Crocodilian Species Research Articles

Early development of the facial region in a non-avian theropod dinosaur

An isolated maxilla of the theropod dinosaur Allosaurus from the Late Jurassic (the Kimmeridgian, 153 million years ago) of Portugal is the first cranial remain of a non-coelurosaurian theropod hatchling reported so far, and sheds new light on the early cranial development of non-avian theropods. Allosaurus hatchlings seem to have been one-seventh or less of the adult length and are thus comparable in relative size to hatchlings of large extant crocodile species, but are unlike the relatively larger hatchlings in coelurosaurs. The snout experienced considerable positive allometry and an increase in tooth count during early development. The element is especially noteworthy for the abundant and well-developed features associated with the paranasal pneumatic system. Pneumatic structures present include all those found in adult allosaurids and most are even more developed than in adult skulls. Together with evidence on the ontogeny of the tympanic pneumatic system in allosaurids, these findings demonstrate that cranial pneumaticity developed early in theropod ontogeny. The strong development of pneumatic features in early ontogenetic stages of non-avian theropods supports the hypothesis that pneumatization of cranial bones was opportunistic and indicates that heterochrony played an important role in the evolution of craniofacial pneumaticity in this group.

West Nile Virus in Alligator, Alligator mississippiensis, Ranches from Louisiana

ABSTRACT West Nile virus (WNV) has been reported to affect various crocodilian species including the American alligator, Alligator mississippiensis, the Nile crocodile, Crocodylus niloticus, and the Morelet's crocodile, Crocodylus moreletii. In the Fall of 2003 an increased number of mortalities were observed at various alligator ranches in Louisiana. Affected animals were reported to have neurologic signs followed by death. At the time West Nile virus (WNV) had already been diagnosed in alligators from Georgia and Florida, but not Louisiana. This report outlines the findings of physical exam, necropsy, histopathology and diagnostic tests of affected animals. Viral isolation, real time RT-PCR and immunohistochemistry have proven to be useful tests for diagnosing WNV in alligators. One interesting aspect of these cases is that only one of the four affected facilities had alligators hatched in Louisiana. The other three had imported hatchlings from Florida and Texas.

Predicting maternal body burdens of organochlorine pesticides from eggs and evidence of maternal transfer in Alligator mississippiensis

Few data exist regarding maternal-embryonal transfer of organochlorine pesticides (OCPs) in reptiles. The objective of the present study was to evaluate maternal transfer of OCPs in American alligators (Alligator mississippiensis) from low-, intermediate-, and high-OCP-exposure sites. Overall, total OCP burdens ranged from less than 0.8 ppb in blood to more than 44,000 ppb in abdominal adipose tissue (wet wt concentrations). Lipid-adjusted ratios of maternal adipose burdens (total OCPs) to yolk burdens were close to one (0.94 +/- 0.31:1), suggesting that animals were in steady state and that OCPs in eggs originated from adipose lipids. In contrast, lipid-adjusted muscle and liver OCP burdens were greater than yolk OCP burdens, suggesting that lipids in muscle were not utilized during oogenesis and that nonlipid liver tissue sequesters OCPs. Predictive equations were derived for several tissues and several OCP analytes with r2 values ranging from 0.40 to 0.99 (p < 0.05). We suggest that yolk burdens are predictive of maternal tissue burdens for certain tissues and OCPs and that certain OCPs are maternally transferred in the American alligator. Furthermore, we suggest that future studies should investigate the applicability of these predictive equations for assessing maternal exposure in other crocodilian species.

Crocodylian forelimb musculature and its relevance to Archosauria.

The musculoskeletal anatomy of the crocodylian forelimb is documented to facilitate functional morphological studies of extant and extinct archosaurs. Comparative descriptions of muscles of the forelimb of several crocodylian species are presented, including attachment sites, innervation, and anatomical functions. The muscular anatomy of the crocodylian forelimb is highly conservative among the different species; however, interspecific differences do occur. Interspecific anatomical variation is interpreted functionally, and discussed in the context of the terrestrial locomotion of crocodylians as it applies to the forelimb. In addition, muscular apomorphies are identified among a phylogenetically diverse sample of extant crocodylians, providing insight into the evolution of forelimb anatomy in a clade of archosaurs possessing highly variable terrestrial locomotor behaviors.

