Crocodylus Moreletii Research Articles

First photon-counting detector computed tomography in the living crocodile: a 3D-Imaging study with special reference to amphibious hearing.

Crocodiles are semi-aquatic animals well adapted to hear both on land and under water. Currently, there is limited information on how their amphibious hearing is accomplished. Here, we describe, for the first time, the ear anatomy in the living crocodile using photon-counting detector computed tomography (PCD-CT) and 3D rendering. We speculate on how crocodiles, despite their closed ear canals, can use tympanic hearing in water that also provides directional hearing. A Cuban crocodile (Crocodylus rhombifer) underwent photon-counting detector computed tomography (PCD-CT), under anesthesia and spontaneous respiration. In addition two seven-month-old C. rhombifer and a juvenile Morelet´s crocodile (Crocodylus moreletii) underwent micro-computed tomography (µCT) and endoscopy. One adult Cuviérs dwarf caiman (Paleosuchus palpebrosus) was micro-dissected and video-recorded. Aeration, earflap, and middle ear morphology were evaluated and compared after 3D modeling. PCD-CT and µCT with 3D rendering and segmentation demonstrated the anatomy of the external and middle ears with high resolution in both living and expired crocodiles. Based on the findings and comparative examinations, we suggest that the superior earflap, by modulating the meatal recess together with local bone conduction, may implement tympanic hearing in submerged crocodiles, including directional hearing.

Variation in the Diet of Hatchling Morelet's Crocodile (Crocodylus moreletii) in the Wild.

The relationship between diet and behavior is essential to understanding an animal's strategies to obtain food, considering ontogenical changes. In reptiles, there is a relationship between the length of the individual and the size of the prey it consumes. Studies have focused on the ontogenetic changes in reptile diets from hatchling to adult, but only a few studies have focused on the transition from hatchling to juvenile. We aimed to describe and analyze the composition, variation, diversity, and overlap in the diet of hatchling Morelet's crocodiles (Crocodylus moreletii) for three size intervals during the hatchling-juvenile transition. We captured 31 hatchling Morelet's crocodiles in an urbanized lagoon in Tabasco. We performed stomach-flushing to determine the diet. Additionally, we estimated the volume, frequency of occurrence, and relative importance of diet items and analyzed the relationship between prey type and the total length of the individuals. The diversity of the hatchling prey suggests a generalist diet. We observed two items not previously described in the diet of hatchling crocodiles. In addition, we found differences in diet between the initial and final size intervals, as increases in the length of prey appeared that they did not consume when they were hatchlings. Our results contribute new information to the dietary changes that occur during the hatchling-juvenile transition.

Digestive proteases of Morelet’s crocodile (Crocodylus moreletii) in three life stages

Introduction: Morelet’s crocodile (Crocodylus moreletii) is a species distributed in the Mexican southeast and threatened due to multiple pressures. Objective: To characterize the digestive proteases in the acid phase (stomach) and alkaline phase (intestine) of three life stages of C. moreletii in captivity (hatchling, juvenile, and adult). Methods: Total alkaline and acid protease activities were quantified using casein and haemoglobin as substrates. Trypsin, chymotrypsin, leucine aminopeptidase, and elastase activities were quantified using synthetic substrates. Protease profiles were analysed by SDS-PAGE and Native-PAGE. Results: The specific activity of acid and alkaline proteases showed differences between the three stages, finding the highest activity in the juveniles. Trypsin, chymotrypsin, leucine aminopeptidase, and elastase activities were higher in hatchlings. There were differences in optimum pH and temperature of acid and alkaline proteases, trypsin, and leucine aminopeptidase between the three stages, demonstrating the diversification of the enzymes according to different stages, as well as the presence of specific isoforms in each stage of C. moreletii. The acid phase zymogram showed four bands with pepsin-like acid activity in the hatchling and juvenile crocodile, while in the adult only two of the four bands were detected. The alkaline zymogram showed that the hatchling had the highest number of activity bands compared to the other stages, corresponding to the high specific activity reported in the alkaline phase. Conclusions: Digestive proteases of Morelet’s crocodile differ in their biochemical characteristics and the number of proteases between hatchling, juvenile, and adult. This could help in the future design of balanced diets as well to the sustainable management and production of this species.

