Crocodilian Species Research Articles

DDE in eggs of two crocodile species from Belize.

Organochlorine (OC) residues were recently detected in nonviable Morelet's crocodile (Crocodylus moreletii) eggs from northern Belize. To further the assessment of contaminant exposure in Belizean crocodiles, nonviable Morelet's crocodile eggs (n = 11) from southern Belize and American crocodile (Crocodylus acutus) eggs (n = 12) from the coastal zones of Belize were screened for 20 OCs. Results indicated p,p-DDE to be the most prevalent OC (96% occurrence) in eggs examined, with concentrations ranging from 5 to 372 ng/g. These concentrations are similar to those observed in crocodile eggs (10-180 ng/g) from northern Belize. A general trend toward higher DDE concentrations in Morelet's crocodile eggs (mean = 103 ppb) compared with American crocodile eggs (mean = 31 ppb) was observed. However, this trend may be due to site-specific contamination rather than differences in interspecific susceptibility to chemical exposure. Other OCs detected in crocodile eggs included the parent compound, p,p-DDT, and its metabolite, p, p-DDD.

Hematology and blood biochemistry of captive mugger crocodiles (Crocodylus palustris).

Comprehensive hematologic and biochemical analyses were conducted on blood from 23 male and 31 female clinically stable captive mugger crocodiles (Crocodylus palustris). Erythrocyte mean corpuscular volume (MCV), potassium, cholesterol, and calcium concentrations were significantly greater in juvenile males than in juvenile females, but no significant differences were determined between parameters of subadult males and subadult females. The mean WBC count and mean heterophil count were significantly higher in adult males than in adult females. Mean uric acid concentration was significantly greater in adult females than in males. Mean erythrocyte count was significantly higher in adults than in juveniles. Adult mean WBC and lymphocyte counts were significantly lower than those of both juveniles and subadults. Subadults had significantly lower mean eosinophil counts than both adults and juveniles. Subadults had significantly lower mean alkaline phosphatase activities than juveniles, whereas the adults had significantly lower aspartate aminotransferase and alanine aminotransferase activities than other groups. Lactate dehydrogenase activities were significantly lower for subadults than for juveniles and adults. Cholesterol concentrations were significantly higher for subadults and juveniles compared with adults. Triglyceride concentration was significantly lower for subadults and highest for juveniles. Glucose concentrations were significantly higher for adults. Blood urea nitrogen was significantly lower for subadults than for both adults and juveniles. Uric acid concentrations were significantly higher for juveniles than for the subadults and adults. The subadult animals also had a significantly lower potassium concentration. The results obtained were then compared with known values for other crocodilian species.

Purification, crystallisation and preliminary X-ray study of haemoglobin from Crocodilis palustris and Crocodilis porosus

The unsolved three-dimensional structure of crocodile haemoglobin and its prospects as a blood substitute have led us to initiate the purification and crystallisation of haemoglobin molecules from crocodile species ( Crocodilis palustris or mugger and Crocodilis porosus or salt water crocodile). The work has resulted in the prevention of polymerisation of naked haemoglobin molecules using N-ethylmaleimide or iodoacetamide. The purified monomeric haemoglobin molecule of C. porosus was crystallised in two different forms and X-ray diffraction data were collected up to 2 Å resolution for both forms. Form I: a=53.62, b=53.55, c=103.77 Å; β=93.35°, space group P2 1, Z=2. Form II: a=71.30, b=54.70, c=80.00 Å; β=106.4°, space group P2 1, Z=2. Structure solution and rigid body refinement of form I data resulted in a model with R free=0.42 and R=0.35.

