Crocodylus Intermedius Research Articles

Population genetic structure in the critically endangered Crocodylus intermedius (Crocodilia: Crocodylidae): a shift in perspective for conservation actions in Colombia

Abstract Conservation actions for threatened species and populations aim to preserve their genetic diversity and prevent issues such as inbreeding or outbreeding depressions. This perspective has been incorporated into the management plans proposed for the critically endangered Orinoco crocodile (Crocodylus intermedius) in Colombia. A previous study, which used mitochondrial cytochrome b and cytochrome c oxidase subunit I, suggested that the in situ population management of the Orinoco crocodile in Colombia does not face genetic restrictions. In this research, we re-evaluated this proposal by using an expanded sampling and additional molecular markers (microsatellite nuclear DNA and the mitochondrial D-loop) that have successfully identified crucial information at the population level in other crocodilians. Our findings reveal, for the first time, a pattern of population structure consisting of three genetic clusters with geographical correspondence, matching three ecoregions in the Colombian Orinoco basin. This pattern might be a historical and current consequence of the ecological, bioclimatic, and/or geographical features of the ecoregion. Additionally, we examined the correspondence with the genetic clusters of the confiscated individuals that formed part of the initial population (F0) of the Colombian ex situ species population and successfully assigned most of them to one of these clusters. The genetically distinct clusters should be regarded as independent management units for conserving and managing the species in Colombia.

First genetic evaluation of a wild population of Crocodylus intermedius: New insights for the recovery of a Critically Endangered species.

During the second third of last century, the Orinoco Crocodile (Crocodylus intermedius) underwent a hunting process driven by the demand from the North American, European, and Japanese leather industry, resulting in a sharp decline of its populations. Currently, only two known remaining populations of this Critically Endangered species persist in the Colombian Orinoquía: in the Guayabero-Duda-Lozada and the Cravo Norte-Ele-Lipa River Systems. The latter has been the only population subject of study, including recent surveys and local conservation initiatives such as egg and hatchling ranching. Despite suggestions for population recovery based on the observed increase in clutches in the area, information regarding its genetic status has been pending assessment. This research aims to provide a genetic characterization of this remaining population and to evaluate the diversity recovered during a period of the egg ranching initiative. For this purpose, we utilized variable molecular markers, specifically 17 microsatellite loci, nuclear DNA. Despite revealing intermediate levels of genetic diversity, we identified an effective population size of 11.5-17, well below the minimum values proposed for short-term subsistence. While no evidence of inbreeding was found, it is acknowledged as a potential risk based on the population's history. Additionally, we detected a historical bottleneck possibly influenced by arid periods affecting the region since the Pleistocene. While the evaluated population presents a unique opportunity for C. intermedius conservation, it also exposes a high risk of entering the extinction vortex. The primary action to be taken is to support the egg and hatchling ranching program, which successfully recovered most of the genetic diversity present in the population.

Reintroduction of adult Orinoco crocodiles: a crucial step towards the species recovery

Reintroduction of adult Orinoco crocodiles: a crucial step towards the species recovery

Hope is the last thing lost: Colombian captive-bred population of the critically endangered Orinoco crocodile (Crocodylus intermedius) is a genetic reservoir that could help to save the species from extinction

A purpose of ex-situ populations is the preservation of genetic variation, but this is a challenging task since genetic diversity is commonly lost through each generation, and so the establishment of management guidelines should be a high priority. Fifty years ago, the National University of Colombia began a breeding program in the Roberto Franco Tropical Station (in Villavicencio, Meta) to conserve the critically endangered Orinoco crocodile Crocodylus intermedius. Despite the large number of individuals raised and kept in captivity, the Station has not been able to release individuals due to a lack of a complete genetic characterization that could determine whether the population is genetically viable. In this study we used a panel of 17 microsatellite loci to overcome this problem. We estimated from the founder animals and the live crocodiles the inbreeding, heterozygosities, the number of alleles, and their richness, and frequencies to understand the effects of managing a captive breeding program without considering genetic profiles. Our results revealed that the living population maintains much of its founder diversity with high levels of heterozygosity and low overall inbreeding, making it suitable for maintaining captive breeding and for implementing wild releases. We estimated the individual genetic diversity of the living crocodiles, as well as their relationships. This information, combined with the size, sex, and location, allowed us to propose combinations and to restructure the breeding groups. We demonstrated that molecular data could be used to improve the management of ex-situ conservation programs well beyond what could be achieved with pedigree information alone.

