Electric Ray Research Articles

A NEW SPECIES OF ACANTHOBOTHRIUM (CESTODA: ONCHOPROTEOCEPHALIDEA), PARASITE OF THE GIANT ELECTRIC RAY NARCINE ENTEMEDOR JORDAN AND STARKS, 1895 (BATOIDEA: TORPEDINIFORMES) FROM MEXICO.

Spiral valves from specimens of the giant electric ray Narcine entemedor Jordan & Starks, 1895 were examined in search of tapeworms at 2 localities of the Mexican tropical Pacific Ocean. Acanthobothrium oceguerai n. sp. is described herein based on material from Ventanilla, Oaxaca and from Acapulco Bay, Guerrero. The new species is a category 6 species, distinguished by being apolytic, retaining proglottids on the strobila until they are gravid, having strobila of 166-322 proglottids, having a small scolex and very long bothridia relative to the scolex, and having abaxial prongs that are short and thin in comparison to the axial prongs, which are longer and more robust. Acanthobothrium oceguerai n. sp. can be differentiated from other members of category 6 by the hooks, which are shorter, more robust, and smaller than those of the other members of this category. The phylogenetic analysis based on the 28S rRNA locus placed Acanthobothrium oceguerai n. sp. as sister to an unidentified species of larval Acanthobothrium from Philadelphia, Pennsylvania. In addition, sequences of the mitochondrial cytochrome oxidase subunit I gene and nuclear 18S rDNA were generated to provide support for future taxon sampling. Acanthobothrium oceguerai n. sp. is the fifth species of cestode reported from N. entemedor in the tropical eastern Pacific.

Baseline polycyclic aromatic hydrocarbon maternal transfer data in Lesser Numbfish Narcine brasiliensis (Elasmobranchii: Batoidea) from an impacted estuary in Southeastern Brazil

Maternal offloading of polycyclic aromatic hydrocarbons (PAHs) poses a significant exposure route for developing embryos, with implications for subsequent generations. Despite known developmental effects regarding fish physiology and behavior, maternal PAH transfer assessments in elasmobranchii are still lacking. This study investigated PAH contamination and maternal transfer in one female Lesser Numbfish (Narcine brasiliensis) electric ray and seven embryos for the first time. Naphthalene was identified as the predominant low molecular weight PAH, and dibenzo[a,h]anthracene was the most abundant high molecular weight compound. Most embryos exhibited some level of PAH exposure, with varying accumulation patterns potentially influenced by size, developmental stage, and yolk absorption rates. Further investigation is warranted to understand the impacts of PAH maternal offloading on elasmobranchii uterine contents and embryos.

Ray bioturbation rates suggest they shape estuary processes

AbstractBioturbation of sediments is a key ecosystem service in estuarine and marine ecosystems, and rays (superorder Batoidea: skates, stingrays, electric rays and shovelnose rays) are among the largest bioturbators, modifying their habitat through foraging and predation. Ray activities cycle nutrients, increase oxygen penetration and re‐stratify sediments. However, given rays are globally threatened, it is unclear to what extent the loss of rays, and the ecosystem services they provide, would affect ecosystem processes. This study assessed the likely amount of sediment displaced annually by rays during foraging activities at an estuary scale. To achieve this, an aerial drone was used to map daily ray bioturbation activity, as evident from the presence of feeding pits. High‐resolution, 2.6 cm px−1, Digital Elevation Models (DEM) were created and used to measure the volume of sediment displaced by feeding pits. We found rays within the Brisbane Water estuary in NSW, Australia excavated 1.20 (±0.68) tonnes of sediment per day within this 1443 m2 intertidal area, or a rate of 575.2 cm3 m−2 per day. This bioturbation rate is relatively high compared to bioturbation rates documented in other ray species. Spatial autocorrelation analysis indicated that the ray feeding pits were significantly clustered by location as well as size (P < 0.01), suggesting size segregation of ray foraging. When bioturbation rates were conservatively extrapolated across measured feeding area in the estuary, we calculated rays displace 57.6 (±32.4) tonnes of sediment per day, or 21.0 (±11.4) kilotonnes per year. This underlines how ray bioturbation likely shape estuary processes, and how the loss of rays and their ecosystem services would likely have considerable impacts on estuarine sedimentary ecosystems. These findings emphasize the ecological importance of rays in an ecosystem and a need to better understand the consequences of anthropogenic pressures to these services.

