Salazar Valenzuela, David
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Preferred name
Salazar Valenzuela, David
Main Affiliation
Quito
Email
davidsalazar@uti.edu.ec
ORCID
Scopus Author ID
26644312900

Research Output
Now showing 1 - 10 of 27
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A new species of harlequin toad (Bufonidae: Atelopus) from Amazonian Ecuador

2024 , Plewnia, Amadeus , Terán-Valdez, Andrea , Culebras, Jaime , Boistel, Renaud , Paluh, Daniel J. , Quezada Riera, Amanda B. , Salazar Valenzuela, David , Guayasamin, Juan Manuel

For nearly four decades, harlequin toads, genus Atelopus, have suffered unparalleled population declines. While this also results in limited understanding of alphataxonomic relationships, these toads face an urgent need for advances in systematics to inform conservation efforts. However, high intraspecific variation and cryptic diversity have hindered a comprehensive understanding of Atelopus diversity. This is particularly exemplified among Amazonian populations related to A. spumarius, where decades of taxonomic work have not been able yet to unravel relationships between the many forms, while the names coined so far have led to taxonomic confusion leaving numer-ous lineages unnamed. A recent comprehensive phylogenetic study has revealed new insights into the systematics of harlequin toads with an emphasis on Amazonian forms, identifying several unnamed lineages. We here describe one of these evolutionary lineages as a new species, restricted to the Ecuadorian Amazon basin, in an integrative taxonomic approach using molecular, morphological, bioacoustic and larval information. With this, we contribute to a better understanding of Atelopus diversity as the baseline of conservation action.

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A First Look at the Inhibitory Potential of Urospatha sagittifolia (Araceae) Ethanolic Extract for Bothrops atrox Snakebite Envenomation

2022 , Vera-Palacios, A.L. , Sacoto-Torres, J.D. , Hernández-Altamirano, J.A. , Moreno, A. , Peñuela-Mora, M.C. , Salazar Valenzuela, David , Mogollón, N.G.S. , Almeida, J.R.

Bothrops atrox snakebites are a relevant problem in the Amazon basin. In this biodiverse region, the ethnomedicinal approach plays an important role as an alternative to antivenom therapy. Urospatha sagittifolia (Araceae) is a plant used for this purpose; however, its neutralizing properties have not been scientifically accessed. To fill this gap, we investigated the ability of U. sagittifolia to modulate the catalytic activity of Bothrops atrox venom, and their toxic consequences, such as local damage and lethality. The venom profile of B. atrox was assessed by chromatography and electrophoresis. Inhibition of the three main enzymatic and medically important toxins from the venom was evaluated using synthetic substrates and quantified by chromogenic activity assays. Additionally, the neutralization of lethality, hemorrhage and edema were investigated by in vivo assays. The possible interactions between venom proteins and plant molecules were visualized by polyacrylamide gel electrophoresis. Finally, the phytochemical constituents present in the ethanolic extract were determined by qualitative and quantitative analyses. The ethanolic extract reduced the activity of the three main enzymes of venom target, achieving ranges from 19% to 81% of inhibition. Our in vivo venom neuralizations assays showed a significant inhibition of edema (38.72%) and hemorrhage (42.90%). Additionally, lethality was remarkably counteracted. The highest extract ratio evaluated had a 75% survival rate. Our data support the biomedical value of U. sagittifolia as a source of natural enzyme inhibitors able to neutralize catalytically active B. atrox venom toxins and their toxic effects. © 2022 by the authors.

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Unlocking the potential of snake venom-based molecules against the malaria, Chagas disease, and leishmaniasis triad

2023 , Almeida J.R., Gomes A. , Mendes B. , Aguiar L. , Ferreira M. , Brioschi M.B.C. , Duarte D. , Nogueira F. , Cortes S. , Salazar Valenzuela, David , Miguel D.C. , Teixeira C. , Gameiro P. , Gomes P.

Malaria, leishmaniasis and Chagas disease are vector-borne protozoal infections with a disproportionately high impact on the most fragile societies in the world, and despite malaria-focused research gained momentum in the past two decades, both trypanosomiases and leishmaniases remain neglected tropical diseases. Affordable effective drugs remain the mainstay of tackling this burden, but toxicicty, inneficiency against later stage disease, and drug resistance issues are serious shortcomings. One strategy to overcome these hurdles is to get new therapeutics or inspiration in nature. Indeed, snake venoms have been recognized as valuable sources of biomacromolecules, like peptides and proteins, with antiprotozoal activity. This review highlights major snake venom components active against at least one of the three aforementioned diseases, which include phospholipases A2, metalloproteases, L-amino acid oxidases, lectins, and oligopeptides. The relevance of this repertoire of biomacromolecules and the bottlenecks in their clinical translation are discussed considering approaches that should increase the success rate in this arduous task. Overall, this review underlines how venom-derived biomacromolecules could lead to pioneering antiprotozoal treatments and how the drug landscape for neglected diseases may be revolutionized by a closer look at venoms. Further investigations on poorly studied venoms is needed and could add new therapeutics to the pipeline. © 2023 The Authors

