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development of the dermal skeleton in alligator mississippiensis (archosauria, crocodylia) with comments on the homology of osteoderms.the dermal skeleton (=exoskeleton) has long been recognized as a major determinant of vertebrate morphology. until recently however, details of tissue development and diversity, particularly among amniotes, have been lacking. this investigation explores the development of the dermatocranium, gastralia, and osteoderms in the american alligator, alligator mississippiensis. with the exception of osteoderms, elements of the dermal skeleton develop early during skeletogenesis, with most initiating os ...200817960802
early diencephalon development in alligator.diencephalon development was investigated in a reptilian embryo, alligator mississipiensis, beginning at a single compartment stage and continuing until internal subdivisions were present within major units. a variety of morphological techniques were used: immunocytochemistry, histochemistry, and cresyl violet staining. the diencephalon begins as a single unit. in the transverse domain, the diencephalon subsequently divides into two: the parencephalon and the synencephalon. the parencephalon the ...200817878715
pathology, physiologic parameters, tissue contaminants, and tissue thiamine in morbid and healthy central florida adult american alligators (alligator mississippiensis).an investigation of adult alligator (alligator mississippiensis) mortalities in lake griffin, central florida, was conducted from 1998-2004. alligator mortality was highest in the months of april and may and annual death count peaked in 2000. bacterial pathogens, heavy metals, and pesticides were not linked with the mortalities. blood chemistry did not point to any clinical diagnosis, although differences between impaired and normal animals were noted. captured alligators with signs of neurologi ...200818436661
embryological development of caiman latirostris (crocodylia: alligatoridae).a standard development embryological series is the primary basis to organize information of any embryological study and is also used to determine the age of eggs and embryos in field conditions. in this article, we calibrate developmental series of the broad-snouted caiman, caiman latirostris, against an established series for alligator mississippiensis. morphometric measures and extend of the opaque-shell banding were also related to embryo age. in earlier stages, external morphological feature ...200818693273
biochemical properties of alligator (alligator mississippiensis) bone collagen.acid-soluble collagen (asc) and pepsin solubilized collagen (psc) isolated and purified from alligator (alligator mississippiensis) bone were studied for molecular size, amino acid profile, secondary structure, and denaturation temperature by sds-page, hplc, circular dichroism, and viscometry. two collagen subunits, alpha1 and alpha2 were identified by sds-page. the molecular masses for alpha1 and alpha2 chains of asc were 124 kda and 111 kda, respectively. the molecular masses were 123 kda for ...200818577462
hypoxia-induced vasoconstriction in alligator (alligator mississippiensis) intrapulmonary arteries: a role for endothelin-1?hypoxic pulmonary vasoconstriction (hpv) is an adaptive response that diverts pulmonary blood flow from poorly ventilated and hypoxic areas of the lung to better ventilated parts, matching blood perfusion to ventilation. hpv is an ancient and highly conserved response expressed in the respiratory organs of all vertebrates. however, the underlying mechanism and the role of the endothelium remain elusive. isolated intrapulmonary arteries (internal diameter <346 microm) from the american alligator ...200818456883
gene expression patterns in juvenile american alligators (alligator mississippiensis) exposed to environmental contaminants.reproductive and developmental abnormalities have been reported in the american alligator (alligator mississippiensis) population from lake apopka, fl, that is chronically exposed to a complex mixture of environmental contaminants. to begin to understand the molecular mechanisms that could lead to the observed abnormalities of the reproductive and endocrine system, we quantified concentrations of the steroid hormones testosterone (t) and estradiol-17beta (e(2)) and expression of steroid hormone ...200818455813
new resources inform study of genome size, content, and organization in nonavian reptiles.genomic resources for studies of nonavian reptiles have recently improved and will reach a new level of access once the genomes of the painted turtle (chrysemys picta) and the green anole (anolis carolinensis) have been published. eleven speakers gathered for a symposium on reptilian genomics and evolutionary genetics at the 2008 meeting of the society for integrative and comparative biology in san antonio, texas. presentations described results of reptilian genetic studies concerning molecular ...200821669805