Length and weight of farmed young Morelet's crocodiles (Crocodylus moreletii) as predictors of their future size

The aim of the study was to determine the earliest time at which the future size (length and weight) of farmed Morelet's crocodiles (Crocodylus moreletii) can be accurately predicted, to establish selection criteria in these individuals. A total of 8040 crocodiles (7394 males and 646 females) hatched from artificially incubated eggs were included. In each crocodile the total length and weight were measured on days 1, 132, 248, 364, 500, 616, 750, and 878 of age. On day 878 crocodiles were classified into five size groups: runt (RT), small (SL), medium (MM), large (LG), and extra-large (EL). The association between evaluations for length and weight, the correlation between length and weight in each measurement, and the differences in length and weight between assessments and sex were determined. Analysis from day 132 through day 878 included both sexes together. Neither length nor weight on day one correlated (> 0.40) with any subsequent evaluation. There was no difference among groups (P > 0.05) between length on day one and size on day 878. Difference was found between length on day 132 and size on day 878 in RT (P < 0.05), and between length on days 248, 364, 616, and 750 and size on day 878 in all the groups (P < 0.05). Difference was found between weight on day one and size on day 878 only in SL (P < 0.05), and between weight on days 132, 248, 364, 616, and 750 and size on day 878 in all the groups (P < 0.05). The size farmed Morelet's crocodiles will have at 878 days can be predicted with weight at 132 and length at 248 days. Use of the ranges of the size groups as selection criteria for growth will allow selecting the future smallest and largest individuals early in the production cycle and to enhance sustainable management of this species.

Characterising a genetic stronghold amidst pervasive admixture: Morelet’s crocodiles (Crocodylus moreletii) in central Yucatan

When backcrosses are fertile, interbreeding between endangered taxa can lead to the admixture of gene pools under threat. One such case pertains to the Mesoamerican crocodile Crocodylus moreletii, a species which shows strong signatures of both recent hybridisation and historic intogression with the American crocodile C. acutus across large parts of its range. In the present paper, we use RAD-seq derived SNPs (4980 nuclear and seven mtDNA loci) to demonstrate that C. moreletii populations inhabiting the region of Calakmul in central Yucatan (Mexico) are rather unaffected by hybridization, despite being surrounded by coastal areas where pervasive admixture has previously been documented. All (based on fastSTRUCTURE) and 96% (based on NGSadmix) of 84 genotyped individuals from 18 sampled waterbodies (locally termed aguadas) were free from nuclear introgression of C. acutus DNA at at threshold of 0.95. Seven individuals (8%) possessed a C. acutus mtDNA haplotype, five of which were derived from two adjacent, rather peripheral aguadas. Spatial inferences based on a DAPC and fineRADstructure further showed that the region of Calakmul is inhabited by three genetic clusters spanning across a set of distinct aguadas each. Taken together, our findings reveal that central Yucatan contains the currently largest documented stronghold of C. moreletii populations only marginally affected by introgression, which has major implications for the conservation management of this important flagship species.