The marine vertebrate faunas from the Late Cretaceous phosphates of Syria

Marine vertebrate faunas from the latest Cretaceous phosphates of the Palmyrides Chain of Syria are described for the first time. Recent fieldwork in the phosphatic deposits of the Palmyra area (mines of Charquieh and Khneifiss, outcrops of Bardeh, Soukkari and Soukhneh) have yielded a rich and diversified assemblage of marine vertebrates, including more than 50 species of chondrichthyes, osteichthyes, squamates, chelonians, plesiosaurians and crocodilians. Selachians are the most abundant and diverse component of the faunas and are represented by at least 34 species of both sharks and rays. Actinopterygians include representatives of six families, the most common being the enchodontids. Squamates are known by six mosasaurid species and an indeterminate varanoid. Chelonians are represented by at least two bothremydids and two chelonioids. Finally, elasmosaurid plesiosaurs and indeterminate crocodilians are also present in the fossil assemblages. The difference in faunal composition observed between the sites is interpreted as being due to palaeoecological preferences related to the Hamad Uplift palaeostructure. The marine vertebrate faunas of Syria show close affinities with those of the latest Cretaceous phosphatic deposits of North Africa and the Middle East and are typical of the southern Tethyan realm. From a biostratigraphical point of view, the selachians are the only suitable material to provide elements of an answer to the long debated question of the age of the Syrian Senonian phosphates. They suggest an Early Maastrichtian age for most of the phosphates of the Palmyrides Chain.

Mercury levels in alligator meat in south Louisiana.

In recent years, environmental contaminants have been recognized as an area of concern for some crocodilian species (Brisbin et al. 1998). Publications in the scientific and popular literature have focused on organic chemicals as potential endocrine disruptors in reptiles, including the American alligator (Guillette and Crain 1996). A recent review suggested environmental contaminants affecting crocodilians may be grouped into three categories; organic chemicals, heavy metals, and radionuclides (Brisbin et al. 1998).

A sequence of progesterone receptor homologue in freshwater crocodile (Crocodylus siamensis)

A sequence of progesterone receptor homologue in freshwater crocodile (Crocodylus siamensis)

In vivo locomotor strain in the hindlimb bones ofAlligator mississippiensisandIguana iguana: implications for the evolution of limb bone safety factor and non-sprawling limb posture

ABSTRACTLimb postures of terrestrial tetrapods span a continuum from sprawling to fully upright; however, most experimental investigations of locomotor mechanics have focused on mammals and ground-dwelling birds that employ parasagittal limb kinematics, leaving much of the diversity of tetrapod locomotor mechanics unexplored. This study reports measurements of in vivo locomotor strain from the limb bones of lizard (Iguana iguana) and crocodilian (Alligator mississippiensis) species, animals from previously unsampled phylogenetic lineages with non-parasagittal limb posture and kinematics. Principal strain orientations and shear strain magnitudes indicate that the limb bones of these species experience considerable torsion during locomotion. This contrasts with patterns commonly observed in mammals, but matches predictions from kinematic observations of axial rotation in lizard and crocodilian limbs. Comparisons of locomotor load magnitudes with the mechanical properties of limb bones in Alligator and Iguana indicate that limb bone safety factors in bending for these species range from 5.5 to 10.8, as much as twice as high as safety factors previously calculated for mammals and birds. Limb bone safety factors in shear (3.9–5.4) for Alligator and Iguana are also moderately higher than safety factors to yield in bending for birds and mammals. Finally, correlations between limb posture and strain magnitudes in Alligator show that at some recording locations limb bone strains can increase during upright locomotion, in contrast to expectations based on size-correlated changes in posture among mammals that limb bone strains should decrease with the use of an upright posture. These data suggest that, in some lineages, strain magnitudes may not have been maintained at constant levels through the evolution of a non-sprawling posture unless the postural change was accompanied by a shift to parasagittal kinematics or by an evolutionary decrease in body size.

Exploring Dinosaur Neuropaleobiology: Computed Tomography Scanning and Analysis of an Allosaurus fragilis Endocast

The unique opportunity to examine an exceptionally well-preserved natural endocranial cast (endocast) from a carnivorous dinosaur of the late Jurassic period, Allosaurus fragilis, was afforded this neurobiologist. The endocast exhibits numerous surface features including the complete vestibular apparatus. Spiral computed tomography scanning revealed multiple internal features including putative blood vessels, connective tissue-like arrays, and a prominent symmetrical density consistent with the putative brain or its cast. The evidence suggests that this organism’s neurobiology resembled closely that of modern crocodylian species and should be included for consideration when examining ideas of Allosaurus evolution, behavior, and eventual extinction.

