Elephantnose Fish Research Articles

Shimmying Schnoz: Elephantnose fish "sees" by doing an electric boogie.

Shimmying Schnoz: Elephantnose fish "sees" by doing an electric boogie.

Genome structures resolve the early diversification of teleost fishes

Accurate species phylogenies are a prerequisite for all evolutionary research. Teleosts are the largest and most diversified group of extant vertebrates, but relationships among their three oldest extant lineages remain unresolved. On the basis of seven high-quality new genome assemblies in Elopomorpha (tarpons, eels), we revisited the topology of the deepest branches of theteleost phylogeny using independent gene sequence and chromosomal rearrangement phylogenomic approaches. These analyses converged to a single scenario that unambiguously places the Elopomorpha and Osteoglossomorpha (arapaima, elephantnose fish) in a monophyletic sister group to all other teleosts, i.e., the Clupeocephala lineage (zebrafish, medaka). This finding resolves more than 50 years of controversy on the evolutionary relationships of these lineages and highlights the power of combining different levels of genome-wide information to solve complex phylogenies.

Wound Healing Metabolites from Peters' Elephant-Nose Fish Oil: An In Vivo Investigation Supported by In Vitro and In Silico Studies.

Gnathonemuspetersii (F. Mormyridae) commonly known as Peters’ elephant-nose fish is a freshwater elephant fish native to West and Central African rivers. The present research aimed at metabolic profiling of its derived crude oil via GC-MS analysis. In addition, wound healing aptitude in adult male New Zealand Dutch strain albino rabbits along with isolated bioactive compounds in comparison with a commercial product (Mebo®). The molecular mechanism was studied through a number of in vitro investigations, i.e., radical scavenging and inhibition of COX enzymes, in addition to in silico molecular docking study. The results revealed a total of 35 identified (71.11%) compounds in the fish oil, belonging to fatty acids (59.57%), sterols (6.11%), and alkanes (5.43%). Phytochemical investigation of the crude oil afforded isolation of six compounds 1–6. Moreover, the crude oil showed significant in vitro hydrogen peroxide and superoxide radical scavenging activities. Furthermore, the crude oil along with one of its major components (compound 4) exhibited selective inhibitory activity towards COX-2 with IC50 values of 15.27 and 2.41 µM, respectively. Topical application of the crude oil on excision wounds showed a significant (p < 0.05) increase in the wound healing rate in comparison to the untreated and Mebo®-treated groups, where fish oil increased the TGF-β1 expression, down-regulated TNF-α, and IL-1β. Accordingly, Peters’ elephant-nose fish oil may be a potential alternative medication helping wound healing owing to its antioxidant and anti-inflammatory activities.

Simulation research of bionic image intensifier based on the retina structure of elephant-nose fish

Enhancing image brightness under low light conditions is crucial. The traditional night vision technology depends on the development of photoelectric materials and accurate image processing algorithms. Inspired by the structure of elephant-nose fish, we construct a bionic image intensifier (BII) model. The BII is a planar array based on the concentrating principle of the compound parabolic concentrator (CPC). This solution is based on pure optical design and independent. Through light tracing, the simulation results show that the brightness of the image is improved and good image uniformity is obtained. Quantitative analysis of the geometric concentration ratio (GCR) and the image uniformity is used to optimize CPC structure parameters. At the same time, we also discuss the influence of CPC structural parameters on image continuity, uniformity and geometric concentration ratio. The optimization results are as follows: the input port diameter is 50 μm, the output port diameter is 10 μm, the height is 90 μm, the GCR is 5.61, and the image uniformity is 95.30%. The comprehensive performance of the BII achieves the best.

A morphological, molecular, and histopathological redescription of Henneguya nyongensis Fomena & Bouix, 1996 (Cnidaria: Myxobolidae) infecting the gills of Peter's elephantnose fish, Gnathonemus petersii (Günther) (Osteoglossiformes: Mormyridae), imported from Nigeria.

