Electric Catfish Research Articles

Immunocytochemical characterization of the synaptic innervation of a single spinal neuron, the electric catfish electromotoneuron

The electric catfish, Malapterurus electricus, possesses electric organs that are innervated by a pair of identifiable electromotoneurons located within the cervical spinal cord. The pattern of synaptic innervation of the electromotoneurons can be revealed by an antibody against the synaptic vesicle protein SV2. Both somata and proximal dendrites are densely innervated. Several transmitters contribute to this innervation. Glutamate, the neurotransmitter of the dorsal root sensory fibers, reveals a weak punctuate immunoreactivity. The previously described electrical synapses of the electromotoneurons were visualized by an antibody against a gap-junctional protein. In contrast to the electromotoneurons of other electric fish, the electric catfish electromotoneurons possess many inhibitory synapses. With antibodies against glycine and against the glycine receptor, a dense immunoreactivity of the surface of the somata and proximal dendrites can be revealed. The glycine receptor-like immunoreactivity exhibits a patch-like distribution similar to that revealed by the anti-SV2 antibody. gamma-Aminobutyric acid (GABA)-immunopositive terminals contribute to the inhibitory electromotoneuron innervations to a lesser degree. The chemical characteristics of the electromotoneuron innervations of Malapterurus resemble those of other spinal motoneurons rather than spinal electromotoneurons of other electric fish. Thus our immunocytochemical study supports the view that the pattern of electromotoneuron innervations in Malapterurus reveals little specialization. The capacity for information processing required for the control of the electric organ discharge appears to be achieved by the increased integrational capacity of the newly evolved multiple dendrites and not by an additional parallel channel specific for the electromotor system.

Temperature Changes Associated with Excitation of the Electric Organ in the African Electric Catfish

By using heat-sensors made from synthetic pyroelectric film, it was shown that excitation of the Malapterurus electric organ brings about first a rapid rise, then a slow fall and finally a very slow rise in the temperature of the organ. Difficulties encountered in determining these rapid temperature changes by the method of employing thermistor probes are pointed out.

Projection of Brain Stem Neurons to the Giant Electromotoneurons in the Cervical Spinal Cord of the Electric Catfish <i>Malapterurus electricus</i>

Two giant electromotoneurons located within the cervical spinal cord form the centerpiece of the electromotor system in the electric catfish Malapterurus electricus. The cytoarchitectural organization suggests a high degree of input convergence onto the electromotoneurons. In order to obtain insights into the connectivities of the electromotor system, pre-neurons of the electromotoneurons within the brain stem and the spinal cord were labelled by application of FITC-dextran and horseradish peroxidase onto the surface of a single electromotoneuron. Our results show that the electromotoneurons receive their main inputs from the nucleus profundus mesencephali within the tegmentum and from large neurons of the medial reticular formation. Both nuclei possess an intimate connection to the optic tectum which mediates orientation responses. This pathway to the electromotoneurons could be instrumental in eliciting electric organ discharge during prey catching. The electric avoidance response in turn could be mediated by the Mauthner neurons which are also labelled. In addition to these neurons, cells of the nucleus fasciculi longitudinalis medialis, the descending octaval nucleus and the nucleus funicularis medialis were labelled. As compared to the corresponding neurons in ictalurid catfish, none of these neurons displays any alteration in its general morphology. It is concluded that the evolution of the electric organ from muscle tissue and the development of a central control system of the electromotor response in Malapterurus involved a minimum of alterations in central nervous system circuitry. In contrast to many other electric fishes the electromotor control is mainly accomplished at the level of the electromotoneurons.

Cytoplasmic segregation and cytoskeletal organization in the electric catfish giant electromotoneuron with special reference to the axon hillock region

