Caiman Crocodilus Research Articles

Estructura poblacional y proporción de sexos en Caiman crocodilus en Caño Negro, Costa Rica

Desde 1986 se han llevado acabo evaluaciones sobre el estado poblacional de Caiman crocodilus (Linnaeus, 1758) en el Refugio Nacional de Vida Silvestre Caño Negro. Sin embargo, solo se conoce información sobre la abundancia y el tamaño poblacional. El objetivo de este estudio fue evaluar la estructura poblacional y proporción de sexos de C. crocodilus en Caño Negro. Se capturó un total de 145 caimanes mediante 22 conteos nocturnos desde Mayo 2004 a Mayo 2005. La mayoría de los individuos presentaron longitudes menores a 60 cm y entre 150 a 180 cm. La proporción de sexos promedio fue de 1: 6.06 hembra/machos, siendo una de las mayores diferencias reportadas para la especie; de mantenerse la proporción de sexos, es de esperar una disminución en la viabilidad poblacional a corto y mediano plazo.

Mitochondrial DNA phylogeography of Caiman crocodilus in Mesoamerica and South America

The Neotropical crocodylian species, Caiman crocodilus, is widely distributed through Mesoamerica, northern South America, and the Amazon basin. Four subspecies are recognized within C. crocodilus, suggesting some geographic variation in morphology. In this study, we utilized mitochondrial DNA (mtDNA) sequence data from 45 individuals of C. crocodilus throughout its range to infer its evolutionary history and population structure, as well as to evaluate genealogical support for subspecies and their geographic distributions. Our molecular phylogenetic results identified five mtDNA haplotype clades with a mean sequence divergence of 3.4%, indicating considerable evolutionary independence among phylogeographic lineages. Our results were also broadly consistent with current subspecific taxonomy, with some important additional findings. First, we found substantial genetic structuring within C. c. fuscus from southern Mesoamerica. Second, though we confirmed the existence of a widespread Amazonian clade, we also discovered a cryptic and divergent mtDNA lineage that was indistinguishable from C. c. crocodilus based on external morphology. Third, we confirm the status of C. c. chiapasius as a distinct evolutionary lineage, and provide evidence that C. c. fuscus may be moving northward and hybridizing with C. c. chiapasius in northern Mesoamerica. Finally, our results parallel previous phylogeographic studies of other organisms that have demonstrated significant genetic structure over shorter geographic distances in Mesoamerica compared with Amazonia. We support conservation efforts for all five independent lineages within C. crocodilus, and highlight the subspecies C. c. chiapasius as a unit of particular conservation concern.

Molecular identification of crocodile species using novel primers for forensic analysis

All crocodilians are under varying degrees of threat due to over exploitation and these species have been listed in Appendix I or II of CITES. The lack of molecular techniques for the identification of confiscated samples makes it difficult to enforce the law. Conclusive forensic identification of species requires a complete gene sequence which is difficult in case of degraded samples. We have developed two novel sets of primers to amplify two partial cytochrome b gene sequences of six crocodile species i.e. Crocodylus palustris, Crocodylus porosus, Crocodylus siamensis, Crocodylus niloticus, Gavialis gangeticus and Caiman crocodilus. These partial sequences were edited to give a complete cyt b gene sequence, which can be used as an effective tool for forensic authentication of crocodile species. A phylogeny of crocodile species was reconstructed using these sequences. The described primers hold great promise in forensic identification of crocodile species, which can aid in the effective enforcement of law and conservation of these ancient species.

Incubação artificial a 28ºC e crescimento inicial de jacaré do pantanal (Caiman crocodilus yacare) em diferentes temperaturas

Twenty Pantanal Caiman (Caiman crocodilus yacare) eggs were artificially incubated at 28°C. During the incubation, three eggs were opened in order to check their viability. 94.11% of hatchability was detected, with the hatching of 16 eggs. The hatched animals were kept under two different temperatures during growth (28oC and 32°C), and submitted to morphometrical analysis. The collected data were analyzed according to the analysis of variance. The characteristics of the weight of the animals and the width of the head did not present significant differences (P > 0.05) between the treatments. The circumference of the belly and width of snout at nostrils were the ones that had the best (P < 0.05) results at 28°C. The other characteristics as total length, tail length ,snout-vent length ,head length, eye length, snout length, width of snout at mid-point and distance between limbs showed better results at 32°C. It may be concluded that temperature variation did not influence the gain of weight, but the temperature of 32°C was the best for the general development of the animals.

