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chronic hypoxic incubation blunts thermally dependent cholinergic tone on the cardiovascular system in embryonic american alligator (alligator mississippiensis).environmental conditions play a major role in shaping reptilian embryonic development, but studies addressing the impact of interactions between chronic and acute environmental stressors on embryonic systems are lacking. in the present study, we investigated thermal dependence of cholinergic and adrenergic cardiovascular tone in embryonic american alligators (alligator mississippiensis) and assessed possible phenotypic plasticity in a chronic hypoxic incubation treatment. we compared changes in ...201323632626
igh loci of american alligator and saltwater crocodile shed light on iga evolution.immunoglobulin loci of two representatives of the order crocodylia were studied from full genome sequences. both alligator mississippiensis and crocodylus porosus have 13 genes for the heavy chain constant regions of immunoglobulins. the ighc locus contains genes encoding four immunoglobulins m (igm), one immunoglobulin d (igd), three immunoglobulins a (iga), three immunoglobulins y (igy), and two immunoglobulins d2 (igd2). iga and igd2 genes were found in reverse transcriptional orientation com ...201323558556
development of sympathetic cardiovascular control in embryonic, hatchling, and yearling female american alligator (alligator mississippiensis).we used arterial tyramine injections to study development of sympathetic actions on in vivo heart rate and blood pressure in embryonic, hatching and yearling female american alligators. tyramine is a pharmacological tool for understanding comparative and developmental sympathetic regulation of cardiovascular function, and this indirect sympathomimetic agent causes endogenous neuronal catecholamine release, increasing blood pressure and heart rate. arterial tyramine injection in hatchling and yea ...201323538224
histological evidence for muscle insertion in extant amniote femora: implications for muscle reconstruction in fossils.since the 19th century, identification of muscle attachment sites on bones has been important for muscle reconstructions, especially in fossil tetrapods, and therefore has been the subject of numerous biological and paleontological studies. at the microscopic level, in histological thin sections, the only features that can be used reliably for identifying tendon-bone or muscle-tendon-bone interactions are sharpey's fibers. muscles, however, do not only attach to the bone indirectly with tendons, ...201323439026
trigeminal nerve morphology in alligator mississippiensis and its significance for crocodyliform facial sensation and evolution.modern crocodylians possess a derived sense of face touch, in which numerous trigeminal nerve-innervated dome pressure receptors speckle the face and mandible and sense mechanical stimuli. however, the morphological features of this system are not well known, and it remains unclear how the trigeminal system changes during ontogeny and how it scales with other cranial structures. finally, when this system evolved within crocodyliforms remains a mystery. thus, new morphological insights into the t ...201323408584
penile anatomy and hypotheses of erectile function in the american alligator (alligator mississippiensis): muscular eversion and elastic retraction.the intromittent organs of most amniotes contain variable-volume hydrostatic skeletons that are stored in a flexible state and inflate with fluid before or during copulation. however, the penis in male crocodilians is notable because its shaft does not seem to change either its shape or bending stiffness as blood enters its vascular spaces before copulation. here i report that crocodilians may have evolved a mechanism for penile shaft erection that does not require inflation and detumescence. di ...201323408539
organizational changes to thyroid regulation in alligator mississippiensis: evidence for predictive adaptive responses.during embryonic development, organisms are sensitive to changes in thyroid hormone signaling which can reset the hypothalamic-pituitary-thyroid axis. it has been hypothesized that this developmental programming is a 'predictive adaptive response', a physiological adjustment in accordance with the embryonic environment that will best aid an individual's survival in a similar postnatal environment. when the embryonic environment is a poor predictor of the external environment, the developmental c ...201323383213
chronic incidental lead ingestion in a group of captive-reared alligators (alligator mississippiensis): possible contribution to reproductive failure.an american alligator (alligator mississippiensis) breeding facility using male and female alligators raised from artificially incubated eggs was established in 1975. these alligators first reproduced at 6 years of age as compared to 10-12 years in wild alligators, but the eggs produced showed a lower hatching rate than those collected from the wild. by age 21 reproduction had failed almost completely. the alligators were sacrificed and tissues collected at necropsy from 44 captive and 15 wild a ...201316290046
pulmonary gas exchange during intermittent ventilation in the american alligator.the present study characterized pulmonary gas exchange in the american alligator, alligator mississipiensis during ventilation and apnea at a body temperature (tb) of 25 degrees c. pulmonary gas exchange parameters were measured on a breath-by-breath basis utilizing a computer-assisted data acquisition system. in addition, paired blood samples were analyzed from left and right atrium during ventilation and voluntary apneas (1, 2, 5 and 10 min). measurements of lung po2 and pco2 indicated that as ...20131626141
gas permeability of american alligator eggs and its anatomical basis.the barrier to gas flux across the eggs of american alligators (alligator mississippiensis) consists of a calcareous shell and an underlying shell membrane of two layers, a limiting membrane facing the embryo and a fibrous membrane facing the shell. the limiting membrane is penetrated by an immense population (averaging 341,188 cm-2) of tiny pores (averaging 0.51 micron in diameter) and a small population (averaging 190 cm-2) of large pores (averaging 34.6 microns in diameter). an estimated 6% o ...20139279920
changes in thyrotropin-releasing hormone levels in alligator stomach during fasting.stomach tissue of the american alligator, alligator mississippiensis, contains substantial levels of thyrotropin-releasing hormone (trh) which behaves identically to the synthetic hormone on radioimmunoassay (ria) and high performance liquid chromatography (hplc). fasting induces a marked increase in gastric tissue levels of this hypophysiotropic hormone, but is without effect on hypothalamic content, suggesting a physiological role for trh in gastric function of this vertebrate.20136415622
an examination of the sensory structures in the oral cavity of the american alligator (alligator mississippiensis).the location and distribution of mucosal sensory structures of the crocodilian oral cavity are poorly understood. although there are several descriptions of these structures in adults, nothing is known about their development. the purpose of this study was to document location, morphology, and relative abundance of these mucosal sensory structures in both hatchling and subadult alligators. numerous mucosal sensory structures and pale staining dome-shaped papillae were observed only in the upper ...201424976263
