RESUMO
Herein, we report three new separate cases of human envenomations by Micrurus hemprichii for the Amazon, which is a biome where envenomations by Micrurus are seldom reported. Two women were bitten after stepping on the snakes and one man was bitten while handling the animal. All cases occurred in the peridomicile, in rural areas. The first case evolved mainly to local symptoms, but the patient was discharged before the identification of the snake and had to be called back for observation before being eventually discharged. In the second case, the patient presented transitory dyspnea and she was discharged after four days in hospital. In the third case, the patient showed only local symptoms, but he was about to receive unnecessary antivenom against coral snakes. Cases like these show the importance of educational problems regarding local venomous snakes in order to avoid bites and to provide the correct hospital treatment. For this, trained professionals in cases involving venomous animals are needed.
Assuntos
Cobras Corais , Mordeduras de Serpentes , Masculino , Animais , Humanos , Feminino , Mordeduras de Serpentes/terapia , Brasil , Antivenenos , Venenos Elapídicos , SerpentesRESUMO
In the present study, we investigated the cardiotoxic potential of Micrurus frontalis venom. Twelve guinea pigs (Cavia porcellus) were distributed in two groups (n = 6), named control and envenomed. Control groups received 0.2 ml of PBS/BSA, while envenomed group received 0.2 ml of the same solution containing 450 µg/kg of M. frontalis venom. Both were intramuscular injections. Electrocardiography, echocardiogram, blood count, and serum biochemistry were performed before and 2 h after inoculation. Necropsy was performed, and histological and ultrastructural analysis of the heart were conducted. First clinical signs were presented as early as 18 min after venom inoculation. All poisoned animals presented flaccid paralysis of both hind and forelimbs, followed by fasciculations and respiratory arrythmia. However, the animals did not die in the first 2 h of poisoning. ECG of the poisoned animals revealed severe ventricular arrythmias, corroborated by reduction of both ejection and shortening fractions, increase in CK, CK-MB, troponin, cardiomyocyte degeneration, fragmentation and mitochondrial damage. M. frontalis venom causes severe heart damage, eliciting both morphological and arrhythmogenic effects after only 2 h of envenomation.
Assuntos
Arritmias Cardíacas/induzido quimicamente , Cardiomiopatias/induzido quimicamente , Venenos Elapídicos/toxicidade , Frequência Cardíaca/efeitos dos fármacos , Miocárdio/patologia , Disfunção Ventricular Esquerda/induzido quimicamente , Função Ventricular Esquerda/efeitos dos fármacos , Animais , Arritmias Cardíacas/sangue , Arritmias Cardíacas/patologia , Arritmias Cardíacas/fisiopatologia , Biomarcadores/sangue , Cardiomiopatias/sangue , Cardiomiopatias/patologia , Cardiomiopatias/fisiopatologia , Cardiotoxicidade , Cobras Corais , Cobaias , Masculino , Miocárdio/metabolismo , Necrose , Fatores de Tempo , Disfunção Ventricular Esquerda/sangue , Disfunção Ventricular Esquerda/patologiaRESUMO
In this study, we investigated the action of varespladib (VPL) alone or in combination with a coral snake antivenom (CAV) on the local and systemic effects induced by Micrurus corallinus venom in rats. Adult male Wistar rats were exposed to venom (1.5 mg/kg - i.m.) and immediately treated with CAV (antivenom:venom ratio 1:1.5 'v/w' - i.p.), VPL (0.5 mg/kg - i.p.), or both of these treatments. The animals were monitored for 120 min and then anesthetized to collect blood samples used for haematological and serum biochemical analysis; after euthanasia, skeletal muscle, renal and hepatic tissue samples were collected for histopathological analysis. M. corallinus venom caused local oedema without subcutaneous haemorrhage or apparent necrosis formation, although there was accentuated muscle morphological damage; none of the treatments prevented oedema formation but the combination of CAV and VPL reduced venom-induced myonecrosis. Venom caused neuromuscular paralysis and respiratory impairment in approximately 60 min following envenomation; CAV alone did not prevent the neurotoxic action, whereas VPL alone prevented neurotoxic symptoms developing as did the combination of CAV and VPL. Venom induced significant increase of serum CK and AST release, mostly due to local and systemic myotoxicity, which was partially prevented by the combination of CAV and VPL. The release of hepatotoxic serum biomarkers (LDH and ALP) induced by M. corallinus venom was not prevented by CAV and VPL when individually administered; their combination effectively prevented ALP release. The venom-induced nephrotoxicity (increase in serum creatinine concentration) was prevented by all the treatments. VPL alone or in combination with CAV significantly prevented the venom-induced lymphocytosis. In conclusion, VPL shows to be effective at preventing the neurotoxic, nephrotoxic, and inflammatory activities of M. corallinus venom. In addition, VPL acts synergistically with antivenom to prevent a number of systemic effects caused by M. corallinus venom.