Hematology, Biochemistry Reference Intervals, and Morphological Description of Peripheral Blood Cells for a Captive Population of Crocodylus intermedius in Colombia.

The Orinoco crocodile (Crocodylus intermedius, Graves, 1918) is the most threatened crocodilian of South America. There is only scarce information available about the physiology of this neotropical crocodile. This study aimed to propose baseline hematological and biochemistry reference data and intervals and a morphological description of the peripheral blood cells of captive C. intermedius. Blood was collected from 318 clinically healthy individuals maintained in captivity at Villavicencio, Colombia. Eight of these individuals were sampled and resampled, and these data were compared. Reference intervals were proposed for hematological values [packed cell volume (PCV), red blood cell count, white blood cell count, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, hemoglobin, and white blood cell count differential counts] and biochemistries [total solids, alanine aminotransferase (ALT), aspartate aminotransferase, alkaline phosphatase, lactate dehydrogenase, creatine kinase, glucose, albumin, cholesterol, uric acid, creatinine, and lactate] including adults and juveniles, males and females' crocodiles. Blood cell morphology for the species is described. Significant differences between sex and age were observed. The intraindividual analysis concluded differences for total solids (P ≤ 0.01) and red blood cell counts (P ≤ 0.01). Some biochemical analytes showed a moderate correlation between them, such as ALT–alkaline phosphatase and ALT–uric acid. We present here novel and baseline data with special importance for the clinical diagnosis, improving the national reintroduction programs from either in situ and ex situ populations.

Unprovoked Mouth Gaping Behavior in Extant Crocodylia

Unprovoked mouth gaping behavior is ubiquitous throughout 24 extant members of Crocodylia, yet information on gaping is limited. Proposed hypotheses for gaping include thermoregulation and the evaluation of potential environmental conditions. To determine temperature effects, we tracked head surface (Tsh), body surface (Tsb), and ambient (Ta) temperatures with insolation utilization and positions. To evaluate potential environmental stimuli, we tested behavioral effects (i.e., open-eye frequency) and recorded conspecific presence, day and night events, and interaction with flies and fish. We included 24 extant species representatives, with detailed assessments of American Alligators (Alligator mississippiensis), Crocodylus siamensis, Crocodylus intermedius, Crocodylus rhombifer, and Crocodylus halli. Observations occurred during a range of Ta (3.89–32.22°C) with mean Tsh consistently higher than both Tsb and Ta across all crocodilians. Differences in Tsh and Ta were most pronounced with head in the sun. However, no significant differences in Tsh and Tsb were detected for A. mississippiensis and Cr. siamensis. Conversely, Cr. halli, Cr. intermedius, and Cr. rhombifer demonstrated statistically higher Tsh. Gaping with open eyes was more common, yet modeling suggested a relationship with closed eyes and temperature. Anecdotal observations indicated weather changes may elicit mouth gaping, and we report the second nocturnal mouth gaping observation (the first for three species). Overall, mixed results indicated unprovoked mouth gaping is a complex behavior, making it difficult to draw clear cause and effect relationships. Future research may benefit from a focus on natural history and quantitative behavioral studies.