quantification of intraskeletal histovariability in alligator mississippiensis and implications for vertebrate osteohistology.bone microanalyses of extant vertebrates provide a necessary framework from which to form hypotheses regarding the growth and skeletochronology of extinct taxa. here, we describe the bone microstructure and quantify the histovariability of appendicular elements and osteoderms from three juvenile american alligators (alligator mississippiensis) to assess growth mark and tissue organization within and amongst individuals, with the intention of validating paleohistological interpretations. results ...201424949239
effects of prolonged lung inflation or deflation on pulmonary stretch receptor discharge in the alligator (alligator mississippiensis).the american alligator (alligator mississippiensis) is a semi-aquatic diving reptile that has a periodic breathing pattern. previous work identified pulmonary stretch receptors, that are rapidly and slowly adapting, as well as intrapulmonary chemoreceptors (ipc), sensitive to co2, that modulate breathing patterns in alligators. the purpose of the present study was to quantify the effects of prolonged lung inflation and deflation (simulated dives) on pulmonary stretch receptors (psr) and/or ipc d ...201424874556
evaluation of four methods for inducing death during slaughter of american alligators (alligator mississippiensis).to evaluate physical methods for inducing death during the slaughter of american alligators (alligator mississippiensis).201424866509
american alligator proximal pedal phalanges resemble human finger bones: diagnostic criteria for forensic investigators.a scientific approach to bone and tooth identification requires analysts to pursue the goal of empirical falsification. that is, they may attribute a questioned specimen to element and taxon only after having ruled out all other possible attributions. this requires analysts to possess a thorough understanding of both human and non-human osteology, particularly so for remains that may be morphologically similar across taxa. to date, forensic anthropologists have identified several potential 'mimi ...201424815617
first record of eocene bony fishes and crocodyliforms from canada's western arctic.discovery of eocene non-marine vertebrates, including crocodylians, turtles, bony fishes, and mammals in canada's high arctic was a critical paleontological contribution of the last century because it indicated that this region of the arctic had been mild, temperate, and ice-free during the early - middle eocene (∼53-50 ma), despite being well above the arctic circle. to date, these discoveries have been restricted to canada's easternmost arctic - ellesmere and axel heiberg islands (nunavut). al ...201424788829
concentrations of trace elements in american alligators (alligator mississippiensis) from florida, usa.concentrations of 28 trace elements (li, mg, al, v, cr, mn, fe, co, ni, cu, zn, ga, as, se, rb, sr, mo, ag, cd, in, sn, sb, cs, tl, hg, pb, and bi) in the livers of juvenile and adult american alligators inhabiting two central florida lakes, lake apopka (la), and lake woodruff national wildlife refuge (lw) and one lagoon population located in merritt island national wildlife refuge (minwr; nasa), were determined. in juveniles from minwr, concentrations of nine elements (li, fe, ni, sr, in, sb, h ...201424698170
biophysics of directional hearing in the american alligator (alligator mississippiensis).physiological and anatomical studies have suggested that alligators have unique adaptations for spatial hearing. sound localization cues are primarily generated by the filtering of sound waves by the head. different vertebrate lineages have evolved external and/or internal anatomical adaptations to enhance these cues, such as pinnae and interaural canals. it has been hypothesized that in alligators, directionality may be enhanced via the acoustic coupling of middle ear cavities, resulting in a p ...201424671963
a repeated-measures analysis of the effects of soft tissues on wrist range of motion in the extant phylogenetic bracket of dinosaurs: implications for the functional origins of an automatic wrist folding mechanism in crocodilia.a recent study hypothesized that avian-like wrist folding in quadrupedal dinosaurs could have aided their distinctive style of locomotion with semi-pronated and therefore medially facing palms. however, soft tissues that automatically guide avian wrist folding rarely fossilize, and automatic wrist folding of unknown function in extant crocodilians has not been used to test this hypothesis. therefore, an investigation of the relative contributions of soft tissues to wrist range of motion (rom) in ...201424664936
in vivo cranial bone strain and bite force in the agamid lizard uromastyx geyri.in vivo bone strain data are the most direct evidence of deformation and strain regimes in the vertebrate cranium during feeding and can provide important insights into skull morphology. strain data have been collected during feeding across a wide range of mammals; in contrast, in vivo cranial bone strain data have been collected from few sauropsid taxa. here we present bone strain data recorded from the jugal of the herbivorous agamid lizard uromastyx geyri along with simultaneously recorded bi ...201424577443
iodine-enhanced micro-ct imaging: methodological refinements for the study of the soft-tissue anatomy of post-embryonic vertebrates.the now widespread use of non-destructive x-ray computed tomography (ct) and micro-ct (µct) has greatly augmented our ability to comprehensively detail and quantify the internal hard-tissue anatomy of vertebrates. however, the utility of x-ray imaging for gaining similar insights into vertebrate soft-tissue anatomy has yet to be fully realized due to the naturally low x-ray absorption of non-mineralized tissues. in this study, we show how a wide diversity of soft-tissue structures within the ver ...201424482316
animal-borne imaging reveals novel insights into the foraging behaviors and diel activity of a large-bodied apex predator, the american alligator (alligator mississippiensis).large-bodied, top- and apex predators (e.g., crocodilians, sharks, wolves, killer whales) can exert strong top-down effects within ecological communities through their interactions with prey. due to inherent difficulties while studying the behavior of these often dangerous predatory species, relatively little is known regarding their feeding behaviors and activity patterns, information that is essential to understanding their role in regulating food web dynamics and ecological processes. here we ...201424454711
influence of tissue, age, and environmental quality on dna methylation in alligator mississippiensis.epigenetic modifications are key mediators of the interactions between the environment and an organism's genome. dna methylation represents the best-studied epigenetic modification to date and is known to play key roles in regulating transcriptional activity and promoting chromosome stability. our laboratory has previously demonstrated the utility of the american alligator (alligator mississippiensis) as a sentinel species to investigate the persistent effects of environmental contaminant exposu ...201424398872
molecular characterization of dental development in a toothed archosaur, the american alligator alligator mississippiensis.few skeletal structures are as informative of the adaptive natural history of vertebrate animals as their teeth. understanding principles of tooth development is key to understanding evolution of the vertebrate dentition in general and emergence of multiple specialized tooth types in particular. morphological and phylogenetic considerations suggest that crocodilians have the most primitive mode of dentition within extant tetrapods, displaying simple, conical, socketed, and continuously replaced ...201424261441