Assuntos
Acetatos/farmacologia , Cobras Corais/fisiologia , Venenos Elapídicos/toxicidade , Indóis/farmacologia , Cetoácidos/farmacologia , Inibidores de Fosfolipase A2/farmacologia , Animais , Biomarcadores/sangue , Transtornos da Coagulação Sanguínea/induzido quimicamente , Transtornos da Coagulação Sanguínea/tratamento farmacológico , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , L-Lactato Desidrogenase/sangue , Fármacos Neuroprotetores/farmacologia , Fosfolipases A2/genética , Fosfolipases A2/metabolismo , Ratos , Ratos WistarRESUMO
We report a case of predation of a large specimen of the Dipsas neuwiedi by a Micrurus corallinus, in the state of Santa Catarina, Brazil. The ingestion reported here is one of the greatest prey / predator ratios registered for genus Micrurus in nature. In this predation event, the ingestion of a large prey limited the M. corallinus locomotion, which did not offer resistance and was not able to move efficiently during the capture.
RESUMO
The Elapidae family comprises 35 snake species in Brazil, with Micrurus ibiboboca being widely distributed in the northeast of the country. Despite the high number of Micrurus species in Brazil, there are few cases of human envenomation in literature. This study describes a clinical report of envenomation due to the bite of M. ibiboboca in the State of Pernambuco, Northeast Brazil, that took place in 2017. The patient presented symptoms of muscle paralysis and sweating. He was admitted to the intensive care unit. A total of 10 ampoules of anti-elapidic serum were administered. The patient complained of local pain that extended through the arm, paresthesia in the lower limbs, headache, and chest pain. Changes in the visual, respiratory, and neurological systems were not observed. This clinical case report on coral snake poisoning is useful for increasing the knowledge on the toxicological action of snake poison and its effect on injured individuals, thereby helping in the clinical evaluation and treatment.(AU)
A família Elapidae compreende 35 espécies de serpentes no Brasil, com Micrurus ibiboboca amplamente distribuída no Nordeste. Apesar do elevado número de espécies de Micrurus no Brasil, são poucos os casos de envenenamento humano na literatura. Descrevemos aqui um relato clínico de envenenamento por picada de M. ibiboboca no Estado de Pernambuco, Nordeste do Brasil, ocorrido em 2017. O paciente apresentava sintomas de paralisia muscular e sudorese. Ele foi internado na Unidade de Terapia Intensiva. Um total de 10 ampolas de soro anti-elapídico foi administrado. O paciente queixava-se de dor local que se estendia pelo braço, parestesia em membros inferiores, cefaleia e dor torácica. Não foram observados alterações nos sistemas de visão, respiratório e neurológico. Este relato de caso clínico de intoxicação por cobra coral é útil para aumentar o conhecimento sobre a ação toxicológica da peçonha da serpente e seu efeito sobre os acidentados, auxiliando na avaliação clínica e no tratamento.(AU)
La familia Elapidae comprende 35 especies de serpientes en Brasil como la Micrurus ibiboboca ampliamente distribuidas en el Noreste. A pesar de lo alto número de especies de Micrurus en Brasil, hay pocos casos de envenenamiento humano en la literatura. Describimos aquí un informe clínico de envenenamiento por mordedura de M. ibiboboca en el estado de Pernambuco, Noreste de Brasil, ocurrido en 2017. El paciente presentaba síntomas de parálisis muscular y sudoración. Fue ingresado en la unidad de cuidados intensivos. Se administraron un total de 10 ampollas de suero antielapídico. El paciente se quejaba de dolor local que se extendía por el brazo, parestesias en las extremidades inferiores, cefalea y dolor torácico. No se observaron cambios en los sistemas visual, respiratorio y neurológico. Este informe de caso clínico sobre la intoxicación por serpiente coral es útil para aumentar el conocimiento sobre la acción toxicológica del veneno de serpientes y su efecto en los individuos lesionados, ayudando así en la evaluación clínica y el tratamiento.(AU)