A Henneguya sp., morphologically resembling Henneguya nyongensis Fomena & Bouix, 1996, was isolated from the gills of Peter's elephantnose fish, Gnathonemus petersii Günther, imported from Nigeria. Plasmodia were located between lamellae and within the gill epithelium, often leading to lamellar fusion. Although slightly smaller, the myxospores from these fish were morphologically consistent with H. nyongensis. In valvular view, spores are elongate, pyriform with a rounded posterior and tapering caudal processes. Myxospore bodies are 9.6-12.3 (mean 11.2) µm long and 4.0-4.7 (mean 4.3) µm wide. Polar capsules are pyriform, elongate, 4.5-5.2 (4.7) µm long and 1.3-1.6 (1.4) µm wide, with a characteristic neck-like structure at the apical end. Sequence generated for the 18S small subunit rRNA gene did not directly match any sequences available on GenBank, but demonstrated 91% nucleotide similarity to an unpublished Henneguya sp. infecting Mormyrus kannume Forsskål. Herein, the description of H. nyongensis is supplemented with new data on histopathology, molecular characterisation, and expanded host and geographical range.

Characterization of objects by electrosensing fish based on the first order polarization tensor

Weakly electric fish generate electric current and use hundreds of voltage sensors on the surface of their body to navigate and locate food. Experiments (von der Emde and Fetz 2007 J. Exp. Biol. 210 3082–95) show that they can discriminate between differently shaped conducting or insulating objects by using electrosensing. One approach to electrically identify and characterize the object with a lower computational cost rather than full shape reconstruction is to use the first order polarization tensor (PT) of the object. In this paper, by considering experimental work on Peters’ elephantnose fish Gnathonemus petersii, we investigate the possible role of the first order PT in the ability of the fish to discriminate between objects of different shapes. We also suggest some experiments that might be performed to further investigate the role of the first order PT in electrosensing fish. Finally, we speculate on the possibility of electrical cloaking or camouflage in prey of electrosensing fish and what might be learnt from the fish in human remote sensing.

How bio-organism is playing its role in the lenses technology

Capitalizing on the low light in the sloppy waterways where it swims, the elephant nose fish gets by having the capacity to spot predators amongst the grime with an interestingly molded retina, the part of the eye that catches light. In another study, specialists looked to the fish's retinal structure to illuminate the configuration of a contact lens that can alter its core interest. Envision a contact lens that self-adjusts inside of milliseconds. That could be groundbreaking for individuals with presbyopia, a hardening of the eye's lens that makes it hard to concentrate on close protests. Presbyopia influences more than 1 billion individuals around the world, half of whom don't have sufficient redress, said the undertaking's pioneer, Hongrui Jiang, Ph.D., of the University of Wisconsin, Madison. Keeping in mind glasses, traditional contact lenses and surgery give some change, these choices all include the loss of difference and affectability, and in addition trouble with night vision. Jiang's thought is to outline contacts that constantly change working together with one's own cornea and lens to recover a man's young vision.

Artificial eye for scotopic vision with bioinspired all-optical photosensitivity enhancer

The ability to acquire images under low-light conditions is critical for many applications. However, to date, strategies toward improving low-light imaging primarily focus on developing electronic image sensors. Inspired by natural scotopic visual systems, we adopt an all-optical method to significantly improve the overall photosensitivity of imaging systems. Such optical approach is independent of, and can effectively circumvent the physical and material limitations of, the electronics imagers used. We demonstrate an artificial eye inspired by superposition compound eyes and the retinal structure of elephantnose fish. The bioinspired photosensitivity enhancer (BPE) that we have developed enhances the image intensity without consuming power, which is achieved by three-dimensional, omnidirectionally aligned microphotocollectors with parabolic reflective sidewalls. Our work opens up a previously unidentified direction toward achieving high photosensitivity in imaging systems.

Species complexes and phylogenetic lineages of Hoferellus (Myxozoa, Cnidaria) including revision of the genus: A problematic case for taxonomy.