Large-area, self-healing block copolymer membranes for energy conversion

Membranes are widely used for separation processes in applications such as water desalination, batteries and dialysis, and are crucial in key sectors of our economy and society1. The majority of technologically exploited membranes are based on solid polymers and function as passive barriers, whose transport characteristics are governed by their chemical composition and nanostructure. Although such membranes are ubiquitous, it has proved challenging to maximize selectivity and permeability independently, leading to trade-offs between these pertinent characteristics2. Self-assembled biological membranes, in which barrier and transport functions are decoupled3,4, provide the inspiration to address this problem5,6. Here we introduce a self-assembly strategy that uses the interface of an aqueous two-phase system to template and stabilize molecularly thin (approximately 35 nm) biomimetic block copolymer bilayers of scalable area that can exceed 10 cm2 without defects. These membranes are self-healing, and their barrier function against the passage of ions (specific resistance of approximately 1 MΩ cm2) approaches that of phospholipid membranes. The fluidity of these membranes enables straightforward functionalization with molecular carriers that shuttle potassium ions down a concentration gradient with exquisite selectivity over sodium ions. This ion selectivity enables the generation of electric power from equimolar solutions of NaCl and KCl in devices that mimic the electric organ of electric rays.

Electron-translucency and partial defects of synaptic basal lamina in the electrocyte synapse of an electric ray (Narke japonica) in 3D embedment-free section electron microscopy.

The synaptic basal lamina of the electrocytes was disclosed to be electron-translucent to some extent when viewed in an en-face direction in embedment-free section transmission electron microscopy (EFS-TEM), and synaptic vesicles located close to the presynaptic membrane were seen through the synaptic basal lamina together with the presynaptic and postsynaptic membranes. This feature of translucency has the potential to analyze possible spatial interrelations in situ between bioactive molecules in the synaptic basal lamina and the synaptic vesicles in further studies. The synaptic basal lamina, appearing as an electron-dense line sandwiched by two parallel lines representing the presynaptic and postsynaptic membranes in ultrathin sections cut right to the synaptic junctional plane in conventional TEM, was not fully continuous but randomly intermittent along its trajectory. Compatible with the intermittent line appearance, the en-face 3D view in embedment-free section TEM revealed for the first time partial irregular defects of the synaptic basal lamina. Considering the known functional significance of several molecules contained in the synaptic basal lamina in the maintenance and exertion of the synapse, its partial defects may not represent its rigid structural features, but its immature structure under remodeling or its dynamic changes in consistency such as the sol/gel transition, whose validity needs further examination. RESEARCH HIGHLIGHTS: In embedment-free section TEM, a 3D en-face view of synaptic basal lamina in situ is reliably possible. The basal lamina en-face is electron-translucent, which makes it possible to analyze spatial interrelation between pre- and post-synaptic components. Partial irregular defects in the basal lamina are revealed in Torpedo electrocytes, suggesting its remodeling or dynamic changes in consistency.

Mitigating bycatch in Mediterranean trammel net fisheries using species-specific gear modifications.

Small-scale fisheries (SSF) use static gear which are thought to interact with marine ecosystems more benignly than towed gear. Despite this, trammel nets, one of the most extensively used type of fishing gear in the Mediterranean SSF, generate large amounts of discards, which can account for 25% or more of the captured biomass. Discarded organisms may include endangered or threatened species such as elasmobranchs, as well as non-commercial invertebrates that damage fishing gear or cause disentanglement delays. We evaluated various trammel-net gear modifications, including (i) the use of a guarding net attached to the footrope, (ii) increasing the length of the rigging twine between the footrope and the netting panel, and (iii) decreasing the mesh size of the outer panels. The last two modifications were successful in lowering captures of the marbled electric ray Torpedo marmorata, which is commonly discarded in the study area. Both sorts of modifications are relatively simple, their manufacturing does not represent an added cost to implement, and most importantly they do not negatively affect the catch of the target species. The current study shows that prior evaluation of the discard profile of distinct métiers is essential to accomplish species-specific gear modifications and underlines the importance of collaboration among scientists, fishers and gear manufacturers.

