RESUMEN

Crotalus durissus ruruima is a rattlesnake subspecies mainly found in Roraima, the northernmost state of Brazil. Envenomings caused by this subspecies lead to severe clinical manifestations (e.g. respiratory muscle paralysis, rhabdomyolysis, and acute renal failure) that can lead to the victim's death. In this review, we comprehensively describe C. d. ruruima biology and the challenges this subspecies poses for human health, including morphology, distribution, epidemiology, venom cocktail, clinical envenoming, and the current and future specific treatment of envenomings by this snake. Moreover, this review presents maps of the distribution of the snake subspecies and evidence that this species is responsible for some of the most severe envenomings in the country and causes the highest lethality rates. Finally, we also discuss the efficacy of the Brazilian horse-derived antivenoms to treat C. d. ruruima envenomings in Roraima state.

Asunto(s)

Crotalus , Animales , Antivenenos , Brasil , Venenos de Crotálidos/química , Venenos de Crotálidos/farmacología , Venenos de Crotálidos/uso terapéutico , Crotalus/anatomía & histología , Crotalus/clasificación , Crotalus/fisiología , Ambiente , Humanos , Dinámica Poblacional

RESUMEN

Rattlesnakes are a diverse clade of pit vipers (snake family Viperidae, subfamily Crotalinae) that consists of numerous medically significant species. We used validated in vitro assays measuring venom-induced clotting time and strength of any clots formed in human plasma and fibrinogen to assess the coagulotoxic activity of the four medically relevant Mexican rattlesnake species Crotalus culminatus, C. mictlantecuhtli, C. molossus, and C. tzabcan. We report the first evidence of true procoagulant activity by Neotropical rattlesnake venom in Crotalus culminatus. This species presented a strong ontogenetic coagulotoxicity dichotomy: neonates were strongly procoagulant via Factor X activation, whereas adults were pseudo-procoagulant in that they converted fibrinogen into weak, unstable fibrin clots that rapidly broke down, thereby likely contributing to net anticoagulation through fibrinogen depletion. The other species did not activate clotting factors or display an ontogenetic dichotomy, but depleted fibrinogen levels by cleaving fibrinogen either in a destructive (non-clotting) manner or via a pseudo-procoagulant mechanism. We also assessed the neutralization of these venoms by available antivenom and enzyme-inhibitors to provide knowledge for the design of evidence-based treatment strategies for envenomated patients. One of the most frequently used Mexican antivenoms (Bioclon Antivipmyn®) failed to neutralize the potent procoagulant toxic action of neonate C. culminatus venom, highlighting limitations in snakebite treatment for this species. However, the metalloprotease inhibitor Prinomastat substantially thwarted the procoagulant venom activity, while 2,3-dimercapto-1-propanesulfonic acid (DMPS) was much less effective. These results confirm that venom-induced Factor X activation (a procoagulant action) is driven by metalloproteases, while also suggesting Prinomastat as a more promising potential adjunct treatment than DMPS for this species (with the caveat that in vivo studies are necessary to confirm this potential clinical use). Conversely, the serine protease inhibitor 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride (AEBSF) inhibited the direct fibrinogen cleaving actions of C. mictlantecuhtli venom, thereby revealing that the pseudo-procoagulant action is driven by kallikrein-type serine proteases. Thus, this differential ontogenetic variation in coagulotoxicity patterns poses intriguing questions. Our results underscore the need for further research into Mexican rattlesnake venom activity, and also highlights potential limitations of current antivenom treatments.

Asunto(s)

Coagulación Sanguínea/efectos de los fármacos , Venenos de Crotálidos/toxicidad , Animales , Antivenenos/inmunología , Factores de Coagulación Sanguínea/metabolismo , Pruebas de Coagulación Sanguínea/métodos , Trastornos de las Proteínas de Coagulación/sangre , Trastornos de las Proteínas de Coagulación/diagnóstico , Trastornos de las Proteínas de Coagulación/etiología , Crotalus/clasificación , Crotalus/genética , México , Pruebas de Neutralización