Assuntos
Animais , Intoxicação , Mordeduras de Serpentes , Cobras CoraisRESUMO
Micrurus surinamensis is a coral snake from the Elapidae family of wide distribution in Amazonia Forest. Its venom contains neurotoxins that induce muscular and respiratory paralysis; however, its cardiovascular action is not yet characterized. The aim of this study was to investigate the cardiotoxic effects caused by M. surinamensis poisoning in rodents. Twelve guinea pigs (Cavia porcellus) were distributed in two groups (n = 6) named as control and envenomed. The control group received 0.2 ml of PBS/BSA via intramuscular injection (IM), while envenomed animals received 0.75 µg of venom per g of body weight, also via IM. Electrocardiographic examination (ECG) and biochemical serum tests were conducted before and 2 h after inoculation. ECG of the envenomed animals revealed severe progressive arrhythmias including atrioventricular block, supraventricular, and ventricular extrasystoles. Serum biochemistry showed significant increase in CK, CK-MB, and LDH enzymes corroborating the skeletal and cardiac muscle damage. Myonecrosis and degeneration were observed in both skeletal and heart muscle; nevertheless, transmission electron microscopy revealed cardiac muscle fibers fragmentation. In conclusion, M. surinamensis venom has a potent cardiotoxic activity eliciting arrhythmogenic effects and heart damage after only 2 h of envenomation.
Assuntos
Arritmias Cardíacas/induzido quimicamente , Cobras Corais , Venenos Elapídicos/toxicidade , Animais , Arritmias Cardíacas/fisiopatologia , Complexos Atriais Prematuros/induzido quimicamente , Complexos Atriais Prematuros/fisiopatologia , Bloqueio Atrioventricular/induzido quimicamente , Bloqueio Atrioventricular/fisiopatologia , Cardiotoxicidade , Cobaias , Frequência Cardíaca/efeitos dos fármacos , Masculino , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/patologia , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/ultraestrutura , Necrose , Fatores de Tempo , Complexos Ventriculares Prematuros/induzido quimicamente , Complexos Ventriculares Prematuros/fisiopatologiaRESUMO
Abstract Introduction: Snakes of the genus Micrurus have fossorial habits, passive temperament and scarce production of powerful venom with neurotoxic characteristics that block the synaptic transmission at the neuromuscular junction. Objective: To present an overview of the neurotoxicity of the Micrurus snake venom, and its functional characterization by ex vivo analysis methods. Materials and methods: A literature review was conducted in MedLine and ScienceDirect using specific terms and their combinations. Search strategy: type of studies: articles on the neurotoxicity of Micrurus snake venom and techniques to determine its neurotoxic activity by in vitro, in vivo and ex vivo models; publication period: articles published until June 2018; publication language: English and Spanish. Results: Out of 88 studies identified in the initial search, 28 were excluded because they did not meet the inclusion criteria (based on reading their titles and abstracts). 8 additional articles (books and reports) were included, since, according to the authors' opinion, they complemented the information reported by the selected studies. The studies included in the review (n=68) were original research papers (n=44), review articles (n = 16), and book chapters, reports, guides and online consultations (n=8). Conclusions: Studies performed using ex vivo muscle and nerve preparations to evaluate the effect of neurotoxins provide a good model for the characterization of the pre-synaptic and post-synaptic effect of the venom produced by snakes of the genus Micrurus.