Recombinant cellular model system for human muscle-type nicotinic acetylcholine receptor α12β1δε

The human muscle-type nicotinic acetylcholine receptor α12β1δε (nAChR) is a complex transmembrane receptor needed for drug screening for disorders like congenital myasthenic syndromes and multiple pterygium syndrome. Until today, most models are still using the nAChR from Torpedo californica electric ray. A simple reproducible cellular system expressing functional human muscle-type nAChR is still missing. This study addressed this issue and further tested the hypothesis that different chaperones, both biological and chemical, and posttranslational modification supporting substances as well as hypothermic incubation are able to increase the nAChR yield. Therefore, Gibson cloning was used to generate transfer plasmids carrying the sequence of nAChR or chosen biological chaperones to support the nAChR folding in the cellular host. Viral transduction was used for stable integration of these transgenes in Chinese hamster ovary cells (CHO). Proteins were detected with Western blot, in-cell and on-cell Western, and the function of the receptor with voltage clamp analysis. We show that the internalization of nAChR into plasma membranes was sufficient for detection and function. Additional transgenic overexpression of biological chaperones did result in a reduced nAChR expression. Chemical chaperones, posttranslational modification supporting substances, and hypothermic conditions are well-suited supporting applications to increase the protein levels of different subunits. This study presents a stable and functional cell line that expresses human muscle-type nAChR and yields can be further increased using the chemical chaperone nicotine without affecting cell viability. The simplified access to this model system should enable numerous applications beyond drug development.Graphical abstractGraphical abstract created with http://biorender.com

Virtual chemical analysis and machine learning-based prediction of polyethylene terephthalate nanoplastics toxicity on aquatic organisms as influenced by particle size and properties

This study focuses on the chemical analysis and prediction of Polyethylene Terephthalate (PET) toxicity, considering the influence of particle size and properties. The effect PET of different sizes (1, 4, 9, 16 and 25 nm coded NP1 to NP5) on aquatic organisms such as Terpedo californica (electric ray fish) and Danio rerio (zebrafish) as model species was evaluated by virtual chemical techniques and machine learning methodology based on Multilayer Perceptrons Artificial Neural Networks (MLP ANN) and Support Vector Machine. The PET NPs was built and characterized in silico and then docked on the acetylcholinesterase (TcAChE) and cytochrome P450 (Zf CYP450) of the organisms, respectively. The results showed that the binding affinities of the NPs increased steadily from – 7.1 kcal mol-1 to – 9.9 kcal mol-1 for NP1 to NP4 and experienced a drop at NP5 (– 8.9 kcal mol-1) for TcAChE. The Zf CYP450 also had a similar pattern ranging from -5.2 kcal mol-1 to -8.1 kcal mol-1. The MLP ANN showed an accuracy of 85.9 % and 77.3 %. In comparison, SVM showed a better PET NPs toxicity prediction with an accuracy of 99.5 % and 99.4% based on the inherent properties of TcAChE and Zf CYP450, respectively.

Assessing artisanal fishers' attitude and perception towards electric rays conservation along Indian coast

In India, electric rays are not targeted by fisheries but form a significant portion of bycatch. Little information exists about their ecology and biology. Fishers’ traditional ecological knowledge can fill the knowledge gap for these historically data-deprived fishes. Hence, we assessed attitudes and perceptions of artisanal fishers towards electric rays' conservation. We gathered information on catch frequency, seasonality, population trends, post-capture usages, and socio-economic values through a semi-structured questionnaire survey. We interviewed 243 fishers at 15 artisanal villages in three states: Tamil Nadu, Andhra Pradesh, and Odisha, along the east coast of India. The survey data was scrutinized, sorted into various categories: demographics, fisheries, and fishers’ traditional knowledge, analysed and visualised as graphs and figures. We also presented qualitative information as general statements or quoted specific comments to better explain our findings. We found that fishers were well aware of electric rays and their electrical discharge. The data indicated that fishers knew the habitat in nearshore sandy bottoms. They get electric rays in their bottom-set gill nets. In general, December, January and February have high electric ray bycatch. Post-capture usage includes take-home consumption, discarding them dead, releasing them alive, and sell to poultry. Fishers discussed health benefits of electric rays’ consumption. They perceived a downward trend in population due to anthropogenic influences: overfishing, pollution and climate change. Fishers’ knowledge and scientific contributions can help develop management plans and conservation strategies. Initiating awareness campaigns within fishing communities and coastal citizens foster positive attitudes, thereby enhancing the electric rays’ conservation.

I Like This New Me: Unravelling Population Structure of Mediterranean Electric Rays and Taxonomic Uncertainties within Torpediniformes.