BackgroundMyxozoans are metazoan parasites whose traditional spore morphology-based taxonomy conflicts DNA based phylogenies. Freshwater species of the genus Hoferellus are parasites of the excretory system, with several members infecting food and ornamental fish species, as well as amphibians. This study aims to increase our understanding of their molecular diversity and development, aspects about which little is known, and to generate a molecular diagnostic tool to discriminate between different pathogenic and non-pathogenic Hoferellus spp.MethodsSSU and ITS rDNA phylogeny, along with morphological descriptions using light and electron microscopy were used to identify and characterize Hoferellus species collected from the urinary system of fishes and frogs. A PCR-based diagnostic assay was designed to differentiate between cryptic Hoferellus spp in cyprinid fishes commonly cultured in Central Europe.ResultsOur phylogenetic results separate the species of Hoferellus into two phylogenetic sublineages which are indistinguishable on the basis of generic morphological traits: 1) The Hoferellus sensu stricto sublineage, which is composed of the type species Hoferellus cyprini, Hoferellus carassii and a cryptic species, Hoferellus sp. detected only molecularly in common carp. 2) The Hoferellus sensu lato sublineage into which the new species we described in this study, Hoferellus gnathonemi sp. n. from the kidney of the elephantnose fish and Hoferellus anurae from reed frogs, are placed together with Hoferellus gilsoni previously sequenced from European eel. Apart from phylogenetic analyses, we also provide novel ultrastructural data on the phagocytotic nature of some Hoferellus plasmodia and on the elusive intracellular stages ascribed to the presporogonic development of this genus.ConclusionsWe provide molecular evidence of the polyphyly of the genus Hoferellus and provide novel morphological details of its members. Based on the presented data, we revise and propose emendation of the genus Hoferellus.

More a finger than a nose: the trigeminal motor and sensory innervation of the Schnauzenorgan in the elephant-nose fish Gnathonemus petersii.

The weakly electric fish Gnathonemus petersii uses its electric sense to actively probe the environment. Its highly mobile chin appendage, the Schnauzenorgan, is rich in electroreceptors. Physical measurements have demonstrated the importance of the position of the Schnauzenorgan in funneling the fish's self-generated electric field. The present study focuses on the trigeminal motor pathway that controls Schnauzenorgan movement and on its trigeminal sensory innervation and central representation. The nerves entering the Schnauzenorgan are very large and contain both motor and sensory trigeminal components as well as an electrosensory pathway. With the use of neurotracer techniques, labeled Schnauzenorgan motoneurons were found throughout the ventral main body of the trigeminal motor nucleus but not among the population of larger motoneurons in its rostrodorsal region. The Schnauzenorgan receives no motor or sensory innervation from the facial nerve. There are many anastomoses between the peripheral electrosensory and trigeminal nerves, but these senses remain separate in the sensory ganglia and in their first central relays. Schnauzenorgan trigeminal primary afferent projections extend throughout the descending trigeminal sensory nuclei, and a few fibers enter the facial lobe. Although no labeled neurons could be identified in the brain as the trigeminal mesencephalic root, some Schnauzenorgan trigeminal afferents terminated in the trigeminal motor nucleus, suggesting a monosynaptic, possibly proprioceptive, pathway. In this first step toward understanding multimodal central representation of the Schnauzenorgan, no direct interconnections were found between the trigeminal sensory and electromotor command system, or the electrosensory and trigeminal motor command. The pathways linking perception to action remain to be studied.

Mind the gap: the minimal detectable separation distance between two objects during active electrolocation

In a food-rewarded two-alternative forced-choice procedure, it was determined how well the weakly electric elephantnose fish Gnathonemus petersii can sense gaps between two objects, some of which were placed in front of complex backgrounds. The results show that at close distances, G. petersii is able to detect gaps between two small metal cubes (2 cm × 2 cm × 2 cm) down to a width of c. 1·5 mm. When larger objects (3 cm × 3 cm × 3 cm) were used, gaps with a width of 2-3 mm could still be detected. Discrimination performance was better (c. 1 mm gap size) when the objects were placed in front of a moving background consisting of plastic stripes or plant leaves, indicating that movement in the environment plays an important role for object identification. In addition, the smallest gap size that could be detected at increasing distances was determined. A linear relationship between object distance and gap size existed. Minimal detectable gap sizes increased from c. 1·5 mm at a distance of 1 cm, to 20 mm at a distance of 7 cm. Measurements and simulations of the electric stimuli occurring during gap detection revealed that the electric images of two close objects influence each other and superimpose. A large gap of 20 mm between two objects induced two clearly separated peaks in the electric image, while a 2 mm gap caused just a slight indentation in the image. Therefore, the fusion of electric images limits spatial resolution during active electrolocation. Relative movements either between the fish and the objects or between object and background might improve spatial resolution by accentuating the fine details of the electric images.