Analysis of highly phosphorylated inositols in avian and crocodilian erythrocytes

Both morphological and paleontological characteristics support the hypothesis of a monophyletic origin of crocodilian and avian groups. However, while the erythrocytes of all birds studied to date are reported to contain high levels of inositol pentakisphosphate (InsP 5), which acts as an allosteric effector of hemoglobin, this molecule has not been reported in crocodilian erythrocytes. In this study we compare the highly phosphorylated inositols in crocodilian and avian erythrocytes using a particularly sensitive analytical procedure. Our aim was to obtain new data which might provide further evidence for the monophyletic origin, or otherwise, of crocodiles and birds. We studied three avian and three crocodilian species. The erythrocytes of the three bird species contained low levels of inositol-3,4,5,6-tetrakisphosphate and inositol-1,3,4,6-tetrakisphosphate, thought to be precursors of Ins(1,3,4,5,6)P 5. The crocodilian erythrocytes studied contained Ins(1,3,4,5,6)P 5 and InsP 6 in higher concentrations than those found in mammal erythrocytes and in other more active cells such as macrophages. Our data provide further evidence of the similarity between crocodilian and avian groups and agree with the hypothesis that both groups evolved from a common ancestor. The process by which the function of inositol phosphates changed from that of intracellular signaling to hemoglobin allosteric effector is discussed.

Ecotoxicology of crocodilians

All species of crocodilians are long-lived, top-level carnivores that are integral components of aquatic, wetland, and marine/estuarine ecosystems. However, they are often excluded from studies on environmental contamination and ecological risk assessments. Available organic (including endocrine disrupters), inorganic, and radionuclide contaminant accumulation and effects studies for crocodilians were reviewed and summarized to facilitate the use of existing data, reveal the primary information gaps, promote the inclusion of crocodilians in environmental contamination studies and ecological risk assessments, encourage further ecotoxicological studies, and assist in the development of future research priorities. Environmental contamination studies were not available for more than half of the world's 23 crocodilian species. The majority of information available (almost 70% of reviewed studies) concerning environmental contaminants and their accumulation and effects on crocodilians was for the American alligator ( Alligator mississippiensis ) as a result of the considerable research effort on the effects of endocrine-disrupting contaminants (EDCs) on the alligator population inhabiting Lake Apopka, Florida and the many studies concerning mercury contamination in the southeastern United States, considered to be the most serious environmental threat to that area. With the exception of the extensive research on the effects of EDCs on Lake Apopka's alligators, research on the effects of environmental contaminants on crocodilians is lacking. The review indicated that the effects of EDCs on crocodilians are not confined to Lake Apopka and may occur in crocodilians in many parts of the world, especially in developing tropical areas where organochlorine pesticides are used extensively. For inorganic contaminants, determining the effects of mercury on crocodilians should be the highest research priority.

Complete mitochondrial DNA sequence of Chinese alligator, Alligator sinensis, and phylogeny of crocodiles

The 16746-neucleotide (nt) sequence of mitochondrial DNA (mtDNA) of Chinese alligator, Alligator sinensis, was determined using the Long-PCR and primer walking methods. As is typical in vertebrates, the mtDNA encodes 13 proteins, 2 rRNA, 22 tRNA genes, and a noncoding control region. The composition of bases is respectively 29.43% A, 24.59% T, 14.86% G, 31.12% C. The gene arrangement differs from the common vertebrate gene arrangement, but is similar to that of other crocodiles. DNA sequence data from 12S rRNA, 16S rRNA, protein-coding genes and combined sequence data were used to reconstruct the phylogeny of reptiles with the MP and ML methods. With this large data set and an appropriate range of outgroup taxa, the authors demonstrate that Chinese alligator is most closely related to American alligator among three crocodilian species, which suppors the traditional viewpoint. According to the branch lengths of ML tree from the combined data set, the primary divergence between Alligator and Caiman genus was dated at about 74.9 Ma, the split between Chinese alligator and American alligator was dated at 50.9 Ma.

