Crocodilian Species Research Articles

Degradation of the crocodile population in the Olifants River Gorge of Kruger National Park, South Africa

Abstract Top predators such as crocodiles often reflect ecosystem degradation. The recent spate of close to 200 Nile crocodile deaths may reflect the ecosystem state of the Olifants–Letaba River system in the Kruger National Park. This paper investigates whether the crocodile deaths were indeed the consequence of a rare and perhaps acute event given the variability in annual population growth rates of crocodilians. Spotlight‐ and helicopter‐based surveys designed to correct for availability and detectability bias were used to estimate population sizes of crocodiles from 2008 to 2010 in and around the Olifants River Gorge, the focal area of crocodile deaths. Correction factors derived from individually observed crocodiles for both spotlight‐ and helicopter‐based counts were lower than those typically used for Nile crocodiles as well as other crocodile species. Even so, corrected spotlight‐ and helicopter‐based estimates were comparable and the number of crocodiles in the focal study area declined significantly from 780 (95% CI: 637–1222) to between 460 (spotlight estimate, 95% CI 375–665) and 505 (aerial estimate, 95% CI: 559–1746) during the period of crocodile deaths. The average annual decline of 35% was at the lower end of the distribution of annual population growth rates across the rivers of Kruger National Park. The crocodile deaths reflect a possible rare event that suggests a degraded crocodile population, possibly the consequences of broad‐scale cascades of environmental deterioration of the Olifants–Letaba River system. Even so, the potential risk of local demise of the population in the focal study area in the short term may be diminished through evolutionary, demographic and spatial resilience inherent within crocodiles that can accommodate the as yet unknown disease dynamics of pansteatitis. Copyright © 2011 John Wiley & Sons, Ltd.

Complete mitochondrial genome sequences of three Crocodylus species and their comparison within the Order Crocodylia

Crocodylus is the largest genus within the Order Crocodylia consisting of eleven species. This paper reports the complete mitochondrial genome sequences of three Crocodylus species, Crocodylus moreletii, Crocodylus johnstoni and Crocodylus palustris, and compares the newly obtained mitochondrial DNA sequences with other crocodilians, available in the public databases. The mitochondrial genomes of C. moreletii, C. johnstoni and C. palustris are 16,827 bp, 16,851 bp and 16,852 bp in length, respectively. These mitochondrial genomes consist of 13 protein coding genes, two ribosomal RNA genes, 22 transfer RNA genes and a non-coding region. The mitochondrial genomes of all the Crocodylus species, studied herein show identical characteristics in terms of nucleotide composition and codon usage, suggestive of the existence of analogous evolutionary patterns within the genus, Crocodylus. The synonymous and non-synonymous substitution rates for all the protein coding genes of Crocodylus were observed in between 0.001 and 0.275 which reveal the prevalence of purifying selection in these genes. The phylogenetic analyses based on complete mitochondrial DNA data substantiate the previously established crocodilian phylogeny. This study provides a better understanding of the crocodilian mitochondrial genome and the data described herein will prove useful for future studies concerning crocodilian mitochondrial genome evolution.

Characterization of Serum Phospholipase A2Activity in Three Diverse Species of West African Crocodiles

Secretory phospholipase A2, an enzyme that exhibits substantial immunological activity, was measured in the serum of three species of diverse West African crocodiles. Incubation of different volumes of crocodile serum with bacteria labeled with a fluorescent fatty acid in the sn-2 position of membrane lipids resulted in a volume-dependent liberation of fluorescent probe. Serum from the Nile crocodile (Crocodylus niloticus) exhibited slightly higher activity than that of the slender-snouted crocodile (Mecistops cataphractus) and the African dwarf crocodile (Osteolaemus tetraspis). Product formation was inhibited by BPB, a specific PLA2 inhibitor, confirming that the activity was a direct result of the presence of serum PLA2. Kinetic analysis showed that C. niloticus serum produced product more rapidly than M. cataphractus or O. tetraspis. Serum from all three species exhibited temperature-dependent PLA2 activities but with slightly different thermal profiles. All three crocodilian species showed high levels of activity against eight different species of bacteria.