RESUMEN

Background:Crotalus durissus is considered one of the most important species of venomous snakes in Brazil, due to the high mortality of its snakebites. The venom of Crotalus durissus contains four main toxins: crotoxin, convulxin, gyroxin and crotamine. Venoms can vary in their crotamine content, being crotamine-negative or -positive. This heterogeneity is of great importance for producing antivenom, due to their different mechanisms of action. The possibility that antivenom produced by Butantan Institute might have a different immunorecognition capacity between crotamine-negative and crotamine-positive C. durissus venoms instigated us to investigate the differences between these two venom groups. Methods:The presence of crotamine was analyzed by SDS-PAGE, western blotting and ELISA, whereas comparison between the two types of venoms was carried out through HPLC, mass spectrometry analysis as well as assessment of antivenom lethality and efficacy. Results:The results showed a variation in the presence of crotamine among the subspecies and the geographic origin of snakes from nature, but not in captive snakes. Regarding differences between crotamine-positive and -negative venoms, some exclusive proteins are found in each pool and the crotamine-negative pool presented more phospholipase A2 than crotamine-positive pool. This variation could affect the time to death, but the lethal and effective dose were not affected. Conclusion:These differences between venom pools indicate the importance of using both, crotamine-positive and crotamine-negative venoms, to produce the antivenom.(AU)

Asunto(s)

Animales , Crotalus/anatomía & histología , Crotalus/clasificación , Crotalus/genética , Venenos de Crotálidos/antagonistas & inhibidores , Antivenenos

RESUMEN

INTRODUCTION: Crotalus envenomations cause serious complications and can be fatal without appropriate treatment. Venom isoforms present and inter/intraspecific variations in the venom composition can result in different symptoms presented by bites by snakes from the same species but from different geographical regions. We comparatively evaluated the local and systemic effects caused by Crotalus durissus terrificus (Cdt), C.d. collilineatus (Cdcolli), and C.d. cascavella (Cdcasc) envenomation. METHODS: Venom chromatography was performed. Proteolytic, phospholipase, and LAAO activities were analyzed. Edema, myotoxicity, hepatotoxicity, nephrotoxicity, and coagulation alterations were evaluated. RESULTS: The venom SDS-PAGE analyses found the presence of convulxin, gyroxin, crotoxin, and crotamine in Cdt and Cdcolli venoms. Crotamine was not present in the Cdcasc venom. Cdt, Cdcollli, and Cdcasc venoms had no proteolytic activity. Only Cdcasc and Cdt venoms had phospholipase activity. LAAO activity was observed in Cdcolli and Cdcasc venoms. Cdcolli and Cdcasc venoms caused 36.7% and 13.3% edema increases, respectively. Cdt venom caused a 10% edema induction compared to those by other venoms. All venoms increased TOTAL-CK, MB-CK, and LDH levels (indicating muscle injury) and ALT, AST, GGT, and ALP levels (markers of liver damage) and were able to induce a neuromuscular blockade. Urea and creatinine levels were also altered in both plasma and urine, indicating kidney damage. Only Cdcolli and Cdcasc venoms increased TAPP and TAP. CONCLUSIONS: Together, these results allow us to draw a distinction between local and systemic effects caused by Crotalus subspecies, highlighting the clinical and biochemical effects produced by their respective venoms.

Asunto(s)

Venenos de Crotálidos/toxicidad , Crotalus/clasificación , Edema/inducido químicamente , Riñón/efectos de los fármacos , Hígado/efectos de los fármacos , Fosfatasa Alcalina/sangre , Fosfatasa Alcalina/efectos de los fármacos , Animales , Creatina Quinasa/sangre , Creatina Quinasa/efectos de los fármacos , Creatinina/sangre , Edema/patología , Electroforesis en Gel de Poliacrilamida , Riñón/patología , L-Lactato Deshidrogenasa/sangre , L-Lactato Deshidrogenasa/efectos de los fármacos , Hígado/patología , Ratones , Modelos Animales , Transaminasas/sangre , Transaminasas/efectos de los fármacos , Urea/sangre

RESUMEN

With the continued adoption of genome-scale data in evolutionary biology comes the challenge of adequately harnessing the information to make accurate phylogenetic inferences. Coalescent-based methods of species tree inference have become common, and concatenation has been shown in simulation to perform well, particularly when levels of incomplete lineage sorting are low. However, simulation conditions are often overly simplistic, leaving empiricists with uncertainty regarding analytical tools. We use a large ultraconserved element data set (>3,000 loci) from rattlesnakes of the Crotalus triseriatus group to delimit lineages and estimate species trees using concatenation and several coalescent-based methods. Unpartitioned and partitioned maximum likelihood and Bayesian analysis of the concatenated matrix yield a topology identical to coalescent analysis of a subset of the data in bpp. ASTRAL analysis on a subset of the more variable loci also results in a tree consistent with concatenation and bpp, whereas the SVDquartets phylogeny differs at additional nodes. The size of the concatenated matrix has a strong effect on species tree inference using SVDquartets, warranting additional investigation on optimal data characteristics for this method. Species delimitation analyses suggest up to 16 unique lineages may be present within the C. triseriatus group, with divergences occurring during the Neogene and Quaternary. Network analyses suggest hybridization within the group is relatively rare. Altogether, our results reaffirm the Mexican highlands as a biodiversity hotspot and suggest that coalescent-based species tree inference on data subsets can provide a strongly supported species tree consistent with concatenation of all loci with a large amount of missing data.