The present study focused on the three species of electric rays known to occur in the Mediterranean Sea: Torpedo torpedo, Torpedo marmorata and Tetronarce nobiliana. Correct identification of specimens is needed to properly assess the impact of fisheries on populations and species. Unfortunately, torpedoes share high morphological similarities, boosting episodes of field misidentification. In this context, genetic data was used (1) to identify specimens caught during fishing operations, (2) to measure the diversity among and within these species, and (3) to shed light on the possible occurrence of additional hidden species in the investigated area. New and already published sequences of COI and NADH2 mitochondrial genes were analyzed, both at a small scale along the Sardinian coasts (Western Mediterranean) and at a large scale in the whole Mediterranean Sea. High levels of genetic diversity were found in Sardinian populations, being significantly different from other areas of the Eastern Mediterranean Sea due to the biotic and abiotic factors here discussed. Sardinian torpedoes can hence be indicated as priority populations/areas to be protected within the Mediterranean Sea. Moreover, sequence data confirmed that only the three species occur in the investigated area. The application of several 'species-delimitation' methods found evidence of cryptic species in the three species outside the Mediterranean Sea, as well as in other genera/families, suggesting the urgent need for future studies and a comprehensive revision of the order Torpediniformes for its effective conservation.

From historical expedition diaries to whole genome sequencing: A case study of the likely extinct Red Sea torpedo ray

AbstractTorpedo rays (Torpedinidae, Torpediniformes) are small to moderately large batoids that produce an electric discharge. They are distributed worldwide in temperate and tropical seas and are, as a result of their bottom‐dwelling behaviour, susceptible to trawl fishing and often end up as victims of bycatch. The distribution ranges of most recognized species seem to be restricted; however, their species‐level systematics is not adequately resolved. In the genus Torpedo, in which many species require revision, there are possibly several undescribed species, while numerous misidentifications add to the complexity of the issue. In the latest lists of living rays, 13 species are accepted in the genus Torpedo, including three of doubtful validity and several recently discovered undescribed species. Among the valid species is the critically endangered, possibly extinct, Torpedo suessii Steindachner, 1898, the Red Sea torpedo, of which only four specimens have been recorded in the literature until now, three of which still exist in the fish collection of the Natural History Museum of Vienna. Museum collections are the most important archive of biodiversity on Earth, and are increasingly being used for various studies, including phylogenetics, population genomics, and biogeography. Nevertheless, molecular analysis of old museum material remains challenging because the genetic material has degraded, is fragmented, and of low quantity. In molecular taxonomy, the necessity of including type specimens as name‐bearing specimens is increasingly recognized. Here, the extended specimen approach was applied to re‐describe the lectotype of T. suessii. The approach included research of historical information and whole genome sequencing, followed by genome assembly and phylogenetic analysis.

Phase volume fraction measurement of vertical oil–water-gas flow using integrated optical-electrical coaxial cross-modal probe sensor

Measuring phase volume fraction is an essential part of petroleum exploration and development. According to the problems that the common sensors are unable to obtain the phase volume fraction of oil–water-gas flow, an integrated optical-electrical coaxial cross-modal probe sensor (IOECCMPS) is designed, and a phase volume fraction system based on IOECCMPS is developed for different oil–water-gas flow. Specifically, the electrical and optical mathematical models of the IOECCMPS were established, and theoretical analysis of electric field distribution and ray tracing results. We also analyzed the sensitivity distribution of the electrical measurement module (EMM). Based on the above results, the effects of structural parameters on its performance are discussed, including the electrode length, electrode thickness, the angle of the monitoring tip, and insulating tube structure. In addition, we also studied the response characteristics of the IOECCMPS in oil–water-gas flow. Furthermore, the IOECCMPS circuit was designed and experimented with on the oil–water-gas flow measurement platform. Experimental results show: the developed IOECCMPS can realize multi-phase measurement under oil–water-gas flow such as liquid flow rate range (0.42–2.92 m3/h), liquid water volume fraction range (50–90%), gas flow rate range (0.21–1.67 m3/h), etc., and the measurement error is within 5%. In the research work of this paper, the developed IOECCMPS can simultaneously accomplish the accurate measurement of phase volume fraction of oil–water-gas flow, which provides a reference for the development of oil production monitoring technology.