recruitment of the diaphragmaticus, ischiopubis and other respiratory muscles to control pitch and roll in the american alligator (alligator mississippiensis).we used electromyography on juvenile american alligators to test the hypothesis that the following muscles, which are known to play a role in respiration, are recruited for aquatic locomotion: m. diaphragmaticus, m. ischiopubis, m. rectus abdominis, m. intercostalis internus, and the m. transversus abdominis. we found no activity with locomotion in the transversus. the diaphragmaticus, ischiopubis, rectus abdominis and internal intercostals were active when the animals executed a head-down dive ...200818344489
increased posthatching mortality and loss of sexually dimorphic gene expression in alligators (alligator mississippiensis) from a contaminated environment.a previous study from our laboratory examining development in neonatal alligators from polluted lake apopka, florida, found numerous differences relative to neonates from a reference site, lake woodruff national wildlife refuge. we postulated that the differences were the result of organizational changes derived from embryonic exposure to environmental contaminants and are related to the poor reproductive success reported in alligators from lake apopka. in this study we examine differences in al ...200818172066
minimal volume regulation after shrinkage of red blood cells from five species of reptiles.red blood cells (rbcs) from most vertebrates restore volume upon hypertonic shrinkage and the mechanisms underlying this regulatory volume increase (rvi) have been studied extensively in these cells. despite the phylogenetically interesting position of reptiles, very little is known about their red cell function. the present study demonstrates that oxygenated rbcs in all major groups of reptiles exhibit no or a very reduced rvi upon approximately 25% calculated hyperosmotic shrinkage. thus, rbcs ...200818424207
temperature effects on pulmonary receptor responses to airway pressure and co2 in alligator mississippiensis.the effects of body temperature (tb) on pulmonary stretch receptor (psr) and co2-sensitive intrapulmonary chemoreceptor (ipc) response characteristics may have important effects on ventilatory control in reptiles. in this study, three questions were addressed: (1) what are the effects of tb on psr and ipc responses to airway pressure (paw) and lung co2 (pco2); (2) what are the effects of acute (less than 12 h) vs chronic (greater than 1 week) changes in tb on both receptor groups; and (3) can pr ...20082515569
the effects of estradiol and testosterone on mullerian-duct regression in the american alligator (alligator mississippiensis).female hatchling alligators were castrated and implanted with a graft of either skeletal muscle tissue or testicular tissue from male hatchlings. following surgery, each female also received a sustained-release pellet (innovative research of america, rockville, md) implanted subcutaneously that delivered one of the following treatments: a control substance (0.1 mg), 17 beta-estradiol (0.01 mg), or testosterone propionate (0.1 mg). treated and final control females were sacrificed 8 weeks after s ...20082583475
the evolution of hoxd-11 expression in the bird wing: insights from alligator mississippiensis.comparative morphology identifies the digits of the wing of birds as 1,2 and 3, but they develop at embryological positions that become digits 2, 3 and 4 in other amniotes. a hypothesis to explain this is that a homeotic frame shift of digital identity occurred in the evolution of the bird wing, such that digits 1,2 and 3 are developing from embryological positions 2, 3 and 4. digit 1 of the mouse is the only digit that shows no late expression of hoxd-11. this is also true for the anterior digi ...200818833328
association of west nile virus with lymphohistiocytic proliferative cutaneous lesions in american alligators (alligator mississippiensis) detected by rt-pcr.west nile virus (wnv) is known to affect captive populations of alligators and, in some instances, cause significant mortalities. alligators have been shown to amplify the virus, serve as a reservoir host, and even represent a source of infection for humans. this study describes a cutaneous manifestation of wnv in captive-reared american alligators (alligator mississippiensis), previously described as lymphohistiocytic proliferative syndrome of alligators (lpsa), based on the findings of gross e ...200819110697
effects of hypoxia on vertebrate blood vessels.hypoxia contracts mammalian respiratory vessels and increases vascular resistance in respiratory tissues of many vertebrates. in systemic vessels these responses vary, hypoxia relaxes mammalian vessels and contracts systemic arteries from cyclostomes. it has been proposed that hypoxic vasoconstriction in cyclostome systemic arteries is the antecedent to mammalian hypoxic pulmonary vasoconstriction, however, phylogenetic characterization of hypoxic responses is lacking. in this study, we characte ...200818214862