Asunto(s)

Biodiversidad , Crotalus/clasificación , Crotalus/genética , Filogenia , Animales , Biología Computacional/métodos , Crotalus/crecimiento & desarrollo , México

RESUMEN

Abstract INTRODUCTION: Crotalus envenomations cause serious complications and can be fatal without appropriate treatment. Venom isoforms present and inter/intraspecific variations in the venom composition can result in different symptoms presented by bites by snakes from the same species but from different geographical regions. We comparatively evaluated the local and systemic effects caused by Crotalus durissus terrificus (Cdt), C.d. collilineatus (Cdcolli), and C.d. cascavella (Cdcasc) envenomation. METHODS: Venom chromatography was performed. Proteolytic, phospholipase, and LAAO activities were analyzed. Edema, myotoxicity, hepatotoxicity, nephrotoxicity, and coagulation alterations were evaluated. RESULTS: The venom SDS-PAGE analyses found the presence of convulxin, gyroxin, crotoxin, and crotamine in Cdt and Cdcolli venoms. Crotamine was not present in the Cdcasc venom. Cdt, Cdcollli, and Cdcasc venoms had no proteolytic activity. Only Cdcasc and Cdt venoms had phospholipase activity. LAAO activity was observed in Cdcolli and Cdcasc venoms. Cdcolli and Cdcasc venoms caused 36.7% and 13.3% edema increases, respectively. Cdt venom caused a 10% edema induction compared to those by other venoms. All venoms increased TOTAL-CK, MB-CK, and LDH levels (indicating muscle injury) and ALT, AST, GGT, and ALP levels (markers of liver damage) and were able to induce a neuromuscular blockade. Urea and creatinine levels were also altered in both plasma and urine, indicating kidney damage. Only Cdcolli and Cdcasc venoms increased TAPP and TAP. CONCLUSIONS: Together, these results allow us to draw a distinction between local and systemic effects caused by Crotalus subspecies, highlighting the clinical and biochemical effects produced by their respective venoms.

Asunto(s)

Animales , Crotalus/clasificación , Venenos de Crotálidos/toxicidad , Edema/inducido químicamente , Riñón/efectos de los fármacos , Hígado/efectos de los fármacos , Urea/sangre , Creatina Quinasa/efectos de los fármacos , Creatina Quinasa/sangre , Creatinina/sangre , Modelos Animales , Edema/patología , Electroforesis en Gel de Poliacrilamida , Fosfatasa Alcalina/efectos de los fármacos , Fosfatasa Alcalina/sangre , Transaminasas/efectos de los fármacos , Transaminasas/sangre , Riñón/patología , L-Lactato Deshidrogenasa/efectos de los fármacos , L-Lactato Deshidrogenasa/sangre , Hígado/patología , Ratones

RESUMEN

The Mojave rattlesnake (Crotalus scutulatus) inhabits deserts and arid grasslands of the western United States and Mexico. Despite considerable interest in its highly toxic venom and the recognition of two subspecies, no molecular studies have characterized range-wide genetic diversity and population structure or tested species limits within C. scutulatus. We used mitochondrial DNA and thousands of nuclear loci from double-digest restriction site associated DNA sequencing to infer population genetic structure throughout the range of C. scutulatus, and to evaluate divergence times and gene flow between populations. We find strong support for several divergent mitochondrial and nuclear clades of C. scutulatus, including splits coincident with two major phylogeographic barriers: the Continental Divide and the elevational increase associated with the Central Mexican Plateau. We apply Bayesian clustering, phylogenetic inference, and coalescent-based species delimitation to our nuclear genetic data to test hypotheses of population structure. We also performed demographic analyses to test hypotheses relating to population divergence and gene flow. Collectively, our results support the existence of four distinct lineages within C. scutulatus, and genetically defined populations do not correspond with currently recognized subspecies ranges. Finally, we use approximate Bayesian computation to test hypotheses of divergence among multiple rattlesnake species groups distributed across the Continental Divide, and find evidence for co-divergence at this boundary during the mid-Pleistocene.