Comparison of plasma dipeptidyl peptidase IV activity in two caiman species: Caiman latirostris and Caiman yacare (Crocodylia, Alligatoridae)

Abstract Dipeptidyl peptidase IV (DPPIV) is a well-characterized protease with broad substrate specificity, functionally-related to the activity of many bioactive peptides. It plays an important role as physiological regulator of a number of peptides that serve as biochemical messengers within the immune system. Plasma DPPIV activity was characterized with respect to temperature, kinetics and concentration dependence in two species of caiman, the broad-snouted caiman (Caiman latirostris) and the black yacare (Caiman yacare). DPPIV activity showed a significant positive correlation from titrations carried out in the presence of different plasma concentrations. DPPIV activity was lower in C. yacare than in C. latirostris at all temperatures tested. C. yacare DPPIV activity showed a significant increase only at higher temperatures whilst C. latirostris plasma demonstrated a strong positive correlation starting at the lowest temperature, probably due to an adaptation for the tolerance of lower temperatures. Exposure of C. latirostris and C. yacare plasma at different time points showed that plasma DPPIV activities were time-dependent, and that the titer-dependent curves were different for the two species. These results revealed that plasma DPPIV activities were different between these two crocodilian species, which could contribute to the differences in susceptibility to infection between them.

The Gavialis–Tomistoma debate: the contribution of skull ontogenetic allometry and growth trajectories to the study of crocodylian relationships

The phylogenetic placement of Tomistoma and Gavialis crocodiles depends largely upon whether molecular or morphological data are utilized. Molecular analyses consider them as sister taxa, whereas morphological/paleontological analyses set Gavialis apart from Tomistoma and other crocodylian species. Here skull allometric trajectories of Tomistoma and Gavialis were contrasted with those of two longirostral crocodylian taxa, Crocodylus acutus and Mecistops cataphractus, to examine similarities in growth trajectories in light of this phylogenetic controversy. Entire skull shape and its two main modules, rostrum and postrostrum, were analyzed separately. We tested differences for both multivariate angles between trajectories and for shape differences at early and late stages of development. Based on a multivariate regression of shape data and size, Tomistoma seems to possess a peculiar rate of growth in comparison to the remaining taxa. However, its morphology at both juvenile and adult sizes is always closer to those of Brevirostres crocodylians, for the entire head shape, as well as the shape of the postrostrum and rostrum. By contrast, the allometric trajectory of Gavialis always begins and ends in a unique region of the multidimensional morphospace. These findings concur with a morphological hypothesis that places Gavialis separate from Brevirostres, and Tomistoma closer to other crocodylids, and provides an additional, and independent, data set to inform on this ongoing phylogenetic discussion.

Urinary Tract Diseases of Reptiles

This article will provide an overview of diseases that affect the urinary system of reptiles. Although this information does not offer a comprehensive review of these disease conditions, more in-depth disease descriptions can be found in the articles and books listed in the references. After a brief summary of the normal gross appearance of the reptile urinary system, the article is divided into etiologic disease categories. A short discussion of the disease conditions of reptiles may be found in each section. For the purposes of this article, chelonian will refer to all of the shelled reptiles. The term “tortoise” will be used to describe the large land animals that have stout elephantine feet. Few references to marine turtle, caecilian, and crocodilian species are included, because these species are rarely presented to companion animal veterinary hospitals.