Individual identification of Crocodylus intermedius (Orinoco crocodile) using tail spot patterns

Introduction: The Conservation Action Plan of the Orinoco crocodile (Crocodylus intermedius) includes in its activities the release of captive-bred specimens back into the wild. By monitoring these specimens in their natural habitat their adaptability is assessed. However, an accurate identification system is necessary to recognize the individuals when they are recaptured. Objetive: Determinate if Swanepoel or Boucher et al. for crocodile identification for the Orinoco crocodile is useful. Methods: A total of 543 Orinoco crocodiles were photographed and each photo was vectorized by drawing dark spots greater than 25% for each scute, in the first 10 lines of double caudal scales of the tail on the right side. Two system codes were evaluated, one is a numeric code described by Swanepoel and the other is an additive code described by Boucher et al. Results: A total of 464 Swanepoel codes and 537 Boucher et al. codes based on the dark spot pattern of the scales on the right side of the tails were generated for the 543 specimens. Both methods yielded high code values, however, the one developed by Boucher et al., with a 98.90% differentiation of the analyzed specimens, worked better. Conclusion: The study confirms that using the method of spots in the tail of crocodiles is an effective tool for identifying individual crocodiles.

Old African fossils provide new evidence for the origin of the American crocodiles

Molecular and morphological phylogenies concur in indicating that the African lineages formerly referred to Crocodylus niloticus are the sister taxon the four Neotropical crocodiles (Crocodylus intermedius, C. moreleti, C. acutus and C. rhombifer), implying a transoceanic dispersal from Africa to America. So far the fossil record did not contribute to identify a possible African forerunner of the Neotropical species but, curiously, the oldest remains referred to the African C. niloticus are Quaternary in age, whereas the oldest American fossils of Crocodylus are older, being dated to the early Pliocene, suggesting that another species could be involved. We re-described, also thanks to CT imaging, the only well-preserved topotipic skull of Crocodylus checchiai Maccagno, 1947 from the late Miocene (Messinian) African site of As Sahabi in Libya. As previously suggested on the basis of late Miocene material from Tanzania, C. checchiai is a valid, diagnosable species. According to our phylogenetic analyses, C. checchiai is related to the Neotropical taxa and could be even located at the base of their radiation, therefore representing the missing link between the African and the American lineages.

Journeying to freedom: the spatial ecology of a reintroduced population of Orinoco crocodiles (Crocodylus intermedius) in Colombia

BackgroundThe Orinoco crocodile (Crocodylus intermedius) is the largest crocodile and the most threatened by extinction in the Neotropics due to overexploitation for the skin trade during the early–middle twentieth century. Knowledge of their ecology is poor in Colombia because long-term armed conflict has restricted fieldwork. In 2015, we reintroduced four captive-reared adult crocodiles, each equipped with a Sirtrack KiwiSat 202 satellite transmitter and monitored their movements from 2015 to 2018.ResultsSeasonal movements were as far 177 km in males and 115 km in females. Home ranges were as large as 55 km2 for males and 16 km2 for females for a single year and 178 km2 and 21 km2, respectively, for males and females over 2 years. Spatial ecological patterns changed drastically by season, with males increasing their home range and females reducing home range during the wet season. We confirmed that daily activity patterns defined as measure by number of locations across the day were not influenced by season.ConclusionsWe believe that seasonal changes in the size and shape of home ranges were associated with patrolling or exploratory behaviors after release, while daily activity behavior was independent of season, sex or size of the animal.

Surveying death roll behavior across Crocodylia

The “death roll” is an iconic crocodylian behaviour, and yet it is documented in only a small number of species, all of which exhibit a generalist feeding ecology and skull ecomorphology. This has led to the interpretation that only generalist crocodylians can death roll, a pattern which has been used to inform studies of functional morphology and behaviour in the fossil record, especially regarding slender-snouted crocodylians and other taxa sharing this semi-aquatic ambush predator body plan. In order to test this hypothesis, we surveyed death roll behaviour across animals representing all extant crocodylian species. Animals were prompted to death roll using two methods of stimulation: a feeding cue and an escape cue. The feeding cue involved presenting each animal with a bait item, to which resistance would be applied during a biting event. The second cue involved capturing each animal with a rope or catch pole, a standard technique for capturing crocodylians, but one that also often prompts an attempt to escape. All species tested, except Paleosuchus palpebrosus, exhibited the behaviour in response to at least one of the stimuli. This included the following slender-snouted species: Gavialis gangeticus, Tomistoma schlegelii, Mecistops cataphractus, Mecistops leptorhynchus, Crocodylus johnstoni, and Crocodylus intermedius. The patterns of death roll behavior observed in this survey suggest that this behaviour is not novel to any one crocodylian clade, morphotype, or dietary niche. Also, the prevalence of death rolling behaviour across Crocodylia in response to perceived threats indicates that it is not solely, or maybe even primarily, a feeding behaviour, but is also utilised during inter- and intra-specific conflict as a means to escape or injure an opponent. The results of this case study highlight the importance of using multiple modern analogues when attempting to correlate form and function across diverse clades, both living and extinct.