Reference ranges for biochemical and haematological values in farmed saltwater crocodile (Crocodylus porosus) yearlings.

To determine reference ranges for healthy yearling farmed saltwater crocodiles by performing routine biochemical and haematological laboratory tests on blood samples. A clinico-pathological study. Blood samples were collected from 120 healthy yearlings from four Northern Territory crocodile farms and body weight and length were measured. All animals had been fasted for 2 days before sample collection. Routine biochemical analytes were determined on 120 samples and haematological values determined on 30 samples (from one farm). Reference ranges for biochemical and haematological values were determined for farmed yearling saltwater crocodiles in the Northern Territory. The results were comparable with published reference ranges for other crocodilian species. Other published results of haematological values from saltwater crocodiles were from very young (6-week-old) hatchlings and older (2- to 4-year-old) crocodiles. Differences in values were presumed to be caused by age-related factors.

Public health risks of ostrich and crocodile meat.

This paper discusses the infectious agents and chemical substances potentially capable of contaminating the meat of ostriches and crocodiles and which thus pose a danger to human handlers and consumers. For ostrich meat, there is no danger from Crimean-Congo haemorrhagic fever or spongiform encephalopathy. Contamination of ostrich meat with salmonellae, chlamydia, pasteurellae, mycobacteria and erysipelas might be possible, but has never been reported. No parasites are known which could be transmitted through ostrich meat to human consumers. Residues from growth hormones, antibiotics and acaricides are potential public health hazards. For crocodile meat, there is a distinct possibility of contamination with salmonellae, depending on housing, feed, slaughter technique and hygiene practices under which the animal is reared. Chlamydial infections are common on some crocodile farms in southern Africa. Mycobacteriosis is extremely rare. Tapeworm cysts have been found in crocodile meat in two cases only. Trichinellosis has been reported on several crocodile farms in Zimbabwe. A generalised coccidiosis with invasion of organs and tissues has been seen in several species of crocodiles, but should present no danger to consumers.

Alleged vertebrate eggs from Upper Cretaceous redbeds, Gobi Desert, are fossil insect (Coleoptera) pupal chambers: Fictovichnus new ichnogenus

Small egg-like structures from the Upper Cretaceous (Campanian) Djadokhta Formation of Mongolia were previously interpreted as casts of crocodile, lizard, and turtle eggs, or as inorganic nodules. Identical structures from coeval redbeds at Bayan Mandahu in northern China indicate the structures are not vertebrate eggs, nor of vertebrate origin. Comparisons with Recent and Quaternary beetle (Coleoptera) pupal chambers show close similarities in size, shape, and the presence of a round to irregular exit hole for the adult beetle. Most importantly, the Cretaceous structures are enveloped by a thin clay-rich zone, which is expected if constructed by beetle larvae but inexplicable in any egg or inorganic nodule model. Additional evidence contradicting a vertebrate egg origin for the structures includes (i) the structures are too small to have been laid by turtle or crocodile species occurring in the Bayan Mandahu redbeds; (ii) the structures are isolated, not in clutches or pairs; and (iii) unlike newly hatched soft-shelled lizard eggs, the Cretaceous structures are not collapsed and show a round to irregular exit hole rather than a slit. It is concluded that the egg-like structures are sand casts (steinkerns) of beetle pupal chambers, probably of Scarabaeidae, Tenebrionidae, or Curculionidae. The Cretaceous pupal chambers are assigned to a new ichnogenus, Fictovichnus, and new ichnospecies, Fictovichnus gobiensis and Fictovichnus parvus.