Occurrence of Electric Ray, Narcine timlei (Bloch & Schneider, 1801) from Rushikulya Estuary, Odisha, India, as an Extension of Its Distribution Range

Occurrence of Electric Ray, Narcine timlei (Bloch & Schneider, 1801) from Rushikulya Estuary, Odisha, India, as an Extension of Its Distribution Range

Modeling the biological growth with a random logistic differential equation

We modeled biological growth using a random differential equation (RDE), where the initial condition is a random variable, and the growth rate is a suitable stochastic process. These assumptions let us obtain a model that represents well the random growth process observed in nature, where only a few individuals of the population reach the maximal size of the species, and the growth curve for every individual behaves randomly. Since we assumed that the initial condition is a random variable, we assigned a priori density, and we performed Bayesian inference to update the initial condition’s density of the RDE. The Karhunen–Loeve expansion was then used to approximate the random coefficient of the RDE. Then, using the RDE’s approximations, we estimated the density f(p, t). Finally, we fitted this model to the biological growth of the giant electric ray (or Cortez electric ray) Narcine entemedor. Simulations of the solution of the random logistic equation were performed to construct a curve that describes the solutions’ mean for each time. As a result, we estimated confidence intervals for the mean growth that described reasonably well the observed data. We fit the proposed model with a training dataset, and the model is tested with a different dataset. The model selection is performed with the square of the errors.

Connectivity between surface and interior in catalytic subunits of acetylcholinesterases inferred from their X-ray structures.

Catalytic activity and function of acetylcholinesterase (AChE; EC 3.1.1.7) have been recognized and studied for over a century and its quaternary and primary structures for about half a century, and its tertiary structure has been known for about 33 years. Clear understanding of relationships between the structure and the function is still pending for this enzyme. Hundreds of crystallographic, static snapshots of AChEs from different sources reveal largely one general backbone conformation with narrow entry into the active center gorge, tightly fit to accept one acetylcholine (ACh) molecule, in contrast to its high catalytic turnover. This short review of available X-ray structures of AChEs from electric ray Torpedo californica, mouse and human, finds some limited, yet consistent deviations in conformations of selected secondary structure elements of AChE relevant for its function. The observed conformational diversity of the acyl pocket loop of AChE, unlike the large Ω-loop, appears consistent with structurally dynamic INS data and solution-based SAXS experiments to explain its dominant role in controlling the size of the active center gorge opening, as well as connectivity between the immediate surroundings of the buried active Ser, and catalytically relevant sites on the AChE surface.

Phylogenetic relationships, host associations, and three new species of a poorly known group of “tetraphyllidean” tapeworms from elasmobranchs

This paper aims to expand understanding of a poorly known group of cestodes that parasitize an intriguingly diverse suite of elasmobranchs. The group's three currently described members (i.e., Pentaloculum macrocephalum, Pentaloculum hoi, and Zyxibothrium kamienae) parasitize an electric ray, a carpet shark, and a skate, respectively. Pentaloculum grahami n. sp. is described from a second genus of carpet shark, specifically Parascyllium collare, in Australia. Zyxibothrium duffyi n. sp. and Zyxibothrium healyae n. sp. are described from the deep-sea skates Brochiraja asperula and Brochiraja spinifera, respectively off New Zealand. The three new species share distinctive bothridia that bear a small number of large, circular, facial loculi and lateral bands of vitelline follicles that converge posterior to the ovary-features which are found in all other members of these genera. Zyxibothrium healyae n. sp. is unique in possessing three, rather than four or five, facial loculi. Zyxibothrium duffyi n. sp. possesses a combination of five facial loculi and vitelline follicles that stop short of the anterior margin of the proglottid. Pentaloculum grahami n. sp. is the largest member of the group with the greatest number of proglottids. Based on striking similarities in scolex morphology, Pentaloculum and Zyxibothrium have been hypothesized to belong to a distinct subgroup of "tetraphyllideans" provisionally designated as Clade 1. Based on sequence data for the D1-D3 region of the 28S rDNA gene generated for species of Zyxibothrium for the first time, we confirm the reciprocal monophyly of both genera as well as the monophyly of Clade 1 and its status as a distinct lineage among the "Tetraphyllidea". This work also suggests that the presence of five facial loculi is homoplasious given this character state is found in members of both genera. The new species expand the host associations of Clade 1 to include additional skate and carpet shark genera. Moving forward we would expect to find additional members of this group parasitizing other species of parascyliid carpet sharks as well as other species of the rajid genus Malacoraja and the arhynchobatid genus Brochiraja. Here we have doubled the number of described species in the taxon referred to as Clade 1 while simultaneously expanding our understanding of the morphology and anatomy of its members. This additional information will help inform the ultimate revision of the ordinal classification of the cestodes to address the highly polyphyletic nature of the order "Tetraphyllidea" as it is currently configured.