Cu2+-dependent hydrolysis of O-hexyl 2,5-dichlorophenyl phosphoramidate by reptile sera

This study shows the EDTA-resistant, Ca2+ and Cu2+-dependent hydrolysis of O-hexyl 2,5-dichlorophenyl phosphoramidate (HDCP) compound in reptiles sera determined by spectrophotometry UV/Vis and chiral chromatography. Samples of ten reptile species were incubated with aliquot of 100 or 400 μM HDCP in presence of 100 or 300 μM Cu2+, or 2.5 mM Ca2+ or 5 mM EDTA at 37 °C for 30–60 min. The results shown an activator effect of Cu2+ on HDCP hydrolysis in freshwater turtles sera (Trachemys scripta, Chelydra serpentina and Macrochelys temminckii) because the levels of 2,5-dichlorophenol (DCP; product hydrolysis) were similar (∼37 μM DCP) to chicken serum (positive control group). The marine turtles (Chelonia mydas and Eretmochelys imbricata) and crocodiles (Crocodylusacutus and Crocodylus moreletii) showed ∼50% less HDCPase activity (13–17 μM DCP) compared to the HDCPase activity of the freshwater turtle species. Terrestrial reptile species (snakes and lizards) showed around 25% of activity (7–13 μM DCP) with both copper concentrations. These Cu2+-dependent hydrolysis were stereospecific to R(+)-HDCP (p˂0.05) in the three freshwater turtle species that showed similar hydrolysis to the chicken serum. However, the Ca2+ did not show a significant activating effect on the HDCPase activity (1–8 μM DCP) in any reptile serum. Their hydrolysis levels were very similar to those of EDTA-resistant activity. The present study demonstrates a Cu2+-dependent A-esterase (HDCPase) activity in turtles and points serum albumin as the cuproprotein responsible for this activity, reinforcing its N-terminal sequence (DAEH) as a catalytic center.

The amphibians and reptiles of the Northern Selva Lacandona:

Chiapas harbors significant biological and cultural diversity. The region known as Selva Lacandona is an ideal example to study what is called the “biocultural axiom”. This neotropical region is inhabited by multiple indigenous groups, such as the Tsotziles, Tseltales, Tojolabales, Ch’oles, Kanjobales, Chujes, Mames, Lacandones (Hach Winik), and Zoques. The herpetofaunistic diversity of Chiapas is currently represented by 107 species of amphibians and 223 species of reptiles. In the Selva Lacandona region a total of 35 species of amphibians and 90 reptiles has been documented, with some areas still remaining to be formally explored. Traditionally, the use of natural resources by native indigenous communities has been linked to the selective use of those species that have economical, traditional, and/or magical-religious value. Many of these human groups have a deep traditional knowledge about the environment in which they live, as well as the diversity of plant, fungal, and animal species with which they have coexisted over millennia. The Nahá and Metzabok communities are inhabited by the Maya-Lacandón del Norte culture. The objective of this study is to identify the herpetofaunistic species diversity found within the Flora and Fauna Protection Areas (APFF´s) of Nahá andMetzabok. Additionally, we analyzed whether the Lacandones from the north have a herpetofaunistic ethnical taxonomic classification system. A total of 67 species that are recognized by the Lacandones were recorded for both APFFs. The Lacandones del Norte classify the herpetofauna into six groups, i.e., Ak (Turtles), Kan (Snakes), Ayim (Crocodiles), Torok (Lizards), Xut (Frogs), and Be’p (Toads). For Metzabok, the three most frequently mentioned species are Bothrops asper, Boa imperator, and Crocodylus moreletii. For Nahá, the three species of most importance are Basiliscus vittatus, Boa imperator, and Kinosternon leucostomum. The differenceslie in the fact that for the Lacandones of Metzabok, the most important animals are those that are represented in their oral narratives, while for the Nahá community; the most important species are those that they usually find on a daily basis when walking along the trails in the jungle.