New Miocene Caribbean gavialoids and patterns of longirostry in crocodylians

Gavialoidea is a clade of slender- and long-snouted crocodylomorphs with a single living species, the Indian gharial Gavialis gangeticus. Because elongated snouts (longirostry) have evolved independently in several crocodylomorph clades, this head shape has been interpreted as an ecological adaptation. How this condition affected patterns of diversification and how longirostrine-associated cranial features changed through adaptive radiations remain poorly understood. Two new small gryposuchine gavialoids, Dadagavialis gunai gen. et sp. nov. (early Miocene, Panama) and Aktiogavialis caribesi sp. nov. (late Miocene, Venezuela), evidence remarkable Miocene diversification of longirostrine forms in the Neotropics and support transmarine biogeographical relations between northern South America, the Caribbean, and southernmost North America before the Isthmus of Panama was fully established. By integrating phylogenetics and geometric morphometrics, we focus on this gavialoid diversity to investigate patterns of longirostry across the crown group of crocodylomorphs (Crocodylia). Analyses revealed that the snout shape of gavialoids has occupied a small, distinct and almost invariable morphospace since the Cretaceous, in contrast with the morphologically labile snout shape of other crocodylians (crocodyloids and alligatoroids). Our results suggest iterative environmental shift occupations throughout gavialoid evolution without major changes in snout proportions, but involving conspicuous rearrangements of the circumorbital bones. The longirostrine gavialoid morphotype is a distinct adaptation for seizing small prey and typically includes short and wide premaxillae and enlarged ‘caniniform’ teeth only at the tip of the snout. In longirostrine crocodyloids (Tomistoma, Crocodylus intermedius), the conservation of powerful bites and ‘caniniforms’ closer to the jaw joints allowed them to exploit a wider range of prey sizes, which could explain their snout shape plasticity. Therefore, the Mio–Pliocene extirpation of gryposuchine gavialoids from the Caribbean by the arrival of Crocodylus is quite unlikely. The last gryposuchine survived throughout the Pliocene in the south-eastern Pacific, where Crocodylus has never been documented.http://zoobank.org/urn:lsid:zoobank.org:pub:34CDBC8B-98E1-4770-8FC3-A77D3DBF4057

Oral and Cloacal Helicobacter Detection in Wild and Captive Orinoco Crocodiles (Crocodylus intermedius) in Venezuela.

Helicobacter species can colonize digestive tract of animals and humans and have been associated with gastrointestinal diseases; however, this genus has not been studied in crocodiles. Our objective was to detect by PCR Helicobacter genus and Helicobacter pylori in oral and cloacal swabs from Orinoco crocodiles of two wild (Cojedes River System and Capanaparo River) and two captive breeding centers (CBCs; Masaguaral Ranch and UNELLEZ) populations. Bacterial DNA was found in 100% of oral samples (10 wild and 10 captives), and in the 95% of cloacal samples (10 wild and 9 captives). In wild populations, Helicobacter spp. was not detected, whereas in CBCs, Helicobacter was detected in 10% of the oral samples, and 66.7% of cloacal samples. H. pylori was detected in two Orinoco crocodiles. Two cloacal non-pylori Helicobacter amplicons were sequenced, showing low similarity (≤97%) to Helicobacter sequences reported. This is the first report of Helicobacter species, including H. pylori in Crocodylus intermedius from CBCs.

