Morphology and phylogenetic relationships of a remarkable new genus and two new species of Neotropical freshwater stingrays from the Amazon basin (Chondrichthyes: Potamotrygonidae)

The morphology and phylogenetic relationships of a new genus and two new species of Neotropical freshwater stingrays, family Potamotrygonidae, are investigated and described in detail. The new genus, Heliotrygon, n. gen., and its two new species, Heliotrygon gomesi, n. sp. (type-species) and Heliotrygon rosai, n. sp., are compared to all genera and species of potamotrygonids, based on revisions in progress. Some of the derived features of Heliotrygon include its unique disc proportions (disc highly circular, convex anteriorly at snout region, its width and length very similar), extreme subdivision of suborbital canal (forming a complex honeycomb-like pattern anterolaterally on disc), stout and triangular pelvic girdle, extremely reduced caudal sting, basibranchial copula with very slender and acute anterior extension, and precerebral and frontoparietal fontanellae of about equal width, tapering very little posteriorly. Both new species can be distinguished by their unique color patterns: Heliotrygon gomesi is uniform gray to light tan or brownish dorsally, without distinct patterns, whereas Heliotrygon rosai is characterized by numerous white to creamy-white vermiculate markings over a light brown, tan or gray background color. Additional proportional characters that may further distinguish both species are also discussed. Morphological descriptions are provided for dermal denticles, ventral lateral-line canals, skeleton, and cranial, hyoid and mandibular muscles of Heliotrygon, which clearly corroborate it as the sister group of Paratrygon. Both genera share numerous derived features of the ventral lateral-line canals, neurocranium, scapulocoracoid, pectoral basals, clasper morphology, and specific patterns of the adductor mandibulae and spiracularis medialis muscles. Potamotrygon and Plesiotrygon are demonstrated to share derived characters of their ventral lateral-line canals, in addition to the presence of angular cartilages. Our morphological phylogeny is further corroborated by a molecular phylogenetic analysis of cytochrome b based on four sequences (637 base pairs in length), representing two distinct haplotypes for Heliotrygon gomesi. Parsimony analysis produced a single most parsimonious tree revealing Heliotrygon and Paratrygon as sister taxa (boot-strap proportion of 70%), which together are the sister group to a clade including Plesiotrygon and species of Potamotrygon. These unusual stingrays highlight that potamotrygonid diversity, both in terms of species composition and undetected morphological and molecular patterns, is still poorly known.

Freshwater stingrays: study of epidemiologic, clinic and therapeutic aspects based on 84 envenomings in humans and some enzymatic activities of the venom

Freshwater stingrays are very common in the Parana, Paraguay, Araguaia, and Tocantins Rivers and tributaries in Brazil. This study presents the clinical aspects of 84 patients injured by freshwater stingrays. Intense pain was the most conspicuous symptom. Skin necrosis was observed in a high percentage of the victims, mostly fishermen and bathers. The initial therapeutic procedures, like immersion of the affected member in hot water were effective in the initial phases of the envenoming, especially in the control of the acute pain; however, they did not prevent skin necrosis. By SDS-PAGE, the freshwater stingray (Potamotrygon falkneri) venom extract presented a major band of approximately 12 kDa. Several other components distributed between 15 and 130 kDa were detected in the venom extract. Many components with molecular mass above 80 and 100 kDa have gelatinolytic and caseinolytic activities, respectively. Hyaluronidase activity was detected only in a component around 84 kDa in P. falkneri venom extract. Our results demonstrated that the presence of these enzymes could explain partially the local clinical pictures presented by patients wounded by freshwater stingray. (C) 2004 Elsevier Ltd. All rights reserved.

The 5S rDNA family evolves through concerted and birth-and-death evolution in fish genomes: an example from freshwater stingrays

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Preliminary data on the feeding habits of the freshwater stingrays Potamotrygon falkneri and Potamotrygon motoro (Potamotrygonidae) from the Upper Paraná River basin, Brazil

As raias da família Potamotrygonidae representam um grupo singular da ictiofauna Neotropical. Apesar de serem antigos os relatos sobre o grupo, ainda são muitas as questões que permanecem sem resposta, sobretudo no que diz respeito à biologia das espécies que ocorrem na Bacia do Paraná-Paraguai. No presente trabalho foi analisada a dieta de Potamotrygon falkneri e Potamotrygon motoro, capturadas no Alto Rio Paraná, a jusante da Usina Hidrelétrica Engenheiro Souza Dias (UHE Jupiá). As duas espécies de raias apresentaram dieta diversificada, ingerindo 14 itens, entre moluscos, crustáceos, insetos e peixes, porém com predominância de insetos aquáticos em diversidade e abundância. Somente um indivíduo de cada espécie ingeriu peixe. Potamotrygon motoro consumiu principalmente Ephemeroptera, enquanto P. falkneri, principalmente Mollusca, Hemiptera e Trichoptera. Os dados aparentemente indicam uma dieta mais especializada de P. motoro, com maior consumo de Ephemeroptera (Baetidae), e uma dieta mais generalizada de P. falkneri. A análise dos indivíduos capturados em três micro-hábitats, que diferem quanto ao tipo de substrato e presença de vegetação marginal, sugere diferenças nos tipos de alimentos consumidos.