Resumen Introducción. Las serpientes del género Micrurus son animales de hábitos fosoriales, de temperamento pasivo y escasa producción de un potente veneno con características neurotóxicas que bloquean la transmisión sináptica en la placa neuromuscular. Objetivo. Presentar un panorama general de la neurotoxicidad del veneno de las serpientes Micrurus y su caracterización funcional mediante métodos de análisis ex vivo. Materiales y métodos. Se realizó una revisión de la literatura en MedLine y ScienceDirect usando términos específicos y sus combinaciones. Estrategia de búsqueda: tipo de estudios: artículos sobre la neurotoxicidad del veneno de serpientes Micrurus y técnicas para determinar su actividad neurotóxica mediante modelos in vitro, in vivo y ex vivo; periodo de publicación: sin límite inicial a junio de 2018; idiomas: inglés y español. Resultados. De los 88 estudios identificados en la búsqueda inicial, se excluyeron 28 por no cumplir los criterios de inclusión (basándose en la lectura de títulos y resúmenes); además, se incluyeron 8 documentos adicionales (libros e informes), que, a criterio de los autores, complementaban la información reportada por las referencias seleccionadas. Los estudios incluidos en la revisión (n=68) correspondieron a las siguientes tipologías: investigaciones originales (n=44), artículos de revisión (n=16) y capítulos de libros, informes, guías y consultas en internet (n=8). Conclusiones. Los estudios que describen el uso de preparaciones ex vivo de músculo y nervio para evaluar el efecto de neurotoxinas ofrecen un buen modelo para la caracterización del efecto presináptico y postsináptico del veneno producido por las serpientes Micrurus.
Assuntos
Humanos , Elapidae , Cobras Corais , Junção Neuromuscular , Fosfolipases A2RESUMO
Envenomation by coral snakes represents a little known burden in Brazilian Amazonia. So far, details on clinical and epidemiological aspects remain obscure in the region. We gathered data from medical charts and from the scientific collection of snakes from Fundação de Medicina Tropical Doutor Heitor Vieira Dourado, finding 26 cases of envenomation by five species of Micrurus in Manaus region, between 1987 and 2018. They represent 0.7% of the snakebites treated in the hospital since the records began, in 1979. Micrurus lemniscatus was responsible for most of the bites (10), followed by M. hemprichii (five), M. spixii (three), M. surinamensis (three) and M. averyi (one). There was no difference between the sexes of the snakes that caused bites. Patients were mostly males, and most of the cases were reported in urban areas. Bites predominated in dry season, and there was a clear geographical segregation among species. We describe seven cases of envenomation, three mild and four severe, all of which evolved to cure. Paresthesia (six), pain (five) and edema (four) were the most common local symptoms. Systemic features such as dyspnea/shallow breath (four), palpebral ptosis (four), blurred vision (three), dysarthria (three) and difficulty to walk (three) were also detected. Two patients bitten by Micrurus sp. and M. hemprichii, showed slight increased serum levels of creatine kinase (reference level <190 U/L), 1184 U/L and 1229 U/L, respectively, indicative of mild systemic myotoxicity. This is the first report of myotoxic manifestation in the envenomation by M. hemprichii. No patient developed respiratory failure, though one bitten by an adult M. spixii required intubation and mechanical ventilation due to decreased level of consciousness during evolution, probably related to induced sedation caused by concurrent alcohol intoxication. All patients were treated with Brazilian Micrurus antivenom (soro antielapídico, median = 10 vials). Six patients were pretreated intravenously with H1 and H2 antagonists and steroids, with two patients developing early adverse reactions. The median length of hospital stay was four days. Envenomations by coral snakes in Manaus region are clinically severe, but rare and sparsely distributed over time, making the detection of epidemiological and clinical patterns a challenge for public health.
Assuntos
Cobras Corais , Mordeduras de Serpentes/epidemiologia , Adolescente , Adulto , Animais , Brasil/epidemiologia , Creatina Quinase , Edema , Feminino , Humanos , Masculino , Dor , ParestesiaRESUMO
Coral snakes constitute a relatively diverse and little known group of venomous snakes. So far, data for this kind of snakebite in the Amazon region are based only on case reports. This study takes advantage of novel data from the Brazilian Health Ministry database from 2010 to 2015 and presents a review of the cases reported in the literature regarding the Amazonian biome both from Brazil and nearby countries. Thirty-four cases reported in the database were used in the study, representing 0.05% of the snakebites in Brazilian Amazonia for that period. The incidence rate was 0.123 cases/100,000 inhabitants/year. The most affected group is that of working age men, suggesting occupational risk. Most of bites were on lower limbs. Pain, edema and paresthesia were the most common symptoms. Systemic symptoms not usually associated with coral snakes envenomings, such as coagulopathy and thrombocytopenia, have been reported in Amazonia. Five patients received less antivenom than indicated by the Health Ministry. Based on these results, we recommend the execution of educational programs to avoid such accidents and to teach both the general public and health professionals the correct treatment for the bites. We also suggest that the covering of Intensive Care Units in the region needs to be improved to avoid deaths.
