity to locate the source of foodstuffs on the bottom of the freshwater river systems in which they live, because the platypus are nocturnal, and close their eyes, ears and nostrils while underwater. In this paper we demonstrate for the first time that platypus are indeed sensitive to electrical waveforms that imitate the electromyogenic potential’s of fleeing prey, and following stimulation show interest in area surrounding the electrodes. We also show that platypus respond with a reflex after stimulation with a square wave, and show that this reflex is directionally tuned to the origin of the electrical pulse, with a preferential sensitivity axis 40 times more sensitive than non-preferred axes. The strong directional sensitivity explains previous discrepancies in the lowest threshold for platypus Electroreception, which we find to be 50 μV cm -1 . Platypus are also sensitive to galvanic fields. We present the data in the light of standardized feeding strategies of the platypus, and discuss the integration of the findings into these feeding strategies. We surrounded our platypus enclosure with a Faraday cage, thereby eliminating excess electrical noise, a suggested new addition to the husbandry regime of platypus.
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platypus Electroreception neuroethology of a novel mammalian sensory system
1994Co-Authors: Paul R. MangerAbstract:For less than a decade it has been known that the platypus is the onlynmammal to truly use Electroreception. The platypus uses itsnelectroreceptive capabilities to locate prey. The studies presented in thisnthesis demonstrate the complexity and integral nature of the three stagesnnecessary for electrolocation. The anatomical basis and neurological basisnof Electroreception in the platypus were studied to elucidate behaviouralnreactions of platypus to electrical stimuli.Behaviourally it has been found that platypus will qattackq annelectrode that is emitting electrical stimuli that imitate the electromyogenicncontractions of fleeing prey items. However, a more interestingnbehavioural result was obtained when a brief (10 ms) square wavenstimulus was presented to the platypus. It was noted that for every squarenwave stimulus, a corresponding rapid saccade of the head of the platypusntowards the stimulus occurred. This saccade had a latency of around 43nms. The platypus would elicit this saccade up to an average of 12 timesnper second, if stimulated at this rate. This short latency and high temporalnfidelity indicate that this saccadic response is a reflex. This saccadicnresponse is also highly directional. If the platypus is stimulated fromnabove, the saccade will occur in an upwards direction. If stimulated fromnbelow, the saccade will occur in a downwards direction, and so on for allndirections. However, it was found that the saccade has a preferentialnsensitivity axis at a direction 80o from the rostral pole of the bill and 20ondown. Therefore, the platypus has two symmetrical electrosensitivitynlobes it uses to scan the bottom of its watery habitat to search for food.nWhen an electrical stimulus is detected, the platypus will rapidly move itsnhead towards this stimulus, in order to touch the fleeing prey with its bill,nand finally to capture the prey.|Anatomical and physiological studies have determined thenprocessing that occurs to mediate this rapid and accurate directionalnresponse. The ultrastructure, as well as the distribution, of thenelectroreceptors and other sensory structures in the bill of the platypus werenstudied. It was found that Electroreception is mediated by a cuff of barennerve terminals located around the papillary portion of the duct of anmucous gland. This contrasts with electroreceptive fish in which a sensoryncell interposes between the environment and the nerve terminals. Anspecialised mechanosensory receptor complex was also found in the billnskin. This consisted of an epidermal qpush-rodq that was seen to beninvested by two vesicle-like chains of nerve terminals. At the basal portionnof the rod a group of around 12 Merkel cells were seen, and in the dermisnbeneath the rod a group of 3 - 6 Paciniform corpuscles were located. Thisnpush-rod mechanoreceptor is analogous in structure with Eimer organsnfound in the skin of the snout of the European mole. A third sensorynstructure, a modified serous gland was also seen in the bill skin of thenplatypus. The papillary portion of the duct of these serous glands wasnmodified to accommodate nerve terminals very similar in structure to thosenfound for the mucous gland electroreceptors. Although no function hasnbeen assigned to this sensory serous gland, anatomical similarities providena basis for presuming an electroreceptive function.The distributions of these three sensory structures across the billnprovide interesting findings in light of the behavioural responses elicited bynelectrical stimulation. The push-rod mechanoreceptors are found acrossnthe entire extent of the bill, however, they are found in increased densitynaround the labial margins of the bill. This distribution is very commonnsense in that the edge of the bill will be the first region to come into contactnwith any tactile stimulation, therefore the edge of the bill requires thenhighest degree of tactile discrimination. Interestingly, the sensory serousngland has a similar distribution to that of the push-rods, and with evidencenof DC sensibility exhibited behaviourally by the platypus, leads to the ideanthat the interplay of these two receptors may be used when localising non-mobile prey items. This may be achieved by using the high tactilendiscrimination, plus the detection of metabolic electrical fields created bynthese non-mobile prey items. However, of most interest is the distributionnof the mucous gland electroreceptors. These electroreceptors are found tonbe distributed in a series of parasagittal stripes along the bill. Thisndistribution of electroreceptors imitates the parallel segments of andirectional antenna. These stripes of electroreceptors are also orthogonal tonthe preferential sensitivity axis found for the behaving platypus. Thus, thenanatomical distribution provides a basis for the changes in directionalnsensitivity to square waves seen in the behaving platypus.n n n
Stephen M Kajiura - One of the best experts on this subject based on the ideXlab platform.