macrogeographic genetic variation in broad-snouted caiman (caiman latirostris).broad-snouted caiman's (caiman latirostris) geographic distribution comprises one of the widest latitudinal ranges among all crocodilians. in this study we analyzed the relationship between geographic distance (along the species latitudinal range) and genetic differentiation using dna microsatellite loci developed for c. latirostris and alligator mississippiensis. the results suggest that there is a consistent relationship between geographic distance and genetic differentiation; however, other b ...200818661469
developmental morphology of the neonatal alligator (alligator mississippiensis) ovary.american alligator (alligator mississippiensis) ovary development is incomplete at hatching. during the months following hatching, the cortical processes of oogenesis started in ovo continues and folliculogenesis is initiated. additionally, the medullary region of the gonad undergoes dramatic restructuring. we describe alligator ovarian histology at hatching, 1 week, 1 month, and 3 months of age in order to characterize the timing of morphological development and compare these findings to chicke ...200817957708
three tiers of genome evolution in reptiles.characterization of reptilian genomes is essential for understanding the overall diversity and evolution of amniote genomes, because reptiles, which include birds, constitute a major fraction of the amniote evolutionary tree. to better understand the evolution and diversity of genomic characteristics in reptilia, we conducted comparative analyses of online sequence data from alligator mississippiensis (alligator) and sphenodon punctatus (tuatara) as well as genome size and karyological data from ...200821669810
differential protein expression in alligator leukocytes in response to bacterial lipopolysaccharide injection.blood was collected from three juvenile alligators (alligator mississippiensis) before, and again 24h after, injection with bacterial lipopolysaccharide (lps). the leukocytes were collected from both samples, and the proteins were extracted. each group of proteins was labeled with a different fluorescent dye and the differences in protein expression were analyzed by two dimensional differential in-gel expressions (2d-dige). the proteins which appeared to be increased or decreased by treatment wi ...200920403750
nematodes collected by gastric lavage from live american alligators, alligator mississippiensis, in florida.stomach nematodes were collected from 151 live american alligators, alligator mississippiensis, from 3 lakes (apopka, griffin, and woodruff) in north-central florida using a gastric lavage technique. four species were identified: dujardinascaris waltoni, ortleppascaris antipini, brevimulticaecum tenuicolle, and larvae of contracaecum sp. of these, d. waltoni was the most prevalent species in all 3 lakes and was more prevalent in lake apopka than in the other 2 lakes. this is the first record of ...200919281296
production of superoxide ions by leukocytes of the american alligator (alligator mississippiensis).this study was conducted to characterize the production of superoxide ions by leukocytes in whole blood of the american alligator (alligator mississippiensis). we used wst-1, a tetrazolium salt which can be reduced to a water-soluble formazan compound with high molar absorptivity at 438 nm, to probe the production of superoxide by alligator leukocytes. incubation of alligator whole blood with wst-1 resulted in a time- and concentration-dependent increase in absorbance of the plasma at 438 nm. th ...200918935969
seasonal variation of the oviduct of the american alligator, alligator mississippiensis (reptilia: crocodylia).the annual oviductal cycle of the american alligator, alligator mississippiensis, is described using light and electron microscopy. previous work done by palmer and guillette ([1992] biol reprod 46:39-47) shed some light on the reproductive morphology of the female alligator oviduct; however, their study was limited and did not report details relating to variation across the reproductive season. we recognize six variable regions of the oviduct: infundibulum, tube, isthmus, anterior uterus, poste ...200919206152
genome evolution in reptilia: in silico chicken mapping of 12,000 bac-end sequences from two reptiles and a basal bird.with the publication of the draft chicken genome and the recent production of several bac clone libraries from non-avian reptiles and birds, it is now possible to undertake more detailed comparative genomic studies in reptilia. of interest in particular are the genomic events that transformed the large, repeat-rich genomes of mammals and non-avian reptiles into the minimalist chicken genome. we have used paired bac end sequences (bess) from the american alligator (alligator mississippiensis), pa ...200919607659
environmental regulation of sex determination in reptiles.the various patterns of environmental sex determination in squamates, chelonians and crocodilians are described. high temperatures produce males in lizards and crocodiles but females in chelonians. original experiments on the effects of incubation at 30 degrees c (100% females) or 33 degrees c (100% males) on development in alligator mississippiensis are described. these include an investigation of the effect of exposing embryos briefly to a different incubation temperature on the sex ratio at h ...20092907800