Generation of a sequence characterized amplified region probe for authentication of crocodilian species.

A 209-base pair (bp) crocodilian-specific sequence characterized amplified region (SCAR) was identified from a 425-bp randomly amplified polymorphic DNA (RAPD) fragment. The 209-bp SCAR was produced from amplifications of DNA extracted from fresh and/or dry meat samples from at least three species of Crocodylus, Caiman crocodylus, and Alligator mississippiensis. No amplification was observed from DNA of other common animal species. The use of SCAR opens the way for quick authentication of crocodilian samples for conservation biology and trade regulation.

Identification of purebred Crocodylus siamensis for reintroduction in Vietnam.

Crocodylus siamensis, the Siamese crocodile, is a critically endangered species of freshwater crocodile previously distributed throughout much of SE Asia. Recovery plans call for reintroductions to the wild using founder individuals currently in captivity, mostly in commercial crocodile farms. On many farms C. siamensis has been intentionally hybridised with either Cuban crocodiles, C. rhombifer, or the estuarine crocodile, C. porosus, and hybrids may be difficult to distinguish morphologically. We report on the combined use of microsatellite and mtDNA genetic markers to determine the species status of potential founder individuals for reintroduction of C. siamensis. Genetic markers were used to characterise 103 captive and wild-caught individuals of C. siamensis, C. rhombifer and C. porosus in Vietnam and to distinguish purebred versus hybrid individuals. Although the microsatellite loci used had some overlap of allele sizes among species, assignment tests allowed differentiation. Four hybrids were identified, two of which had not been recognised morphologically as hybrids, and one of these was thought to be a C. siamensis suitable for reintroduction. Ten of the identified purebred C. siamensis were subsequently released into Cat Tien National Park in southern Vietnam.

New Extinct Mekosuchine Crocodile from Vanuatu, South Pacific

Abstract We describe a new species of crocodile (Reptilia: Crocodyloidea: Mekosuchinae) from a maxilla recovered at the Arapus archaeological site, on the island of Efate, Vanuatu, South Pacific. As with mekosuchine species in New Caledonia and Fiji, Mekosuchus kalpokasi sp. nov. was a small, possibly terrestrial carnivore that is now extinct. The differences between the Efate specimen and previously described species of Mekosuchus warrant recognition of a new species. Based on its association with Efate's earliest known human inhabitants, dating approximately 3000 cal yr B.P., the extinction of M. kalpokasi and other insular mekosuchines may have been anthropogenic. The lack of adequately dated pre-Quaternary and Quaternary vertebrate fossil records from Vanuatu, New Caledonia, and Fiji (as well as other smaller islands) precludes determining the timing and route of dispersal of mekosuchine crocodyloids.

Proton leak in hepatocytes and liver mitochondria from archosaurs (crocodiles) and allometric relationships for ectotherms.