Asunto(s)

Crotalus/genética , Flujo Génico , Variación Genética , Animales , Secuencia de Bases , Teorema de Bayes , Núcleo Celular/genética , Crotalus/clasificación , ADN Mitocondrial/genética , Ecosistema , Genética de Población , México , Filogenia , Filogeografía , Factores de Tiempo , Estados Unidos

RESUMEN

The venoms from two species of rock rattlesnakes and an intergrade population were studied. Differences were noted in SDS-PAGE and RP-HPLC profiles and only the venom from the intergrade population showed low procoagulant activity. Also, a Crotoxin-like neurotoxic PLA2 was identified in the venom of C. l. klauberi, the most toxic of the analyzed venoms. This is the first report of such a toxin in C. l. klauberi from Aguascalientes, Mexico.

Asunto(s)

Venenos de Crotálidos/química , Venenos de Crotálidos/toxicidad , Crotalus/clasificación , Animales , Cromatografía Líquida de Alta Presión , Coagulantes , Electroforesis en Gel de Poliacrilamida , Dosificación Letal Mediana , México , Ratones , Neurotoxinas

RESUMEN

Although the Mexican Highlands has the highest diversity of small-bodied rattlesnakes in the world, studies on the species found throughout this region have been relatively scarce. This has led to challenges with examining venom phenotypic characteristics, as well as species misidentifications and misclassifications. In the current study we investigated venom variation among four subspecies of Crotalus lepidus (C. l. klaluberi, C. l. lepidus, C. l. maculosus, C. l. morulus) and four subspecies of C. willardi (C. w. amabilis, C. w. obscurus, C. w. silus, and C. w. willardi) that inhabit regions of southwestern United States and central México. SDS-PAGE patterns show the presence of many of the major compounds found in other rattlesnake venoms, although minor variations in protein banding patterns and intensity are recognizable. Most notably, PI-metalloproteinase (SVMP) bands appear to be very faint to absent in northern C. l. lepidus and C. l. klauberi subspecies, but are fairly prominent in all other C. lepidus and C. willardi subspecies. Enzyme activity assays revealed that C. lepidus subspecies exhibit higher SVMP and thrombin-like activities when compared to C. willardi subspecies. Significant differences between subspecies were also observed for kallikrein-like serine protease, L-amino acid oxidase, and phosphodiesterase activities, although these differences appear to be random and fail to follow a geographical or phylogenetic trend. The same relationship was also observed for fibrinogenolytic and coagulation assays. Toxicity assays conducted on lab mice (Mus musculus), house geckos (Hemidactylus frenatus), and house crickets (Acheta domestica) revealed varying toxicities between subspecies, with C. l klauberi being the most toxic towards mice (LD50 = 1.36 µg/g) and house geckos (LD50 = 0.17 µg/g), and C. w. silus being most toxic to house crickets (LD50 = 1.94 µg/g). These results provide additional evidence that geographical isolation, natural selection, and adaptive evolution in response to diets may be driving forces contributing to population-level variation in venom composition.

Asunto(s)

Venenos de Crotálidos/química , Venenos de Crotálidos/toxicidad , Crotalus/clasificación , Animales , Venenos de Crotálidos/enzimología , Electroforesis en Gel de Poliacrilamida , Gryllidae , Lagartos , Metaloproteasas/metabolismo , México , Ratones , Fenotipo , Sudoeste de Estados Unidos

RESUMEN

Venomous snakes often display extensive variation in venom composition both between and within species. However, the mechanisms underlying the distribution of different toxins and venom types among populations and taxa remain insufficiently known. Rattlesnakes (Crotalus, Sistrurus) display extreme inter- and intraspecific variation in venom composition, centered particularly on the presence or absence of presynaptically neurotoxic phospholipases A2 such as Mojave toxin (MTX). Interspecific hybridization has been invoked as a mechanism to explain the distribution of these toxins across rattlesnakes, with the implicit assumption that they are adaptively advantageous. Here, we test the potential of adaptive hybridization as a mechanism for venom evolution by assessing the distribution of genes encoding the acidic and basic subunits of Mojave toxin across a hybrid zone between MTX-positive Crotalus scutulatus and MTX-negative C. viridis in southwestern New Mexico, USA. Analyses of morphology, mitochondrial and single copy-nuclear genes document extensive admixture within a narrow hybrid zone. The genes encoding the two MTX subunits are strictly linked, and found in most hybrids and backcrossed individuals, but not in C. viridis away from the hybrid zone. Presence of the genes is invariably associated with presence of the corresponding toxin in the venom. We conclude that introgression of highly lethal neurotoxins through hybridization is not necessarily favored by natural selection in rattlesnakes, and that even extensive hybridization may not lead to introgression of these genes into another species.