characterization of phospholipase a(2) activity in serum of the american alligator (alligator mississippiensis).pla(2) is a diverse class of enzymes with a broad spectrum of physiological functions. secretory pla(2) isoforms have been reported to exhibit important innate immune function in higher vertebrates. this study was conducted to characterize pla(2) activity in the serum of the american alligator (alligator mississippiensis). we used a glycerophospholipid with a fatty acid in the sn-2 position labeled with a fluorescent probe (bodipy) to detect and quantify alligator serum pla(2) activity. incubati ...200919642205
surgical removal of right-to-left cardiac shunt in the american alligator (alligator mississippiensis) causes ventricular enlargement but does not alter apnoea or metabolism during diving.crocodilians have complete anatomical separation between the ventricles, similar to birds and mammals, but retain the dual aortic arch system found in all non-avian reptiles. this cardiac anatomy allows surgical modification that prevents right-to-left (r-l) cardiac shunt. a r-l shunt is a bypass of the pulmonary circulation and recirculation of oxygen-poor blood back to the systemic circulation and has often been observed during the frequent apnoeic periods of non-avian reptiles, particularly d ...200919837897
multiyear multiple paternity and mate fidelity in the american alligator, alligator mississippiensis.we examined multiple paternity during eight breeding events within a 10-year period (1995-2005) for a total of 114 wild american alligator nests in rockefeller wildlife refuge in south-west louisiana. our goals included examining (i) within population variation in multiple paternity among years, (ii) variation in multiple paternity in individual females and (iii) the potential for mate fidelity. to accomplish this, in the current study, eggs were sampled from 92 nests over 6 years and analysed a ...200919804377
parentage test in broad-snouted caimans (caiman latirostris, crocodylidae) using microsatellite dna.in this study, microsatellite markers, developed for alligator mississipiensis and caiman latirostris, were used to assess parentage among individuals from the captive colony of caiman latirostris at the university of são paulo, in piracicaba, são paulo, brazil. many of the females in the colony were full siblings, which made maternal identification difficult due to genotypic similarity. even so, the most likely mother could be identified unambiguously among offspring in most of the clutches stu ...200921637468
a cineradiographic study of lung ventilation in alligator mississippiensis.the skeletal and visceral kinematics of lung ventilation of the american alligator (alligator mississippiensis) was examined using cineradiography, pneumotachometry, and intrapulmonary pressure recording. the respiratory pattern of a. mississippiensis is intermittent and diphasic. the inspiratory lung volume is retained during the non-ventilatory period through closure of the glottis. the aspiration pump of a. mississippiensis consists of multiple components: visceral movement, pubic rotation, g ...200919768831
dipeptidyl peptidase iv activity in the blood of the american alligator (alligator mississippiensis).dipeptidyl peptidase iv (dpp4) enzyme activity, associated with cell surface and soluble cd26, was measured in alligator plasma and whole blood. dpp4 activity was higher in whole blood than in the plasma, presumably due to the inclusion of both membrane-bound cd26 on the surface of t-cells and scd26 in the plasma. the plasma dpp4 activity was measured within 5 min after the addition of the substrate, and maximal accumulation of product was reached at 120 min. alligator whole blood dpp4 activity ...200919665574
morphology and histochemistry of juvenile american alligator (alligator mississippiensis) nephrons.here we present a detailed morphological description of the alligator (alligator mississippiensis) kidney and nephron. we present a series of histological, histochemical, and immunohistochemical markers that clearly define the seven regions of the alligator nephron. the alligator kidney is composed of many paired (mirrored) lobules on each kidney (lobe). single nephrons span the width of lobules three times. the fine structure of glomeruli, lying in rows spanning the height of the lobule, is res ...200919685509
the importance of the m. diaphragmaticus to the duration of dives in the american alligator (alligator mississippiensis).we tested the hypothesis that the crocodilian m. diaphragmaticus extends the duration of dives by disabling this muscle in a group of juvenile american alligators and comparing the duration of their dives to the duration of the dives of animals in which the muscle remained intact. we studied the groups while they were fasting, 1h after they had eaten a meal with a density that was either greater or less than water, and at 22 and 28 degrees c. we found that the duration of dives was longer for th ...200919328664