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Disentangling the Anacondas: Revealing a New Green Species and Rethinking Yellows †

2024 , Rivas J.A. , De La Quintana P. , Mancuso M. , Pacheco L.F. , Rivas G.A. , Mariotto S. , Salazar Valenzuela, David , Baihua M.T. , Baihua P. , Burghardt G.M. , Vonk F.J. , Hernandez E. , García-Pérez J.E. , Fry B.G. , Corey-Rivas S.

Anacondas, genus Eunectes, are a group of aquatic snakes with a wide distribution in South America. The taxonomic status of several species has been uncertain and/or controversial. Using genetic data from four recognized anaconda species across nine countries, this study investigates the phylogenetic relationships within the genus Eunectes. A key finding was the identification of two distinct clades within Eunectes murinus, revealing two species as cryptic yet genetically deeply divergent. This has led to the recognition of the Northern Green Anaconda as a separate species (Eunectes akayima sp. nov), distinct from its southern counterpart (E. murinus), the Southern Green Anaconda. Additionally, our data challenge the current understanding of Yellow Anaconda species by proposing the unification of Eunectes deschauenseei and Eunectes beniensis into a single species with Eunectes notaeus. This reclassification is based on comprehensive genetic and phylogeographic analyses, suggesting closer relationships than previously recognized and the realization that our understanding of their geographic ranges is insufficient to justify its use as a separation criterion. We also present a phylogeographic hypothesis that traces the Miocene diversification of anacondas in western South America. Beyond its academic significance, this study has vital implications for the conservation of these iconic reptile species, highlighting our lack of knowledge about the diversity of the South American fauna and the need for revised strategies to conserve the newly identified and reclassified species. © 2024 by the authors.

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Venom versatility: Dynamic anticoagulant and procoagulant variations between and within Bothrocophias (toad-head) and basal Bothrops (lance-head) pit vipers

2025 , Lachlan A. Bourke , Salazar Valenzuela, David , Marco Mancuso , Diego R. Quirola , Amaru Loaiza-Lange , Christina N. Zdenek , Matthew R. Lewin , Ernesto Arbeláez-Ortiz , Bryan G. Fry

Pinpointing the emergence of toxicological evolutionary novelties can be challenging. In American pit vipers, anticoagulant venoms are the paradigm, with a notable exception being the genus Bothrops, which are typically procoagulant. A recent study found that the basal Bothrops (B. pictus) is anticoagulant, raising two competing hypotheses: ancestral Bothrops were anticoagulant with procoagulant venom evolving later, or ancestral Bothrops were procoagulant with anticoagulant venom in B. pictus being a derived trait. To help resolve this, we tested venoms of the sister genus Bothrocophias for pathophysiological actions upon blood clotting. The Ecuadorian Bothrocophias venoms (B. campbelli, B. lojanus, and B. microphthalmus) were compared to Bothrops pictus. Both Bothrocophias lojanus and B. pictus inhibited various blood clotting enzymes, but B. pictus was more potently anticoagulant. Intriguingly, B. campbelli and B. microphthalmus were procoagulant. Both B. microphthalmus populations activated prothrombin, but Zamora Chinchipe locality also activated Factors X and VII. Bothrocophias campbelli showed a novel activity, using Factor Va in a calcium-dependent manner as a cofactor to activate prothrombin, the first time this has been shown for any viperid venom. Organismal phylogenetics failed to resolve the relative positions of B. campbelli and B. lojanus, thus we were unable to ascertain the ancestral trait. To resolve this, more phylogenetic research and venom testing with other Bothrocophias species is needed. Neutralisation tests revealed differential efficacy of PoliVal-ICP (Instituto Clodomiro Picado) and Soro Antibotrópico (Instituto Butantan) antivenoms. Together, these findings aid in designing evidence-based clinical-management strategies and provide foundational data for reconstructing venom evolution

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Bothrops atrox from Ecuadorian Amazon: Initial analyses of venoms from individuals

2021 , Patiño R.S.P. , Salazar Valenzuela, David , Medina-Villamizar E. , Mendes B. , Proaño-Bolaños C. , da Silva S.L. , Almeida J.R.