It has previously been shown that mitochondrial proton conductance decreases with increasing body mass in mammals and is lower in a 250-g lizard than the laboratory rat. To examine whether mitochondrial proton conductance is extremely low in very large reptiles, hepatocytes and mitochondria were prepared from saltwater crocodiles ( Crocodylus porosus) and freshwater crocodiles ( Crocodylus johnstoni). Respiration rates of hepatocytes and liver mitochondria were measured at 37 degrees C and compared with values obtained for rat or previously measured for other species. Respiration rates of hepatocytes from either species of crocodile were similar to those reported for lizards and approximately one fifth of the rates measured using cells from mammals (rat and sheep). Ten-to-thirty percent of crocodile hepatocyte respiration was used to drive mitochondrial proton leak, similar to the proportion in other species. Respiration rates of crocodile liver mitochondria were similar to those of mammalian species. Proton leak rate in isolated liver mitochondria was measured as a function of membrane potential. Contrary to our prediction, the mitochondrial proton conductance of liver mitochondria from crocodiles was greater than that of liver mitochondria from lizards and was similar to that of rats. The acyl composition of liver mitochondrial phospholipids from the crocodiles was more similar to that in mitochondria from rats than in mitochondria from lizards. The relatively high mitochondrial proton conductance was associated with a relatively small liver, which seems to be characteristic of crocodilians. Comparison of data from a number of diverse ectothermic species suggested that hepatocyte respiration rate may decrease with body mass, with an allometric exponent of about -0.2, similar to the exponent in mammalian hepatocytes. However, unlike mammals, liver mitochondrial proton conductance in ectotherms showed no allometric relationship with body size.

Mercury in Morelet's Crocodile Eggs from Northern Belize

Recent studies have examined mercury accumulation in crocodilians. However, though most researchers have focused on tissue concentrations, few have examined mercury levels in crocodilian eggs. In July 1995, we analyzed mercury in 31 nonviable Morelet's crocodile ( Crocodylus moreletii) eggs collected from eight nests across three localities in northern Belize. All eggs were found to contain mercury. Based on an individual egg basis, mean concentration of mercury for all three localities was among the lowest reported for any crocodilian species. When localities were examined separately, mean concentrations for Laguna Seca and Gold Button Lagoon were comparable to those observed in other studies, and the mean for Sapote Lagoon was the lowest ever reported. Based on mean nest concentrations, mercury in eggs from Laguna Seca was approximately two- and tenfold higher than for Gold Button Lagoon and Sapote Lagoon, respectively. Variability in mercury concentrations among localities is likely the result of site-specific differences in mercury input, bioavailabilty, and bioaccumulation. Mercury concentrations were relatively uniform in eggs from the same nest and among nests from the same localities. The presence of mercury in Morelet's crocodile eggs suggests exposure in adult females, developing embryos, and neonates. However, crocodiles in these areas show no overt signs of mercury toxicity, and no indication of population decline is evident. A paucity of data on the effects of mercury on crocodilians precludes meaningful speculation as to the biological significance of tissue and egg concentrations. Controlled laboratory studies and long-term population monitoring are needed to address these questions.

An extinct Pleistocene endemic mekosuchine crocodylian from Fiji

ABSTRACT Isolated cranial and postcranial elements represent a new genus and species of endemic crocodilian, Volia athollandersoni, from presumed Pleistocene cave deposits of Fiji. Preliminary phylogenetic assessment indicates that it is a mekosuchine crocodylid. This material sheds further light on the Pleistocene tetrapod fauna of the southwestern Pacific islands.

Status of crocodiles in the U Minh Thuong Nature Reserve, southern Vietnam

Both species of native crocodile, Siamese Crocodile Crocodylus siamensis and Estuarine Crocodile C. porosus, are seriously threatened in the wild in Vietnam. The swamp forest of the U Minh region in southern Vietnam was recently suggested to harbor the last remaining wild Estuarine Crocodiles in the country. We investigated the status of crocodiles in the U Minh Thuong Nature Reserve by conducting field surveys and interviewing local people. Field surveys found no signs of living wild crocodiles, and interview results strongly suggested that wild crocodiles have not occurred at U Minh Thuong Nature Reserve for perhaps as long as 30 years.

Effects of exposure of crocodiles to sublethal concentrations of Petroleum waste drilling fluid in the Niger Delta basin of Midwestern Nigeria.