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Electroreception in marine fishes chondrichthyans
Journal of Fish Biology, 2019Co-Authors: Kyle C Newton, Andrew B Gill, Stephen M KajiuraAbstract:Electroreception in marine fishes occurs across a variety of taxa and is best understood in the chondrichthyans (sharks, skates, rays, and chimaeras). Here, we present an up-to-date review of what is known about the biology of passive Electroreception and we consider how electroreceptive fishes might respond to electric and magnetic stimuli in a changing marine environment. We briefly describe the history and discovery of Electroreception in marine Chondrichthyes, the current understanding of the passive mode, the morphological adaptations of receptors across phylogeny and habitat, the physiological function of the peripheral and central nervous system components, and the behaviours mediated by Electroreception. Additionally, whole genome sequencing, genetic screening and molecular studies promise to yield new insights into the evolution, distribution, and function of electroreceptors across different environments. This review complements that of Electroreception in freshwater fishes in this special issue, which provides a comprehensive state of knowledge regarding the evolution of Electroreception. We conclude that despite our improved understanding of passive Electroreception, several outstanding gaps remain which limits our full comprehension of this sensory modality. Of particular concern is how electroreceptive fishes will respond and adapt to a marine environment that is being increasingly altered by anthropogenic electric and magnetic fields.
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Electroreception in the obligate freshwater stingray potamotrygon motoro
Marine and Freshwater Research, 2015Co-Authors: Lindsay L Harris, Christine N Bedore, Stephen M KajiuraAbstract: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 motoroandreplicatethemeasurementsinabehaviouralassaytoquantifyP.motoroelectrosensitivity.Medianorientation distance toprey-simulating electricfieldswas2.73 cm,andthe medianvoltagegradient detected was0.20mVcm � 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 (0.2 m Vc m � 1 v. 0.6 nV cm � 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.
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Electroreception in the euryhaline stingray dasyatis sabina
The Journal of Experimental Biology, 2009Co-Authors: David W Mcgowan, Stephen M KajiuraAbstract:SUMMARY This study quantified the electrosensitivity of a euryhaline elasmobranch, the Atlantic stingray ( Dasyatis sabina ) across a range of salinities. Specimens from a permanent freshwater (FW) population in the St Johns River system, FL, USA, were compared with stingrays from the tidally dynamic Indian River Lagoon in east Florida, USA. Behavioral responses of stingrays to prey-simulating electric stimuli were quantified in FW (0 p.p.t., ρ=2026Ω cm), brackish (15 p.p.t., ρ=41 Ω cm) and full strength seawater (35 p.p.t., ρ=19 Ω cm). This study demonstrated that the electrosensitivity of D. sabina is significantly reduced in FW. In order to elicit a feeding response, stingrays tested in FW required an electric field 200–300× greater than stingrays tested in brackish and saltwater (median FW treatments=1.4 μV cm –1 , median brackish–saltwater treatments=6 nV cm –1 ), and the maximum orientation distance was reduced by 35.2%, from 44.0 cm in the brackish and saltwater treatments to 28.5 cm in FW. The St Johns River stingrays did not demonstrate an enhanced electrosensitivity in FW, nor did they exhibit reduced sensitivity when introduced to higher salinities. Stingrays from both populations responded similarly to the prey-simulating stimulus when tested at similar salinities, regardless of their native environment. The reduction in electrosensitivity and detection range in FW is attributed to both an environmental factor (electrical resistivity of the water) and the physiological function of the ampullary canals. The plasticity of this sensory system to function across such a wide environmental range demonstrates its adaptive significance.
