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"Crocodilians."
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Crocs
Get the scoop on some of nature's most fearsome predators and discover the unexpected ways humans and crocodilians are similar in the sixth installment in the Just Like Us! series. Fun facts and a hilarious mix of photographs and full-color cartoon illustrations combine to captivate reluctant readers.
Book
Biology and evolution of crocodylians
Biology and Evolution of Crocodylians is a comprehensive review of current knowledge about the world's largest and most famous living reptiles. Gordon Grigg's authoritative and accessible text and David Kirshner's stunning interpretive artwork and colour photographs combine expertly in this contemporary celebration of crocodiles, alligators, caimans and gharials. This book showcases the skills and capabilities that allow crocodylians to live how and where they do. It covers the biology and ecology of the extant species, conservation issues, crocodylian-human interaction and the evolutionary history of the group, and includes a vast amount of new information; 25 per cent of 1100 cited publications have appeared since 2007. Richly illustrated with more than 500 colour photographs and black and white illustrations, this book will be a benchmark reference work for crocodylian biologists, herpetologists and vertebrate biologists for years to come.
eBook
The relative withdrawal of GFAP—An essential component of brain evolution
The glial fibrillary acidic protein (GFAP) is the principal intermediate filament protein and histochemical marker for astroglia. It appears contradictory that there are extended GFAP-poor or even GFAP-free areas in the brains of various vertebrate clades: cartilaginous and ray-finned fishes, and amniotes. The “Relevant Subsections: Extended GFAP-free areas in various vertebrates” section in this study reviews our GFAP mapping studies on the brains of 58 species within these clades, as well as mappings from other authors, and demonstrates that these areas appeared independently from one another in the more advanced groups of different clades; it raises the supposition that the lack of GFAP is an apomorphic phenomenon. The GFAP expression has withdrawn mainly relatively: the GFAP-immunonegative areas increased more than the immunopositive ones. Primarily, regions that expanded and increased in complexity during evolution lack GFAP immunopositivity (except for their perivascular glia). The absence of GFAP expression, however, does not indicate the lack of astroglia. In the areas immunonegative to GFAP, astrocytes were visualized using other markers, such as glutamine synthetase or S-100 protein. In birds and mammals, lesions induced GFAP expression in these areas. It shows that the ability to express GFAP is not lost but has become facultative. These data suggest that the lack of GFAP production may provide an evolutionary advantage. The “Discussion” section relates the GFAP “withdrawal” to other steps of evolution: the increasing complexity and thickening of the brain wall, as well as the appearance of the astrocytes, particularly protoplasmic astrocytes, and then examines the proposed evolutionary advantages and disadvantages of the absence of GFAP. The role of the relative “withdrawal” of GFAP expression in brain evolution remains to be definitively answered. The most probable candidates may include the absence of synthesizing an unnecessary protein, improved adaptation of astrocytes to the demands of neurons, and an increased capacity for synaptic plasticity. In contrast, one must consider that the withdrawal of GFAP may not be a primary phenomenon but rather a consequence of the evolution of neural networks.
Journal Article
Alligators
\"Did you know that alligators are the largest reptiles in North Americaor that they survived the mass-extinction that wiped out most animals on the planet 65 million years ago? Learn fascinating facts like these and more all in the pages of this book\"--Provided by publisher.
Book
Crocodylus porosus Gut Bacteria: A Possible Source of Novel Metabolites
Crocodiles are remarkable animals that have the ability to endure extremely harsh conditions and can survive up to a 100 years while being exposed to noxious agents that are detrimental to Homo sapiens. Besides their immunity, we postulate that the microbial gut flora of crocodiles may produce substances with protective effects. In this study, we isolated and characterized selected bacteria colonizing the gastrointestinal tract of Crocodylusporosus and demonstrated their inhibitory effects against three different cancerous cell lineages. Using liquid chromatography-mass spectrometry, several molecules were identified. For the first time, we report partial analyses of crocodile’s gut bacterial molecules.