Factors Affecting the Number of Caimans Seen during Spotlight Surveys in the Mamirauá Reserve, Brazilian Amazonia

Between 1995 and 1998 we studied the effects of water level, moon phase, and site on the number of caimans observed in spotlight surveys in the Mamirauá Sustainable Development Reserve, Brazilian Amazonia. Multiple linear regression analyses including water level of the Amazon River and the moon phase explained 91 and 73% of the variance in number of Melanosuchus niger seen in spotlight surveys in Lago Mamirauá and Cano Mamirauá, respectively, and 60 and 76%, respectively, of the variance in the number of Caiman crocodilus seen. Water level had a statistically significant and negative effect on the number of M. niger and C. crocodilus seen. Moon phase had no significant effect on the number of C. crocodilus seen, but more M. niger were detected in Lago Mamirauá on nights with more moon light. The regression equations derived for Lago Mamirauá and Cano Mamirauá did not adequately predict the variation in numbers seen in 18 other water bodies in the Mamirauá Reserve. Analysis of covariance showed an interaction between water level and site on the numbers of M. niger and C. crocodilus observed in the spotlight surveys in these water bodies, indicating that the effect of water level depends on the site. In these analyses, moon phase did not have a significant effect on either species, and there was no interaction between moon phase and site. To monitor natural tendencies, or impacts (e.g., controlled commercial hunting), on caiman populations of Mamirauá Reserve, it will be necessary to undertake regular spotlight surveys in many water bodies of all types at a narrow range of water level to have confidence in the results.

Cross-species amplification of microsatellites in crocodilians: assessment and applications for the future

Microsatellite DNA loci have emerged as the dominant genetic tool for addressing questions associated with genetic diversity in many wildlife species, including crocodilians. Despite their usefulness, their isolation and development can be costly, as well as labour intensive, limiting their wider use in many crocodilian species. In this study, we investigate the cross-species amplification success of 82 existing microsatellites previously isolated for the saltwater crocodile (Crocodylus porosus) in 18 non-target crocodilian species; Alligator sinensis, Caiman crocodylus, Caiman latirostris, Caiman yacare, Melanosuchus niger, Paleosuchus palpebrosus, Crocodylus acutus, Mecistops cataphractus, Crocodylus intermedius, Crocodylus johnstoni, Crocodylus mindorensis, Crocodylus moreletii, Crocodylus niloticus, Crocodylus novaeguineae, Crocodylus palustis, Crocodylus rhombifer, Crocodylus siamensis, and Osteolaemus tetraspis. Our results show a high level of microsatellites cross-amplification making available polymorphic markers for a range of crocodilian species previously lacking informative genetic markers.

Feeding Behavior of Two Sympatric Caiman Species, Melanosuchus niger and Caiman crocodilus, in the Brazilian Amazon

We studied the feeding behaviors of two sympatric species of caimans (Melanosuchus niger and Caiman crocodilus) during the dry season in the Mamirauá Sustainable Development Reserve, Amazonas State, Brazil. Observations were made in 50 × 13 m plots located along the land-water interface. We investigated the influence of interspecific density and the effects of temperature and water depth on the feeding behaviors of both species. We identified three principal categories of feeding behavior: trapping (with the body perpendicular to the shore, the caiman captures prey swimming close to the shore), active search (with the head under the water, the caiman searches for benthic prey), and jumping (leaping partially out of the water and capturing fish or other under water invertebrates prey). Using multiple linear regression, we found that water temperature had a negative effect on trapping by M. niger; and water depth did not affect feeding behaviors in either species. Density of M. niger did not affect either the density or the frequency of feeding by C. crocodilus. Results suggest that environmental factors have little influence on the feeding behaviors of the caimans we studied, and there is probably little interspecific competition for food during the dry season.