Asunto(s)

Venenos de Crotálidos/química , Crotalus/genética , Evolución Molecular , Hibridación Genética , Neurotoxinas/química , Animales , Venenos de Crotálidos/genética , Crotalus/clasificación , ADN Mitocondrial/genética , NADH Deshidrogenasa/genética , Neurotoxinas/genética , New Mexico , Análisis de Componente Principal , Carácter Cuantitativo Heredable

RESUMEN

Rattlesnakes (Crotalus and Sistrurus) represent a radiation of approximately 42 species distributed throughout the New World from southern Canada to Argentina. Interest in this enigmatic group of snakes continues to accrue due, in part, to their ecomorphological diversity, contributions to global envenomations, and potential medicinal importance. Although the group has garnered substantial attention from systematists and evolutionary biologists for decades, little is still known regarding patterns of lineage diversification. In addition, few studies have statistically quantified broad-scale biogeographic patterns in rattlesnakes to ascertain how dispersal occurred throughout the New World, particularly among the different major biomes of the Americas. To examine diversification and biogeographic patterns in this group of snakes we assemble a multilocus data set consisting of over 6700bp encompassing three nuclear loci (NT-3, RAG-1, C-mos) and seven mitochondrial genes (12S, 16S, ATPase6, ATPase8, ND4, ND5, cytb). Fossil-calibrated phylogenetic and subsequent diversification rate analyses are implemented using maximum likelihood and Bayesian inference, to examine their evolutionary history and temporal dynamics of diversity. Based on ancestral area reconstructions we explore dispersal patterns throughout the New World. Cladogenesis occurred predominantly during the Miocene and Pliocene with only two divergences during the Pleistocene. Two different diversification rate models, advocating diversity-dependence, are strongly supported. These models indicate an early rapid radiation followed by a recent speciation rate decline. Biogeographic analyses suggest that the high elevation pine-oak forests of western Mexico served as a major speciation pump for the majority of lineages, with the desert biome of western North America colonized independently at least twice. All together, these results provide evidence for rapid diversification of rattlesnakes throughout the Mexican highlands during the Neogene, likely in response to continual orogenesis of Mexico's major mountain systems, followed by more recent dispersal into desert and tropical biomes.

Asunto(s)

Crotalus/clasificación , Crotalus/genética , Especiación Genética , Filogenia , Animales , Teorema de Bayes , Núcleo Celular/genética , Clima Desértico , Bosques , Fósiles , Genes Mitocondriales/genética , Funciones de Verosimilitud , México , América del Norte , Filogeografía

RESUMEN

We used mitochondrial DNA sequence data from 151 individuals to estimate population genetic structure across the range of the Western Diamondback Rattlesnake (Crotalus atrox), a widely distributed North American pit viper. We also tested hypotheses of population structure using double-digest restriction site associated DNA (ddRADseq) data, incorporating thousands of nuclear genome-wide SNPs from 42 individuals. We found strong mitochondrial support for a deep divergence between eastern and western C. atrox populations, and subsequent intermixing of these populations in the Inter-Pecos region of the United States and Mexico. Our nuclear RADseq data also identify these two distinct lineages of C. atrox, and provide evidence for nuclear admixture of eastern and western alleles across a broad geographic region. We identified contrasting patterns of mitochondrial and nuclear genetic variation across this genetic fusion zone that indicate partially restricted patterns of gene flow, which may be due to either pre- or post-zygotic isolating mechanisms. The failure of these two lineages to maintain complete genetic isolation, and evidence for partially-restricted gene flow, imply that these lineages were in the early stages of speciation prior to secondary contact.

Asunto(s)

Crotalus/clasificación , Flujo Génico , Especiación Genética , Filogenia , Animales , Teorema de Bayes , Núcleo Celular/genética , Crotalus/genética , ADN Mitocondrial/genética , Genética de Población , Haplotipos , México , Modelos Genéticos , Polimorfismo de Nucleótido Simple , Densidad de Población , Aislamiento Reproductivo , Análisis de Secuencia de ADN , Estados Unidos