Journal Article
The evolution of crocodilian nesting ecology and behavior
Crocodilians comprise an ancient and successful lineage of archosaurs that repeatedly raises questions on how they survived a mass extinction and remained relatively unchanged for ~100 million years. Was their success due to the change‐resistant retention of a specific set of traits over time (phylogenetic conservatism) or due to flexible, generalist capabilities (e.g., catholic diets, phenotypic plasticity in behavior), or some combination of these? We examined the evolution of reproductive ecology and behavior of crocodilians within a phylogenetic perspective, using 14 traits for all 24 species to determine whether these traits were phylogenetically constrained versus (ecologically) convergent. Our analysis revealed that the ancestral crocodilian was a mound nester that exhibited both nest attendance and defense. Nesting mode exhibited 4–5 transformations from mound to hole nesting, a convergence of which habitat may have been a driving factor. Hole nesters were more likely to nest communally, but this association may be biased by scale. Although there were exceptions, mound nesters typically nested during the wet season and hole nesters during the dry season; this trait was relatively conserved, however. About two‐thirds of species timed their nesting with the wet season, while the other third timed their hatching with the onset of the wet season. Nest attendance and defense were nearly ubiquitous and thus exhibited phylogenetic conservatism, but attendance lodging was diverse among species, showing multiple reversals between water and burrows. Collectively, our analysis reveals that reproductive trait evolution in crocodilians reflects phylogenetic constraint (nest attendance, nest defense), ecological convergence (seasonal timing of nesting, nest attendance lodging), or both (mode of nesting). Some traits (e.g., communal nesting and mode of nesting) were autocorrelated. Our analysis provides a framework for addressing hypotheses raised for why there has been trait convergence in reproductive ecology and behavior in crocodilians and why some traits remained phylogenetically conserved. Our analysis reveals that reproductive trait evolution in crocodilians reflects phylogenetic constraint (nest attendance, nest defense), ecological convergence (seasonal timing of nesting, nest attendance lodging), or both (mode of nesting). Our analysis provides a framework for addressing hypotheses raised for why there has been trait convergence in reproductive ecology and behavior in crocodilians and why some traits remained phylogenetically conserved.
Journal Article
Spatial and temporal variation in nest temperatures forecasts sex ratio skews in a crocodilian with environmental sex determination
Species displaying temperature-dependent sex determination (TSD) are especially vulnerable to the effects of a rapidly changing global climate due to their profound sensitivity to thermal cues during development. Predicting the consequences of climate change for these species, including skewed offspring sex ratios, depends on understanding how climatic factors interface with features of maternal nesting behaviour to shape the developmental environment. Here, we measure thermal profiles in 86 nests at two geographically distinct sites in the northern and southern regions of the American alligator’s (Alligator mississippiensis) geographical range, and examine the influence of both climatic factors and maternally driven nest characteristics on nest temperature variation. Changes in daily maximum air temperatures drive annual trends in nest temperatures, while variation in individual nest temperatures is also related to local habitat factors and microclimate characteristics. Without any compensatory nesting behaviours, nest temperatures are projected to increase by 1.6–3.7°C by the year 2100, and these changes are predicted to have dramatic consequences for offspring sex ratios. Exact sex ratio outcomes vary widely depending on site and emission scenario as a function of the unique temperature-by-sex reaction norm exhibited by all crocodilians. By revealing the ecological drivers of nest temperature variation in the American alligator, this study provides important insights into the potential consequences of climate change for crocodilian species, many of which are already threatened by extinction.
Journal Article
Evidence of cryptic lineages within a small South American crocodilian: the Schneider’s dwarf caiman Paleosuchus trigonatus (Alligatoridae: Caimaninae)
Schneider’s dwarf caiman Paleosuchus trigonatus is one of the smallest living crocodilians. Due to its broad distribution, cryptic behavior, and small home range, the species is well suited for the study of phylogeographic patterns on a continental scale. Additionally, this species is under threat due to habitat loss, trade and harvest, but is considered at low conservation risk by the IUCN. In the present study we test the hypothesis that P. trigonatus is comprised of geographically structured lineages. Phylogenetic reconstructions of the mitochondrial cytochrome b gene and single locus species discovery methods revealed the existence of two well-supported lineages within P. trigonatus —an Amazonian and Guianan lineage. Fossil calibrated divergence of these lineages was estimated to have occurred in the Late Miocene (7.5 Ma). The hypothesis that the Atlantic coast drainages might have been colonized from the southeast or central Amazon is supported by demographic metrics and relatively low genetic diversity of the Coastal and upper Branco populations when compared to the Amazon basin populations. The Amazon basin lineage is structured along an east-west gradient, with a sharp transition in haplotype frequencies to the east and west of the Negro and Madeira rivers. These lineages are already under anthropogenic threat and, therefore, are conservation dependent. Recognition of these lineages will foster discussion of conservation future of P. trigonatus and these lineages.
Journal Article