differential incubation temperatures result in dimorphic dna methylation patterning of the sox9 and aromatase promoters in gonads of alligator (alligator mississippiensis) embryos.environmental factors are known to influence sex determination in many nonmammalian vertebrates. in all crocodilians studied thus far, temperature is the only known determinant of sex. however, the molecular mechanisms mediating the effect of temperature on sex determination are not known. aromatase (cyp19a1) and sox9 play critical roles in vertebrate sex determination and gonadogenesis. here, we used a variety of techniques to investigate the potential roles of dna methylation patterning on cyp ...201424227754
three crocodilian genomes reveal ancestral patterns of evolution among archosaurs.to provide context for the diversification of archosaurs--the group that includes crocodilians, dinosaurs, and birds--we generated draft genomes of three crocodilians: alligator mississippiensis (the american alligator), crocodylus porosus (the saltwater crocodile), and gavialis gangeticus (the indian gharial). we observed an exceptionally slow rate of genome evolution within crocodilians at all levels, including nucleotide substitutions, indels, transposable element content and movement, gene f ...201425504731
scaling the feeding mechanism of captive alligator mississippiensis from hatchling to juvenile.small changes in size can lead to potential performance consequences and may influence an organism's ability to utilize resources in its environment. as the american alligator (alligator mississippiensis) transitions between neonate, juvenile and adult habitats (ontogenetic niche shifts), there are inevitably dynamic changes in their feeding performance. this study sought to investigate the scaling of the feeding mechanism and its performance from hatchling to juvenile size classes in a. mississ ...201425390506
comparison of metabolic substrates in alligators and several birds of prey.on average, avian blood glucose concentrations are 1.5-2 times those of mammals of similar mass and high concentrations of insulin are required to lower blood glucose. whereas considerable data exist for granivorous species, few data are available for plasma metabolic substrate and glucoregulatory hormone concentrations for carnivorous birds and alligators. birds and mammals with carnivorous diets have higher metabolic rates than animals consuming diets with less protein whereas alligators have ...201425043840
slow isotope turnover rates and low discrimination values in the american alligator: implications for interpretation of ectotherm stable isotope data.stable isotope analysis has become a standard ecological tool for elucidating feeding relationships of organisms and determining food web structure and connectivity. there remain important questions concerning rates at which stable isotope values are incorporated into tissues (turnover rates) and the change in isotope value between a tissue and a food source (discrimination values). these gaps in our understanding necessitate experimental studies to adequately interpret field data. tissue turnov ...201423303328
gastric nematode diversity between estuarine and inland freshwater populations of the american alligator (alligator mississippiensis, daudin 1802), and the prediction of intermediate hosts.we examined the variation of stomach nematode intensity and species richness of alligator mississippiensis from coastal estuarine and inland freshwater habitats in florida and georgia, and integrated prey content data to predict possible intermediate hosts. nematode parasitism within inland freshwater inhabiting populations was found to have a higher intensity and species richness than those inhabiting coastal estuarine systems. this pattern potentially correlates with the difference and diversi ...201425426417
in ovo and in vitro susceptibility of american alligators (alligator mississippiensis) to avian influenza virus infection.avian influenza has emerged as one of the most ubiquitous viruses within our biosphere. wild aquatic birds are believed to be the primary reservoir of all influenza viruses; however, the spillover of h5n1 highly pathogenic avian influenza (hpai) and the recent swine-origin pandemic h1n1 viruses have sparked increased interest in identifying and understanding which and how many species can be infected. moreover, novel influenza virus sequences were recently isolated from new world bats. crocodili ...201525380354
morphogenesis and patterning of the phallus and cloaca in the american alligator, alligator mississippiensis.in most animals, reproduction by internal fertilization is facilitated by an intromittent organ, such as the penis in amniote vertebrates. recent progress has begun to uncover the mechanisms of mammalian external genital development; however, comparatively little is known about the development of the reptilian penis and clitoris. here, we describe the development of the phallus and cloaca in the american alligator, alligator mississippiensis. the embryonic precursor of the penis and clitoris is ...201524993090
size, sex and individual-level behaviour drive intrapopulation variation in cross-ecosystem foraging of a top-predator.large-bodied, top-predators are often highly mobile, with the potential to provide important linkages between spatially distinct food webs. what biological factors contribute to variation in cross-ecosystem movements, however, have rarely been examined. here, we investigated how ontogeny (body size), sex and individual-level behaviour impacts intrapopulation variation in cross-ecosystem foraging (i.e. between freshwater and marine systems), by the top-predator alligator mississippiensis. field s ...201525327480
chronic hypercapnic incubation increases relative organ growth and reduces blood pressure of embryonic american alligator (alligator mississippiensis).reptilian nests can experience natural hypoxic and hypercapnic conditions. we incubated alligator eggs at a female-only producing temperature (30°c) in three conditions: 21% o2/0.04% co2, 21% o2/3.5% co2 and 21% o2/7% co2. alligator embryos chronically incubated in high co2 were markedly hypotensive (blood pressure reduced by 46%) and had relatively (mass-specific) enlarged hearts (dry mass increased by 20%), lungs (dry mass increased by 17%), and kidneys (dry mass increased by 14%). this study ...201525499241
biomonitoring heavy metal pollution using an aquatic apex predator, the american alligator, and its parasites.monitoring the bioaccumulation of chemical elements within various organismal tissues has become a useful tool to survey current or chronic levels of heavy metal exposure within an environment. in this study, we compared the bioaccumulations of as, cd, cu, fe, pb, se, and zn between the american alligator, alligator mississippiensis, and its parasites in order to establish their use as bioindicators of heavy metal pollution. concomitant with these results, we were interested to determine if para ...201526555363
estimating cranial musculoskeletal constraints in theropod dinosaurs.many inferences on the biology, behaviour and ecology of extinct vertebrates are based on the reconstruction of the musculature and rely considerably on its accuracy. although the advent of digital reconstruction techniques has facilitated the creation and testing of musculoskeletal hypotheses in recent years, muscle strain capabilities have rarely been considered. here, a digital modelling approach using the freely available visualization and animation software blender is applied to estimate cr ...201526716007
trpv4 associates environmental temperature and sex determination in the american alligator.temperature-dependent sex determination (tsd), commonly found among reptiles, is a sex determination mode in which the incubation temperature during a critical temperature sensitive period (tsp) determines sexual fate of the individual rather than the individual's genotypic background. in the american alligator (alligator mississippiensis), eggs incubated during the tsp at 33 °c (male producing temperature: mpt) yields male offspring, whereas incubation temperatures below 30 °c (female producing ...201526677944
