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Nematoda of the genus Echinocephalus Molin, 1858 include species from the Gnathostomatidae family, the adult stages of which parasitize the stomach and spiral intestine of elasmobranchs as their final hosts. In the present study, we describe Echinocephalus spinosus n. sp. found parasitizing the spiral valve of the freshwater stingray Potamotrygon motoro from the Tapajós River, in the Amazon Basin, in the state of Pará, Brazil. In the study we performed morphological (light and scanning electron microscopy) and molecular (small subunit ribosomal ribonucleic acid (SSU rDNA) and mitochondrial cytochrome c oxidase I sequencing) analyses. E. spinosus n. sp. is only the second species of the Echinocephalus genus described from a strictly freshwater environment. The SSU rDNA based phylogenetic analyses showed Echinocephalus clade as a sister lineage of Gnathostoma, and that the new species arises as a sister to Echinocephalus cf. pseudouncinatus. Time-calibrated phylogenetic analysis revealed that the origin of the freshwater Echinocephalus coincides with the recently proposed origin of the freshwater host potamotrygonin stingray, namely the late Oligocene to early Miocene, when the western Amazon was dominated by the Pebas wetlands, an epicontinental marine/freshwater system. [ABSTRACT FROM AUTHOR]

The lack of clarity regarding the taxonomy of the ocellate river stingray (Potamotrygon motoro) and the absence of previous studies regarding its genetic diversity and population structure makes this species vulnerable to overexploitation, being now the second species of freshwater ray most extracted and exported for ornamental purposes in Colombia. The aim of this work was to determine the population genetic structure and genetic diversity of P. motoro in the Colombian Amazon and Orinoco basins. A total of 110 samples collected from six sub-basins of the Orinoco and in two sub-basins of the Amazon, were analyzed by amplification and sequencing of two fragments of the mitochondrial genes, Cytochrome oxidase subunit I (COI) (532 bp), and Cytochrome b (Cytb) (429 bp). Haplotype networks were constructed, followed by an analysis of molecular variance (AMOVA). The most probable number of genetic groups (K) was evaluated by means of Bayesian inference using BAPS. One shared haplotype was found between the Colombian Amazon and Orinoco basins for COI but no shared haplotypes were found for Cytb. A K of 4 was found, differentiating three of the four units by sub-basins. A high and significant FSTwas found when comparing the two basins, suggesting significant genetic differentiation between basins for both mitochondrial gene fragments. These results suggest that P. motoro populations in Colombia should be managed as independent units in each basin for conservation and extraction purposes. [ABSTRACT FROM AUTHOR]

Freshwater stingrays cause many serious human injuries, but identification of the offending species is uncommon. The present case involved a large freshwater stingray, Potamotrygon motoro (Chondrichthyes: Potamotrygonidae), in the Araguaia River in Tocantins, Brazil. Appropriate first aid was administered within ~15 min, except that an ice pack was applied. Analgesics provided no pain relief, although hot compresses did. Ciprofloxacin therapy commenced after ~18 h and continued seven days. Then antibiotic was suspended; however, after two more days and additional tests, cephalosporin therapy was initiated, and proved successful. Pain worsened despite increasingly powerful analgesics, until debridement of the wound was performed after one month. The wound finally closed ~70 days after the accident, but the patient continued to have problems wearing shoes even eight months later. Chemistry and pharmacology of Potamotrygon venom and mucus, and clinical management of freshwater stingray envenomations are reviewed in light of the present case. Bacterial infections of stingray puncture wounds may account for more long-term morbidity than stingray venom. Simultaneous prophylactic use of multiple antibiotics is recommended for all but the most superficial stingray wounds. Distinguishing relative contributions of venom, mucus, and bacteria will require careful genomic and transcriptomic investigations of stingray tissues and contaminating bacteria.

Sperm maturation, as a process through which spermatozoa acquire the ability for motility activation and fertilization, is well‐known for many groups of animals. This process takes place in a taxon‐specific manner in different parts of male reproductive tract. In contrast to most fish with external fertilization, a large number of animals have internal fertilization where transit through the epididymis of the male reproductive tract is necessary for the completion of sperm maturation. Although Chondrichthyes are fishes, they exhibit internal fertilization and possess specific male genital anatomy that resembles mammals. The existence of sperm maturation in the epididymis of cartilaginous fishes has been proposed but has yet to be confirmed. In this study, we used mature ocellate river stingrays Potamotrygon motoro, as a representative of Chondrichthyes, collected during the natural spawning period and evaluated sperm motility parameters during transit through the male reproductive tract, and upon contact with uterine fluid. Our data demonstrate that spermatozoa acquire motility after transit through the epididymis and are stored in a motile state within a specific organ – the seminal vesicles. Moreover, these motile spermatozoa are able to increase their velocity under the influence of uterine fluid in the female reproductive tract. Sexually mature ocellate river stingrays (Potamotrygon motoro, representative of Chondrichthyes) possess specific features of male gametes: (1) their spermatozoa acquire motility after leaving the testes during the transit through the epididymis; (2) thereafter spermatozoa are stored in a motile state within a specific male organ – the seminal vesicles; and (3) these motile spermatozoa are able to change their motility parameters under the influence of uterine fluid in the female reproductive tract. Based on the changes in these parameters during sperm transit through the male reproductive tract and upon contact with uterine fluid, we have confirmed the occurrence of epididymal sperm maturation and suggested the occurrence of capacitation stage in ocellate river stingrays. [ABSTRACT FROM AUTHOR]