Occurrence of freshwater stingrays (Chondrichthyes: Potamotrygonidae) in the Uruguay River and its tributaries, Uruguay, South America.

Four records of potamotrygonids in the Uruguay River and its tributaries in Paysandu, Uruguay are reported in this paper. The first one was a specimen caught in 1934, of undetermined sex and weighing 120 kg and with a disc width of ca 150 cm. The second specimen, caught in 1998, was also of undetermined sex; it weighed 50 kg total weight and its disc width measured 103 cm. The third specimen was caught in 2001; it was an adult male, weighed 114 kg total weight and its disc width measured ca 110 cm. The fourth one, caught in 2004, was a female, 11 kg in total weight and with a disc width of 80 cm. According to the size and general description, specimens were identified as Potamotrygon brachyura, to date the only potamotrygonid confirmed for Uruguay.

Morphological characterization of the venom secretory epidermal cells in the stinger of marine and freshwater stingrays

Marine and freshwater stingrays are characterized by the presence of one to three mineralized serrated stingers on the tail, which are covered by epidermal cells secreting venom. When these animals are dorsally touched, the stinger can be introduced into the aggressor by a whip reflex mechanism of the tail, causing severe mechanical injuries and inoculating the venom. Accidents in humans are frequent causing intense local pain, oedema and erythema. Bacterial secondary infection is also common. In addition, injuries involving freshwater stingrays frequently cause a persistent cutaneous necrosis. The exact localization of the venom secretory epidermal cells in the stinger is controversial, but it is known that it is preferentially located in the ventrolateral grooves. A comparative morphological analysis of the stinger epidermal tissue of different marine and freshwater Brazilian stingray species was carried out. The results indicate that in freshwater species there is a larger number of protein secretory cells, of two different types, spread over the whole stinger epidermis, while in marine species the protein secretory cells are located only around or inside the stinger ventrolateral grooves. These differences between the stingers of the two groups can justify the more severe envenomation accidents with the freshwater species when compared with the marine species. (c) 2007 Elsevier Ltd. All rights reserved.

Histopathological changes induced by extracts from the tissue covering the stingers of Potamotrygon falkneri freshwater stingrays

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Injuries by marine and freshwater stingrays: history, clinical aspects of the envenomations and current status of a neglected problem in Brazil

Stingrays are a group of rays - cartilaginous fish related to sharks - that have whiplike tails with barbed, usually venomous spines and are found around the world, especially the marine species. Despite recent reports of accidents involving these fish, they are not aggressive, reacting only when stepped on or improperly handled. Injuries by stingrays are seldom mentioned by historians, although they have always been present in riverine communities of inland waters and in South American coasts. Indeed, envenomations by stingrays are quite common in freshwater and marine fishing communities. Although having high morbidity, such injuries are neglected because they have low lethality and usually occur in remote areas, which favor the use of folk remedies. In the present review article, historical aspects of injuries caused by stingrays in Brazil and their distribution on the coast of Sao Paulo state and riverine communities of the North, Midwest and Southeast regions were studied. In addition, other aspects were analyzed such as clinical features, therapeutic methods, preventive measures and trends in occurrence of these accidents in the country, particularly in areas in which freshwater stingrays had not been previously registered, being introduced after breaching of natural barriers.

Cleaning interactions between shrimps (Palaemonidae) and freshwater stingrays (Potamotrygonidae) in the Parana River, Southeastern Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

First identification of interspecies hybridization in the freshwater stingrays Potamotrygon motoro and P-falkneri (Myliobatiformes, Potamotrygonidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comparative study on extracts from the tissue covering the stingers of freshwater (Potamotrygon falkneri) and marine (Dasyatis guttata) stingrays