ontogeny of the middle-ear air-sinus system in alligator mississippiensis (archosauria: crocodylia).modern crocodylians, including alligator mississippiensis, have a greatly elaborated system of pneumatic sinuses invading the cranium. these sinuses invade nearly all the bones of the chondrocranium and several bony elements of the splanchnocranium, but patterns of postnatal paratympanic sinus development are poorly understood and documented. much of crocodylomorph--indeed archosaurian--evolution is characterized by the evolution of various paratympanic air sinuses, the homologies of which are p ...201526398659
incubation history prior to the canonical thermosensitive period determines sex in the american alligator.despite the widespread occurrence of environmental sex determination (esd) among vertebrates, our knowledge of the temporal dynamics by which environmental factors act on this process remains limited. in many reptiles, incubation temperature determines sex during a discrete developmental window just prior to and coincident with the differentiation of the gonads. yet, there is substantial variation in sex ratios among different clutches of eggs incubated at identical temperatures during this peri ...201526183894
similarity of crocodilian and avian lungs indicates unidirectional flow is ancestral for archosaurs.patterns of airflow and pulmonary anatomy were studied in the american alligator (alligator mississippiensis), the black caiman (melanosuchus niger), the spectacled caiman (caiman crocodilus), the dwarf crocodile (osteolaemus tetraspis), the saltwater crocodile (crocodylus porosus), the nile crocodile (crocodylus niloticus), and morelet's crocodile (crocodylus moreletii). in addition, anatomy was studied in the orinoco crocodile (crocodylus intermedius). airflow was measured using heated thermis ...201526141868
alligators and crocodiles have high paracellular absorption of nutrients, but differ in digestive morphology and physiology.much of what is known about crocodilian nutrition and growth has come from animals propagated in captivity, but captive animals from the families crocodilidae and alligatoridae respond differently to similar diets. since there are few comparative studies of crocodilian digestive physiology to help explain these differences, we investigated young alligator mississippiensis and crocodylus porosus in terms of (1) gross and microscopic morphology of the intestine, (2) activity of the membrane-bound ...201526060211
new insight into the anatomy of the hyolingual apparatus of alligator mississippiensis and implications for reconstructing feeding in extinct archosaurs.anatomical studies of the cranium of crocodilians motivated by an interest in its function in feeding largely focused on bite force, the jaw apparatus and associated muscles innervated by the trigeminal nerve. however, the ossified and cartilaginous elements of the hyoid and the associated hyolingual muscles, innervated by the facial, hypoglossal and glossopharyngeal nerves, received much less attention. crocodilians are known to retain what are ancestrally the 'rhythmic hyobranchial behaviors' ...201526018316
identification and characterization of the androgen receptor from the american alligator, alligator mississippiensis.androgens are essential for the development, reproduction, and health throughout the life span of vertebrates, particularly during the initiation and maintenance of male sexual characteristics. androgen signaling is mediated by the androgen receptor (ar), a member of the steroid nuclear receptor superfamily. mounting evidence suggests that environmental factors, such as exogenous hormones or contaminants that mimic hormones, can disrupt endocrine signaling and function. the american alligator (a ...201525974402
the good, the bad, and the unknown: microbial symbioses of the american alligator.vertebrates coexist with microorganisms in diverse symbiotic associations that range from beneficial to detrimental to the host. most research has aimed at deciphering the nature of the composite microbial assemblage's genome, or microbiome, from the gastrointestinal (gi) tract and skin of mammals (i.e., humans). in mammals, the gi tract's microbiome aids digestion, enhances uptake of nutrients, and prevents the establishment of pathogenic microorganisms. however, because the gi tract microbiome ...201525888944
small sample sizes in the study of ontogenetic allometry; implications for palaeobiology.quantitative morphometric analyses, particularly ontogenetic allometry, are common methods used in quantifying shape, and changes therein, in both extinct and extant organisms. due to incompleteness and the potential for restricted sample sizes in the fossil record, palaeobiological analyses of allometry may encounter higher rates of error. differences in sample size between fossil and extant studies and any resulting effects on allometric analyses have not been thoroughly investigated, and a lo ...201525780770
tooth counts through growth in diapsid reptiles: implications for interpreting individual and size-related variation in the fossil record.tooth counts are commonly recorded in fossil diapsid reptiles and have been used for taxonomic and phylogenetic purposes under the assumption that differences in the number of teeth are largely explained by interspecific variation. although phylogeny is almost certainly one of the greatest factors influencing tooth count, the relative role of intraspecific variation is difficult, and often impossible, to test in the fossil record given the sample sizes available to palaeontologists and, as such, ...201525689039
endogenous and exogenous estrogens during embryonic development affect timing of hatch and growth in the american alligator (alligator mississippiensis).prenatal exposure to estrogenic endocrine disrupting chemicals (edcs) can affect length of gestation and body mass and size of offspring. however, the dose, timing, and duration of exposure as well as sex and strain of the experimental animals determine the direction and magnitude of these effects. in this study, we examined the effects of a one-time embryonic exposure to either 17 β-estradiol (e2) or bisphenol a (bpa) on rate of development and growth in american alligators (alligator mississip ...201525687799
a comparative examination of odontogenic gene expression in both toothed and toothless amniotes.a well-known tenet of murine tooth development is that bmp4 and fgf8 antagonistically initiate odontogenesis, but whether this tenet is conserved across amniotes is largely unexplored. moreover, changes in bmp4-signaling have previously been implicated in evolutionary tooth loss in aves. here we demonstrate that bmp4, msx1, and msx2 expression is limited proximally in the red-eared slider turtle (trachemys scripta) mandible at stages equivalent to those at which odontogenesis is initiated in mic ...201525678399
bioprospecting the american alligator (alligator mississippiensis) host defense peptidome.cationic antimicrobial peptides and their therapeutic potential have garnered growing interest because of the proliferation of bacterial resistance. however, the discovery of new antimicrobial peptides from animals has proven challenging due to the limitations associated with conventional biochemical purification and difficulties in predicting active peptides from genomic sequences, if known. as an example, no antimicrobial peptides have been identified from the american alligator, alligator mis ...201525671663