Freshwater stingray accidents cause an immediate, intense, and unrelieved pain which is followed by edema, erythema and necrosis formation. Treatment for stingray envenomation is based on administration of analgesic, antipyretic and anti-inflammatory drugs. Concerning pain control, it is prescribed to immerse punctured limb on hot water to alleviate pain. There are no studies demonstrating specific targets on which stingray venom acts to promote pain. Therefore, the aim of this work was to investigate some mechanisms of Potamotrygon motoro venom (PmV) that contribute to nociception induction. Evaluating spontaneous pain behavior in mice injected i.pl. with PmV, it was seen that PmV induced both neurogenic and inflammatory pain. PmV also induced hyperalgesia in both mice and rats, evaluated through electronic von Frey and rat paw pressure test, respectively. Partial inhibition of hyperalgesia was observed in mice treated with cromolyn or promethazine, which indicated that mast cell and histamine via H1 receptor participate in the inflammatory pain. To search for some targets involved in PmVinduced hyperalgesia, the participation of TRPV1, calcium channels, neurokinins, CGRP, and norepinephrine, was evaluated in rats. It was seen that PmV-induced hyperalgesia occurs with the participation of neurokinins, mainly via NK1 receptor, CGRP, and calcium influx, through both P/Q and L-type voltage-dependent calcium channels, besides TRPV1 activation. The data presented herein indicate that PmV causes hyperalgesia in rodents which is dependent on the participation of several neuroinflammatory mediators. [ABSTRACT FROM AUTHOR]

An outbreak of a novel disease characterized by serious hemorrhage in the abdomen, ascites and bleaching of the liver was recorded in the freshwater cultured stingray Potamotrygon motoro , which is a cartilaginous fish related to sharks, in Panyu, Guangdong province of South China. The bacterial isolates from the lesions of diseased P. motoro exhibited the same phenotypic traits and biochemical characteristics and were identified for the first time as Citrobacter freundii according to biochemical characteristics and molecular identification with the 16S rRNA gene. In challenge trials, P. motoro injected intraperitoneal with the C. freundii P2 developed similar pathological signs to the naturally diseased fish. Furthermore, histopathology of diseased fish infected with C. freundii showed moderate lipid degeneration in the liver, macrophage aggregations of the lymphoid tissue in the spleen, and microglia aggregation in the brain. [ABSTRACT FROM AUTHOR]

The article presents a case study of a 13-year-old female captive-born orange-spot freshwater stingray with an acute caudodorsal swelling. The captive-born ocellate river stingray underwent an ultrasonography using manual restraint and revealed an irregular organized intracoelomic mass of mixed echogenicity. The orange-spot freshwater stingray has also underwent a surgical excision as well as radiation and chemotherapy for treating dysgerminomas.

Freshwater stingrays cause many serious human injuries, but identification of the offending species is uncommon. The present case involved a large freshwater stingray, Potamotrygon motoro (Chondrichthyes: Potamotrygonidae), in the Araguaia River in Tocantins, Brazil. Appropriate first aid was administered within ~15 min, except that an ice pack was applied. Analgesics provided no pain relief, although hot compresses did. Ciprofloxacin therapy commenced after ~18 h and continued seven days. Then antibiotic was suspended; however, after two more days and additional tests, cephalosporin therapy was initiated, and proved successful. Pain worsened despite increasingly powerful analgesics, until debridement of the wound was performed after one month. The wound finally closed ~70 days after the accident, but the patient continued to have problems wearing shoes even eight months later. Chemistry and pharmacology of Potamotrygon venom and mucus, and clinical management of freshwater stingray envenomations are reviewed in light of the present case. Bacterial infections of stingray puncture wounds may account for more long-term morbidity than stingray venom. Simultaneous prophylactic use of multiple antibiotics is recommended for all but the most superficial stingray wounds. Distinguishing relative contributions of venom, mucus, and bacteria will require careful genomic and transcriptomic investigations of stingray tissues and contaminating bacteria. [ABSTRACT FROM AUTHOR]