Mind The Gap! Detection of gaps between objects during active electrolocation in Gnathonemus petersii

Event Abstract Back to Event Mind The Gap! Detection of gaps between objects during active electrolocation in Gnathonemus petersii Katharina Behr1, Dominik Holtkamp1, Gesche Neusel1 and Gerhard Von Der Emde1* 1 University of Bonn, Zoology, Germany The elephantnose fish Gnathonemus petersii generates electrical signals (electric organ discharges, EODs), which build up an electric field around the fish’s body. The animals perceive their own electrical emissions with cutaneous electroreceptor organs. During active electrolocation, objects are recognized by analysing the electric images, which they project onto the skin of the fish during each EOD. G. petersii and other mormyrids are nocturnal and use active electrolocation to orient in their habitat in complete darkness at night. In our project, we determined how well the fish could detect gaps between two metal objects in front of complex backgrounds. We trained the fish in a food-rewarded two-alternative forced-choice procedure to swim to two metal cubes (2cm x 2cm x 2cm) with a gap between them, which served as the positive stimulus. The alternative negative stimulus was a solid object of equal length with no gap. Our results show that G. petersii is able to detect gaps down to a width of about 0.2 cm. Discrimination performance was better (0.1 cm gap size) when the objects were placed in front of a moving plastic or water plant background. This indicates that movements in the environment play an important role for object identification. In addition, we determined the correlation between gap size and the distance, in which gaps could be detected. We found that G. petersii is able to detect a 1 cm gap up to a distance of 4 cm, and a 0.5 cm gap up to a distance of 3 cm. Keywords: background movement, electric image, gap detection, Orientation, spatial resolution, weakly electric fish Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster Presentation (see alternatives below as well) Topic: Sensory: Electrosensory Citation: Behr K, Holtkamp D, Neusel G and Von Der Emde G (2012). Mind The Gap! Detection of gaps between objects during active electrolocation in Gnathonemus petersii. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00232 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Apr 2012; Published Online: 07 Jul 2012. * Correspondence: Dr. Gerhard Von Der Emde, University of Bonn, Zoology, Bonn, 53115, Germany, vonderemde@uni-bonn.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Katharina Behr Dominik Holtkamp Gesche Neusel Gerhard Von Der Emde Google Katharina Behr Dominik Holtkamp Gesche Neusel Gerhard Von Der Emde Google Scholar Katharina Behr Dominik Holtkamp Gesche Neusel Gerhard Von Der Emde PubMed Katharina Behr Dominik Holtkamp Gesche Neusel Gerhard Von Der Emde Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

The Schnauzenorgan-response of Gnathonemus petersii

BackgroundElectric fish navigate and explore their dark and turbid environment with a specialised electric sense. This active electrolocation involves the generation and perception of an electric signal and fish have proven to be useful model systems for the investigation of sensory-motor interactions. A well studied example is the elephantnose fish, Gnathonemus petersii, which has a characteristic and unique elongated chin covered with hundreds of electroreceptor organs. This highly moveable so-called Schnauzenorgan constitutes the main fovea of the active electrosensory system. Here we present first evidence for a sensory-motor loop relating active electrical sensing to active motor exploration of the environment.ResultsBoth anatomical and behavioural evidence have shown that the moveable Schnauzenorgan is crucial for prey localization. Here we show for the first time that a motor response (Schnauzenorgan-response, SOR) can be elicited by novel electrosensory stimuli. The SOR could be triggered with highest reliability by novel electrical stimuli near the Schnauzenorgan and, to a lesser extend, near the head of the animal. The probability of evoking the response depended on the magnitude of the amplitude change of the electric input, with bigger changes eliciting SORs more reliably. Similarly, increasing the distance of the stimulus reduced the response. In this respect the SOR is comparable to the well described novelty response, a transient acceleration of the production rate of electric signals, although the latter occurs at a shorter delay and can also be evoked by non-electrical stimuli.ConclusionOur experiments show a novel motor response that is mediated by the active electric sense of Gnathonemus petersii. This response will allow a detailed analysis of the neural system underlying direct interaction between sensory and motor processes in future experiments.