A seasonally dependent change in the distribution and physiological condition of Caiman crocodilus yacare in the Paraguay River Basin

The distribution and physiological condition of 116 Caiman crocodilus yacare was assessed over one year in the Southern Pantanal. Body mass and intermediary plasma metabolites were measured at three different time periods, representing large differences in the abundance of surface water. During the wet season the study site was completely submerged under water and C.c. yacare were distributed evenly throughout. High levels of [glucose] and [triglyceride] in the plasma indicated regular feeding. As the dry season progressed C.c. yacare became increasingly crowded around the remaining ponds. They showed a reduction in plasma [glucose] and [triglyceride], and an increase in plasma [β-hydroxy-butyrate], signifying that they were feeding less and utilising fat reserves. At this sampling period, ~40% of the male C. c. yacare that were &gt;10 years old inhabited dry grassland and did not have access to water. These animals were significantly lighter than males of a similar length that had immediate water access, and plasma [uric acid] indicated that they had not fed for a long time and were metabolising tissue proteins. Essentially, the adult male C.c. yacare that inhabited dry grassland were in a state of energy deficiency. This was so severe in some animals that recovery seemed unlikely. The study suggests that fluctuations in the abundance of surface ground water may influence the size and structure of the C. c. yacare population in the Pantanal.

Phylogenetic relationships of South American Alligatorids and the Caiman of Madeira River

We analyzed DNA sequences of the mitochondrial cytochrome b gene (cyt b), the nuclear Recombination Activating Gene 1 (RAG1) and the myelocytomatosis oncogene (MYC) to infer the phylogenetic relationship of Caiman crocodilus and Caiman yacare, and other South American alligatorid crocodilian species. Phylogenetic relationships were robustly supported with Paleosuchus sister to Melanosuchus and Caiman. Phylogenetic relationships of C. crocodilus and C. yacare were unclear as these two species share mitochondrial and nuclear haplotypes. Specifically this sharing occurs among specimens of C. yacare and C. crocodilus from the Madeira River drainage. Two potential explanations stand out: secondary contact followed by hybridization, and differentiation along a cline. Current data cannot resolve between these two competing hypotheses. In comparison with C. yacare and C. crocodilus, Paleosuchus trigonatus and Paleosuchus palpebrosus are very well differentiated and also show surprising haplotypic diversity in spite of their phenotypic similarity.

Polymorphism of Exon 3 of MHC Class II B Gene in Chinese Alligator ( Alligator sinensis)

The polymorphism of MHC class II B gene in 14 Chinese alligators was analyzed, which came from three different areas: a wild population from Xuancheng, Anhui, a captive population from Changxing, Zhejiang, and a captive population from Anhui Research Center for Reproduction of Chinese Alligators. The gene fragment was amplified using a pair of specific primers designed from the MHC gene sequence of the spectacled caiman. A total of 34 sequence haplotypes of exon 3 were detected in the sampled Chinese alligators. The numbers of haplotypes of the 3 Chinese alligator populations were 15, 10, and 9, respectively. The overall estimation of the MHC polymorphism in the Chinese alligator population was higher than those in mammals and in cyprinid fish. The rates of nonsynonymous substitutions ( d N) occurred at a significantly lower frequency than that of synonymous substitutions ( d S), which were not consistent with the common rule. This result might suggest that the polymorphism of exon 3 seemed not to be maintained by the balancing selection. The neutrality test of Tajima excluded the null hypothesis that the polymorphism of exon 3 was generated by a random drift, and the fact that D = −0.401 indicated an excess of rare mutations in the Chinese alligator. The nucleotide diversity of the sequences and the phylogenetic relations were also analyzed, and the results suggested that there was no significant difference in genetic diversity among the 3 populations of Chinese alligator.