A new crocodylian from the Early Eocene of south-eastern Queensland and a preliminary investigation of the phylogenetic relationships of crocodyloids

Kambara implexidens sp. nov. is the second crocodylomorph from the Early Eocene (Ypresian) Tingamarra Local Fauna at Boat Mountain, near the township of Murgon, southeastern Queensland. Kambara is now the best represented genus of early Tertiary crocodylomorphs yet collected from Australia. The new species differs from Kambara murgonensis in several features, the most significant of which is possession of an interlocking dentition. Both species occur in a single stratigraphic horizon, possibly indicating two sympatric populations. The presence of adults and hatclings, coupled with the rarity of intermediately sized animals in the Murgon sample suggests the area may have been used as a nesting ground by one or both species. The new material permits a detailed reassessment of the phylogenetic relationships of Australia's Tertiary crocodylians, and provides impetus for a preliminary investigation into the relationships of many putative crocodylid stem taxa. We define Crocodyloidea and Crocodylidae as the descent community and crown group respectively of extant crocodylids (species of Crocodylus, Osteolaemus tetraspis and Tomistoma schlegelii) so as to place these taxa in a taxonomy reflecting phylogenetic relationships. Our results tentatively suggest that Mekosuchinae, as defined previously, is polyphyletic; Harpacochampsa camfieldensis is more closely related to Crocodylidae, whereas all other mekosuchines appear to represent a relic Gondwanan radiation of plesiomorphic crocodyloids, outwardly similar to several early Tertiary Northern Hemisphere forms of comparable grade such as Asiatosuchus germanicus and ‘Crocodylus’ affinis. Within Mekosuchinae (excluding Harpacochampsa camfieldensis), species of Kambara form a clade with Australosuchus clarkae. This clade forms an unresolved trichotomy with species of Pallimnarchus and Mekosuchini (species of Baru, Mekosuchus, Quinkana and Trilophosuchus rackhami). A previous trend in the study of crocodylomorph phylogeny has been to exclude from consideration characters thought to be associated with adaptive complexes, as this was seen to introduce unnecessary homoplasy. We challenge this assumption. Detailed investigation of the distribution of such characters among crocodylians can provide significant evolutionary information at varying taxonomic levels.

The functional morphology of goat oviductal secretory cells

Caiman latirostris is a South American crocodilian species characterized as a sentinel of the presence of endocrine-disrupting compounds (EDCs). Evaluating developmental events in hormone-dependent organs, such as the oviduct, is crucial to understand physiological postnatal development, to identify putative periods of exposure sensitive to EDCs, and/or to identify biomarkers useful to evaluate the effects of EDC exposure. In this study, we describe the histomorphological features of C. latirostris oviducts by establishing the ontogeny of changes at cellular, tissue and molecular levels from the neonatal to the pre-pubertal juvenile stages. Since the histological diagnosis of the adenogenic oviduct lies on a group of features, here we defined a histofunctional score system and a cut-off value to distinguish between preadenogenic and adenogenic oviducts. Our results showed that the maturation of the C. latirostris oviduct is completed postnatally and characterized by changes that mimic the pattern of histological modifications described for the mammalian uterus. Ontogenic changes in the oviductal epithelium parallel changes at subepithelial level, and include collagen remodeling and characteristic spatial-temporal patterns of α-actin and desmin. The expression pattern of estrogen receptor alpha and progesterone receptor evidenced that, even at early postnatal developmental stages, the oviduct of C. latirostris is a target organ of endogenous and environmental hormones. Besides, oviductal adenogenesis seems to be an estrogen-dependent process. Results presented here provide not only insights into the histophysiological aspect of caiman female reproductive ducts but also new tools to better characterize caimans as sentinels of endocrine disruption.

Generic affinities among crocodilians as revealed by DNA fingerprinting with a Bkm-derived probe.