nutrient and organochlorine pesticide concentrations in american alligator eggs and their associations with clutch viability.since the early 1900s, the lakes of the ocklawaha basin in central florida have experienced ecological degradation due to anthropogenic development. one species affected by this degradation is the american alligator alligator mississippiensis, which has suffered from poor clutch viability and embryo mortality. although some studies indicate that organochlorine pesticides (ocps) may be involved, ocps do not account for all of the variation seen in hatch rates. indeed, nutrition and non-ocp contam ...200920218499
differential limb scaling in the american alligator (alligator mississippiensis) and its implications for archosaur locomotor evolution.bipedalism evolved multiple times within archosaurs, and relatively shorter forelimbs characterize both crocodyliforms and nonavian dinosaurs. analysis of a comprehensive ontogenetic sequence of specimens (embryo to adult) of the sauropodomorph massospondylus has shown that bipedal limb proportions result from negative forelimb allometry. we ask, is negative forelimb allometry a pattern basal to archosaurs, amplified in certain taxa to produce bipedalism? given the phylogenetic position of extan ...200919462445
exhaustive exercise training enhances aerobic capacity in american alligator (alligator mississippiensis).the oxygen transport system in mammals is extensively remodelled in response to repeated bouts of activity, but many reptiles appear to be 'metabolically inflexible' in response to exercise training. a recent report showed that estuarine crocodiles (crocodylus porosus) increase their maximum metabolic rate in response to exhaustive treadmill training, and in the present study, we confirm this response in another crocodilian, american alligator (alligator mississippiensis). we further specify the ...200919533151
atmospheric oxygen level affects growth trajectory, cardiopulmonary allometry and metabolic rate in the american alligator (alligator mississippiensis).recent palaeoatmospheric models suggest large-scale fluctuations in ambient oxygen level over the past 550 million years. to better understand how global hypoxia and hyperoxia might have affected the growth and physiology of contemporary vertebrates, we incubated eggs and raised hatchlings of the american alligator. crocodilians are one of few vertebrate taxa that survived these global changes with distinctly conservative morphology. we maintained animals at 30 degrees c under chronic hypoxia (1 ...200919376944
ultrasonography of reproductive structures and hormonal correlates of follicular development in female american alligators, alligator mississippiensis, in southwest louisiana.ultrasonography has been used effectively to study reproduction in a variety of reptile species, but its application to crocodilians has been relatively limited. we present results from a study testing the efficacy of using ultrasonography to monitor reproduction in the american alligator, alligator mississippiensis. ultrasound results were then compared with plasma hormone levels. a total of 124 females were examined during march, april, may, and early june (2001-2003). ultrasound results were ...200919344723
gizzard shad thiaminase activity and its effect on the thiamine status of captive american alligators alligator mississippiensis.adult mortality and low egg hatch rate were observed among american alligators alligator mississippiensis in lake griffin, florida, between 1998 and 2003. previous studies show that the alligator mortality is due to neurological impairment associated with thiamine (vitamin bt) deficiency. this study determined the rate of thiaminase activity in gizzard shad dorosoma cepedianum, a fish often eaten by alligators, and examined the thiamine status of captive adult alligators fed only gizzard shad. w ...200920218498
functional specialization and ontogenetic scaling of limb anatomy in alligator mississippiensis.crocodylians exhibit a fascinating diversity of terrestrial gaits and limb motions that remain poorly described and are of great importance to understanding their natural history and evolution. their musculoskeletal anatomy is pivotal to this diversity and yet only qualitative studies of muscle-tendon unit anatomy exist. the relative masses and internal architecture (fascicle lengths and physiological cross-sectional areas) of muscles of the pectoral and pelvic limbs of american alligators (alli ...201020148991
gonadal mrna expression levels of tgfbeta superfamily signaling factors correspond with post-hatching morphological development in american alligators.paracrine factor signaling regulates many aspects of vertebrate gonadal development. we investigated key ovarian and testicular morphological markers of the american alligator (alligator mississippiensis) during the first 5 months post-hatching and correlated gonadal development with mrna expression levels of a suite of regulatory factors. in both sexes, we observed significant morphology changes, including ovarian follicle assembly and meiotic progression of testicular germ cells. concomitant w ...201020110644