Bothrops atrox is the most clinically relevant snake species within the Amazon region, which includes Ecuadorian territories. It comprises a large distribution, which could contribute to the genetic and venomic variation identified in the species. The high variability and protein isoform diversity of its venom are of medical interest, since it can influence the clinical manifestations caused by envenomation and its treatment. However, in Ecuador there is insufficient information on the diversity of venomic phenotypes, even of relevant species such as B. atrox. Here, we characterized the biochemical and toxicological profiles of the venom of six B. atrox individuals from the Ecuadorian Amazon. Differences in catalytic activities of toxins, elution profiles in liquid chromatography, electrophoretic patterns, and toxic effects among the analyzed samples were identified. Nonetheless, in the preclinical testing of antivenom, two samples from Mera (Pastaza) required a higher dose to achieve total neutralization of lethality and hemorrhage. Taken together, these data highlight the importance of analyzing individual venoms in studies focused on the outcomes of envenoming. © 2021 Elsevier Ltd

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A roadmap for harlequin frog systematics, with a partial revision of Amazonian species related to Atelopus spumarius

2025 , STEFAN LÖTTERS , PHILIPP BÖNING , SALVADOR BAILON , JOSE DANIEL BARROS CASTAÑEDA , RENAUD BOISTEL , ALESSANDRO CATENAZZI , JUAN C. CHAPARRO , GERMÁN CHÁVEZ , ANGEL CHUJUTALLI , LAURENT COEN , LUIS A. COLOMA , ANDREW J. CRAWFORD , JAIME CULEBRAS , JUAN CARLOS CUSI MARTÍNEZ , JUAN MANUEL DAZA , IGNACIO DE LA RIVA , DENISE J. ELLWEIN , RAFFAEL ERNST , SANDRA V. FLECHAS , ANTOINE FOUQUET , JUAN MANUEL GUAYASAMIN , CHRISTOPHER HEINE , RAFAEL F. JORGE , ALISHA JUNG , KARL-HEINZ JUNGFER , NATHALIE KAFFENBERGER , HENRIK KREHENWINKEL , ENRIQUE LA MARCA , MARGARITA LAMPO , GUIDO F. MEDINA RANGEL , LUDVIG ORSEN , DANIEL J. PALUH , JOSÉ LUIS PÉREZ GONZALEZ , JONATHAN PERRIN , AMANDA B. QUEZADA RIERA , JUAN PABLO REYES-PUIG , BERNARDO ROCA-REY ROSS , DANIELA C. RÖSSLER , LUIS ALBERTO RUEDA SOLANO , Salazar Valenzuela, David , JOSEFA CELSA SEÑARIS VAZQUEZ , MORGANE SOWINSKI , ANDREA TERÁN-VALDEZ , ANGIE TOVAR-ORTIZ , MICHAEL VEITH , PABLO VENEGAS , RUDOLF VON MAY , TIMM WEITKAMP , AMADEUS PLEWNIA

Harlequin frogs, genus Atelopus, are a species-rich group of bufonid anurans from the Neotropics with more than 100 species. For nearly four decades now, this group has suffered from massive population declines. Almost all species are threatened with extinction, and many populations and several species are considered extinct or possibly extinct. This results in a limited sampling available for studies on harlequin frog systematics, especially in terms of molecular genetic information. However, efficient conservation of harlequin frogs requires an improved taxonomy. This is further complicated through the circumstance that many Atelopus species are relatively poor in external morphological characters combined with a high level of intra-specific character variation (e.g. coloration and body size). At the same time, cryptic diversity exists with well differentiated species (supported by osteology and molecular genetics) almost indistinguishable by external morphology. We compiled the largest dataset to date for mitochondrial (12S, 16S, cyt b) and nuclear (POMC, RAG1) markers and present a phylogeny (likelihood and Bayesian inference methods) including 152 samples from 104 populations scattered over the entire geographic range of the genus. Four allo- or parapatric main clades are distinguished: I. Sierra Nevada; II. Venezuelan-Andean; III. Andean-Chocó-Central American (with the ignescens and the varius-longirostris clades); and IV Amazonian (containing the tricolor and the flavescens-spumarius clades). The phylogenetic relationships within these clades remain to be resolved. Taxonomic implications included both splitting and lumping, but taxonomic action is here only taken for populations related to A. spumarius from western Amazonia. Besides redescriptions of A. spumarius sensu stricto and A. colomai, we describe two new species based on morphology, skull osteology and bioacoustics. Additional yet understudied populations from Amazonia may be allocated to these species or may represent additional undescribed taxa.

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Feeding ecology of the Terciopelo pit viper snake (Bothrops asper) in Ecuador

2023 , Loaiza-Lange A. , Székely D , Torres-Carvajal O. , Tinoco N. , Salazar Valenzuela, David , Székely P.