Ethnopharmacological relevance Animal oils and fats from the fishes Electrophorus electricus and Potamotrygon motoro , the reptiles Boa constrictor , Chelonoidis denticulata ( Geochelone denticulata ) and Melanosuchus niger and the riverine dolphin Inia geoffrensis are used as anti-inflammatory agents in the Peruvian Amazon. The aim of the study was to assess the topic anti-inflammatory effect of the oils/fats as well as to evaluate its antimicrobial activity and fatty acid composition. Materials and methods The oils/fats were purchased from a traditional store at the Iquitos market of Belen, Peru. The topic anti-inflammatory effect was evaluated by the mice ear edema induced by arachidonic acid (AA) and 12-O-tetradecanoylphorbol-13-acetate (TPA) at the dose of 3 mg oil/ear. Indomethacine and nimesulide were used as reference anti-inflammatory drugs. The application resembles the traditional topical use of the oils. The antimicrobial effect of the oils/fats was assessed by the microdilution test against reference strains of Escherichia coli , Staphylococcus aureus and Salmonella enteritidis . The fatty acid composition of the oils/fats (as methyl esters) was determined by GC and GC–MS analysis after saponification. Results All oils/fats showed topic anti-inflammatory activity, with better effect in the TPA-induced mice ear edema assay. The most active drugs were Potamotrygon motoro , Melanosuchus niger and Geochelone denticulata . In the AA-induced assay, the best activity was found for Potamotrygon motoro and Electrophorus electricus oil. The oil of Electrophorus electricus also showed a weak antimicrobial effect with MIC values of 250 µg/mL against Escherichia coli ATCC 25922 and Salmonella enteritidis -MI. The main fatty acids in the oils were oleic, palmitic and linoleic acids. Conclusions Topical application of all the oils/fats investigated showed anti-inflammatory activity in the mice ear edema assay. The effect can be related with the identity and composition of the fatty acids in the samples. This study gives support to the traditional use of animal oils/fats as ant-inflammatory agents in the Peruvian Amazon. However, new alternative should be encouraged due to the conservation status of several of the animal sources of the crude drugs. [ABSTRACT FROM AUTHOR]

Abstract: Invasion by bacteria can influence the course of healing of wounds acquired in aquatic environment. In this study, the bacteria present in Potamotrygon motoro stingray mucus and in the Alto Paraná river water were identified, and their ability to induce tissue injury and resist antibiotics was determined. Biochemical identification analysis showed that 97% of all bacterial isolates were Gram negative, Aeromonas spp., Enterobacter cloacae and Citrobacter freundii being the species most prevalent. Gelatinase and caseinase were produced by Aeromonas hydrophila, Aeromonas sobria and Pseudomonas aeruginosa strains. Erythrocyte hemolysis assay showed that A. sobria, A. hydrophila and to a lesser extent, other Gram-negative bacteria produced hemolysin. It was also observed that molecules released in culture by these bacteria were toxic to human epithelial cells. Antibiogram results showed that 68% of all bacterial isolates were resistant to at least one type of antibiotic, mainly B-lactams. Finally, it was demonstrated that although P. motoro venom was toxic to epithelial cells it did not influence bacterial proliferation. In summary, the results obtained in this work indicate that during the accident, the mucus of P. motoro and the environmental water may transfer into the wound pathogenic multi-resistant bacteria with the potential to cause severe secondary infections. [Copyright &y& Elsevier]

In the present study, Aeromonas (A.) hydrophila was isolated from a captive-bred adult freshwater stingray (Potamotrygon motoro) reared at a commercial aquarium in Korea. The stingray had bites on its fins, hemorrhages on the ventral part, and congested internal organs. A bacterium was isolated from kidney and subsequently identified as A. hydrophila. Based on phylogenetic analysis results, the isolate in the present study (SNUAh-LA1) was most closely related to A. hydrophila AH10 (China) and A. hydrophila AKR1 (Korea). It is most likely that the pathogen infection resulted from Potamotrygon motoro cohabiting with ricefish (Oryzias latipes). [ABSTRACT FROM AUTHOR]

Abstract: Freshwater stingrays (Potamotrygon motoro) are known to cause human accidents through a sting located in its tail. In the State of Goiás, this accident happens especially during the fishing season of the Araguaia River. The P. motoro venom extracted from the sting presented hyaluronidase activity. The enzyme was purified by gel filtration on Sephacryl S-100 and ion-exchange chromatography on SP-Sepharose. A typical procedure provided 376.4-fold purification with a 2.94% yield. The molecular weight of the purified enzyme was 79kDa as estimated by gel filtration on Sephacryl S-100. The K m and V max values for hyaluronidase, using hyaluronic acid as substrate, were 4.91μg/ml and 2.02U/min, respectively. The pH optimum for the enzyme was pH 4.2 and maximum activity was obtained at 40°C. The hyaluronidase from P. motoro was shown to be heat instable, being stabilized by bovine albumin and DTT, and inhibited by Fe2+, Mn2+, Cu2+ and heparin. [Copyright &y& Elsevier]