functional morphology of the alligator mississippiensis larynx with implications for vocal production.sauropsid vocalization is mediated by the syrinx in birds and the larynx in extant reptiles; but whereas avian vocal production has received much attention, the vocal mechanism of basal reptilians is poorly understood. the american alligator (alligator mississippiensis) displays a large vocal repertoire during mating and in parent-offspring interactions. although vocal outputs of these behaviors have received some attention, the underlying mechanism of sound production remains speculative. here, ...201525657203
factors affecting individual foraging specialization and temporal diet stability across the range of a large "generalist" apex predator.individual niche specialization (ins) is increasingly recognized as an important component of ecological and evolutionary dynamics. however, most studies that have investigated ins have focused on the effects of niche width and inter- and intraspecific competition on ins in small-bodied species for short time periods, with less attention paid to ins in large-bodied reptilian predators and the effects of available prey types on ins. we investigated the prevalence, causes, and consequences of ins ...201525645268
influence of collection time on hematologic and immune markers in the american alligator (alligator mississippiensis).crocodilians are important keystone species and indicators of environmental health. much remains unknown, however regarding utility of field-collected crocodilian blood samples for ecologic assessments. field sampling sites are also often distant to analysis centers, necessitating development of new techniques and panels of assays that will yield environmentally relevant data. stability and viability of hematological and immunological indices have been of particular interest for linking ecosyste ...201525560415
estrogen receptor 1 (esr1; erα), not esr2 (erβ), modulates estrogen-induced sex reversal in the american alligator, a species with temperature-dependent sex determination.all crocodilians and many turtles exhibit temperature-dependent sex determination where the temperature of the incubated egg, during a thermo-sensitive period (tsp), determines the sex of the offspring. estrogens play a critical role in sex determination in crocodilians and turtles, as it likely does in most nonmammalian vertebrates. indeed, administration of estrogens during the tsp induces male to female sex reversal at a male-producing temperature (mpt). however, it is not clear how estrogens ...201525714813
[direct allosteric interaction of oxygen and bicarbonate: n-acetyl-alanyl-seryl-phenylalanine, n-terminal sequence of the beta-chains of the haemoglobins of nil crocodile (crocodylusniloticus) and mississippi crocodile (alligator mississippiensis) (author's transl)].to elucidate the molecular mechanism of the direct allosteric exchange of oxygen and hydrogen carbonate in the hemoglobins of crocodiles, the n-terminal sequence of the beta-chains of the crocodiles of the nile (crocodylus niloticus) and of the mississippi (alligator mississippiensis) was studied. the n-terminal end of the peptide is blocked. by mass spectrometry the n-terminal sequences of both species were found to be n-acetyl-alanyl-seryl-phenylalanine. these data explain the absence of hemog ...20167303821
vascular patterns in the heads of crocodilians: blood vessels and sites of thermal exchange.extant crocodilians are a highly apomorphic archosaur clade that is ectothermic, yet often achieve large body sizes that can be subject to higher heat loads. therefore, the anatomical and physiological roles that blood vessels play in crocodilian thermoregulation need further investigation to better understand how crocodilians establish and maintain cephalic temperatures and regulate neurosensory tissue temperatures during basking and normal activities. the cephalic vascular anatomy of extant cr ...201627677246
scale-dependent habitat selection and size-based dominance in adult male american alligators.habitat selection is an active behavioral process that may vary across spatial and temporal scales. animals choose an area of primary utilization (i.e., home range) then make decisions focused on resource needs within patches. dominance may affect the spatial distribution of conspecifics and concomitant habitat selection. size-dependent social dominance hierarchies have been documented in captive alligators, but evidence is lacking from wild populations. we studied habitat selection for adult ma ...201627588947
coronary blood flow in the anesthetized american alligator (alligator mississippiensis).coronary circulation of the heart evolved early within ectothermic vertebrates and became of vital importance to cardiac performance in some teleost fish, mammals and birds. in contrast, the role and function of the coronary circulation in ectothermic reptiles remains largely unknown. here, we investigated the systemic and coronary arterial responses of five anesthetized juvenile american alligators (alligator mississippiensis) to hypoxia, acetylcholine, adenosine, sodium nitroprusside, isoprote ...201626436857
developmental plasticity of mitochondrial function in american alligators, alligator mississippiensis.the effect of hypoxia on cellular metabolism is well documented in adult vertebrates, but information is entirely lacking for embryonic organisms. the effect of hypoxia on embryonic physiology is particularly interesting, as metabolic responses during development may have life-long consequences, due to developmental plasticity. to this end, we investigated the effects of chronic developmental hypoxia on cardiac mitochondrial function in embryonic and juvenile american alligators (alligator missi ...201627707718
how doth the little crocodilian: analyzing the influence of environmental viscosity on feeding performance of juvenile alligator mississippiensis.wetland habitats are used as nursery sites for hatchling and juvenile alligators (alligator mississippiensis), where they utilize prey from aquatic and terrestrial settings. however, little is known about how viscosity of the medium influences feeding performance. we hypothesized that timing and linear excursion feeding kinematic variables would be different for individuals feeding on prey above the water compared with the same individuals feeding underwater. individuals were fed immobile fish p ...201627706023
peptides from american alligator plasma are antimicrobial against multi-drug resistant bacterial pathogens including acinetobacter baumannii.our group has developed a new process for isolating and identifying novel cationic antimicrobial peptides from small amounts of biological samples. previously, we identified several active antimicrobial peptides from 100 μl of plasma from alligator mississippiensis. these peptides were found to have in vitro antimicrobial activity against pseudomonas aeruginosa and staphylococcus aureus. in this work, we further characterize three of the novel peptides discovered using this process: apo5, apo6, ...201627542832
fusion patterns in the skulls of modern archosaurs reveal that sutures are ambiguous maturity indicators for the dinosauria.the sutures of the skulls of vertebrates are generally open early in life and slowly close as maturity is attained. the assumption that all vertebrates follow this pattern of progressive sutural closure has been used to assess maturity in the fossil remains of non-avian dinosaurs. here, we test this assumption in two members of the extant phylogenetic bracket of the dinosauria, the emu, dromaius novaehollandiae and the american alligator, alligator mississippiensis, by investigating the sequence ...201626862766
host use and seasonality of culex (melanoconion) iolambdis (diptera: culicidae) from eastern florida, usa.culex (melanoconion) iolambdis (dyar, 1918) is a mosquito (diptera: culicidae) species found throughout much of tropical america, including southern florida. relatively few reports are available regarding the ecology of cx. iolambdis, despite its widespread distribution and putative involvement in transmission of venezuelan equine encephalitis virus. to quantify habitat and host utilization, adults of cx. iolambdis were sampled from resting shelters at a field site in vero beach, florida, over a ...201627712940