Dim light vision – Morphological and functional adaptations of the eye of the mormyrid fish, Gnathonemus petersii

The African weakly electric fish Gnathonemus petersii is well known for its electrosensory capabilities. These animals can detect and distinguish objects through active electrolocation in complete darkness. Because of their nocturnal lifestyle, a low contribution of vision for orientation and object detection has been expected. However, as we show in this review, the retina of G. petersii is highly specialized with hundreds of rods and tens of cones grouped together in bundles in a complex way, ensheathed by a tapetum lucidum. The structure of the bundles goes beyond what would be expected if only photon catch was supposed to be increased. During daytime, the structure of these “macro-receptors” changes dramatically depending on retinomotor movements. During the day, the rods and cones are located in different compartments of the bundle, separated by a narrow canal in the form of a “bottle neck”. Investigations on cell structure and neurochemistry in the retina indicate a general organization that is simpler in terms of bipolar and ganglion cell diversity than in tetrachromatic species such as goldfish, yet similar in terms of neurochemical differentiation of amacrine cells. In both respects, the inner retina of the elephantnose fish bears the greatest similarity to catfish and some deep-sea fish retinae. Neuronal circuits and bundle structure give hints of possible adaptations for contrast and/or movement detection. Behavioral experiments suggest that, in contrast to the vision specialists Lepomis gibbosus, pattern detection of G. petersii is not affected by higher spatial frequencies. A pattern of low spatial frequencies, however, was equally well detected by G. petersii and L. gibbosus. Optomotor response experiments indicate that motion vision is important for Gnathonemus, narrowing down the search for the functional specialization of the Gnathonemus retina and providing a starting point for work on multisensory integration in these fish.

1910 Interval fluctuation in the stationary phase of eods in elephant-nose fish

1910 Interval fluctuation in the stationary phase of eods in elephant-nose fish

Structure of electric organ discharge series in elephant-nose fish

Structure of electric organ discharge series in elephant-nose fish

Auditory sensitivity and psychophysical tuning curves in the elephant nose fish,Gnathonemus petersii

Hearing sensitivity and psychophysical tuning curves were determined for the mormyridGnathonemus petersii. Pure tone hearing thresholds were determined from 100 Hz to 2,500 Hz, with best sensitivity being about −31 dB (re: 1 dyne/ cm2) from 300 Hz to 1,000 Hz. In order to determine frequency tuning of the auditory system, psychophysical tuning curves (PTC's) were measured with the masker presented simultaneously with, or just ahead of, the 500 Hz test signal. The sound level for different frequencies needed to just mask the test tone were determined from 100 to 800 Hz. Maximum masking occurred in both forward and simultaneous conditions when the masker and the test tone were at the same frequency. As the masker was moved in frequency from 500 Hz, higher sound levels of maskers were needed to afford masking of the test tone. The data were similar in simultaneous and forward masking, with theQ 10 dB, a measure of sharpness of tuning, being about 5 in both cases. Data were compared for other species for which behavioral thresholds and PTC's are available.Gnathonemus hears about as wide a range of frequencies as the goldfish,Carassius auratus, although the PTC's for the two species are strikingly different. The PTC's forGnathonemus resemble those determined in a forward-masking paradigm for the clown knife fish,Notopterus chitala, even thoughGnathonemus has a wider hearing bandwidth.