Nicotinic acetylcholine receptor structural pharmacology and gating transitions.

Our lab focuses on using structural and functional approaches to understand signaling by ligand-gated ion channels in the nervous system. A major emphasis is on understanding nicotinic receptor pharmacology from a structural perspective. Here I will present some of our recent work using the muscle-type nicotinic receptor from the Torpedo ray as a structurally tractable reference for the human receptor at the neuromuscular junction. I will focus on how toxins from animals and plants, as well as drugs used in the clinic, act on the receptor, and how we can use this information to understand state transitions that underlie ion channel gating. These studies have revealed a new class of allosteric site at the junction of the extracellular and transmembrane domains that small molecules can leverage to modulate channel desensitization. Our findings suggest that stabilizing a desensitized-like non-conducting state, through this allosteric site, is an important alternative mechanism for antagonizing the receptor.

Muscle-type nicotinic acetylcholine receptor structure, function, and pharmacology.

Nicotinic acetylcholine receptors mediate fast chemical transmission throughout the central and peripheral nervous systems. The nicotinic receptor subtype found on the motor endplate at the neuromuscular junction has been an important model system for understanding receptor structure, function, signaling, and pharmacology. The nicotinic receptor found in the electric organs of fish, including the Torpedo ray, is homologous to the human muscle-type nicotinic receptor and serves as an abundant natural source for biochemical and structural studies. Here we leverage the Torpedo nicotinic receptor in structural biology and electrophysiological studies to understand how clinically relevant drug classes regulate receptor conformation and activity. The findings reveal how different types of functional antagonists stabilize distinct non-conducting states to inhibit neuromuscular transmission.

Comparative cranio-mandibular myology of three species of Batoidea from the Southern Gulf of California, Mexico.

The mandibular apparatus of batoids (skates, electric rays, guitarfishes, stingrays, and sawfishes) is composed of a few skeletal elements to which the muscular bundles, responsible for all movements involved in the feeding mechanism, are inserted. The description of the different mandibular morphologies can help to understand the different feeding guilds in this group. In this study, we examined the cranio-mandibular myology of adult Rostroraja velezi, Narcine entemedor, and Zapteryx exasperata, three species of rays that coexist in the Southern Gulf of California, Mexico. This study described the muscles on the ventral and the dorsal surfaces for each species, identified the origins and insertions of these muscles, as well as the general characteristics of muscle morphology. There were 17 and 18 muscle bundles attached to the feeding apparatus, including five on the dorsal surface. Only the levator rostri, which elevates the rostrum during feeding, showed considerable differences in shape and size among species. The muscles of the adductor complex showed the greatest differences in size among the three species. N. entemedor presented the exclusive muscle X in the lower mandibular area and the extreme reduction of the coracohyoideus in the pharyngeal area derived from the absence of the basihyal cartilage. The information generated in our study supports the morphological specialization of electric rays (N. entemedor) for an almost exclusive suction feeding strategy.

Subcellular metal partitioning as a novel tool in ecotoxicological elasmobranch assessments: The case of lesser numbfish (Narcine brasiliensis) affected by the Mariana dam disaster in Southeastern Brazil

This study comprises a novel report on subcellular metal partitioning and metallothionein (MT) metal detoxification efforts in lesser numbfish (Narcine brasiliensis) electric ray specimens, as well as the first assessment on MT contents in any ray electric organ. Individuals sampled from an area in Southeastern Brazil affected by the Mariana dam rupture disaster were assessed concerning subcellular metal partitioning and MT metal-detoxification in the liver, gonads, electric organ and muscle of both adults and embryos. Yolk was also assessed when available. Relative total and heat-stable (bioavailable) metal and metalloid comparisons between adults and embryos in different developmental stages demonstrates maternal transfer of both total and bioavailable metals and significant MT associations demonstrate the detoxification of As, Ag, Mn, Ni, Cd, Co, Cu, Se and V through this biochemical pathway. Our findings expand the lacking ecotoxicological assessments for this near-threatened species and indicates significant ecological concerns, warranting further biomonitoring efforts.