Cave-dwelling crocodiles of Central Belize

We provide the results on the first systematic effort to study cave-dwelling crocodiles in central Belize. For nearly three decades, managers at Runaway Creek Nature Reserve have frequently observed crocodile tracks and trackways in caves, while subterranean observations of crocodiles were less frequent. We surveyed five caves previously identified as crocodile habitat by wading (up to waist deep) and kayaking; we also deployed trail cameras in five of six flooded caves. Crocodiles were directly observed in two caves and trail camera footage was captured of a crocodile exiting a third cave. Given that introgression between Morelet’s Crocodile (Crocodylus moreletii (A.H.A. Duméril &amp; Bibron, 1851)) and the American Crocodile (Crocodylus acutus Cuvier, 1807) is high throughout their sympatric range and none of the crocodiles were captured, all individuals were identified as Crocodylus acutus x C. moreletii?. Additionally, in the five caves previously identified as crocodile habitat, we identified at least 16 potential prey species including two invertebrate, four fish, one turtle, one bird, several bat, and eight non-bat mammal species via direct observation and trail cameras. Capture, examination, and stomach flushes of cave-dwelling crocodiles, as well as continued monitoring of vertebrates via trail cameras, additional prey species surveys, monitoring of cave temperatures, and developing detailed cave maps of crocodile caves are highly recommended to obtain the information to both characterize crocodile cave use and optimally manage cave resources.

BIRD-HERPETOFAUNA INTERACTIONS IN THE USUMACINTA RIVER BASIN, MEXICO

Interspecific interactions between vertebrates of different groups are common but also complex and of great importance for community structure. In particular, predation, considered a trophic interaction, plays a significant role in food webs structure and selective effects on prey in natural ecosystems. In this paper we provide new information on the trophic relationship between birds and herpetofauna (reptiles and amphibians) in the complex and biodiverse Usumacinta river basin, through 10 observations recorded between 2012 and 2021. The observations show interactions for feeding purposes of eight bird species, including herons (Tigrisoma mexicanum), jays (Psilorhinus morio), raptors (Caracara cheriway, Pseudastur albicollis, Harpagus bidentatus, Buteo plagiatus), puffbirds (Malacoptila panamensis), and ducks (Dendrocygna autumnalis), with snakes (Coniophanes quinquevittatus), turtles (Chelydra rossignonii, Trachemys venusta), lizards (Iguana iguana, Sceloporus serrifer), crocodiles (Crocodylus moreletii), and frogs (Smilisca baudinii).

Relationships between female size, egg size, clutch size, and hatchling size in Morelet’s crocodile

Resources are limited by the environment in which an individual is found and can be influenced by natural selection. Evolutionary trade-offs in the reptilian reproductive effort literature have focused on optimal egg size. The objective of this study was to test egg size, clutch size, female size and hatching size in Morelet’s Crocodile (Crocodylus moreletii). Thirteen nests, 13 post-oviposition females, and 434 eggs were evaluated, from which 292 (67.2%) neonates hatched. No correlation was found between clutch size and egg size; however, the Gaussian model best explained the relationship between egg volume and mass. The relationship between TL of the female and egg size may be explained in that the size of the egg has a defined limit even when the female continues to increase in TL. Other factors may influence clutch size, such as environmental factors, reproductive adult quality, diet, the of the females, and captive conditions.

Serum concentrations of corticosterone and sex hormones and their relationship in farmed Morelet’s crocodile (Crocodylus moreletii)

Background: Crocodile farming aims to produce high-quality skins from captive crocodilians. Captivity usually exposes the animals to stressful conditions, resulting in increased serum corticosterone (CORT) levels that correlate negatively with those of sex hormones and reproductive success. Objective: To evaluate serum concentrations of CORT and sex hormones and their relationship in farmed Morelet’s crocodiles (Crocodylus moreletii) during the non-breeding (NBS) and breeding (BS) seasons. Methods: The study included 59 adult crocodiles (29 females and 30 males). One blood sample was collected in NBS (n=31) and BS (n=28) from each crocodile to determine serum concentrations of CORT, estradiol (E2), progesterone (P4), and testosterone (T). Crocodiles were kept in mixed-sex groups and were fed once or twice a week throughout the study. Results: In females, CORT was higher in NBS (p&lt;0.05) but had no correlation with E2 or P4 in any season (p&gt;0.05). In males, CORT was similar in NBS and BS (p&gt;0.05) and had no correlation with T (p&gt;0.5). Conclusion: The CORT levels had no effect on sex hormones. This could be explained by low CORT levels resulting from farming conditions where the animals were not exposed to severe or chronic stress.