Assuntos
Cobras Corais , Mordeduras de Serpentes/epidemiologia , Animais , Brasil/epidemiologia , Edema , Feminino , Humanos , Masculino , Dor , ParestesiaRESUMO
The evolution of an aquatic lifestyle from land dwelling venomous elapids is a radical ecological modification, bringing about many evolutionary changes from morphology to diet. Diet is an important ecological facet which can play a key role in regulating functional traits such as venom composition and prey-specific targeting of venom. In addition to predating upon novel prey (e.g., fish, fish eggs and invertebrates), the venoms of aquatic elapids also face the challenge of increased prey-escape potential in the aquatic environment. Thus, despite the independent radiation into an aquatic niche on four separate occasions, the venoms of aquatic elapids are evolving under convergent selection pressures. Utilising a biolayer interferometry binding assay, this study set out to elucidate whether crude venoms from representative aquatic elapids were target-specific to the orthosteric site of postsynaptic nicotinic acetylcholine receptor mimotopes of fish compared to other terrestrial prey types. Representatives of the four aquatic lineages were: aquatic coral snakes representative was Micrurus surinamensis;, sea kraits representative was Laticauda colubrina; sea snakes representatives were two Aipysurus spp. and eight Hydrophis spp; and water cobras representative was Naja annulata. No prey-specific differences in crude venom binding were observed from any species tested, except for Aipysurus laevis, which showed slight evidence of prey-potency differences. For Hydrophis caerulescens, H. peronii, H. schistosus and M. surinamensis, there was a lack of binding to the orthosteric site of any target lineage. Subsequent testing on the in vitro chick-biventer cervicis muscle preparation suggested that, while the venoms of these species bound postsynaptically, they bound to allosteric sites rather than orthosteric. Allosteric binding is potentially a weaker but faster-acting form of neurotoxicity and we hypothesise that the switch to allosteric binding is likely due to selection pressures related to prey-escape potential. This research has potentially opened up the possibility of a new functional class of toxins which have never been assessed previously while shedding light on the selection pressures shaping venom evolution.
RESUMO
We analyzed the hypothesis that the lack of synchronization between the mating and ovulation period of Micrurus frontalis (BRT clade) is indicative of the capacity of females to store sperm. Conversely, since these reproductive events occur in the same season for Micrurus corallinus (BRM clade), sperm storage is not expected. Thus, we analyzed the reproductive cycle of female M. corallinus and M. frontalis, and investigated the occurrence of sperm storage. Our results showed that these two species of coral snakes (clades BRM and BRT) possess different reproductive cycles. Micrurus frontalis exhibits an extensive reproductive period encompassing three seasons (summer, autumn and winter), while M. corallinus directs secondary vitellogenesis and ovulation to the hottest period of the year (spring and summer). We confirm, for the first time, the strategy of sperm storage (SSr) in females of the genus Micrurus. We observed sperm storage receptacles located in the non-glandular uterus in all seasons of the year for M. corallinus and in spring, summer and autumn in M. frontalis. Furthermore, the presence of SSr in females in the non-reproductive (post-ovulatory) period, the verification of myoid cells around the receptacles and secretion of neutral carbohydrates in the lumina of SSrs may indicates a long-term storage. The posterior infundibulum is another possible region of sperm storage by the presence of tubular ciliated gland; however, reproductive studies with other species of the genus are necessary for a better understanding of the reproductive strategies of the BRT and BRM clades.