Conservation status and regional habitat priorities for the Orinoco crocodile: Past, present, and future.

Conservation of large predator species has historically been a challenge because they often overlap in resource utilization with humans; furthermore, there is a general lack of in-depth knowledge of their ecology and natural history. We assessed the conservation status of the Orinoco crocodile (Crocodylus intermedius), defining regional habitat priorities/crocodile conservation units (RHP/CCU) and regional research priorities (RRP) for this species. We also estimated a species distribution model (SDM) to define current suitable areas where the species might inhabit and/or that might be successfully colonized. The SDM area obtained with a suitable habitat probability ≥ 0.5 was 23,621 km2. Out of 2,562 km2 are included within protected areas in both Colombia (1,643 km2) and Venezuela (919 km2), which represents only 10.8% of C. intermedius’ potential range. Areas such as Laguna de Chigüichigüe (flood plain lagoon) exhibited an increase in population abundance. In contrast, localities such as the Cojedes and Manapire Rivers reported a significant reduction in relative abundance values. In Colombia, disparity in previous survey methods prevented accurate estimation of population trends. Only one study in this country described an increase over a 13 years span in the Ele, Lipa, and Cravo Norte River populations based on nest surveys. We defined 34 critical areas (16 in Colombia, 17 in Venezuela, and one covering both countries) where we need to preserve/research/monitor and/or generate management actions, 10 RHP/CCU (six from Venezuela and four from Colombia) and 24 RRP (11 from Venezuela, 12 from Colombia, and one in both countries). Caño Guaritico (Creek) and the Capanaparo River in Venezuela and the Ele, Lipa, Cravo Norte River System and the Guayabero River in Colombia were defined as areas with the most optimal conditions for long-term preservation and maintenance of C. intermedius populations. We conclude that the conservation status of this species is still critical, which implies the necessity to increase efforts to recover the species, especially in Colombia, to guarantee its survival as a structural and functional component of the ecosystems it inhabits.

Mitogenomic investigation reveals a cryptic lineage of Crocodylus in Cuba

The American crocodile, Crocodylus acutus (Cuvier, 1807), is the most widely distributed crocodylian in the Americas, and coexists with the endemic and critically endangered Cuban crocodile, Crocodylus rhombifer Cuvier, 1807. Although these species are morphologically distinguishable, previous studies have shown that they are more genetically related to each other than either of them are to continental C. acutus. Here, we characterize the mitochondrial genome of Cuban C. acutus and analyze the resulting data relative to previously published whole mitochondrial genomes to reconstruct patterns of variation and phylogenetic placement within Crocodylus. We sequenced 13,776 basepairs, representing 82% of the entire genome including five (COI, COII, ATP8, ND3, ND4L) of the 13 protein-coding genes and 16 of the 22 tRNAs. Independent gene analysis of nucleotide diversity and genetic distance of Tamura-Nei demonstrated that the 16S rRNA, 12S rRNA, and COI genes are the most conserved in Crocodylus, while ND6 was the most variable (approximately 9%). Phylogenetic analysis confirmed that Cuban C. acutus forms a well-supported sister relationship with C. rhombifer, in contrast to continental C. acutus that clusters with Crocodylus intermedius Graves, 1819. The results are consistent with the hypothesis that Antillean C. acutus represents a cryptic lineage with genetic divergence at the species level. The ability to fully evaluate the taxonomic status of the Caribbean lineage of C. acutus still requires more comprehensive population samplings across the range as well as nuclear DNA sequence data. Of more immediate consequence, our results provide important information to be integrated into current Crocodylus conservation strategies in Cuba.

Multiple Paternity in a Reintroduced Population of the Orinoco Crocodile (Crocodylus intermedius) at the El Frío Biological Station, Venezuela.