Intervalos de referência bioquímica para Crocodylus moreletii e Crocodylus acutus criados em cativeiro na Lagoa Alcuzahue, Colima México

ABSTRACT Crocodylus moreletii and Crocodylus acutus are two endangered crocodile species endemic to Mexico. In this descriptive cross-sectional study, a total of 58 crocodiles (30 females and 28 males) were examined to determine and evaluate 24 blood biochemical indicators associated with energy, lipid, protein, mineral and enzymatic metabolic processes. Most of the serum biochemistry parameters were similar among sexes by species. However, male crocodiles showed higher triacylglycerol concentration and alkaline phosphatase activity, and lower globulin concentration than females. There were some significant differences between species. Total bilirubin, triacylglycerol, carbon dioxide, and hydrogen carbonate were higher in Crocodylus moreletii, and urea nitrogen, creatinine, alanine aminotransferase, and aspartate aminotransferase were higher in Crocodylus acutus. These reference values are very important for the protection of crocodiles. The calculated confidence intervals could be used to detect alert situations when at least 5% of the sampled crocodiles would fall outside of the calculated reference interval for a given parameter.

Potential distribution of hybrids between [i]Crocodylus acutus[/i] and [i]Crocodylus moreletii[/i] on the Mexican Pacific coast outside the natural hybridisation zone

In Mexico, Crocodylus acutus is widely distributed along the Pacific coast, while C. moreletii occurs on the Gulf of Mexico. Both species converge in the Yucatán peninsula where natural hybridisation is reported, and later it was also reported in the Gulf of Mexico. Unfortunately, due to translocations and stochastic events, currently there are hybrids of both species on the coast of Oaxaca and Guerrero. In this study, we evaluated the potential colonisation areas of the hybrids on the Pacific coast through ecological niche analyses. The results indicate that the hybrid crocodiles and the parent species share preferences in at least three climatic variables: average temperature range, isothermality, and minimum temperature of the coldest month. Furthermore, it was found that the climatic niche of the hybrids is more similar to that of the C. moreletii leaving reminiscent areas for C. moreletii in Nuevo León, San Luis Potosí and small areas far from the coast in Veracruz, coinciding with what was previously reported by molecular analysis. On the other hand, the climatic niche of the hybrid crocodiles is also sufficiently similar to that of C. acutus, having the possibility to colonise the Pacific coast extensively, leaving reminiscent small areas for C. acutus on the northern coast of Sinaloa, southern of Sonora, central coast of Oaxaca and small inland areas of the Pacific coast. Keywords: Crocodilians, ecological niche, hybrids, species model distributions, conservation, Mexico

Effectiveness of Morelet's crocodile as a bioindicator of metal pollution and metallothionein response to spatial variations of metal exposure

• Significant differences for mercury between the factors tissue:site were detected. • Significant differences for zinc between the factors tissue:site were detected. • Metallothioneins in blood plasma were detected in all sites but in erythrocytes detection frequency was lower than 20%. Several studies have assessed the potential of crocodylians as bioindicators of environmental contamination. In this study, the Morelet's crocodile ( Crocodylus moreletii ) was used as a bioindicator of metal pollution across five locations in southeastern Mexico classified as having high, medium, and low anthropogenic impact. Total length and sex were determined for each animal and concentrations of metals and metallothioneins (MTs) were determined by using non-destructive tissues. Mercury (Hg) concentrations in crocodile blood and scutes generally exhibited a decreasing pattern from the higher impacted site to the lower impacted site ( x 2 (14) = 185.42, p < 0.001), suggesting that concentrations in these samples are sensitive enough to identify difference in the bioavailability of Hg within crocodile populations. The highest concentrations were detected in scutes from Laguna Guerrero (Hg = 0.60 ± 0.217 µg/g w.w.) and Nichupté-Bojorquez (Cd = 14.99 ± 2.95 µg/g w.w., Cu = 58.66 ± 11.29 µg/g w.w., Zn = 80.86 ± 80.54 µg/g w.w.). MTs in blood plasma were detected at all sites (27.48 ± 4.78 µg/mL) but was low in erythrocytes detection frequency, suggesting this latter fraction may not be useful for MTs analysis. In general, our study supports the utility of crocodiles as bioindicators of xenobiotic metal pollution. However, it is necessary for such studies to perform assays for specific MT isoforms and the effective concentrations of metals bound to this protein, and to determine metal concentrations in multiple environmental matrices from the sites under evaluation.