Temperature variation in nests of Caiman crocodilus (Crocodylia: Alligatoridae)

Caiman crocodilus is a widely distributed species in the Neotropics; however, studies of incubation temperatures in wildlife are uncommon. Incubation temperature in four nests of Caiman crocodilus were measured with a digital thermometer, in the National Wildlife Refuge Cano Negro, Costa Rica. Average temperatures in these four nests (no. 1-4) were 32.13 + 0.92 °C (no. 1), 32.46 + 0.77 °C (no. 2), 33.60 + 0.95 °C (no. 3), and 31.78 + 2.30 °C (no. 4). Temperature variations recorded showed higher temperatures than those reported from other studies in Cano Negro. The temperatures registered in this study will lead to a higher proportion of males within the caiman population, reducing the number of future reproducing females and, therefore, in the population viability.

Caiman Bite

Caiman crocodilus, commonly called the spectacled caiman, is a very widely distributed resident of the western-hemisphere wetlands. Caiman bites to humans can cause trauma and infection. There are few reports of caiman bites; however, there is information about bites by other members of the same family, including Alligator mississippiensis. A case of acute caiman bite to the hand is described, including initial treatment and outcome. The bite resulted in multiple lacerations, interarticular fracture, and infection. One of the lacerations was closed, and the patient was started on moxifloxacin hydrochloride. Preventive care and treatment including wound care and antibiotics are discussed. The patient recovered with only a slight long-term functional deficit.

Biomechanics of the rostrum in crocodilians: A comparative analysis using finite‐element modeling

This article reports the use of simple beam and finite-element models to investigate the relationship between rostral shape and biomechanical performance in living crocodilians under a range of loading conditions. Load cases corresponded to simple biting, lateral head shaking, and twist feeding behaviors. The six specimens were chosen to reflect, as far as possible, the full range of rostral shape in living crocodilians: a juvenile Caiman crocodilus, subadult Alligator mississippiensis and Crocodylus johnstoni, and adult Caiman crocodilus, Melanosuchus niger, and Paleosuchus palpebrosus. The simple beam models were generated using morphometric landmarks from each specimen. Three of the finite-element models, the A. mississippiensis, juvenile Caiman crocodilus, and the Crocodylus johnstoni, were based on CT scan data from respective specimens, but these data were not available for the other models and so these--the adult Caiman crocodilus, M. niger, and P. palpebrosus--were generated by morphing the juvenile Caiman crocodilus mesh with reference to three-dimensional linear distance measured from specimens. Comparison of the mechanical performance of the six finite-element models essentially matched results of the simple beam models: relatively tall skulls performed best under vertical loading and tall and wide skulls performed best under torsional loading. The widely held assumption that the platyrostral (dorsoventrally flattened) crocodilian skull is optimized for torsional loading was not supported by either simple beam theory models or finite-element modeling. Rather than being purely optimized against loads encountered while subduing and processing food, the shape of the crocodilian rostrum may be significantly affected by the hydrodynamic constraints of catching agile aquatic prey. This observation has important implications for our understanding of biomechanics in crocodilians and other aquatic reptiles.

Pressor responses to alligator Angiotensin I and some analogs in the spectacled caiman ( Caiman crocodilus)

Discovery of the chemical structure of alligator ( Alligator mississipiensis) [Asp 1, Val 5, Ala 9]-Angiotensin I (ANG I) has permitted the investigation of cardiovascular responses to this peptide and its analogs in spectacled caimans ( Caiman crocodilus), close relatives of alligators. ANG I and [Asp 1, Val 5]- Angiotensin II (ANG II) i.v. gave dose-dependent increases in mean arterial pressure but there was no pressor response to [Val 4]-ANG III (ANG III). Pressor responses to a series of doses of ANG II were compared with a range of doses of norepinephrine (NE) and epinephrine (E) which were found to be only about 1/100 as potent as ANG II on a molar basis. The replacement of d-leu 10in the alligator ANG I molecule with l-leu 10 almost stopped its conversion to ANG II and attenuated the pressor response. [Asp 1, Val 5, Ala 9]-ANG I (1–9), and ANG (1–7) both failed to increase arterial blood pressure, even at the relatively high non-physiological test dose of 194 pmol kg bw −1 i.v. Captopril blocked angiotensin converting enzyme (ACE) and prevented the pressor response to ANG I whereas the mammalian AT 1 inhibitor Losartan attenuated, but did not completely block the pressor response to ANG II. These are the first experiments which test the cardiovascular responses to alligator ANG I and its analogues in any crocodilian species.