RESUMEN

The longtailed rattlesnakes of western Mexico represent an enigmatic group of poorly known venomous snake species: Crotalus ericsmithi, C. lannomi, and C. stejnegeri. In the 120 years since their discovery, fewer than twenty individuals have been deposited in natural history collections worldwide. These three species share similar morphological traits, including a particularly long tail that has been interpreted as either an ancestral condition among rattlesnakes or as derived within the longtailed group. An understanding of the phylogenetic distinctiveness and relationships among the longtailed rattlesnakes, and their relationships to other rattlesnake groups, has previously been hampered by a dearth of comparative material and tissues for collection of DNA sequence data. Facilitated by the recent availability of tissue samples from multiple individuals of each species, we estimate the phylogenetic relationships among the longtailed rattlesnakes and their placement among other rattlesnake groups, using DNA sequence data from three mitochondrial and three nuclear gene fragments. We explore phylogenetic signal in our data using Bayesian and maximum likelihood methods, species tree analyses and hypothesis testing. Our results strongly support the monophyly of longtailed rattlesnakes and suggest the three species diverged from each other during the mid to late Pliocene or early Pleistocene (~1.5-5.6 mya). Contrary to prevailing hypotheses, we find no evidence for an early or basal divergence of the longtailed clade within the rattlesnake tree, and instead estimate that it diverged relatively recently (~6.8 mya) from its sister lineage, composed of the diamondback rattlesnakes (C. atrox group) and the prairie rattlesnakes (C. viridis group). With our added sampling of lineages and identification of previously used problematic sequences, we provide a revised hypothesis for relationships among Crotalus species, yet underscore the need for future studies and new data to deliver a well-supported robust estimate of rattlesnake relationships.

Asunto(s)

Evolución Biológica , Crotalus/clasificación , Filogenia , Animales , Teorema de Bayes , Núcleo Celular/genética , Crotalus/genética , ADN Mitocondrial/genética , Funciones de Verosimilitud , México , Modelos Genéticos , Filogeografía , Análisis de Secuencia de ADN

RESUMEN

This study aimed at describing daily and seasonal variation in the activity of a population of South-American rattlesnakes (Crotalus durissus) in a savanna like habitat (Cerrado) in Southeastern Brazil. Seasonal and daily activities of snakes were evaluated by the number of captures of snakes during road surveys, accidental encounters, and relocations by radio-tracking. Our results show that climatic variables such as air temperature and rainfall have little influence on the activity pattern of rattlesnakes. Our findings indicate that rattlesnakes spend most of the day resting and most of the night in ambush posture. The South-American rattlesnake is active throughout the year with a discrete peak in activity of males during the matting season. The possibility of maintaining activity levels even during the coldest and driest season can facilitate the colonization of several habitats in South America. This possibility currently facilitates the colonization of deforested areas by rattlesnakes.

Asunto(s)

Conducta Animal/fisiología , Ritmo Circadiano/fisiología , Crotalus/fisiología , Animales , Crotalus/clasificación , Femenino , Masculino , Conducta Predatoria/fisiología , Estaciones del Año

RESUMEN

The rock rattlesnakes Crotalus lepidus comprise a group (lepidus, klauberi, morulus and maculosus) of poorly known mountain cold-tolerant snakes in Mexico. In particular, Crotalus lepidus morulus is a snake endemic of the northeast of Mexico, whereas Crotalus lepidus klauberi and C. l. lepidus are distributed in some regions of the north and central Mexico and southern U. S. Until now very little data are available from C. lepidus subspecies from Mexico, as the terrain inhabited by these snakes is generally steep and rugged. In this work, we have determined some biochemical and biological properties of C. l. morulus, C. l. klauberi and C. l. lepidus crude venoms. Some minor differences in venoms were noted in SDS-PAGE, HPLC profile and MALDI-TOF mass spectrometry analysis. Partial sequences of metalloproteinases, phospholipases A2 (PLA2) and galactose-specific lectins were identified in the venoms. Venoms of C. l. klauberi and C. l. lepidus had significantly higher hemorrhagic and lethal activities than C. l. morulus venom. Proteolytic activity in azocasein was higher in C. l. morulus venom, whereas gelatin hydrolysis was higher in C. l. klauberi. Fibrinogenolytic and PLA2 activities were very similar in all venoms tested. The histological observations in the gastrocnemius muscle damaged by venoms from all the subspecies confirmed myonecrotic and hemorrhagic activities (at 3 and 24 h), which resulted in a poor regenerative response after 14 days. However, C. l. lepidus and C. l. klauberi venom induced a higher increase in the plasma activity of creatine kinase (CK), evidencing higher myotoxicity, whereas paw edema-inducing activity was higher in C. l. lepidus venom. The results indicate that the venoms from the three subspecies have similar protein profiles in electrophoresis, HPLC and molecular weight determinations. However, differences were found in the biological activities in mice. Notably, the venoms of C. l. lepidus and C. l. klauberi present higher toxicity (lower LD50) and hemorrhagic activity than C. l. morulus venom.