The cytoplasm of the highly polarized nerve cell is permanently segregated into domains with differing organellar composition. The mechanisms maintaining this segregation are largely unknown. In order to elucidate the potential role of cytoskeletal elements in this process we compared the cytoplasmic segregation within the giant electromotoneuron of the electric catfish ( Malapterurus electricus) with the distribution of binding sites for antibodies against elements of the cytoskeleton. Most prominent cytoplasmic segregations include the formation of a subplasmalemmal cortical structure free of Nissl bodies and Golgi cisternae, the separation within the soma of domains containing rough endoplasmic reticulum and filament-rich domains, and the soma-axon transition. The cytoplasmic transition at the axon hillock forms a distinct borderline where Nissl bodies, Golgi cisternae and the bulk of lysosomes abruptly terminate and are excluded from the axoplasm. Synaptic vesicles and mitochondria are free to pass compartmental borders. Tropomyosin, spectrin, and α-actinin reveal a rather homogeneous immunofluorescence throughout the neuron. In contrast, neurofilament protein and tubulin display a distinctly increased immunofluorescence in the subplasmalemmal cortical layer, in dendrites as well as in the axon. The increase in immunofluorescence at the axon hillock exactly depicts the small transition zone from the somatic cytoplasm rich in Nissl bodies, Golgi cisternae and lysosomes to the differently structured axoplasm. The picture is similar for β-tubulin, tyrosinylated and detyrosinylated α-tubulin. Detyrosinylated tubulin (glu-tubulin, which is contained in microtubules of increased stability) shows the most prominent enrichment in the axon. The distribution of myosin is comparable to that of neurofilament protein but there is less difference in immunofluorescence between the domains. Our results would be compatible with a role of microtubules together with (the closely associated) neurofilaments in the segregation of neuronal cytoplasmic domains. Active transport as well as stable binding to the somatic cytoskeleton might counteract a homogeneous cytoplasmic distribution of the various classes of organeiles by diffusion.

Cytoarchitectural organization of the electromotor system in the electric catfish (Malapterurus electricus)

The cytoarchitectural organization of the electromotor system of the electric catfish (Malapterurus electricus) was investigated in order to obtain insight into the neuronal reorganization accompanying the functional transition of a presumptive previous motor system to an electromotor system eliciting electric organ discharge. The electric catfish possesses two giant electromotoneurons situated within the rostral spinal cord. Intracellular dye injections have revealed the enormous extension of the dendritic tree of electromotoneurons. About 50 primary dendrites span the entire lateral funicle and intermediate grey matter, and reveal an extensive contralateral projection. The giant dendritic tree (1.2 mm in rostrocaudal direction) presumably receives inputs from all ascending and descending pathways of the spinal cord. Electromotoneurons and motoneurons receive the same type of fibre inputs, and electromotoneurons and interneurons are connected through common presynaptic elements. The innervation pattern of the electromotoneurons and spinal motoneurons is similar. Synaptic terminals with round synaptic vesicles often reveal chemical contacts and gap junctions. Furthermore, dendrites of the two electromotoneurons form juxtapositions (ephapses) with each other and also with spinal interneurons. Our results suggest that the two electromotoneurons are homologous to median (primary) spinal motoneurons and are the central structures of the electromotor system within the central nervous system of the electric catfish. A high capability of information processing can be attributed to the giant dendritic trees from functional considerations. This presumably enables the electromotoneurons to elicit an electric organ discharge in different behavioural contexts with a minimum of functional reorganization.

Temporal patterning of electric organ discharges in the African electric catfish, Malapterurus electricus (Gmelin)

This paper is the first detailed analysis of situation-specific temporal patterning of electric organ discharges (EODs) in a strong electric fish. Using a resident-intruder paradigm EODs were recorded during interactions between dyads composed of Malapterurus electricus (Gmelin) and four different types of fish: (1) conspecifics; (2) large prey-type mid-water fish, goldfish (Carassius auratus, Linnaeus 1758) and tilapia (Oreochromis melanotheron, Ruppel, 1852); (3) a sympatric competitor, Polypterus palmas (Ayres 1850) and (4) a larger, threatening catfish, Clarias sp. An analysis of the EODs emitted showed that in the presence of conspecifics the average EOD volley consisted of a single long-duration, low frequency train of EODs. The presence of the midwater fish (goldfish and Tilapia) elicited volleys consisting of two short trains, and P. palmas elicited long duration volleys with two trains and long inter-train intervals. Finally, an attacking Clarias resulted on average in volleys consisting of two high-frequency trains of EODs. With nonconspecific partner species resident electric catfish emitted volleys with more pulses, more trains that were longer in duration and higher in frequency than the EODs in volleys emitted by intruder electric catfish with the same species stimulus fish.

Axonal transport studied in a single vertebrate neuron: the giant electromotor neuron of the electric catfish, Malapterurus electricus.