Cross-species microsatellite amplification in South American Caimans (Caiman spp and Paleosuchus palpebrosus)

Microsatellite DNA markers have been used to assess genetic diversity and to study ecological behavioral characteristics in animals. Although these markers are powerful tools, their development is labor intensive and costly. Thus, before new markers are developed it is important to prospect the use of markers from related species. In the present study we investigated the possibility of using microsatellite markers developed for Alligator mississipiensis and Caiman latirostris in South American crocodilians. Our results demonstrate the use of microsatellite markers for Paleosuchus palpebrosus, Caiman crocodilus and Caiman yacare.

Population genetic analysis of Caiman crocodilus (Linnaeus, 1758) from South America

The genetic structure of Caiman crocodilus was investigated using a 1085 bp mtDNA fragment of the cytochrome b gene. Inferences were based on 125 individuals from nine localities in Peru, Brazil and French Guiana. With the exception of Mamiraua Lake, Anavilhanas Archipelago and the Tapara Community which show a signal of demographic expansion, the sampled localities are in a mutation-drift genetic equilibrium. Divergence between the Amazon basin and extra-Amazon basin localities is significant; however, inference from Nested Clade Analysis cannot distinguish between continuous range expansion, long distance colonization or past fragmentation; however, past fragmentation is unlikely due to low number of mutational steps separating these two regions. The divergence is probably maintained by the reduced ability of C. crocodilus to cross salt water barriers. Within the Amazon basin, continuous range expansion without isolation-by-distance is the most likely process causing genetic structuring. The observed genetic patterns are compatible with the ecology of C. crocodilus, and history of human exploitation. As commercial hunting depleted more valuable species, C. crocodilus expanded its range and ecological niche, prompting hunters to harvest it. Following a period of intense hunting, C. crocodilus is now experiencing recovery and a second population expansion especially in protected areas.

Characterization of MHC class II genes from an ancient reptile lineage, Sphenodon (tuatara)

The organization and evolution of major histocompatibility complex (MHC) genes vary considerably among vertebrate lineages. MHC genes have been well characterized in mammals, birds, amphibians and fish, but little is known about their organization in reptiles, despite the fact that reptiles occupy an important phylogenetic position for understanding the evolutionary history of both mammalian and avian MHC genes. Here we describe the characterization of the first MHC class II B cDNA sequences from a non-avian reptile, the tuatara (Sphenodon spp.). Three class II B sequences were isolated from a tuatara cDNA library, and four additional partial sequences were isolated by reverse transcriptase-polymerase chain reaction. Six of these sequences appear to belong to the same gene family, which we have named SppuDAB. The remaining sequence (named SppuDBB) shares only 43.9% amino acid similarity with SppuDAB and thus appears to represent a separate gene family. SppuDBB may be a non-classical locus as it does not contain all the conserved residues expected of a classical MHC class II gene. Southern blot analysis indicates that only a single copy of SppuDBB exists in tuatara, but that multiple loci related to SppuDAB are present. The SppuDAB sequences have the highest amino acid similarity (57.2-62.4%) with class II B sequences from the spectacled caiman, but only 26.4-48.7% similarity with sequences from other vertebrates. The tuatara sequences do not strongly group with other reptile sequences on a phylogenetic tree, reflecting the antiquity of the Sphenodon lineage and the lack of closely related sequences for comparison.