Stress responses in captive Crocodylus moreletii associated with metal exposure

Environmental pollution by metals has repercussions on wildlife health. It is known that some metals can have an influence on the neuroendocrine stress response, and at the same time, metals have pro-oxidant effects that can overwhelm the antioxidant system and cause oxidative stress. This study evaluates the association of metals with neuroendocrine stress activity and biomarkers of oxidative stress in 42 captive female Morelet's crocodiles (Crocodylus moreletii). We measured five metals of ecotoxicological importance (Hg, Cd, Pb, Cu and Zn), and three biomarkers of the oxidative stress response in the liver: glutathione (GSH) and glutathione disulfide (GSSG) as markers for antioxidant system and thiobarbituric acid reactive substances (TBARS) for oxidative damage. We also measured one biomarker of the neuroendocrine response to stress: corticosterone (B) in blood plasma. The mean ± SD concentrations of metals in the liver expressed in μg/g (dw) were: Cd: 0.004 ± 0.003, Hg: 0.014 ± 0.019, Cu: 0.017 ± 0.013, Zn: 0.043 ± 0.035, Pb: 0.16 ± 0.256. The mean ± SD of GSH was 0.42 ± 0.35 nmol/mg protein, the mean ± SD of GSSG was 0.24 ± 0.20 nmol/mg protein, the mean ± SD concentrations of TBARS were 0.36 ± 0.21 nmol/mg protein, and the mean ± SD of B was 393.57 ± 405.14 pg/mL. Hg presented a significant negative relationship with corticosterone. Cd had a negative relationship with both GSH and GSSG; meanwhile, Zn showed a negative relationship with TBARS levels, could be a protective element against hepatic oxidative damage. Finally, B had negative relationship with oxidative damage. The connection found between Hg and the neuroendocrine stress response, as well as the correlations of Cd and Zn with oxidative damage and antioxidant activity should be studied further, given their toxicological importance and implications for the conservation of C. moreletii and other crocodilians.

N-mixture models provide informative crocodile (Crocodylus moreletii) abundance estimates in dynamic environments.

Estimates of animal abundance provide essential information for population ecological studies. However, the recording of individuals in the field can be challenging, and accurate estimates require analytical techniques which account for imperfect detection. Here, we quantify local abundances and overall population size of Morelet’s crocodiles (Crocodylus moreletii) in the region of Calakmul (Campeche, Mexico), comparing traditional approaches for crocodylians (Minimum Population Size—MPS; King’s Visible Fraction Method—VFM) with binomial N-mixture models based on Poisson, zero-inflated Poisson (ZIP) and negative binomial (NB) distributions. A total of 191 nocturnal spotlight surveys were conducted across 40 representative locations (hydrologically highly dynamic aquatic sites locally known as aguadas) over a period of 3 years (2017–2019). Local abundance estimates revealed a median of 1 both through MPS (min–max: 0–89; first and third quartiles, Q1–Q3: 0–7) and VFM (0–112; Q1–Q3: 0–9) non-hatchling C. moreletii for each aguada, respectively. The ZIP based N-mixture approach shown overall superior confidence over Poisson and NB, and revealed a median of 6 ± 3 individuals (min = 0; max = 120 ± 18; Q1 = 0; Q3 = 18 ± 4) jointly with higher detectabilities in drying aguadas with low and intermediate vegetation cover. Extrapolating these inferences across all waterbodies in the study area yielded an estimated ~10,000 (7,000–11,000) C. moreletii present, highlighting Calakmul as an important region for this species. Because covariates enable insights into population responses to local environmental conditions, N-mixture models applied to spotlight count data result in particularly insightful estimates of crocodylian detection and abundance.