Axonal transport was studied using a single vertebrate neuron, the giant electromotor neuron of the electric catfish, Malapterurus electricus. The electric organs of this strongly electric fish are innervated by two neurons whose axons form one electric nerve each. After injection of [35S]methionine into the spinal cord at the level of the two perikarya radioactively labelled material is exported by fast flow as a small wave with a velocity of 5.8 mm/h and a somal release time of 91 min (29 degrees C). Slow flow investigated between 15 and 39 days had a velocity of 1.36 mm/d at 29 degrees C. Analysis of radiolabelled proteins by polyacrylamide gel electrophoresis revealed different patterns of labelling between slow and fast flow. The relative molecular mass of the two major proteins labelled on slow flow correspond to actin and tubulin. Labelled proteins of higher relative molecular mass may correspond to neurofilament proteins. Our results suggest that this vertebrate single-neuron and single-axon system can be used successfully for axonal transport studies.

The electromotor system of the electric catfish (Malapterurus electricus): a fine-structural analysis.

The electromotor system of the electric catfish (Malapterurus electricus) consists of two large ganglion cells situated in the spinal cord, two single axons containing electric nerves and two large electric organs with several million electroplaque cells. The small, irregularly stacked electroplaque cells possess at their center a crater-like indentation from which a stalk like protrusion arises. Many synaptic contacts derived from a single axon collateral are carried on lobe-like protrusions at the terminal knob of this stalk. The electric nerve consists of a large myelinated axon (diameter: 25 micron) surrounded by many layers of connective tissue cells. The two ganglion cells (200 micron in diameter) are rich in elements of the rough endoplasmic reticulum, Golgi apparatus and lysosomal structures. The cytoplasm of the soma changes its appearance towards the voluminous axon hillock (50 micron in diameter) which these organelles do not enter. The cell soma is perforated in a tunnel-like manner by blood capillaries, axons and processes of glial cells. The cell soma and dendrites are covered with two types of synapse. One type forms mixed chemical and electrical (gap junctions) contacts with intermediate attachment plaques. The other type is only chemical in nature. This system may be useful in the study of an identified vertebrate giant neuron.

On a new species of electric catfish from Kainji, Nigeria, with some observations on its biology

A new species of electric catfish,Malapterurus minjiriya, from Kainji, Nigeria, is described and a key for separating it from the two other known species is given. Notes on some aspects of the biology of the electric catfishes in Lake Kainji, Nigeria are included.

Acetylcholine, ATP, and proteoglycan are common to synaptic vesicles isolated from the electric organs of electric eel and electric catfish as well as from rat diaphragm.

Cholinergic synaptic vesicles were isolated from the electric organs of the electric eel (Electrophorus electricus) and the electric catfish (Malapterurus electricus) as well as from the diaphragm of the rat by density gradient centrifugation followed by column chromatography on Sephacryl-1000. This was verified by both biochemical and electron microscopic criteria. Differences in size between synaptic vesicles from the various tissue sources were reflected by their elution pattern from the Sephacryl column. Specific activities of acetylcholine (ACh; in nmol/mg of protein) of chromatography-purified vesicle fractions were 36 (electric eel), 2 (electric catfish), and 1 (rat diaphragm). Synaptic vesicles from all three sources contained ATP in addition to ACh (molar ratios of ACh/ATP, 9-12) as well as binding activity for an antibody raised against Torpedo cholinergic synaptic vesicle proteoglycan. Synaptic vesicles from rat diaphragm contained binding activity for the monoclonal antibody asv 48 raised against a rat brain 65-kilodalton synaptic vesicle protein. Antibody asv 48 binding was absent from electric eel and electric catfish synaptic vesicles. These antibody binding results, which were obtained by a dot blot assay on isolated vesicles, directly correspond to the immunocytochemical results demonstrating fluorescein isothiocyanate staining in the respective nerve terminals. Our results imply that ACh, ATP, and proteoglycan are common molecular constituents of motor nerve terminal-derived synaptic vesicles from Torpedo to rat. In addition to ACh, both ATP and proteoglycan may play a specific role in the process of cholinergic signal transmission.

Social Behavior of the African Electric Catfish, Malapterurus electricus, during Intra‐ and Interspecific Encounters

AbstractUsing a “resident‐intruder” protocol, we observed spacing strategies and agonistic behavior in the African electric catfish, Malapterurus electricus, as it encountered conspecifics and equal‐sized members of three other species (a bichir, a tilapia, and goldfish). M. electricus defended a familiar shelter site. The catfish employed different locomotor and electric behavioral strategies, depending on the intruder species. In conspecific interactions, M. electricus engaged in ritualized fights, including lateral and open‐mouth displays, occasionally escalating to bites. Electric organ discharges were rare. In contrast, in interspecific encounters contacts were limited to brief touches with frequent use of electric organ discharge volleys. Our data indicate that M. electricus discriminates between con‐specifics and other species. We postulate that such a discrimination may be mediated by chemical and/or mechanical cues.