chronic ingestion of coal fly-ash contaminated prey and its effects on health and immune parameters in juvenile american alligators (alligator mississippiensis).coal-burning power plants supply approximately 37 % of the electricity in the united states. however, incomplete combustion produces ash wastes enriched with toxic trace elements that have historically been disposed of in aquatic basins. organisms inhabiting such habitats may accumulate these trace elements; however, studies investigating the effects on biota have been primarily restricted to shorter-lived, lower-trophic organisms. the american alligator (alligator mississippiensis), a long-live ...201627475646
methyltestosterone alters sex determination in the american alligator (alligator mississippiensis).effects of xenobiotics can be organizational, permanently affecting anatomy during embryonic development, and/or activational, influencing transitory actions during adulthood. the organizational influence of endocrine-disrupting contaminants (edc's) produces a wide variety of reproductive abnormalities among vertebrates that exhibit temperature-dependent sex determination (tsd). typically, such influences result in subsequent activational malfunction, some of which are beneficial in aquaculture. ...201627401264
alterations in eicosanoid composition during embryonic development in the chorioallantoic membrane of the american alligator (alligator mississippiensis) and domestic chicken (gallus gallus).eicosanoids are signaling lipids known to regulate several physiological processes in the mammalian placenta, including the initiation of parturition. though all amniotes construct similar extraembryonic membranes during development, the composition and function of eicosanoids in extraembryonic membranes of oviparous reptiles is largely unknown. the majority of effort placed in eicosanoid investigations is typically targeted toward defining the role of specific compounds in disease etiology; how ...201627401262
evaluating the effect of sample type on american alligator (alligator mississippiensis) analyte values in a point-of-care blood analyser.the assessment of wildlife health has been enhanced by the ability of point-of-care (poc) blood analysers to provide biochemical analyses of non-domesticated animals in the field. however, environmental limitations (e.g. temperature, atmospheric humidity and rain) and lack of reference values may inhibit researchers from using such a device with certain wildlife species. evaluating the use of alternative sample types, such as plasma, in a poc device may afford researchers the opportunity to dela ...201627382469
morphological characteristics regulating phallic glans engorgement in the american alligator.the distal part of the crocodilian phallus consists of a bulbous glans containing well-developed vascular tissues that can inflate before or during sexual activity, enlarging and elaborating the glans into a complex, though still functionally undefined, copulatory structure. an enlarged glans putatively interacts with the female cloaca and may change the shape of her reproductive tract to facilitate insemination and increase the probability of fertilization. here, we investigated the cellular-le ...201627252199
blood and plasma biochemistry reference intervals for wild juvenile american alligators ( alligator mississippiensis ).: american alligators ( alligator mississippiensis ) are one of the most studied crocodilian species in the world, yet blood and plasma biochemistry information is limited for juvenile alligators in their northern range, where individuals may be exposed to extreme abiotic and biotic stressors. we collected blood samples over a 2-yr period from 37 juvenile alligators in may, june, and july to establish reference intervals for 22 blood and plasma analytes. we observed no effect of either sex or bl ...201627224213
molecular cloning and characterization of the aryl hydrocarbon receptors and aryl hydrocarbon receptor nuclear translocators in the american alligator.aryl hydrocarbon receptor (ahr), a ligand-activated transcription factor, binds to a variety of chemical compounds including various environmental contaminants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin. this receptor regulates expression of target genes through dimerization with the ahr nuclear translocator (arnt). since ahr-arnt signaling pathways differ among species, characterization of ahr and arnt is important to assess the effects of environmental contamination and for understanding the ...201627174749
hepatic and renal trace element concentrations in american alligators (alligator mississippiensis) following chronic dietary exposure to coal fly ash contaminated prey.little is known about the propensity of crocodilians to bioaccumulate trace elements as a result of chronic dietary exposure. we exposed 36 juvenile alligators (alligator mississippiensis) to one of four dietary treatments that varied in the relative frequency of meals containing prey from coal combustion waste (ccw)-contaminated habitats vs. prey from uncontaminated sites, and evaluated tissue residues and growth rates after 12 mo and 25 mo of exposure. hepatic and renal concentrations of arsen ...201627149145
postembryonic nephrogenesis and persistence of six2-expressing nephron progenitor cells in the reptilian kidney.new nephron formation (nephrogenesis) ceases in mammals around birth and is completely absent in adults. in contrast, postembryonic nephrogenesis is well documented in the mesonephric kidneys of fishes and amphibians. the transient mesonephros in reptiles (including birds) and mammals is replaced by the metanephros during embryogenesis. thus, one may speculate that postembryonic nephrogenesis is restricted to the mesonephric kidney. previous reports have suggested the metanephros of non-avian re ...201627144443
environmentally relevant concentrations of nitrate increase plasma testosterone concentrations in female american alligators (alligator mississippiensis).anthropogenic nitrogen is a ubiquitous environmental contaminant that is contributing to the degradation of freshwater, estuarine, and coastal ecosystems worldwide. the effects of environmental nitrate, a principal form of nitrogen, on the health of aquatic life is of increasing concern. we exposed female american alligators to three concentrations of nitrate (0.7, 10 and 100mg/l no3-n) for a duration of five weeks and five months from hatch. we assessed growth, plasma sex steroid and thyroid ho ...201627118707
variations in hepatic biomarkers in american alligators (alligator mississippiensis) from three sites in florida, usa.sub-individual biomarkers are sub-lethal biological responses commonly used in the assessment of wildlife exposure to environmental contaminants. in this study, we examined the activity of glutathione-s-transferase (gst) and lactate dehydrogenase (ldh), and metallothionein (mt) concentrations among captive-raised alligator hatchlings, wild-caught juveniles, and wild-caught adults. juveniles and adults were collected from three locations in florida (usa) with varying degrees of contamination (i.e ...201627111470
comparative histology of some craniofacial sutures and skull-base synchondroses in non-avian dinosaurs and their extant phylogenetic bracket.sutures and synchondroses, the fibrous and cartilaginous articulations found in the skulls of vertebrates, have been studied for many biological applications at the morphological scale. however, little is known about these articulations at the microscopic scale in non-mammalian vertebrates, including extant archosaurs (birds and crocodilians). the major goals of this paper were to: (i) document the microstructure of some sutures and synchondroses through ontogeny in archosaurs; (ii) compare thes ...201627111332