Genetic fingerprint profiles have been successfully used for establishing biological relationships, in linkage analysis, and in studies of population structure but have not so far been used for ascertaining phylogenetic relationships among related groups of species and genera. This is largely because these profiles are thought to evolve too rapidly to be informative over large time intervals. However, we show here that among the Crocodilia, whose phylogeny is a debated issue, these profiles can provide phylogenetically useful information. By using the probe Bkm-2(8), DNA fingerprints with distinct bands distributed in the size range 0.5-23.0 kb were obtained for individuals of 18 species belonging to seven of the eight genera of crocodilians. These genetic profiles showed individual-, species-, and restriction enzyme-specific patterns. In addition, striking differences were observed in the copy number of Bkm-related sequences in genomes of different crocodilian species. The qualitative data from DNA fingerprint profiles, and quantitative data on copy number variation in Bkm-related sequences, suggest that these genera belong to two distinct groups, one of which includes Alligator, Paleosuchus, and Caiman; the other includes Crocodylus, Osteolaemus, Tomistoma, and Gavialis. A close relationship between Tomistoma and Gavialis is also suggested by these results.

Evolution of the WANCY region in amniote mitochondrial DNA.

In most vertebrate mitochondrial genomes, the site for initiation of light-strand replication, OL, is found within a cluster of five transfer RNA (tRNA) genes (tRNA(Trp), tRNA(Ala), tRNA(Asn), tRNA(Cys), and tRNA(Tyr)). This region and part of the adjacent cytochrome c oxydase subunit I (COI) gene were sequenced for two crocodilian, two turtle, and one snake species and for Sphenodon punctatus; part of the adjacent nicotinamide adenine dinucleotide dehydrogenase subunit 2 (ND2) gene was also sequenced for the crocodilian and turtle species. All had the typical vertebrate gene order. The turtles and the snake have a lengthy noncoding sequence between the tRNA(Asn) and tRNA(Cys) genes that we assumed to be homologous to the mammalian OL. The crocodilians and Sphenodon lack such a sequence, a condition they share with birds. Most proposed phylogenies for the amniotes require that OL at this position was lost at least twice during their diversification or was evolved independently more than once. Within the five tRNA genes, frequencies of substitutions are much higher in loops than in stems. Many loops vary dramatically in size among the species; in the most extreme case, the D-arm of the Sphenodon tRNA(Cys) is a "D-arm replacement" loop of seven nucleotides. Frequency of transitions in stems is relatively uniform across tRNAs, but frequency of transversions varies greatly. Mismatches in stems are infrequent, and their relative frequency in a specific tRNA is unrelated to the frequency of substitution in the corresponding gene. Several features of mammalian mitochondrial tRNAs are conserved in WANCY tRNAs throughout amniotes. The inferred initiation codon for COI is GTG in crocodilians, turtles, and the snake, a condition they share with fishes, certain amphibians, and birds. TTG appears to be the initiation codon for COI in Sphenodon; if correct, this would be a novel initiation codon for vertebrate mitochondrial DNA. Phylogenetic analyses of the inferred amino acid sequences of ND2 and COI support the sister-group relationship of birds and crocodilians and suggest that mammals are an early derived lineage within the amniotes.

The Evolution of Viviparity in Lizards

he birth of a relatively welldeveloped neonate-viviparity-is commonly considered a characteristic unique to mammals. However, this reproductive mode is exhibited by some species of all vertebrate classes except the jawless fishes (agnathans) and the birds. Among the reptiles, viviparity has evolved almost 100 times among the 5500 or so species of squamates (lizards and snakes). In contrast, all of the approximately 250 species of turtles, 21 species of crocodilians, and 2 species of tuatara are oviparous, producing only shelled eggs (Blackburn 1982, 1985, Shine 1985). In this article, I briefly discuss current work examining the ecological factors correlated with the evolu-

How caimans protect fish stocks in western Brazilian Amazonia – a case for maintaining the ban on caiman hunting

Rubber tapper communities along the large white-water rivers of central-western Brazilian Amazonia rely heavily on local fish stocks all year round. This subsistence fishing faces severe competition from commercial fishing boats from urban centres, which in some areas have over-fished the economically most important fish species. In the Juntá River and its oxbow lakes, two species of freshwater crocodilians – the black and the spectacled caiman – indirectly benefit subsistence fishermen by disrupting commercial fishing operations. The gill-nets used by commercial fishing boats are often damaged beyond immediate repair by the caimans as they make easy pickings of the catch. This appears to deter overharvesting of important fish stocks in many sections of the river. In contrast, subsistence fishermen use fishing gear that is rarely damaged by caimans. It would seem that caimans at their present numbers offer protection to local fish stocks by reducing the efficiency and financial viability of commercial fisheries, which would otherwise rapidly reduce fish yields for local rubber tappers.