Fading of the last giants: an assessment of habitat availability of the Sunda gharial Tomistoma schlegelii and coverage with protected areas

Abstract The Sunda gharial Tomistoma schlegelii is, with 2500–3000 remaining specimens, one of the least studied and at the same time most endangered crocodile species. Inhabiting peat swamps in Southeast Asia, threats affecting the species are mainly associated with habitat loss and illegal hunting. The effectiveness of the existing reserve network in Southeast Asia for the protection of the Sunda garial was assessed by combining spatially explicit habitat analyses derived from land cover information with species distribution modelling. Subsequently, possible improvements of the existing reserve network are derived from the habitat availability analyses. The results of the spatially explicit analyses indicate that suitable habitats for the Sunda gharial in Southeast Asia, i.e. peat swamps and riverine forests, are highly fragmented. Spatial coverage of remaining habitats with protected areas fulfilling IUCN standards generally varies among regions and is best in Indonesia. However, large, currently unprotected suitable areas remain in Sumatra. Establishment of 10 additional, already proposed reserves may improve the protection of major parts of the remaining suitable habitats of the Sunda gharial. According to the results of this study, the reserve network protecting this species could be significantly improved by expanding it to include seven national reserves not currently listed by the IUCN and an additional 10 reserves that have recently been proposed. Improvements and extensions of the existing reserve networks in Southeast Asia are pivotal to guarantee the long‐term survival of the Sunda gharial. Copyright © 2010 John Wiley & Sons, Ltd.

Molecular phylogenetic analyses of genus Crocodylus (Eusuchia, Crocodylia, Crocodylidae) and the taxonomic position of Crocodylus porosus

The genus Crocodylus consists of 11 species including the largest living reptile, Crocodylus porosus. The current understanding of the intrageneric relationships between the members of the genus Crocodylus is sparse. Even though members of this genus have been included in many phylogenetic analyses, different molecular approaches have resulted in incongruent trees leaving the phylogenetic relationships among the members of Crocodylus unresolved inclusive of the placement of C. porosus. In this study, the complete mitochondrial genome sequences along with the partial mitochondrial gene sequences and a nuclear gene, C-mos were utilized to infer the intrageneric relationships among Crocodylus species with a special emphasis on the phylogenetic position of C. porosus. Four different phylogenetic methods, Neighbour Joining, Maximum Parsimony, Maximum Likelihood and Bayesian inference, were utilized to reconstruct the crocodilian phylogeny. The uncorrected pairwise distances computed in the study, show close proximity of C. porosus to C. siamensis and the tree topologies thus obtained, also consistently substantiated this relationship with a high statistical support. In addition, the relationship between C. acutus and C. intermedius was retained in all the analyses. The results of the current phylogenetic study support the well established intergeneric crocodilian phylogenetic relationships. Thus, this study proposes the sister relationship between C. porosus and C. siamensis and also suggests the close relationship of C. acutus to C. intermedius within the genus Crocodylus.

Artisanal fisheries characteristics of the fresh water reaches of lower Nun River, Niger Delta, Nigeria.

A frame survey of fishing communities was carried out, employing the complete census technique, to assess the artisanal fisheries characteristics of the fresh water reaches of lower nun river for a period of two year, Eleven Community lie along the stretch of the study area. The total number of 4718 fishers with 1645 canoe units employing various fishing gear resulted to a fishers density of 3 fishers per canoe unit. A total of 29 fin fish families were recorded. Seasonally occurring fresh water crustacean. Attaya gaboneensis and palacemon paucidens were present. Etheria elliptica, an oyster was also present. A specie of fresh water clam, Galacea Paradoxa from the family Donacidae was present. Trichechus senegelensis (Manattee) was occasionally captured by local hunter during the flood period. Hippopotamus amphibious (Hippopotamus) was reported from isolated places but they were rare. A specie of Otta, Lutra macullicolis was present. Three species of crocodiles, Crococdylus niloticus Crocodylus cataphractus (Alligator) and Osteolaemus tetraspsis were also present. The Nile monitor, Veramus niloticus and the aquatic snake, Anoscopus sp. And three species of water turtle, Kimxy erosa, Pelumedusa sp and Peliosus sp were also present. The commonest fishing method employed was local fishponds (50.8%) and the least was gill nets (1.6%). Drift net caught the highest fish (8.01kg) per gear, while local fishponds was the least 0.25 kg. The annual catch per canoe was recorded for local fishponds (167. 84kg), while the lowest was assorted traps (14.7kg). Drift not recorded the highest annual for local fishponds. The mean biomass of 25.04 of fish catch of 20.2kg per fisher and the lowest value (4.53kg) was recorded per boat, total catch of 37903. 6kg, annual producing estimate of 434.81 tonnes, standing struck of 2.27 km-2 and of twenty two million, seven hundred and forty two thousand one hundred and sixty naira (N22742160) was estimated. The reduced annual income per fisher in the study was four thousand, eight hundred and twenty naira, thirty kobo. There is therefore the, urgent need for effective management of the Nun river fisheries, to improve on the living standard of the people.