periods of cardiovascular susceptibility to hypoxia in embryonic american alligators (alligator mississippiensis).during embryonic development, environmental perturbations can affect organisms' developing phenotype, a process known as developmental plasticity. resulting phenotypic changes can occur during discrete, critical windows of development. critical windows are periods when developing embryos are most susceptible to these perturbations. we have previously documented that hypoxia reduces embryo size and increases relative heart mass in american alligator, and this study identified critical windows whe ...201627101296
the utility of captive animals in actualistic research: a geometric morphometric exploration of the tooth row of alligator mississippiensis suggesting ecophenotypic influences and functional constraints.captive broad snouted crocodylians are generally thought to have wider, shorter rostra than their wild counterparts. interpreted to reflect morphological change in response to the conditions of captivity, this qualitative pattern could affect the utility of these animals in a variety of fields of research. however, due to relative ease of access and availability of life history data, captive animals are often utilized in actualistic research. thus, this issue should be addressed in more detail. ...201627098092
the influence of thermal signals during embryonic development on intrasexual and sexually dimorphic gene expression and circulating steroid hormones in american alligator hatchlings (alligator mississippiensis).incubation temperatures experienced by developing embryos exert powerful influences over gonadal sex determination and differentiation in many species. however, the molecular mechanisms controlling these impacts remain largely unknown. we utilize the american alligator to investigate the sensitivity of the reproductive system to thermal signals experienced during development and ask specifically whether individuals of the same sex, yet derived from different incubation temperatures display persi ...201627080549
in ovo treatment with an estrogen receptor alpha selective agonist causes precocious development of the female reproductive tract of the american alligator (alligator mississippiensis).the molecular signaling processes involved the differentiation of the müllerian duct (md) into the female reproductive tract, or oviduct, in non-mammalian vertebrates are not well understood. studies in mammals and birds indicate that steroid hormones play a role in this process, as the embryonic md has been shown to be vulnerable to exogenous estrogens and progestins and environmental endocrine disrupting contaminants. in a previous study, developmental treatment with an estrogen receptor α (er ...201626994582
post-hatching development of mitochondrial function, organ mass and metabolic rate in two ectotherms, the american alligator (alligator mississippiensis) and the common snapping turtle (chelydra serpentina).the ontogeny of endothermy in birds is associated with disproportionate growth of thermogenic organs and increased mitochondrial oxidative capacity. however, no similar study has been made of the development of these traits in ectotherms. for comparison, we therefore investigated the metabolism, growth and muscle mitochondrial function in hatchlings of a turtle and a crocodilian, two ectotherms that never develop endothermy. metabolic rate did not increase substantially in either species by 30 d ...201626962048
presence of breeding birds improves body condition for a crocodilian nest protector.ecological associations where one species enhances habitat for another nearby species (facilitations) shape fundamental community dynamics and can promote niche expansion, thereby influencing how and where species persist and coexist. for the many breeding birds facing high nest-predation pressure, enemy-free space can be gained by nesting near more formidable animals for physical protection. while the benefits to protected species seem well documented, very few studies have explored whether and ...201626934602
low cost of pulmonary ventilation in american alligators (alligator mississippiensis) stimulated with doxapram.to determine the costs of pulmonary ventilation without imposing severe oxygen limitations or acidosis that normally accompany exposures to hypoxia or hypercapnia, we opted to pharmacologically stimulate ventilation with doxapram (5 and 10 mg kg(-1)) in alligators. doxapram is used clinically to alleviate ventilatory depression in response to anaesthesia and acts primarily on the peripheral oxygen-sensitive chemoreceptors. using this approach, we investigated the hypothesis that pulmonary ventil ...201626896538
rna-seq analysis of the gonadal transcriptome during alligator mississippiensis temperature-dependent sex determination and differentiation.the american alligator (alligator mississippiensis) displays temperature-dependent sex determination (tsd), in which incubation temperature during embryonic development determines the sexual fate of the individual. however, the molecular mechanisms governing this process remain a mystery, including the influence of initial environmental temperature on the comprehensive gonadal gene expression patterns occurring during tsd.201626810479
global dna methylation loss associated with mercury contamination and aging in the american alligator (alligator mississippiensis).mercury is a widespread environmental contaminant with exposures eliciting a well-documented catalog of adverse effects. yet, knowledge regarding the underlying mechanisms by which mercury exposures are translated into biological effects remains incomplete. dna methylation is an epigenetic modification that is sensitive to environmental cues, and alterations in dna methylation at the global level are associated with a variety of diseases. using a liquid chromatography tandem mass spectrometry-ba ...201626748003
urinary phthalate metabolites in american alligators (alligator mississippiensis) from selected florida wetlands.phthalates have been shown to cause endocrine disruption in laboratory animals and are associated with altered development of the reproductive system in humans. further, human have significant exposure to phthalates. however, little is known concerning the exposure of wildlife to phthalates. we report urinary phthalate metabolite concentrations from fifty juvenile alligators from three florida lakes and a site in the everglades. urinary phthalate monoester concentrations varied widely among alli ...201626743198
hexavalent chromium is cytotoxic and genotoxic to american alligator cells.metals are a common pollutant in the aquatic ecosystem. with global climate change, these levels are anticipated to rise as lower ph levels allow sediment bound metals to be released. the american alligator (alligator mississippiensis) is an apex predator in the aquatic ecosystem and is considered a keystone species; as such it serves as a suitable monitor for localized pollution. one metal of increasing concern is hexavalent chromium (cr(vi)). it is present in the aquatic environment and is a k ...201626730726
ontogeny of bite force in a validated biomechanical model of the american alligator.three-dimensional computational modeling offers tools with which to investigate forces experienced by the skull encountered during feeding and other behaviors. american alligators (alligator mississippiensis) generate some of the highest measured bite forces among extant tetrapods. a concomitant increase in bite force accompanies ontogenetic increases in body mass, which has been linked with dietary changes as animals increase in size. because the flattened skull of crocodylians has substantial ...201728363902