Evaluation of Biological Activity of Oil Crocodylus moreletii on Glucose levels Using a Diabetic Model

There are some reports which show that omega-3 fatty acids extracted from either animals or plants can be used to reduce glucose levels in diabetic patients; however, the results are very confusing; perhaps this phenomenon is due to the different protocols used. Analyzing these data, this study aimed to evaluate the biological activity of the oil extracted from Crocodylus moreletii at a dose of 100, 200, and 300 µl/kg using metformin glibenclamide and sodium oleate as controls in a diabetic rat model. The results showed that oil Crocodylus moreletii lowered glucose levels in a dose-dependent manner than untreated diabetic rats. Furthermore, the effects produced by Crocodylus moreletii oil and sodium oleate on glucose concentration were very similar. However, the biological activity exerted by glibenclamide and metformin on glucose levels was different from to effect induced by Crocodylus moreletii oil and sodium oleate. In conclusion, the biological activity of Crocodylus moreletii oil is interesting and could be considered a therapeutic alternative for the treatment of diabetes.

Trace element concentrations in caudal scutes from Crocodylus moreletii and Crocodylus acutus in Belize in relation to biological variables and land use

Crocodylus moreletii (Morelet’s crocodile) and Crocodylus acutus (American crocodile) are generalist, apex predators of subtropical aquatic habitats in Central America. As top predators, crocodiles may be exposed to high levels of micro pollutants, such as trace elements via bioaccumulation that enter the food web as a consequence of human activities. As such, the status of their population can be considered indicative of that of the entire ecosystem – i.e., crocodiles constitute as genuine indicator species. In this study, we report on the concentrations of trace elements found in the caudal scutes of 178 specimens of C. acutus and C. moreletii from Belize. Our objectives were three-fold: (1) to assess variation in trace element concentration between species, sexes, age classes and body index; (2) to identify areas with elevated exposure to trace elements by comparing concentrations in the scutes of crocodiles at various sites in Belize; and (3) to explore links between crocodile trace element load and local land use. All elements tested (Hg, Pb, Cd, As, Cu, Zn, Co) could be detected in at least some scutes. Many of the readings of As and Co were under or close to the detection limit and were not further analyzed. Relatively high Hg concentrations were observed in adults from Chiquibul Forest (median 3.170 µg/g) and Ambergris Caye (0.834 µg/g). Concentrations of Hg and Pb tended to be higher in adult animals than in juveniles, especially in C. acutus. On the other hand, concentrations of Cd, Cu and Zn were higher in juveniles than in subadult adult animals. Concentrations of Cu were higher in C. acutus than in C. moreletii, but otherwise no species-effects were found for the other trace elements. We found a negative correlation between Hg and Zn concentrations; correlations among Cd, Pb, Cu and Zn concentrations tended to be positive. In both juveniles and adults, animals with high concentrations of Zn had lower body-indices (a proxy for physiological condition). None of the other element concentrations correlated with the body-index. Specimens of C. acutus were more often sampled at coastal sites, while C. moreletii sampling points were typically closer to agricultural or forested areas. A canonical correlation analysis revealed a significant association between trace element load and habitat characteristics. Animals sampled inland, near submontane forests, contained higher levels of Hg, while animals sampled near agricultural, urban or lowland habitats tended to have higher concentrations of Cd, Pb, Cu and Zn. This study identifies the most prevalent trace element concentrations impacting Belizean watersheds while highlighting the exposure risk to non-essential trace elements in less-urbanised areas or protected areas.