Aspectos morfológicos de células da série eritrocítica de Caiman crocodilus yacare (Daudin, 1802; Reptilia, crocodilia)

Com o objetivo de estudar o sistema hematopoético do réptil Caiman crocodilus yacare, foram utilizados cinco exemplares hígidos e jovens (aproximadamente um ano de idade), provenientes de São Paulo e de Mato Grosso do Sul. Amostras de sangue periférico foram colhidas em EDTA, através da punção do seio venoso cervical, e da medula óssea por punção aspirativa do osso femural. Estudo histológico da medula óssea femural foi realizado através da coloração por HE, Giemsa e técnica de Gomori para fibras reticulínicas. Os esfregaços de sangue e de medula foram processados para coloração panótica (Leishman ou Rosenfeld). A presença de sítios hematopoéticos ativos foi demonstrada histologicamente nos cortes transversais do fêmur, principalmente no terço distal. As células da linhagem eritrocítica foram encontradas dentro dos vasos capilares sinusóides medulares, na região central do osso. As células precursoras desta linhagem estavam aderidas à parede do vaso, e suas sucessoras distribuídas em direção ao centro do sinusóide à medida que amadureciam. Nos esfregaços de medula, as células imaturas da linhagem eritrocítica mostraram-se arredondadas e com núcleo predominantemente frouxo, em contraposição às células maduras, de núcleo condensado e forma em geral elíptica. Foram vistos pró-eritroblastos, eritroblastos basofílicos, policromáticos e ortocromáticos, e finalmente eritrócitos.

Roadkills of vertebrates in Venezuela

This paper presents an analysis of vertebrate roadkills in five different habitats of tropical South America. Observations of vertebrate roadkills were conducted in 1978, on a 572 km road between Caracas and Mantecal/Apure in Venezuela, during the rainy season (June-October). During five passages on this route, which includes five distinct habitats, 79 vertebrate carcasses - mammals and reptiles - were found. If we assume that the carcasses remain for two days on the road, vehicles can be expected to strike 350 spectacled caimans Caiman crocodilus Linnaeus, 1758 (Alligatoridae) during the rainy season alone. Similar calculations for other species yield 313 snakes and lizards, 294 opossums Didelphis marsupialis Linnaeus, 1758 (Didelphidae), 220 crab-eating foxes Cerdocyon thous (Linnaeus, 1776) (Canidae), 129 tamanduas Tamandua tetradactyla (Linnaeus, 1758) (Myrmecophagidae), 55 capybaras Hydrochaerus hydrochaeris (Linnaeus, 1766) (Hydrochaeridae) and 37 eastern cottontails Sylvilagus floridanus Allen, 1890 (Leporidae). Numerous papers have been published on vertebrates killed by vehicles on roads in Europe, North America, and Australia, and several papers are available regarding vertebrate roadkills in Africa and Asia. From South America there are several papers on vertebrates, birds, and mammals, whereas from Venezuela only one and it deals with iguanas (Iguana iguana Linnaeus, 1758, Iguanidae).

Genetic diversity and population structure of Amazonian crocodilians

AbstractWe used the mitochondrial cytochrome b gene to study the population genetic structure of Melanosuchus niger (Brazil: Negro and Purus Rivers, Lake Janauacá; French Guiana: Kaw River swamps), and Caiman crocodilus (Brazil: Purus River, Lake Janauacá; French Guiana: Kaw River swamps). We found 10 haplotypes in M. niger and 9 haplotypes in C. crocodilus. Nested clade analysis indicated that isolation‐by‐distance was an important population dynamic in M. niger, but was unable to differentiate between isolation‐by‐distance, historical fragmentation or range expansion in C. crocodilus. Fu's Fs statistic supported the hypothesis of a demographic expansion in one out of four and two out of three sampled localities of M. niger and C. crocodilus, respectively. Populations of M. niger in central Amazonia also appeared to show differentiation that was correlated with water type. These results are compatible with the life‐style of these two crocodilians; C. crocodilus is a habitat generalist and appears to disperse rapidly to newly available habitats, while M. niger is a more sedentary habitat specialist. Both species appear to be recovering from unregulated over‐harvesting, however, their responses are life‐history and, potentially, ecologically‐dependent.