RESUMO
Bites by Micrurus snakes in Brazilian Amazon represent about 0.4% of snakebite registered in that area. There is not information available about the M. annellatus snakebites In this report, we describe a case of envenoming caused by Micrurus annellatus bolivianus recorded in the municipality of Cruzeiro do Sul, state of Acre, western Brazilian Amazon. On admission, the patient was suffering from mild pain, mild edema and paraesthesia restricted to the site of the bite, darkened vision and nausea. Laboratorial evaluation revealed unclottable blood which improved only after 3 days of follow-up. Envenoming was classified as moderate, and 50 ml of antielapid serum was administered. The next day after the incident, vital signs were normal and the patient had mild thrombocytopenia (133,000/mm3). The patient did not present any bleeding during the hospitalization. On the fourth day after admission, the patient was discharged alleging no complaints. The patient showed coagulopathy, a rare condition in cases of Micrurus bites. Some areas where there is a lack of knowledge on coral snakebites are listed in this manuscript.
Assuntos
Cobras Corais , Venenos Elapídicos/intoxicação , Mordeduras de Serpentes/terapia , Animais , Antivenenos/uso terapêutico , Transtornos da Coagulação Sanguínea/induzido quimicamente , Brasil , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
The processes of follicular development, ovulation, egg capture, and egg transport vary among vertebrates. Therefore, analysis of the reproductive tract of several lineages is needed for understanding the evolutionary changes of the reproductive system. In turtles, the ovulated eggs are released into the coelomic cavity and taken up by one of the two oviducts, a phenomenon called extrauterine migration of eggs. However, the process of egg uptake in lizards is different. The egg is ovulated directly into the infundibulum, and oocyte uptake by the contralateral oviduct rarely occurs. The same pattern has been hypothesized to occur in snakes. To test this hypothesis, we analyzed the reproductive tract of female Micrurus corallinus preserved in zoological collections. We examined the anatomical characteristics of the infundibulum and ovary and compared the reproductive output between the ovaries to verify the mechanism of egg capture and the anatomical viability of extrauterine migration of eggs. The reproductive output of the right ovary was higher than that of the left ovary, and the higher number of eggs in the right oviduct is due exclusively to the production of the ipsilateral ovary. Several anatomical features prevent extrauterine migration of eggs, including the asymmetry of the reproductive system, the arrangement of the ovarian follicles in a single row, and the formation of a wrapping around the ovary and infundibulum by the visceral pleuroperitoneum membrane (preventing against ectopic eggs). Therefore, the hypothesis of egg capture by the contralateral oviduct is anatomically infeasible in M. corallinus and possibly in other snakes. Anat Rec, 301:1936-1943, 2018. © 2018 Wiley Periodicals, Inc.
Assuntos
Oócitos/fisiologia , Ovário/fisiologia , Oviductos/fisiologia , Reprodução/fisiologia , Animais , Cobras Corais , Feminino , Ovário/anatomia & histologia , Oviductos/anatomia & histologiaRESUMO
A proteomic analysis of the soluble venom of the coral snake Micrurus pyrrhocryptus is reported in this work. The whole soluble venom was separated by RP-HPLC and the molecular weights of its components (over 100) were determined by mass spectrometry. Three main sets of components were identified, corresponding to peptides with molecular masses from 5 to 8â¯kDa, proteins from 12 to 16â¯kDa and proteins from 20 to 30â¯kDa. Two components were fully sequenced: one α-neurotoxic peptide of 7210â¯Da with slight blocking activity of the nicotinic acetylcholine receptor (nAChR) and a phospholipase A2 (PLA2) with molecular weight 13517â¯Da and no effect on the nAChR. PLA2 activity was evaluated for all RP-HPLC components. In addition, N-terminal sequence was obtained for eleven components using Edman degradation. Among these, three were similar to known PLA2's, six to three-finger toxins (3FTx) and one to Kunitz-type serine protease inhibitors. Two-dimensional gel electrophoresis of the venom allowed the separation of about thirty spots with components of molecular weights from 25 to 70â¯kDa. Seventeen spots were recovered from the gel, digested with trypsin and the corresponding peptides (85) were sequenced by MS/MS allowing identification of amino acid sequences with similarities to snake venom metalloproteases (SVMP), PLA2's, L-amino acid oxidases (LAAO), acetylcholinesterases (AChE) and serine proteases (SP). In addition, LC-MS analysis of peptides obtained from tryptic digestion of whole soluble venom allowed the identification of 695 peptides, whose amino acid sequence could correspond to at least 355 components found in other snake venoms, where C-type lectins, vespryns, zinc finger proteins, and waprins were found, among others. These results show the complexity of the venom and provide important knowledge for future work on identification and activity determination of venom components from this coral snake.