intramuscular epinephrine results in reduced anesthetic recovery time in american alligators (alligator mississippiensis) undergoing isoflurane anesthesia.inhalants are commonly used to anesthetize reptiles, but volatile anesthetics have been associated with prolonged recovery times. the objective of this study was to determine the effects of intramuscular (im) epinephrine on anesthetic recovery times following isoflurane anesthesia in a population of subadult american alligators ( alligator mississippiensis ). in this prospective randomized crossover study, five clinically healthy alligators were anesthetized for 90 min with the use of isoflurane ...201728363062
effects of plant protein diets on the health of farmed american alligators (alligator mississippiensis).the objective of this prospective, blinded study was to compare plasma biochemical values and gross and histologic evaluation of kidney and liver from american alligators ( alligator mississippiensis ) fed extruded diets with protein derived from animal or plant sources. alligators in two treatment groups were fed an extruded diet with protein derived primarily from plant products for 7 (n = 20) or 10 (n = 20) mo prior to harvest. a control group (n = 20) was fed a commercial diet with protein d ...201728363051
joint histology in alligator mississippiensis challenges the identification of synovial joints in fossil archosaurs and inferences of cranial kinesis.archosaurs, like all vertebrates, have different types of joints that allow or restrict cranial kinesis, such as synovial joints and fibrous joints. in general, synovial joints are more kinetic than fibrous joints, because the former possess a fluid-filled cavity and articular cartilage that facilitate movement. even though there is a considerable lack of data on the microstructure and the structure-function relationships in the joints of extant archosaurs, many functional inferences of cranial ...201728330922
ontogenetic comparisons of standard metabolism in three species of crocodilians.due in part to their large size, aggressive temperament, and difficulty in handling, there are few physiological studies of adult crocodilians in the literature. as a result, studies comparing individuals across an ontogenetic series and comparisons among species are also lacking. we addressed this gap in knowledge by measuring standard metabolic rates (smr) of three species of crocodilians (crocodylus porosus, c. johnsoni, and alligator mississippiensis), and included individuals that ranged fr ...201728182696
dietary selenomethionine administration in the american alligator (alligator mississippiensis): hepatic and renal se accumulation and its effects on growth and body condition.selenium (se) is an essential trace nutrient, but in excess, it can induce toxicity. incomplete combustion of coal produces coal combustion wastes, which are enriched in se and often disposed of in aquatic basins. while a multitude of studies have investigated se accumulation in vertebrates, few studies have examined its effects on longer-lived top trophic carnivores, such as the american alligator (alligator mississippiensis). in this study, alligators were fed one of three dietary treatments: ...201728150020
improved genome assembly of american alligator genome reveals conserved architecture of estrogen signaling.the american alligator, alligator mississippiensis, like all crocodilians, has temperature-dependent sex determination, in which the sex of an embryo is determined by the incubation temperature of the egg during a critical period of development. the lack of genetic differences between male and female alligators leaves open the question of how the genes responsible for sex determination and differentiation are regulated. insight into this question comes from the fact that exposing an embryo incub ...201728137821
metabolic responses to chronic hypoxic incubation in embryonic american alligators (alligator mississippiensis).chronic hypoxic incubation is a common tool used to study developmental changes in reduced o2 conditions, and it has been useful for identifying phenotypically plastic periods during ontogeny in laboratory settings. reptilian embryos can be subjected to natural hypoxia due to nesting strategy, and recent studies have been important in establishing the phenotypic responses of several species to low developmental oxygen. in particular, the cardiovascular responses of american alligators (alligator ...201727584614
cathelicidin antimicrobial peptide from alligator mississippiensis has antibacterial activity against multi-drug resistant acinetobacter baumanii and klebsiella pneumoniae.alligator mississippiensis (american alligator), a member of order crocodilia, lives in bacteria-laden environments but is not often known to succumb to bacterial infections. their serum has been shown to have antibacterial activity beyond that of human serum, and it is believed that this activity is partially due to cationic antimicrobial peptides (camps). camps are produced by many organisms as part of the innate immune system. camps are attractive possible therapies against multi-drug resista ...201728089718
variation in perfluoroalkyl acids in the american alligator (alligator mississippiensis) at merritt island national wildlife refuge.this study aimed to quantify concentrations of fifteen perfluoroalkyl acids (pfaas) in the plasma of american alligators (alligator mississippiensis) inhabiting wetlands surrounding the kennedy space center (ksc) in florida, usa located at merritt island national wildlife refuge (minwr). approximately 10 male and 10 female alligators (ntotal = 229) were sampled each month during 2008 and 2009 to determine if seasonal or spatial trends existed with pfaa burden. pfos represented the highest plasma ...201727689886
salmonella enterica serovar pomona infection in farmed juvenile american alligators ( alligator mississippiensis).a fatal epizootic of salmonellosis occurred in farmed juvenile american alligators in louisiana. six animals were examined. gross lesions included severe fibrinonecrotizing enterocolitis, necrotizing splenitis, coelomic effusion, and perivisceral and pulmonary edema. microscopic examination revealed severe necrotizing enterocolitis and splenitis with intralesional bacteria and pneumocyte necrosis with fibrin thrombi. salmonella enterica serovar pomona was isolated from intestine and lung. clinic ...201727879442
perfluorinated alkyl acids in plasma of american alligators (alligator mississippiensis) from florida and south carolina.the present study aimed to quantitate 15 perfluoroalkyl acids (pfaas) in 125 adult american alligators at 12 sites across the southeastern united states. of those 15 pfaas, 9 were detected in 65% to 100% of samples: perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid (pfda), perfluoroundecanoic acid (pfuna), perfluorododecanoic acid, perfluorotridecanoic acid (pftria), perfluorotetradecanoic acid, perfluorohexanesulfonic acid (pfhxs), and perfluorooctane sulfonate (pfos). male ...201727543836
insulin-like growth factor i (igf-i) in chinese alligator, alligator sinensis: molecular characterization, tissue distribution and mrna expression changes during the active and hibernating periods.the chinese alligator alligator sinensis is an endangered species endemic to china, up to date, little is known about the regulation of its growth and development. insulin-like growth factor i (igf-i) plays a vital role in regulating vertebrate growth and development. in this study, the full-length cdna of igf-i in chinese alligator (caigf-i) was obtained for the first time, it contains 890-bp nucleotides encoding a 153-amino acid precursor, the mature caigf-i consists of 70 amino acids by cleav ...201726582344
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