Retinal projections in the electric catfish (Malapterurus electricus).

The poorly developed visual system of the electric catfish was studied with silver-degeneration methods. Retinal projections were entirely contralateral to the hypothalamic optic nucleus, the lateral geniculate nucleus, the dorsomedial optic nucleus, the pretectal nuclei including the cortical nucleus, and the optic tectum. The small size and lack of differentiation of the visual system in the electric catfish suggest a relatively small role for this sensory system in this species.

Intracellular transport in neurons.

Intracellular transport in neurons.

Observations on the food and feeding habits of the African electric catfish Malapterurus electricus (Gmelin)

The diet and feeding habits of the African electric catfish Malapterurus electricus in their natural habitat in Lake Kainji, and in the River Niger, downstream of Kainji dam, Nigeria, have been described and compared. The study showed the electric catfish is a voracious piscivore. It feeds on cichlids, clupeids, schilbeids and other available fish species. From the size distribution, numbers and composition of the small prey fish species examined in electric catfish stomachs, it was inferred that the powerful high‐frequency electric organ discharge volleys serve as major predatory mechanism.

Ethological observations on the electric organ discharge behaviour of the electric catfish, Malapterurus electricus (Pisces)

1. Electric organ discharge (EOD) volleys emitted by the electric catfish, Malapterurus electricus, were recorded and sampled for 108 consecutive hours from the fish's natural habitat, a selected study area in the Swashi River, a tributary of the man-made Lake Kainji in Nigeria. 2. M. electricus intermittently generates different types of EOD volleys that start with a high-frequency phase, and range in duration from 2 ms to over 8 s with from 2 to over 600 pulses (EODs). 3. The catfish's EOD activity exhibited a daily activity rhythm which was correlated with local changes in light intensity. The EOD activity remained at a constant level throughout the day from 0700 h to 1800 h. Shortly after sunset, between 1800 h and 1900 h, it increased fivefold to its peak value at 1900 h. The occurrence of EOD volleys declined throughout the night with a noticeable drop to the daytime low after sunrise between 0600 h and 0700 h. During the first 6 h following sunset, the volleys were significantly longer and consisted of more EODs than the daytime volleys. It is inferred that M. electricus feeds most successfully during the early hours of the night. 4. A hitherto unknown type of Malapterurus EOD activity was discovered: during night-time, volleys consisting of more than 16 EODs were occasionally preceded by a low-frequency train of from 1 to 11 EODs. The occurrence rate of these pre-volley EODs was positively correlated with the duration of the ensuing volley (and its number of EODs). The peak pre-volley activity occurred during the first 4 h after sunset, with an average of 38% of all volleys preceded by this type of activity. The adaptive significance of the nocturnal pre-volley EODs as prey detection mechanism is discussed.

Electro-orientation in the passive electric catfish,Ictalurus nebulosus LeS

By means of conditioning experiments it was demonstrated in the laboratory that catfish show compass-orientation using more or less homogeneous, horizontally directed electric fields. Similar fields occur in their habitat.

Synaptic release of radioactivity after intrasomatic injection of choline-3H into an identified cholinergic interneuron in abdominal ganglion of Aplysia californica.