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Electroreception in neonatal bonnethead sharks sphyrna tiburo
Marine Biology, 2003Co-Authors: Stephen M KajiuraAbstract:The ability of sharks to orient to weak electric fields is well documented, but a detailed analysis of orientation pathways is lacking. Digital video analysis was used to quantify the behavioral response of naive neonatal bonnethead sharks, Sphyrna tiburo, to prey-simulating weak electric fields. Sharks less than 24 h post-parturition failed to demonstrate a positive feeding response to the electrodes whereas vigorous biting at the electrodes was observed in all sharks greater than 32 h post-parturition. Orientation behaviors were classified as one of five types: "straight" approach, "single turn," "overshoot," "spiral tracking," and "orient without biting." One-third of all orientations were elicited at stimulus intensities of less than 20 nV cm−1. The median electric stimulus threshold for initiation of orientation was 47 nV cm−1 and the minimum was less than 1 nV cm−1. Most orientations to the dipole were from a distance of less than 10 cm with a maximum orientation distance of 22 cm. The innate feeding response to electric stimuli is demonstrated for the first time in a chondrichthyan fish.
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Electroreception in juvenile scalloped hammerhead and sandbar sharks
The Journal of Experimental Biology, 2002Co-Authors: Stephen M Kajiura, Kim N HollandAbstract:The unique head morphology of sphyrnid sharks might have evolved to enhance electrosensory capabilities. The ‘enhanced Electroreception’ hypothesis was tested by comparing the behavioral responses of similarly sized carcharhinid and sphyrnid sharks to prey-simulating electric stimuli. Juvenile scalloped hammerhead sharks Sphyrna lewini and sandbar sharks Carcharhinus plumbeus oriented to dipole electric fields from the same maximum distance (approximately 30 cm) and thus demonstrated comparable behavioral-response thresholds (<1 nV cm ‐1 ). Despite the similarity of response threshold, the orientation pathways and behaviors differed for the two species. Scalloped hammerheads typically demonstrated a pivot orientation in which the edge of the cephalofoil closest to the dipole remained stationary while the shark bent its trunk to orient to the center of the dipole. By contrast, sandbars swam in a broader arc towards the center of the dipole. The different orientation patterns are attributed to the hydrodynamic properties of the cephalofoil, which enables the hammerheads to execute sharp turns at high speed. The greater trunk width of the sandbar sharks prevented them from demonstrating the same degree of flexibility. Therefore, although the sphyrnid head morphology does not appear to confer a greater sensitivity to prey-simulating dipole electric fields, it does provide (1) a greater lateral search area, which may increase the probability of prey encounter, and (2) enhanced maneuverability, which may aid in prey capture. Movies available on-line
Peter Giere - One of the best experts on this subject based on the ideXlab platform.
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distinct development of peripheral trigeminal pathways in the platypus ornithorhynchus anatinus and short beaked echidna tachyglossus aculeatus
Brain Behavior and Evolution, 2012Co-Authors: Ken W.s. Ashwell, Craig D. Hardman, Peter GiereAbstract:The extant monotremes (platypus and echidnas) are believed to all be capable of Electroreception in the trigeminal pathways, although they differ significantly in the number and distribution of electroreceptors. It has been argued by some authors that Electroreception was first developed in an aquatic environment and that echidnas are descended from a platypus-like ancestor that invaded an available terrestrial habitat. If this were the case, one would expect the developmental trajectories of the trigeminal pathways to be similar in the early stages of platypus and short-beaked echidna development, with structural divergence occurring later. We examined the development of the peripheral trigeminal pathway from snout skin to trigeminal ganglion in sectioned material in the Hill and Hubrecht collections to test for similarities and differences between the two during the development from egg to adulthood. Each monotreme showed a characteristic and different pattern of distribution of developing epidermal sensory gland specializations (electroreceptor primordia) from the time of hatching. The cross-sectional areas of the trigeminal divisions and the volume of the trigeminal ganglion itself were also very different between the two species at embryonic ages, and remained consistently different throughout post-hatching development. Our findings indicate that the trigeminal pathways in the short-beaked echidna and the platypus follow very different developmental trajectories from the earliest ages. These findings are more consistent with the notion that the platypus and echidna have both diverged from an ancestor with rudimentary Electroreception and/or trigeminal specialization, rather than the contention that the echidna is derived from a platypus-like ancestor.