Vasoactive intestinal peptide-immunoreactive cerebrospinal fluid-contacting neurons in the reptilian lateral septum/nucleus accumbens.

By means of immunocytochemical demonstration of vasoactive intestinal peptide (VIP) an accumulation of cerebrospinal fluid (CSF)-contacting neurons was found in a circumscribed region of the nucleus accumbens/lateral septum of eleven reptilian (chelonian, lacertilian, ophidian, crocodilian) species. Basal processes of these cells contribute to a subependymal plexus whose density displays considerable interspecific variation. VIP-immunoreactive nerve fibers occur also in the lateral septum and the nucleus accumbens where they encompass immunonegative cells in a basket-like pattern. The CSF-contacting neurons are surrounded by columnar ependymocytes frequently arranged in a pseudostratified manner. These specialized arrays of ependymal cells, however, occupy a more extended area than the VIP-immunoreactive CSF-contacting neurons and can be traced from the rostro-ventral pole of the lateral ventricle to the interventricular foramen. These observations suggest the existence of a telencephalic site of CSF-contacting neurons which may be more widespread than hitherto thought and which may participate in a circumventricular system of the lateral ventricle. Previous studies mainly performed with birds indicate that the VIP-immunoreactive CSF-contacting neurons of the nucleus accumbens might form a part of the "encephalic" (extraretinal and extrapineal) photoreceptor. However, further experiments are required to test this supposition since the VIP-immunoreactive neurons of the nucleus accumbens remained unlabeled by antibodies against bovine rodopsin and chicken cone-opsin in all eleven species analysed in this investigation.

New tertiary sebecosuchians (Crocodylomorpha) from South America: Phylogenetic implications

A new family, genus and species of a sebecosuchian crocodile from the late Paleocene of northwestern Argentina is described. This new taxon shows several apomorphic conditions such as the bent premaxillae, very high posterior part of the jugal, bent pterygoids, 3 pairs of procumbent teeth and a broad retroarticular process. The cladistic analysis carried out places this taxon as the sister group of Sebecus. The sebecosuchians are defined as a natural group restricted to South America. The baurusuchids come from several upper Cretaceous localities of southeastern Brazil, and northwest of Patagonia. The bretesuchids were found in the middle Paleocene of Brazil, late Paleocene and late Eocene of Argentina. The wider geographical and chronological distribution corresponds to the sebecids. They are registered from the early Paleocene in Patagonia and Bolivia to the middle Miocene in Colombia. The sebecosuchians were strong predators and probably more terrestrial in habits than other crocodilians. The lateral c...

On the effect of temperature-dependent sex determination on sex ratio and survivorship in crocodilians

The sex ratio of alligators and crocodiles is strongly biased towards females, often as high as 10 females to 1 male. Skewed sex ratios (that is, ratios other than 1:1) are commonly found in species exhibiting environmental sex determination. In crocodilians the temperature of egg incubation is the environmental factor determining sex. If the temperature is cool, around 30 °C, the hatchlings are all female. Warmer temperatures, around 34 °C, hatch all males. The probability that any particular individual female will successfully reproduce herself is low due to high mortalities of eggs, hatchlings and immatures. However, the crocodilia have great survivorship: no (classified) species of alligator or crocodile has become extinct despite extensive hunting and loss of habitat. We develop a nonlinear age-structured model for the population dynamics of alligators and crocodiles based on key life-history data. From our modelling we conclude that: (i) sex ratio is constrained by survivorship considerations; and (ii) temperature-dependent sex determination in crocodilians is a compromise providing the advantages of sexual reproduction while maintaining an unbalanced sex ratio.