A novel multiplex PCR assay for the identification of Indian crocodiles

Illegal hunting has been a major threat for the survival of wildlife fauna, including the three crocodile species that India harbours: Crocodylus palustris, Crocodylus porosus and Gavialis gangeticus. Although law prevents trade on these species, illicit hunting for trade continues to threaten the survival of these endangered species; conservation strategies therefore require a rapid molecular identification technique for Indian crocodiles. A multiplex polymerase chain reaction (PCR) assay with species-specific primers, considered as one of the most effective molecular techniques, is described herein. The primers were designed to yield species-specific sized amplicons. The assay discriminates the three Indian crocodile species unambiguously within a short time period using only simple agarose gel electrophoresis. We recommend this multiplex PCR assay to be used in the identification of Indian crocodile species.

Vocalization in juvenile crocodilians.

Evidence is presented that the grunts and distress calls of juvenile alligators (Alligator mississipiensis) are examples of graded calls, which are given in different form depending largely on contest. Representative sonagrams of the distress calls of three other species of crocodilians (Caiman crocodilus, Crocodylus niloticus, and Crocodylus siamensis) are presented and compared with sonagrams of alligator distress calls. These findings are discussed in light of current knowledge of the bioacoustics of other vertebrates.

Standardized Reference Ideogram for Physical Mapping in the Saltwater Crocodile (Crocodylus porosus)

Basic cytogenetic data, such as diploid number and general chromosome morphology, are available for many reptilian species. Here we present a detailed cytogenetic examination of the saltwater crocodile (Crocodylus porosus) karyotype, including the creation of the first fully annotated G-band standard ideogram for any crocodilian species. The C. porosus karyotype contains macrochromosomes and has a diploid number of 34. This study presents a detailed description of each chromosome, permitting unambiguous chromosome identification. The fully annotated standardized C. porosus ideogram provides the backbone to a standard nomenclature system which can be used to accurately identify specific band locations. Seven microsatellite containing fosmid clones were fluorescently labeled and used as fluorescent in situ hybridization (FISH) probes for physical localization. Chromosome locations for each of these FISH probes were successfully assigned, demonstrating the utility of the fully annotated ideogram for genome mapping.

A revision of the Dubois crocodylians, Gavialis bengawanicus and Crocodylus ossifragus, from the Pleistocene Homo erectus beds of Java

ABSTRACT Revision of the two extinct Javanese crocodylian species Gavialis bengawanicus Dubois, 1908, and Crocodylus ossifragus Dubois, 1908, indicates that only the former is valid and that the latter is a junior subjective synonym of the extant C. siamensis Schneider, 1801. Gavialis bengawanicus is diagnosed by a relatively small number of maxillary and dentary teeth, a modest maxillary process developed into the lacrimal, a W-shaped maxillo-palatine suture, a planar skull table, occlusal pits present exclusively on the dentaries, and relatively small and subcircular supratemporal fossae at maturity. It is the best-known extinct Gavialis, and it probably represents the only valid extinct Gavialis species known outside the Indian subcontinent. Both crocodylians from Java have been found exclusively along with the Stegodon-Homo erectus fauna, which is considered to be largely the result of an Early Pleistocene dispersal from the Siwaliks Hills via the so-called Siva–Malayan route. It is not clear if the dispersal of Gavialis from the Indian subcontinent to Java necessarily required the crossing of salt water barriers, but the possible occurrence of Gavialis remains in Sulawesi and Woodlark, two islands located east of the Huxley and Wallace lines that were never connected to the mainland, can be explained by inferring a marine dispersal. According to the present knowledge of the past distribution of Gavialis, this genus originated in the Indo-Pakistani area in the early Miocene and during the Quaternary dispersed to the Sunda region, possibly reaching western-most Oceania.