Static bioassay were carried out using two aquatic crocodiles (the short nosed crocodile, Osteolemus tetraspis and the Nile crocodile, Crocodilus niloticus) as test organisms in soft natural dilution water, with Petroleum waste drilling fluid as the test material, at 28 +/- 2 degrees C. Comparison of results for the control and different concentrations of the waste drilling fluid were made by means of the F-statistic method. Both crocodile species exhibited a high insensitivity to the undiluted waste drilling fluid and the different dilutions. Differences in concentration of waste drilling fluid did not influence the response of crocodiles to the potential toxicant. Percentage of deaths which was never greater than 0.2% in control tanks was not significantly different from that in test tanks where mortality values of organisms was typically 1.6% or less in most cases. There was a delay toxicant-induced mortality effect.

Alligator aromatase cDNA sequence and its expression in embryos at male and female incubation temperatures.

In all species of crocodilians, sex is determined not by genetic mechanisms, but by the temperature at which the egg is incubated. In the American alligator (Alligator mississippiensis) the thermosensitive period (TSP) for sex determination is a 7- to 10-day window within stages 21-24 of development, around the middle third of the incubation period. Treating embryos with estrogen during the TSP produces female offspring, even at male incubation temperatures. Conversely, blocking embryonic estrogen synthesis at female-inducing temperature prevents development of the female phenotype. Therefore, it has been suggested that estrogen plays a role in determination of sex in the alligator. Estrogen is produced from an androgen substrate by cytochrome P450 aromatase (CYP19). If estrogen plays a critical role in sex determination, there should be differences in aromatase expression between embryos at male- and female-producing temperatures during the TSP. Therefore, to address this question, we cloned and characterized the alligator CYP19 cDNA. Based on the sequence information, a quantitative kinetic reverse transcriptase-polymerase chain reaction (TaqMan) assay was designed to measure expression of the alligator aromatase gene in RNA extracted from the gonadal and brain regions of alligator embryos incubated at male- or female-producing temperatures from prior to the TSP through hatching. Aromatase expression was detected in the brain region from the earliest stage tested (stage 20) through hatching. The hypothalamus had significantly higher expression than the forebrain or hindbrain in both male and female embryos. Expression was not significantly different in the gonadal region between embryos at male and female temperatures until after the TSP, when there was a dramatic increase in expression at female temperature. These data indicate that aromatase expression and, thus, estrogen production, are not the initial trigger for sex determination but play an essential role in ovarian differentiation in the alligator. J. Exp. Zool. 290:439-448, 2001.

HERPETOFAUNA DIVERSITY OF UJUNG KULON NATIONAL PARK AN INVENTORY RESULT IN 1990

A seven week study of the Ujung Kulon National Park, West Java, Indonesia was conducted between July 29 and 17 September 1990. The purpose of the study was to compile an inventory of the reptile and amphibian species present in the National Park. 14 Anura, 16 Lacertilia, 17 Ophidian, 2 Testudinta and one Crocodile species were identified. Two Lacertilia, one Testudinata and 10 Ophidiasprecies are new record for the park. A tentative comparison was made between our result and a study of the region by Martens (1957) in 1955 and 1956. Management suggestion for the conservation of herpetofauna of Ujung Kulon National Park are discussed along with suggestion for further research.

Experimental inoculation of broad-nosed caimans (Caiman latirostris) and Siamese crocodiles (Crocodylus siamensis) with Mycoplasma alligatoris.

An outbreak of mycoplasmosis caused by Mycoplasma alligatoris resulted in the death or euthanasia of 60 American alligators (Alligator mississippiensis) from a population of 74 captive bull alligators in Florida in 1995. The natural reservoir, routes of transmission, and host range of M. alligatoris are unknown. This study was undertaken to determine whether crocodilian species other than American alligators are susceptible to M. alligatoris. Six broad-nosed caimans (Caiman latirostris) and six Siamese crocodiles (Crocodylus siamensis) were experimentally inoculated with 10(6) colony forming units (CFU) of M. alligatoris instilled through the glottis. Two caimans and two crocodiles were used as negative controls. Six and four American alligators were used as positive and negative controls, respectively. Three of six (50%) inoculated caimans died within 10 wk postinoculation (PI) of severe mycoplasmosis. Gross necropsy, histopathologic, and culture results were similar for broad-nosed caimans and American alligators. None of the inoculated Siamese crocodiles developed mycoplasmosis, though M. alligatoris was isolated from the tonsils in three of six (50%) animals at necropsy. All the inoculated crocodilians that survived showed significant seroconversion by 6-8-wk PI (P < 0.05). The infective dose 50% (ID50) and lethal dose 50% (LD50) of M. alligatoris for the broad-nosed caiman are 10(6) CFU when instilled through the glottis, which is similar to that of the American alligator. Although the host range of M. alligatoris is not restricted to the American alligator, the organism does not appear to be pathogenic for Siamese crocodiles. Other species of crocodilians may be susceptible to infection with M. alligatoris, and this organism should be considered when the rapid onset of clinical signs of pneumonia, polyarthritis, pericarditis, and death occur.