The success of a reintroduction program is determined by the ability of individuals to reproduce and thrive. Hence, an understanding of the mating system and breeding strategies of reintroduced species can be critical to the success, evaluation and effective management of reintroduction programs. As one of the most threatened crocodile species in the world, the Orinoco crocodile (Crocodylus intermedius) has been reduced to only a few wild populations in the Llanos of Venezuela and Colombia. One of these populations was founded by reintroduction at Caño Macanillal and La Ramera lagoon within the El Frío Biological Station, Venezuela. Twenty egg clutches of C. intermedius were collected at the El Frío Biological Station for incubation in the lab and release of juveniles after one year. Analyzing 17 polymorphic microsatellite loci from 335 hatchlings we found multiple paternity in C. intermedius, with half of the 20 clutches fathered by two or three males. Sixteen mothers and 14 fathers were inferred by reconstruction of multilocus parental genotypes. Our findings showed skewed paternal contributions to multiple-sired clutches in four of the clutches (40%), leading to an overall unequal contribution of offspring among fathers with six of the 14 inferred males fathering 90% of the total offspring, and three of those six males fathering more than 70% of the total offspring. Our results provide the first evidence of multiple paternity occurring in the Orinoco crocodile and confirm the success of reintroduction efforts of this critically endangered species in the El Frío Biological Station, Venezuela.

Similarity of Crocodilian and Avian Lungs Indicates Unidirectional Flow Is Ancestral for Archosaurs

Patterns of airflow and pulmonary anatomy were studied in the American alligator (Alligator mississippiensis), the black caiman (Melanosuchus niger), the spectacled caiman (Caiman crocodilus), the dwarf crocodile (Osteolaemus tetraspis), the saltwater crocodile (Crocodylus porosus), the Nile crocodile (Crocodylus niloticus), and Morelet's crocodile (Crocodylus moreletii). In addition, anatomy was studied in the Orinoco crocodile (Crocodylus intermedius). Airflow was measured using heated thermistor flow meters and visualized by endoscopy during insufflation of aerosolized propolene glycol and glycerol. Computed tomography and gross dissection were used to visualize the anatomy. In all species studied a bird-like pattern of unidirectional flow was present, in which air flowed caudad in the cervical ventral bronchus and its branches during both lung inflation and deflation and craniad in dorsobronchi and their branches. Tubular pathways connected the secondary bronchi to each other and allowed air to flow from the dorsobronchi into the ventrobronchi. No evidence for anatomical valves was found, suggesting that aerodynamic valves cause the unidirectional flow. In vivo data from the American alligator showed that unidirectional flow is present during periods of breath-holding (apnea) and is powered by the beating heart, suggesting that this pattern of flow harnesses the heart as a pump for air. Unidirectional flow may also facilitate washout of stale gases from the lung, reducing the cost of breathing, respiratory evaporative water loss, heat loss through the heat of vaporization, and facilitating crypsis. The similarity in structure and function of the bird lung with pulmonary anatomy of this broad range of crocodilian species indicates that a similar morphology and pattern of unidirectional flow were present in the lungs of the common ancestor of crocodilians and birds. These data suggest a paradigm shift is needed in our understanding of the evolution of this character. Although conventional wisdom is that unidirectional flow is important for the high activity and basal metabolic rates for which birds are renowned, the widespread occurrence of this pattern of flow in crocodilians indicates otherwise. Furthermore, these results show that air sacs are not requisite for unidirectional flow, and therefore raise questions about the function of avian air sacs.

The Biology and Conservation Status of the American Crocodile in Colombia

Abstract Along with the Orinoco and Cuban Crocodiles (Crocodylus intermedius and Crocodylus rhombifer), the American Crocodile (Crocodylus acutus) is among the most threatened crocodylian species in the Americas. Although this species is distributed widely, its IUCN “threat category” in several countries is “of concern.” We review the literature dealing with the biology and conservation status of C. acutus in Colombia and assess its Extent of Occurrence (EoO) and its EoO-Habitat Status. We propose a way to estimate the effective area of optimal habitable occurrence on the basis of the EoO (EoO-Effective Habitable Area). We found that only 37% of the national territories have been sampled in ecological studies during the last decade. The relatively few reports of abundance values and the lack of long-term projects that can produce accurate estimates of population sizes make it difficult to establish the conservation status of this species in Colombia. Our analyses indicate that the EoO-Habitat Status has a...