Asunto(s)

Venenos de Crotálidos/química , Venenos de Crotálidos/toxicidad , Crotalus/clasificación , Animales , Cromatografía Líquida de Alta Presión , Creatina Quinasa/sangre , Edema/inducido químicamente , Edema/patología , Electroforesis en Gel de Poliacrilamida , Fibrinógeno/metabolismo , Dosificación Letal Mediana , Masculino , Metaloproteasas/metabolismo , México , Ratones , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/metabolismo , Fosfolipasas A2/metabolismo , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción

RESUMEN

The basic knowledge on neoplasms is increasing quickly; however, few advances have been achieved in clinical therapy against tumors. For this reason, the development of alternative drugs is relevant in the attempt to improve prognosis and to increase patients survival. Snake venoms are natural sources of bioactive substances with therapeutic potential. The objective of this work was to identify and characterize the antitumoral effect of Crotalus durissus terrificus venom (CV) and its polypeptide, crotoxin, on benign and malignant tumors, respectively, pituitary adenoma and glioblastoma. The results demonstrated that CV possess a powerful antitumoral effect on benign (pituitary adenoma) and malignant (glioblastoma multiforme) tumors with IC50 values of 0.96 ± 0.11 ìg/mL and 2.15 ± 0.2 ìg/mL, respectively. This antitumoral effect is cell-cycle-specific and dependent on extracellular calcium, an important factor for crotoxin phospholipase A2 activity. The CV antitumoral effect can be ascribed, at least partially, to the polypeptide crotoxin that also induced brain tumor cell death. In spite of the known CV nephrotoxicity and neurotoxicity, acute treatment with its antitumoral dose established in vitro was not found to be toxic to the analyzed animals. These results indicate the biotechnological potential of CV as a source of pharmaceutical templates for cancer therapy.(AU)

Asunto(s)

Humanos , Animales , Venenos/análisis , Anticuerpos Antineoplásicos , Crotalus/clasificación , Terapias Complementarias/tendencias , Adenoma/prevención & control

RESUMEN

Blood examination by microhaematocrit and haemoculture of 459 snakes belonging to 37 species revealed 2.4% trypanosome prevalence in species of Viperidae (Crotalus durissus and Bothrops jararaca) and Colubridae (Pseudoboa nigra). Trypanosome cultures from C. durissus and P. nigra were behaviourally and morphologically indistinguishable. In addition, the growth and morphological features of a trypanosome from the sand fly Viannamyia tuberculata were similar to those of snake isolates. Cross-infection experiments revealed a lack of host restriction, as snakes of 3 species were infected with the trypanosome from C. durissus. Phylogeny based on ribosomal sequences revealed that snake trypanosomes clustered together with the sand fly trypanosome, forming a new phylogenetic lineage within Trypanosoma closest to a clade of lizard trypanosomes transmitted by sand flies. The clade of trypanosomes from snakes and lizards suggests an association between the evolutionary histories of these trypanosomes and their squamate hosts. Moreover, data strongly indicated that these trypanosomes are transmitted by sand flies. The flaws of the current taxonomy of snake trypanosomes are discussed, and the need for molecular parameters to be adopted is emphasized. To our knowledge, this is the first molecular phylogenetic study of snake trypanosomes.

Asunto(s)

Colubridae/parasitología , Filogenia , Trypanosoma/clasificación , Trypanosoma/genética , Tripanosomiasis/veterinaria , Viperidae/parasitología , Animales , Bothrops/clasificación , Bothrops/parasitología , Colubridae/clasificación , Crotalus/clasificación , Crotalus/parasitología , ADN Protozoario/análisis , ADN Ribosómico/análisis , Evolución Molecular , Interacciones Huésped-Parásitos , Datos de Secuencia Molecular , Psychodidae/parasitología , Análisis de Secuencia de ADN , Trypanosoma/fisiología , Trypanosoma/ultraestructura , Tripanosomiasis/parasitología , Tripanosomiasis/transmisión , Viperidae/clasificación