A New Horned Crocodile from the Plio-Pleistocene Hominid Sites at Olduvai Gorge, Tanzania

BackgroundThe fossil record reveals surprising crocodile diversity in the Neogene of Africa, but relationships with their living relatives and the biogeographic origins of the modern African crocodylian fauna are poorly understood. A Plio-Pleistocene crocodile from Olduvai Gorge, Tanzania, represents a new extinct species and shows that high crocodylian diversity in Africa persisted after the Miocene. It had prominent triangular “horns” over the ears and a relatively deep snout, these resemble those of the recently extinct Malagasy crocodile Voay robustus, but the new species lacks features found among osteolaemines and shares derived similarities with living species of Crocodylus.Methodology/Principal FindingsThe holotype consists of a partial skull and skeleton and was collected on the surface between two tuffs dated to approximately 1.84 million years (Ma), in the same interval near the type localities for the hominids Homo habilis and Australopithecus boisei. It was compared with previously-collected material from Olduvai Gorge referable to the same species. Phylogenetic analysis places the new form within or adjacent to crown Crocodylus.Conclusions/SignificanceThe new crocodile species was the largest predator encountered by our ancestors at Olduvai Gorge, as indicated by hominid specimens preserving crocodile bite marks from these sites. The new species also reinforces the emerging view of high crocodylian diversity throughout the Neogene, and it represents one of the few extinct species referable to crown genus Crocodylus.

Two complete mitochondrial genomes of Crocodylus and implications for crocodilians phylogeny

AbstractThe complete mitochondrial (mt) genomes of two crocodilians: Crocodylus palustris and Crocodylus mindorensis, were sequenced in order to examine their gene and genome features. Additionally, we intended to increase the amount of molecular data suitable for phylogenetic analysis. Their gene orders conform to other crocodilians that have been sequenced, except the arrangement of two tRNA genes differ from other vertebrates, showing that the gene order of crocodilians is remarkably conserved. Phylogenetic analyses (maximum likelihood, Bayesian inference) based on the mt protein-coding genes at the nucleotide level were performed among crocodilians for which complete mt genomes were available. The results suggest that the gharial (Gavialis gangeticus) joins the false gharial (Tomistoma schlegelii) on a common branch, that constitutes a sister group to traditional Crocodylidae. In this report, Mecistops cataphractus is evidently most closely related to Osteolaemus tetraspis. They are isolated as sister taxon from the main clades in Crocodylus. Regarding Paleosuchus, it appears as sister group to Caiman within the Alligatoridae. In particular, relationships among species of Crocodylus (true crocodiles) are discussed.

Mugger ( Crocodylus palustris ) Population in and around Vadodara City, Gujarat State, India

Monitoring of over a two decade period (1987–2007) of mugger ( Crocodylus palustris ) population of River Vishwamitri (Gujarat State, India) indicates the present status of the species in and around Vadodara City to be the most noticeable and unique. The population found in Vishwamitri-Dhadhar River System represents a unique case study of relationship between a crocodilian species and humans. The population of muggers is growing with at the rate of 7.77 animals per year and has reached over 100. Also, mugger conflict is increasing; a total of 292 muggers were rescued from human settlements and translocated, including 38% small (under 1 m), 48% large (1 – 2 m) and 14% huge sized (over 2 m) muggers. But few of them returned to the same location in the Vishwamitri River. A total of 14 crocodile attacks were recorded, including six that were fatal. The present study provides recommendations and an action plan for the long-term mugger conservation in the area.