Stingrays are elasmobranchs found along the seacoast and in some rivers of Brazil. Pain is the most conspicuous symptom observed in patients wounded by the bilaterally retroserrate stingers located in the tail, which are covered by glandular and integument tissues. In addition, cutaneous necrosis is commonly observed in injuries caused by freshwater stingrays. The aim of this work was to characterize and compare certain properties of tissue extracts obtained from the glandular tissues covering the stinger apparatus of Potamotrygon falkneri and Dasyatis guttata stingrays. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), tissue extracts have similar bands above 80kDa, but most differences were observed below this molecular mass. Lethal, dermonecrotic and myotoxic activities were detected only in P. falkneri tissue extract. Edematogenic activity was similar and dose dependent in both tissue extracts. Nociceptive activity was verified in both tissue extracts, but P. falkneri presented a two-fold higher activity than D. guttata tissue extract. No direct hemolysis, phospholipase A(2) and coagulant activities were observed in both tissue extracts. Antigenic cross-reactivity was noticed by ELISA and Western blotting, using antisera raised in rabbits. Species-specific sera reacted with several components of both tissue extracts, noticeably above 22 kDa. Both tissue extracts presented gelatinolytic, caseinolytic and fibrinogenolytic activities, which were not caused by the action of metalloproteinases. Hyaluronidase activity was detected only in P. falkneri tissue extract. Our experimental observations suggest that P. falkneri tissue extract is more toxic than D. guttata tissue extract. These results may explain why injuries caused by freshwater stingrays are more severe in human accidents. (c) 2007 Elsevier Ltd. All rights reserved.

Activity and habitat use of two species of stingrays (Myliobatiformes: Potamotrygonidae) in the upper Paraná River basin, Southeastern Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A new species of Potamotrygonocestus Brooks & Thorson, 1976 (Eucestoda : Tetraphyllidea) from Plesiotrygon iwamae Rosa, Castello & Thorson (Mylliobatoidea : Potamotrygonidae) and a redescription of Potamotrygonocestus chaoi Marques, Brooks & Araujo, 2003

Potamotrygonocestus Brooks & Thorson, 1976 is currently represented by six recognised species of tetraphyllidean cestodes inhabiting Neotropical freshwater stingrays. Potamotrygonid stingrays examined to date have included only a single specimen of Plesiotrygon iwamae. Only one species of tetraphyllidean, Potamotrygonocestus chaoi Marques, Brooks & Araujo, 2003, has been described from this host, and this description was based on limited material. New efforts to document the diversity in this host species resulted in the collection of eight additional specimens of P. iwamae, one of these from the upper Rio Solimoes, at Sao Paulo de Olivenca Amazonas during September, 2003, and seven from the Baia do Marajo, Para, during November, 2003. The specimen from the upper Solimoees was found to be infected with P. chaoi. Voucher material from this stingray was used for the redescription of this cestode, which is characterized by strobila 8.78-22.83 mm long and a great number of proglottides, 58-93; the new material provided strobilar length and proglottis counts for complete worms. Potamotrygonocestus marajoara n. sp. is the second species of this genus reported from Plesiotrygon iwamae, although it appears to be restricted to the lower Amazon. This new species resembles P. chaoi in possessing filitriches and blade-like spinitriches on the scolex, cephalic peduncle and cirrus, but differs from other species of the genus in the number of testes, which is 44 on average per proglottis, and by having apical sucker measuring 95-175 mu m in length. Additional data on the distribution and morphology of the microtriches and a detailed description of the female reproductive system are also provided in this study.

Arraias em rios da região Sudeste do Brasil: locais de ocorrência e impactos sobre a população

INTRODUÇÃO: No presente trabalho objetivamos descrever o processo de colonização da Bacia do Alto Paraná, Sudeste do Brasil, por arraias, demonstrando sua atual situação e provável tendência, os impactos gerados e discutindo algumas ações de manejo e medidas mitigadoras. MÉTODOS: Foram realizadas entrevistas com ribeirinhos e profissionais de saúde para o levantamento de informações sobre a ocorrência de arraias e acidentes associados a estes animais, além de coletas e observações subaquáticas de potamotrigonídeos, entre 2004 e 2009, em localidades situadas nos Estados de São Paulo, Paraná e Mato Grosso do Sul, no Sudeste, Sul e parte do Centro-Oeste do Brasil. RESULTADOS: Três espécies de arraias foram identificadas na área de estudo, demonstrando utilizar os caminhos abertos pela Hidrovia Tietê-Paraná para se dispersarem. Dezesseis vítimas de acidentes envolvendo esses animais foram encontradas, notadamente banhistas e pescadores, chamando a atenção pelo fato dos casos não serem notificados e apresentarem elevada morbidade, com marcante incapacidade temporária para o trabalho. CONCLUSÕES: Este é o primeiro relato de invasão biológica envolvendo espécies de elasmobrânquios conhecido na literatura e, pelas arraias estarem colonizando áreas densamente povoadas e ampliando sua área de distribuição a cada ano, é de se esperar que sua interação negativa com humanos se intensifique, provocando alterações importantes no perfil epidemiológico dos acidentes por animais peçonhentos ocorridos no sudeste brasileiro.

Registro de ocorrência de duas espécies de potamotrigonídeos na região do Alto Rio Paraná e algumas considerações sobre sua biologia

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)