Assuntos
Cobras Corais , Venenos Elapídicos/química , Proteômica , Sequência de Aminoácidos , Animais , Linhagem Celular Tumoral , Venenos Elapídicos/enzimologia , Venenos Elapídicos/toxicidade , Fenômenos Eletrofisiológicos/efeitos dos fármacos , Humanos , Camundongos , PeptídeosRESUMO
BACKGROUND: Tar seep deposits in South America historically are well-known for their rich record of fossil mammals, contrasting with only a few formal reports of reptile remains. Here we report a new snake fauna recovered from two tar pits from Venezuela. The fossil remains come from two localities: (a) El Breal de Orocual, which comprises an inactive tar seep estimated to be Plio/Pleistocene in age; and (b) Mene de Inciarte, an active surface asphalt deposit with an absolute age dating to the late Pleistocene. METHODS: The taxonomic identity of all specimens was assessed via consultation of the relevant literature and comparison with extant specimens. The taxonomic assignments are supported by detailed anatomical description. RESULTS: The Mene de Inciarte snake fauna comprises vertebral remains identified as the genus Epicrates sp. (Boidae), indeterminate viperids, and several isolated vertebrae attributable to "Colubridae" (Colubroidea, sensu Zaher et al., 2009). Amongst the vertebral assemblage at El Breal de Orocual, one specimen is assigned to the genus Corallus sp. (Boidae), another to cf. Micrurus (Elapidae), and several others to "Colubrids" (Colubroides, sensu Zaher et al., 2009) and the Viperidae family. CONCLUSIONS: These new records provide valuable insight into the diversity of snakes in the north of South America during the Neogene/Quaternary boundary. The snake fauna of El Breal de Orocual and Mene de Inciarte demonstrates the presence of Boidae, Viperidae, "colubrids", and the oldest South American record of Elapidae. The presence of Corallus, Epicrates, and viperids corroborates the mosaic palaeoenvironmental conditions of El Breal de Orocual. The presence of Colubroides within both deposits sheds light on the palaeobiogeographical pattern of caenophidians snake colonization of South America and is consistent with the hypothesis of two episodes of dispersion of Colubroides to the continent.
RESUMO
The processes of follicular development, ovulation, egg capture, and egg transport vary among vertebrates. Therefore, analysis of the reproductive tract of several lineages is needed for understanding the evolutionary changes of the reproductive system. In turtles, the ovulated eggs are released into the coelomic cavity and taken up by one of the two oviducts, a phenomenon called extrauterine migration of eggs. However, the process of egg uptake in lizards is different. The egg is ovulated directly into the infundibulum, and oocyte uptake by the contralateral oviduct rarely occurs. The same pattern has been hypothesized to occur in snakes. To test this hypothesis, we analyzed the reproductive tract of female Micrurus corallinus preserved in zoological collections. We examined the anatomical characteristics of the infundibulum and ovary and compared the reproductive output between the ovaries to verify the mechanism of egg capture and the anatomical viability of extrauterine migration of eggs. The reproductive output of the right ovary was higher than that of the left ovary, and the higher number of eggs in the right oviduct is due exclusively to the production of the ipsilateral ovary. Several anatomical features prevent extrauterine migration of eggs, including the asymmetry of the reproductive system, the arrangement of the ovarian follicles in a single row, and the formation of a wrapping around the ovary and infundibulum by the visceral pleuroperitoneum membrane (preventing against ectopic eggs). Therefore, the hypothesis of egg capture by the contralateral oviduct is anatomically infeasible in M. corallinus and possibly in other snakes.