To test the hypothesis that the preference for ketone bodies rather than lipids as oxidative fuel in elasmobranchs evolved in response to the appearance of urea-based osmoregulation, we measured total non-esterified fatty acids (NEFA) in plasma as well as maximal activities of enzymes of intermediary metabolism in tissues from marine and freshwater elasmobranchs, including: the river stingray Potamotrygon motoro (<1 mmol l-1 plasma urea); the marine stingray Taeniura lymma, and the marine shark Chiloscyllium punctatum (>300 mmol l-1 plasma urea); and the euryhaline freshwater stingray Himantura signifer, which possesses intermediate levels of urea. H. signifer also were acclimated to half-strength seawater (15‰) for 2 weeks to ascertain the metabolic effects of the higher urea level that results from salinity acclimation. Our results do not support the urea hypothesis. Enzyme activities and plasma NEFA in salinity-challenged H. signifer were largely unchanged from the freshwater controls, and the freshwater elasmobranchs did not show an enhanced capacity for extrahepatic lipid oxidation relative to the marine species. Importantly, and contrary to previous studies, extrahepatic lipid oxidation does occur in elasmobranchs, based on high carnitine palmitoyl transferase (CPT) activities in kidney and rectal gland. Heart CPT in the stingrays was detectable but low, indicating some capacity for lipid oxidation. CPT was undetectable in red muscle, and almost undetectable in heart, from C. punctatum as well as in white muscle from T. lymma. We propose a revised model of tissue-specific lipid oxidation in elasmobranchs, with high levels in liver, kidney and rectal gland, low or undetectable levels in heart, and none in red or white muscle. Plasma NEFA levels were low in all species, as previously noted in elasmobranchs. D-β-hydroxybutyrate dehydrogenase (ᴅ-β-HBDH) was high in most tissues confirming the importance of ketone bodies in elasmobranchs. However, very low ᴅ-β-HBDH in kidney from T. lymma indicates that interspecific variability in ketone body utilization occurs. A negative relationship was observed across species between liver glutamate dehydrogenase activity and tissue or plasma urea levels, suggesting that glutamate is preferentially deaminated in freshwater elasmobranchs because it does not need to be shunted to urea production as in marine elasmobranchs. [ABSTRACT FROM AUTHOR]

Hunting tactics of potamotrygonid freshwater rays remain unreported under natural conditions. Three main foraging tactics of Potamotrygon falkneri and P. motoro are described here based on underwater observations in the upper Paraná River. Both species displayed similar behaviors. The most common tactic was to undulate the disc margins close to, or on, the bottom and thus stirring the substrate and uncovering hidden preys. Another tactic was to charge upon prey concentrated in the shallows. The least common tactic was to pick out prey adhered to the substrate. The first tactic is widespread in several species of marine rays in the Dasyatidae, whereas the remainder (especially picking up prey on substrata above water surface) may be restricted to the Potamotrygonidae.

Potamotrygon boesemani, new species, is described from the Corantijn river drainage in Surinam. The species has a diagnostic dorsal color pattern formed by deep orange to red ocellated spots of irregular form, encircled by relatively broad black rings. Potamotrygon boesemani is distinguished from other ocellated congeners (P. motoro, P. henlei and P. leopoldi) by the more intensely colored ocelli, which are usually yellow in the latter species. From P. motoro it is also distinguished by the darker dorsal background coloration, by the broader black contour of the dorsal ocelli, and by the irregular form of the ocelli as compared to the more rounded shape in the latter species. From P. henlei and P. leopoldi, it is distinguished by the lack of ocelli on tail. From the tentatively identified specimen of P. ocellata, which also has dark orange ocelli, the irregular contour of the ocelli in the new species is also distinctive. The teeth are relatively smaller and in greater number than in P. motoro and P. ocellata, with up to 45 rows in the upper jaw.

We determined the first complete mitochondrial genome sequence ofPotamotrygon motorofrom South American freshwater stingrays. The total length ofP. motoromitogenome is 17,448 bp, which consists of 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and a control region, with the genome organization and gene order being identical to that of the typical vertebrate. The overall nucleotide composition is 32.3% A, 24.4% T, 30.5% C and 12.8% G. These data will provide useful molecular information for phylogenetic relationships within the family Potamotrygonidae species. [ABSTRACT FROM PUBLISHER]