Elementos claves para la conservación in situ de Crocodylus intermedius derivados del seguimiento de metapoblaciones y hábitats en Arauca, Colombia

Con base en metodología para detección en campo de individuos desarrollada conforme a las características de los grupos de la especie en el Departamento de Arauca, en cuanto a su distribución y concentración temporal, se efectuaron recorridos y visitas a dichos sitios en diferentes años con el fin de determinar las presiones y amenazas que tenía y tiene el caimán llanero en los caños y ríos principales del departamento y en consecuencia plantear opciones de conservación in situ, a través de selección de áreas a proteger empleando al Crocodylus intermedius como especie sombrilla. En el presente documento, a partir de la combinación de datos publicados (BARAHONA y BONILLA, 1999) e inéditos (principalmente de CLAVIJO, 1992, 1997; ANZOLA et al., 2012) relacionados con el seguimiento a la metapoblación del Cocodrilo del Orinoco en el Departamento de Arauca, se define su estado actual y combinando dicha información con las conclusiones y recomendaciones del trabajo efectuado a través de PROCAIMAN en el 2008, se formulan elementos claves para el establecimiento de áreas y programas de conservación in situ de Crocodylus intermedius en los Llanos Orientales de Colombia.

Aislamiento y serotipificación de Salmonella sp. en estanques con Crocodylus intermedius y testudines cautivos en Villavicencio - Colombia

Objetivo. Determinar la presencia de microorganismos del género Salmonella sp. en el ambiente acuático de los ejemplares Crocodylus intermedius y testudines en la Estación de Biología Tropical Roberto Franco (EBTRF). Materiales y métodos. En este estudio se utilizó la metodología estándar para aislar e identificar microorganismos del género Salmonella sp., a partir de muestras de agua y sedimento de 52 estanques (nEstanques Crocodylus=25; nEstanques testudines=27); se procedió a serotipificar los aislamientos por el método convencional de Kaufmann-White y se realizaron pruebas de sensibilidad a antimicrobianos por la técnica de Kirby Bauer. Resultados. Se determinó la presencia de Salmonella sp., en un 33% del total de estanques muestreados. El 29% de los aislamientos de Salmonella sp. serotipificados, correspondió al serogrupo B; los serogrupos C, C1, C2 y D1 presentaron menores porcentajes. Con las pruebas de sensibilidad a antimicrobianos se determinó que el 100% de los aislamientos fueron sensibles a norfloxacina. Conclusiones. La ocurrencia de Salmonella sp., en los estanques de la EBTRF fue del 33%, con la mayor presencia del serogrupo B, donde se encuentran especies con características ampliamente zoonóticas. Con los resultados obtenidos es necesario el seguimiento de las normas de bioseguridad establecidas en la estación para el manejo de las poblaciones allí mantenidas y evitar de esa manera la ocurrencia de cuadros zoonóticos.

β-Keratins in crocodiles reveal amino acid homology with avian keratins

The DNA sequences encoding beta-keratin have been obtained from Marsh Mugger (Crocodylus palustris) and Orinoco Crocodiles (Crocodylus intermedius). Through the deduced amino acid sequence, these proteins are rich in glycine, proline and serine. The central region of the proteins are composed of two beta-folded regions and show a high degree of identity with beta-keratins of aves and squamates. This central part is thought to be the site of polymerization to build the framework of beta-keratin filaments. It is believed that the beta-keratins in reptiles and birds share a common ancestry. Near the C-terminal, these beta-keratins contain a peptide rich in glycine-X and glycine-X-X, and the distinctive feature of the region is some 12-amino acid repeats, which are similar to the 13-amino acid repeats in chick scale keratin but absent from avian feather keratin. From our phylogenetic analysis, the beta-keratins in crocodile have a closer relationship with avian keratins than the other keratins in reptiles.