Micronuclei and Nuclear Buds Induced by Cyclophosphamide in Crocodylus moreletii as Useful Biomarkers in Aquatic Environments.

Simple SummaryCrocodiles are territorial reptiles that are exposed to both aquatic and terrestrial environments. Analyzing their state of health and the environment in which they live is essential to detect changes that could affect them by exposure to agents that damage their genetic material, putting their health or other species that share said habitat, including humans, at risk. There are several ways to determine exposure to harmful agents, a very simple and direct one is to analyze the nuclei of blood cells under a microscope, a test that can also be carried out directly in their habitat and that gives rapid results on the effects of agents on those at that moment they are exposed. This study demonstrates the possibility of analyzing the blood of Crocodylus moreletii to quickly analyze its exposure to toxic agents in a sample of its blood by evaluating two abnormal structures in its cells under the microscope, demonstrating that evidence of damage can be observed only by analyzing a drop of their blood.Micronuclei (MN) are used to assess genotoxic exposure, whereas nuclear buds (NBs) have been linked to genotoxic events. Crocodylus moreletii was studied to identify MN and NBs. Three groups were formed: Group 1 (water) and groups 2 and 3 (7 or 10 mg/kg of cyclophosphamide). A drop of blood was obtained daily from the claw tip at 0 to 120 h. Spontaneous micronucleated erythrocytes (MNEs) and erythrocytes with nuclear buds (NBEs) were counted. The frequencies of micronucleated young erythrocytes (MNYEs) and NB young erythrocytes (NBYEs) were evaluated, including the ratio of young erythrocytes (YE)/1000 total erythrocytes. No significant differences were observed in the YE proportion on sampling days; group 1 did not show differences for any parameter, whereas group 2 showed significant differences in MNEs and NBEs, and group 3 showed differences in NBEs and NBYEs. Some mitotic activity in circulation was observed in YEs. In conclusion, NBEs could be a more sensitive biomarker to genotoxic damage than MNEs. The identification of these biomarkers leads us to propose Crocodylus moreletii as a possible environment bioindicator because these parameters could be useful to analyze the in vivo health status of these reptiles and for biomonitoring genotoxic pollutants in their habitats.

Blood cell morphology and leukocyte differential of Morelet’s crocodile (Crocodylus moreletii) (Crocodylidae)

The objective of the study was to determine the morphological characteristics of peripheral blood cells (erythrocytes, leukocytes, thrombocytes) and the leukocyte differential count (heterophils, eosinophils, basophils, lymphocytes, monocytes, azurophils) of captive Morelet’s crocodiles (Crocodylus moreletii) from Veracruz, Mexico. Peripheral blood from 80 apparently healthy farmed crocodiles (39 subadults [19 females, 20 males] and 41 adults [18 females, 23 males]) was examined for morphology through stained blood smears and manual count was used for the leukocyte differential. Blood was collected during the non-breeding (n = 42) and breeding (n = 38) seasons. Blood examination indicated similar morphological characteristics of blood cells in subadult and adult individuals and in females and males in both seasons. Erythrocytes were the largest blood cells and lymphocytes the smallest. The leukocyte differential count showed that lymphocytes were the most abundant leukocytes and basophils the least numerous. The percentages of some leukocytes showed difference by season (non-breeding and breeding) in subadult and adult males (p &lt; 0.05) and by size (subadults and adults) in males and females but only in the non-breeding season (p &lt; 0.05). The leukocytes that showed the greatest variation were lymphocytes, heterophils and eosinophils. The knowledge of blood cell morphology and the leukocyte differential count in healthy farmed Morelet’s crocodiles will allow the accurate diagnosis of some diseases of captive and wild individuals.