RESUMO
A new species of elapid snake of the genus Micrurus is described herein, from the states of Rondônia and Mato Grosso, in the western Brazilian Amazon. The new species has a single anal plate, a unique characteristic shared with members of the M. hemprichii species group. It can be distinguished from the other members of this group by having a parietal reddish band in juveniles (absent in adults) and the absence of brownish or orange-yellow dorsal body bands. In addition, this species is distinguished from M. hemprichii by its lower number of body triads, and from M. ortoni by its lower numbers of ventrals and subcaudals scales
RESUMO
Micrurus surinamensis is an aquatic member of the genus Micrurus. This species is known for its highly specialized venom and distinctive diet, mostly made of aquatic vertebrates. Here, we explore both external (head and body) and skull shape morphologies in M.surinamensis, comparing it with two terrestrial species of the genus (M.lemniscatus and M.spixii) and to aquatic and terrestrial species of distantly related groups. We use both traditional and geometric morphometrics to determine whether the presence of similar traits in head shape morphology is rather the result of adaptive convergences between M.surinamensis and other aquatic species, or whether it is the product of phylogenetic conservatism within the genus. Results from both traditional and geometric morphometrics show that M.surinamensis can be considered convergent with aquatic species, mainly in the skull shape. Micrurus surinamensis differs from the two terrestrial species of Micrurus by having a wider head, smaller distance between nostrils, and a long tail. Geometric morphometric analysis shows that despite having an extremely conserved skull and mandible shape, M.surinamensis shows a longer supratemporal and quadrate bones than in terrestrial Micrurus, indicating a larger gape for this species. A more kinetic skull combined with a larger gape would allow M.surinamensis to feed on fish, which represent larger and wider prey that contrast with the elongate prey, which compose the main diet of species in the genus Micrurus. Our results illustrate the importance of both phylogenetic conservatism and adaptation in shaping species morphology.
RESUMO
Strong spatial sorting of genetic variation in contiguous populations is often explained by local adaptation or secondary contact following allopatric divergence. A third explanation, spatial sorting by stochastic effects of range expansion, has been considered less often though theoretical models suggest it should be widespread, if ephemeral. In a study designed to delimit species within a clade of venomous coralsnakes, we identified an unusual pattern within the Texas coral snake (Micrurus tener): strong spatial sorting of divergent mitochondrial (mtDNA) lineages over a portion of its range, but weak sorting of these lineages elsewhere. We tested three alternative hypotheses to explain this pattern-local adaptation, secondary contact following allopatric divergence, and range expansion. Collectively, near panmixia of nuclear DNA, the signal of range expansion associated sampling drift, expansion origins in the Gulf Coast of Mexico, and species distribution modeling suggest that the spatial sorting of divergent mtDNA lineages within M. tener has resulted from genetic surfing of standing mtDNA variation-not local adaptation or allopatric divergence. Our findings highlight the potential for the stochastic effects of recent range expansion to mislead estimations of population divergence made from mtDNA, which may be exacerbated in systems with low vagility, ancestral mtDNA polymorphism, and male-biased dispersal.
Assuntos
DNA Mitocondrial/genética , Elapidae/genética , Fluxo Gênico , Haplótipos , Animais , Evolução Molecular , México , Filogenia , Estados UnidosRESUMO
Micrurus clarki is an uncommon coral snake distributed from the Southeastern Pacific of Costa Rica to Western Colombia, for which no information on its venom could be found in the literature. Using a 'venomics' approach, proteins of at least nine families were identified, with a moderate predominance of three-finger toxins (3FTx; 48.2%) over phospholipase A2 (PLA2; 36.5%). Comparison of this venom profile with those of other Micrurus species suggests that it may represent a more balanced, 'intermediate' type within the dichotomy between 3FTx- and PLA2-predominant venoms. M. clarki venom was strongly cross-recognized and, accordingly, efficiently neutralized by an equine therapeutic antivenom against M. nigrocinctus, revealing their high antigenic similarity. Lethal activity for mice could be reproduced by a PLA2 venom fraction, but, unexpectedly, not by fractions corresponding to 3FTxs. The most abundant venom component, hereby named clarkitoxin-I, was identified as a short-chain (type I) 3FTx, devoid of lethal effect in mice, whose target remains to be defined. Its amino acid sequence of 66 residues shows high similarity with predicted sequences of venom gland transcripts described for M. fulvius, M. browni, and M. diastema.