Thoroughly documenting prey items and diet composition is crucial for understanding a predator’s role in the ecosystem. In gape restricted predators, such as snakes, documenting and analyzing the type and size of the prey is important to interpret their ecological role. We describe the diet patterns of a species of venomous snake, the Terciopelo pit viper (Bothrops asper), from its Ecuadorian populations. Examining the gastrointestinal contents of museum specimens collected over an extensive area of the Pacific lowlands of Ecuador, we encountered 69 identifiable prey items from four major taxonomic groups (amphibians, centipedes, mammals, and reptiles). We evaluated the observed composition of prey to check for differences between sexes and size-classes. To complement our observations of the Terciopelo species complex throughout their distribution, we carried out a systematic literature review. Our data show an ontogenetic shift in diet, with a transition from more diverse diet in juveniles towards a mammal-specialized diet in adults, and distinct proportion of prey taxa between the sexes in the juvenile size class. Copyright 2023 Loaiza-Lange et al.

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Divergence of tropical pitvipers promoted by independent colonization events of dry montane Andean habitats

2019 , Salazar Valenzuela, David , Kuch U. , Torres-Carvajal O. , Valencia J.H. , Gibbs H.L.

Aim: A poorly explored feature of the origin and maintenance of Neotropical biodiversity is how the evolutionary dynamics of colonization and differentiation in relation to lowland and highland habitats has impacted lineage formation. Most speciation models for this region have focused on vicariant events, whereas the need to assess the influence of demographic processes has been recognized only recently. We evaluate if the origin of Andean montane lineages of terciopelo pitvipers is explained by either of two historical processes that represent distinct phylogeographic mechanisms: differentiation by isolation within the highlands or different dispersal events from the lowlands. Location: Western Ecuador. Taxon: Terciopelo pitvipers (Bothrops asper species complex). Methods: We use genomic data and genetic clustering analyses, evaluation of historical migration between genetic clusters and demographic model selection to investigate recent diversification events in South America using a vertebrate group rarely explored in phylogeographic studies: tropical Andean snakes. Specifically, the origin of two Ecuadorian montane lineages of terciopelo pitvipers was evaluated given ambiguous phylogenetic relationships with the presumably ancestral Pacific lowland lineage. Results: Discrepancies of evolutionary relationships previously obtained with tree-like methods are resolved through the use of modelling approaches. We found strong support for the independent origin of montane lineages based on topologies inferred by maximum-likelihood trees and modelling approaches that take into account possible gene flow. This suggests dispersal rather than in-situ differentiation as the most likely mechanism by which the montane linages originated. Main conclusions: Recent large-scale studies have found support for identifying dispersal events as important drivers of diversification in the Neotropical region. We contribute to these ideas by identifying a fine-scale case in a rarely studied group of animals -Andean snakes- in which river valleys acted as an entrance for the upward colonization of montane dry habitats and subsequent ecological diversification. © 2019 John Wiley & Sons Ltd

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Path for recovery: an ecological overview of the Jambato Harlequin Toad (Bufonidae: Atelopus ignescens) in its last known locality, Angamarca Valley, Ecuador

2024 , Mateo A. Vega-Yánez , Amanda B. Quezada-Riera , Blanca Rios-Touma , María del Carmen Vizcaíno-Barba , William Millingalli , Orlando Ganzino , Luis A. Coloma , Elicio E. Tapia , Nadine Dupérré , Mónica Páez-Vacas , David Parra-Puente , Daniela Franco-Mena , Gabriela Gavilanes , Salazar Valenzuela, David , Carlos A. Valle , Juan M. Guayasamin

The Jambato Harlequin toad (Atelopus ignescens), a formerly abundant species in the Andes of Ecuador, faced a dramatic population decline in the 1980s, with its last recorded sighting in 1988. The species was considered Extinct by the IUCN until 2016, when a fortuitous discovery of one Jambato by a local boy reignited hope. In this study, we present findings from an investigation conducted in the Angamarca parish, focusing on distribution, abundance, habitat preferences, ecology, disease susceptibility, and dietary habits of the species. In one year we identified 71 individuals at different stages of development in various habitats, with a significant presence in agricultural mosaic areas and locations near water sources used for crop irrigation, demonstrating the persistence of the species in a complex landscape, with considerable human intervention. The dietary analysis based on fecal samples indicated a diverse prey selection, primarily comprising arthropods such as Acari, Coleoptera, and ants. Amphibian declines have been associated with diseases and climate change; notably, our study confirmed the presence of the pathogen Batrachochytrium dendrobatidis (Bd), but, surprisingly, none of the infected Jambatos displayed visible signs of illness. When analyzing climatic patterns, we found that there are climatic differences between historical localities and Angamarca; the temporal analysis also exposes a generalized warming trend. Finally, in collaboration with the local community, we developed a series of management recommendations for terrestrial and aquatic environments occupied by the Jambato.

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