Synaptic release of radioactivity after intrasomatic injection of choline-3H into an identified cholinergic interneuron in abdominal ganglion of Aplysia californica.H Koike, E R Dandel, and J H SchwartzH Koike, E R Dandel, and J H SchwartzPublished Online:01 Jul 1974https://doi.org/10.1152/jn.1974.37.4.815MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByFunctional compartmentalization of energy production in neural tissueBrain Research, Vol. 585, No. 1-2Regional differences in extracellular choline dependency of acetylcholine synthesis in the rat brainNeuroscience Research, Vol. 11, No. 1Axonal transport studied in a single vertebrate neuron: the giant electromotor neuron of the electric catfish, Malapterurus electricusNeuroscience Research, Vol. 6, No. 3The generation and modulation of endogenous rhythmicity in the aplysia bursting pacemaker neurone R15Progress in Biophysics and Molecular Biology, Vol. 46, No. 1The pharmacology of molluscan neuronsProgress in Neurobiology, Vol. 23, No. 1-2The relative contributions of the receptors and cholinesterases to the effects of acetylcholine on the hearts of bivalve molluscsGeneral Pharmacology: The Vascular System, Vol. 11, No. 1Controlled micro release of pharmacological agents: Measurements of volume ejected in vitro through fine tipped glass microelectrodes by pressureNeuropharmacology, Vol. 18, No. 2Effects of some naturally occurring quaternary ammonium bases on snail nerve cells activityComparative Biochemistry and Physiology Part C: Comparative Pharmacology, Vol. 64, No. 2Amplitude and rate of decay of post-tetanic potentiation are controlled by different mechanismsBrain Research, Vol. 157, No. 1Ionic mechanism and receptor properties underlying the responses of snail nerve cells to acetylcholineComparative Biochemistry and Physiology Part C: Comparative Pharmacology, Vol. 61, No. 1A potential screening technique for neurotransmitters in the CNS: Model studies in the cat spinal cordBrain Research, Vol. 137, No. 1A radioautographic analysis in the light and electron microscope of identified Aplysia neurons and their processes after intrasomatic injection of l-[3H]fucoseBrain Research, Vol. 112, No. 2Drug-induced changes in behaviour and ganglionic acetylcholine concentration of the leechNeuropharmacology, Vol. 14, No. 8 More from this issue > Volume 37Issue 4July 1974Pages 815-27 https://doi.org/10.1152/jn.1974.37.4.815PubMed4837776History Published online 1 July 1974 Published in print 1 July 1974 Metrics

Physiology and ultrastructure of electrotonic junctions. 3. Giant electromotor neurons of Malapterurus electricus.

Physiology and ultrastructure of electrotonic junctions. 3. Giant electromotor neurons of Malapterurus electricus.M V Bennett, Y Nakajima, and G D PappasM V Bennett, Y Nakajima, and G D PappasPublished Online:01 Mar 1967https://doi.org/10.1152/jn.1967.30.2.209MoreSectionsPDF (4 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByThe first developing “mixed” synapses between vestibular sensory neurons mediate glutamate chemical transmissionNeuroscience, Vol. 58, No. 1Axonal transport studied in a single vertebrate neuron: the giant electromotor neuron of the electric catfish, Malapterurus electricusNeuroscience Research, Vol. 6, No. 3Morphology of dendrite bundles in the cervical spinal cord of the rat: A light microscopic studyExperimental Neurology, Vol. 100, No. 1The electromotor system of the electric catfish (Malapterurus electricus): A fine-structural analysisCell and Tissue Research, Vol. 247, No. 3Intracellular and extracellular electrophysiology of nigral dopaminergic neurons—3. Evidence for electrotonic couplingNeuroscience, Vol. 10, No. 2Responses of identified neurons in the buccal ganglia of helix pomatia to stimulation of ganglionic nervesComparative Biochemistry and Physiology Part A: Physiology, Vol. 72, No. 4Junctional mechanisms at group Ia synapsesProgress in Neurobiology, Vol. 12, No. 1Neuronal gap junctions and morphologically mixed synapses in the spinal cord of a teleost, Sternarchus albifrons (gymnotoidei)Brain Research, Vol. 143, No. 1Electrotonic coupling between frog spinal motoneurons. An electrophysiological and morphological studyBrain Research, Vol. 138, No. 2Criteria for distinguishing between monosynaptic and polysynaptic transmissionBrain Research, Vol. 105, No. 1Electrotonic coupling between motoneurones in the abducens nucleus of the catExperimental Brain Research, Vol. 21, No. 2Physiological and morphological correlation of the functional syncytium in the bivalve myocardiumComparative Biochemistry and Physiology Part A: Physiology, Vol. 44, No. 1Regional differentiation of the axon: A review with special reference to the concept of the multiplex neuronBrain Research, Vol. 47, No. 2Electronic coupling between teleost oculomotor neurons; restriction to somatic regions and relation to function of somatic and dendritic sites of impulse initiationBrain Research, Vol. 38, No. 2Morphological demonstration of electronic coupling of neurons by way of presynaptic fibersBrain Research, Vol. 36, No. 2Coupling Between Cells of the Trigeminal Mesencephalic Nucleus8 November 2016 | Journal of Dental Research, Vol. 49, No. 6Organization of the cellular membranesProgress in Biophysics and Molecular Biology, Vol. 20 More from this issue > Volume 30Issue 2March 1967Pages 209-35 https://doi.org/10.1152/jn.1967.30.2.209PubMed6045195History Published online 1 March 1967 Published in print 1 March 1967 Metrics

The use of the name torpedo for the electric catfish

The use of the name torpedo for the electric catfish