RESUMEN

The western diamondback rattlesnake (Crotalus atrox) is a prominent member of North American desert and semi-arid ecosystems, and its importance extends from its impact on the region's ecology and imagery, to its medical relevance as a large deadly venomous snake. We used mtDNA sequences to identify population genetic structure and historical demographic patterns across the range of this species, and relate these to broader patterns of historical biogeography of desert and semi-arid regions of the southwestern USA and adjacent Mexico. We inferred a Late Pliocene divergence between peninsular and continental lineages of Crotalus, followed by an Early Mid Pleistocene divergence across the continental divide within C. atrox. Within desert regions (Sonoran and Chihuahuan Deserts, Southern Plains, and Tamaulipan Plain) we observed population structure indicating isolation of populations in multiple Pleistocene refugia on either side of the continental divide, which we attempt to identify. Evidence of post-glacial population growth and range expansion was inferred, particularly in populations east of the continental divide. We observed clear evidence of (probably recent) gene flow across the continental divide and secondary contact of haplotype lineages. This recent gene flow appears to be particularly strong in the West-to-East direction. Our results also suggest that Crotalus tortugensis (Tortuga Island rattlesnake) and a population of 'C. atrox' inhabiting Santa Cruz Island (in the Gulf of California) previously suggested to be an unnamed species, are in fact deeply phylogenetically nested within continental lineages of C. atrox. Accordingly, we suggest C. tortugensis and 'C. atrox' from Santa Cruz Island be placed in the synonymy of C. atrox.

Asunto(s)

Crotalus/genética , ADN Mitocondrial/genética , Filogenia , Animales , Arizona , California , Crotalus/clasificación , ADN Mitocondrial/química , Clima Desértico , Genética de Población , Geografía , Haplotipos , México , Modelos Genéticos , Datos de Secuencia Molecular , Análisis de Secuencia de ADN , Texas

RESUMEN

A survey is made of the taxonomic literature on South American rattlesnakes (genus Crotalus, family Viperidae). Two main areas are emphasized: the attribution of the names proposed in the eighteenth century by Linnaeus and Laurenti, and the current scheme of division in subspecies. The attribution of names is examined based on the original descriptions and on relevant previous and contemporary literature. The presently adopted scheme, proposed by Klauber (1941, 1972) is found not entirely satisfactory, but reasonable enough--besides being hallowed by use. The scheme of geographical differentiation, intrinsically important and with broad practical implications (differentiation of the venom) is found to be the culmination of a long series of deficient analyses, and in urgent need of proper investigation.

Asunto(s)

Crotalus/clasificación , Animales , Venenos de Crotálidos/clasificación , América del Sur

RESUMEN

En este trabajo se hace un estudio comparativo de los cariotipos, proteínas plasmáticas y microestructúra de las escamas de crotalus durissus cumanensis y C. pifanorum. Los cromosomas fueron obtenidos en cultivos de linfocitos en medio 199 adicionado con 10 por ciento de suero de ternera, tratado con fitohemaglutinina M (12 mg/ml) y Concanavalina A (31,2 mg/ml) al quinto día de cultivo se adicionó colchicina 10 mg/ml por 24 horas. Las proteínas de la sangre fueron separadas por electrofóresis. El plasma se corrió sobre cellogel en tampón veronal sódico. La concentración de proteínas plasmáticas se determinó por el método de Lowry. Las escamas se lavaron con alcohol al 90 por ciento, acetona, se cubrieron con oro y se observaron en un microscopio de Barrido H-500. Las dos especies presentan un número diploide de cromosomas igual a 36 (16 macro y 20 microcromosomas), en C. d. cumanensis, hembra, los pares 1,2,3,5,6 son metacéntricos y 7,8 son submetacéntricos, en C. pifanorum, hembra, los pares 1,2,3,8 son metacéntricos y 5,6,7 submetacéntricos. Hay heteromorfismo en el par 4 de ambas especies, siendo el cromosoma Z metacéntrico y el W submetacéntrico. La electróforesis de las proteínas plasmáticas de C. d. cumanensis presentó cuatro bandas de migración bien definidas y el electroferograma cuatro picos: albúmina, alfa-2-globulina y beta con gamma globulina, mientras C pifanorum mostró cinco bandas de migración bien definidas y el electroferograma cuatro picos: albúmina, alfa-1-globulina, una mezcla alfa-2 con beta globulina y gamma globulina. En general se notó un ligero aumento en la movilidad de las cuatro primeras fracciones en C. pifanorum y la presencia de una fracción de gamma globulina bien definida. Las dos especies presentan diferencias en la microestructúra de las escamas dorsales

Asunto(s)

Animales , Clasificación/métodos , Crotalus/clasificación , Electroforesis de las Proteínas Sanguíneas/métodos , Proteínas Sanguíneas/análisis , Serpientes