The Amino Acid Sequences of the α- and β-Globin Chains of Hemoglobin from the Aldabra Giant Tortoises, Geochelone gigantea

Abstract Tetrameric hemoglobins (Hbs) A and D were isolated from red blood cells of the Aldabra giant tortoises, Geochelone gigantea, by a hydrophobic interaction chromatography. After reduction and S-pyridylethylation, two sets of two types of α-chains (α-1 and α-2) and one β-chain were purified from the major Hb A and minor Hb D in molar ratios of about 1:1:2, respectively, by a reversed-phase column chromatography. The complete amino acid sequences of the three globin-chains from Hb A were determined: 141 amino acid residues for the two α-chains and 146 amino acid residues for the β-chain. Using computer analysis (amino acid maximum homology), the two α-chains shared a 96.5% sequence identity and had low sequence identities (37.8% for α-1 and 35.8% for α-2) with the β-chain of the same species, G. gigantea. We constructed a phylogenetic tree of 28 primary globin structures from Reptilia (7 species of squamates, 4 species of turtles, 3 species of crocodiles and 1 species of sphenodontids), including the...

Status, distribution and conservation of crocodiles in Sri Lanka

Two species of crocodile occur in Sri Lanka, namely the marsh crocodile ( Crocodylus palustris) and the estuarine crocodile ( Crocodylus porosus), confined largely to the low-country in the first peneplain. Both species have declined in range and number since the turn of the century, mainly through over-hunting for hide and meat in the past, and conversion of their habitat to other land-uses by man at present. They have been completely extirpated from the Jaffna peninsula in the north. The study on the status and distribution of crocodiles was carried out from 1991 to 1996 during which crocodiles were recorded from 113 localities, 105 of which were inhabited by the marsh crocodile ( C. palustris), while 33 localities harboured the estuarine crocodile ( C. porosus). The two species were sympatric in 25 localities. Of the 105 localities from which C. palustris were recorded, it was considered rare in 62, common in 35, abundant in five, and perhaps extinct recently in three. Of the 41 large river systems, 32 were found to support crocodiles. Both species of crocodile are particularly abundant and secure in the country's two premier conservation areas: the Ruhuna National Park in the south-east and the Wilpattu National Park in the north-west. It is estimated that there could be at least 1220 marsh crocodiles, and perhaps no more than 300 estuarine crocodiles in Sri Lanka. Crocodiles are being threatened by indiscriminate destruction of the island's mangroves and marsh vegetation for human habitation and prawn farming. In Sri Lanka, the marsh crocodile is known to tolerate concentrations of salt higher than that in sea water for a long time. The estuarine crocodile is known to move a considerable distance in land from the coast. The strong territorial behaviour among the male estuarine crocodiles may perhaps help space the individuals. Crocodiles have a poor image in Sri Lanka. Most rural people consider them a serious and potentially dangerous pest and so do not regret their disappearance from their neighbourhood. Marsh crocodiles can be ranched, but the concept of sustainable utilization of wildlife in general is still anathema to a large segment of the population in Sri Lanka. On the other hand, if crocodiles could benefit people, they are not likely to become extinct.