Transthyretin gene (TTR) intron 1 elucidates crocodylian phylogenetic relationships

Transthyretin (TTR) is an attractive candidate for use in phylogenetic analysis because it is a short, single-copy nuclear gene with regions that are highly conserved across evolutionarily-divergent organisms from Xenopus laevis to Homo sapiens. To explore its utility as a phylogenetic marker, the complete intron one region (789-805 bp) was sequenced in 22 crocodylian species. Detailed analyses of intron 1 resolved the three expected lineages, Alligatorids, Crocodylids, and Gavialids, and offered additional evidence for the utility of synapomorphic indels in elucidating higher-level phylogenetic relationships. When used in conjunction with other genetic and morphological data sets, intron 1 should be a valuable tool in the investigation of other closely related taxa.

Molecular Identification of Indian Crocodile Species: PCR‐RFLP Method for Forensic Authentication*

South East Asian countries are known for illegal poaching and trade of crocodiles clandestinely, to be used in skin, medicinal, and cosmetic industries. Besides crocodiles being listed in the Convention on International Trade in Endangered Species of Wild Fauna and Flora, India has its Wildlife Protection Act, 1972 for conservation of crocodile species. Hitherto, lack of any rapid and reliable technique for examinations of crocodile-based crime exhibits such as skin, bones, etc. has been a major problem for an effective promulgation of law on illegal trade. DNA-based identification of species using PCR-RFLP technique for an apt identification of all the three Indian crocodile species namely, Crocodylus porosus, Crocodylus palustris and Gavialis gangeticus is presented here. A 628 bp segment of cytochrome b gene was amplified using novel primers followed by restriction digestion with three enzymes i.e., HaeIII, MboI, and MwoI, separately and in combination. The technique has produced a species-specific pattern for identifying the three crocodile species individually, which fulfills the requirement for its forensic application. It is expected that the technique will prove handy in identification of all the three Indian crocodile species and strengthen conservation efforts.

Geochemical study of vertebrate fossils from the Upper Cretaceous (Santonian) Csehbánya Formation (Hungary): Evidence for a freshwater habitat of mosasaurs and pycnodont fish

The diverse vertebrate remains from the Upper Cretaceous freshwater settings at Iharkút, Hungary, contain two fossil groups, Pycnodontiformes fish and Mosasauridae that are almost exclusively known from marine palaeo-environments. Hence, their appearance in alluvial sediments is very unusual. Trace element and isotope compositions of the remains have been analyzed to investigate the taphonomy and the ecological differences among the different fossil groups present at Iharkút. All examined fossils have undergone post-depositional diagenetic alteration, which resulted in high concentrations of REE, U, and Fe, together with almost complete homogenization of δ 18O CO3 values. Similar REE patterns in different fossils suggest a common origin for all remains, hence the discovered species most likely lived in the same local ecosystem. Despite partial diagenetic overprinting, the δ 18O PO4 values of the fossils indicate sufficient taxon-specific isotopic diversity to permit some broad conclusions on the palaeo-environment of the fossils. In particular, it is apparent that the isotopic composition of the Pycnodontiformes fish and Mosasauridae remains is most compatible with a freshwater palaeo-habitat and incompatible with a marine palaeo-environment. In addition, the Sr concentration and isotope data indicate that the Pycnodontiformes and Mosasauridae likely lived predominantly in a freshwater environment and were not simply occasional visitors to the Iharkút river ecosystem. Regarding other fossil groups, high δ 18O PO4 values of Alligatoroidea and Iharkutosuchus teeth suggest that these small crocodile species might have inhabited swamps and ponds where the water was relatively rich in 18O due to evaporation.

Distribution of Endogenous Retroviruses in Crocodilians

Knowledge of endogenous retroviruses (ERVs) in crocodilians (Crocodylia) is limited, and their distribution among extant species is unclear. Here we analyzed the phylogenetic relationships of these retroelements in 20 species of crocodilians by studying the pro-pol gene. The results showed that crocodilian ERVs (CERVs) cluster into two major clades (CERV 1 and CERV 2). CERV 1 clustered as a sister group of the genus Gammaretrovirus, while CERV 2 clustered distantly with respect to all known ERVs. Interestingly, CERV 1 was found only in crocodiles (Crocodylidae). The data generated here could assist future studies aimed at identifying orthologous and paralogous ERVs among crocodilians.