posthatching development of alligator mississippiensis ovary and testis.we investigated ovary and testis development of alligator mississippiensis during the first 5 months posthatch. to better describe follicle assembly and seminiferous cord development, we used histochemical techniques to detect carbohydrate-rich extracellular matrix components in 1-week, 1-month, 3-month, and 5-month-old gonads. we found profound morphological changes in both ovary and testis. during this time, oogenesis progressed up to diplotene arrest and meiotic germ cells increasingly intera ...201020013789
environmental influence on yolk steroids in american alligators (alligator mississippiensis).the egg yolk serves as a significant source of maternally derived steroids that are available to the embryo during early development. altered deposition of yolk steroids can change the developmental trajectory of the embryo and have long lasting or permanent consequences. alligators from contaminated environments have shown significant reproductive and developmental dysfunction, and it is unclear if altered deposition of yolk steroids could be a contributing factor. alligator eggs were collected ...201020650885
pentadactyl ground state of the manus of alligator mississippiensis and insights into the evolution of digital reduction in archosauria.the three-fingered state of the avian manus poses intriguing questions about the evolution of digit reduction. although digit reduction in most tetrapods appears to be the product of straightforward digit loss, avian digit reduction may have occurred with a dissociation of digit position from digit identity. the three digits of birds have the ancestral identities of i, ii, and iii but develop from an early pentadactyl ground state from digital anlage 2, 3, and 4. a series of hypotheses have been ...201020564580
turning crocodilian hearts into bird hearts: growth rates are similar for alligators with and without right-to-left cardiac shunt.the functional and possible adaptive significance of non-avian reptiles' dual aortic arch system and the ability of all non-avian reptiles to perform central vascular cardiac shunts have been of great interest to comparative physiologists. the unique cardiac anatomy of crocodilians - a four-chambered heart with the dual aortic arch system - allows for only right-to-left (r-l; pulmonary bypass) cardiac shunt and for surgical elimination of this shunt. surgical removal of the r-l shunt, by occludi ...201020639429
proteome analysis of the leukocytes from the american alligator (alligator mississippiensis) using mass spectrometry.mass spectrometry was used in conjunction with gel electrophoresis and liquid chromatography, to determine peptide sequences from american alligator (alligator mississippiensis) leukocytes and to identify similar proteins based on homology. the goal of the study was to generate an initial database of proteins related to the alligator immune system. we have adopted a typical proteomics approach for this study. proteins from leukocyte extracts were separated using two-dimensional gel electrophores ...201020920849
ultrastructure of spermiogenesis in the american alligator, alligator mississippiensis (reptilia, crocodylia, alligatoridae).testicular samples were collected to describe the ultrastructure of spermiogenisis in alligator mississipiensis (american alligator). spermiogenesis commences with an acrosome vesicle forming from golgi transport vesicles. an acrosome granule forms during vesicle contact with the nucleus, and remains posterior until mid to late elongation when it diffuses uniformly throughout the acrosomal lumen. the nucleus has uniform diffuse chromatin with small indices of heterochromatin, and the condensatio ...201020715150
assessing potential risk to alligators, alligator mississippiensis, from nutria control with zinc phosphide rodenticide baits.nutria, myocastor coypus, populations must be reduced when they cause substantial wetland damage. control can include the rodenticide zinc phosphide, but the potential impacts to american alligators, alligator mississippiensis, must be assessed. the mean amount of zinc phosphide per nutria found in nutria carcasses was 50 mg. risk assessment determined that a conservative estimate for maximum exposure would be 173 mg zinc phosphide for a 28 kg alligator, or 6.2 mg/kg. probit analysis found an ld ...201020431861
the provenance of alveolar and parabronchial lungs: insights from paleoecology and the discovery of cardiogenic, unidirectional airflow in the american alligator (alligator mississippiensis).birds and mammals evolved greater aerobic abilities than their common ancestor had. this required expansion of the cardiopulmonary system's capacity for gas exchange, but while directional selection for this expanded capacity resulted in extremely similar avian and mammalian hearts, strikingly different lungs arose, and the reasons for this divergence in lung morphology are not understood. in birds, gas exchange occurs in the lungs as air moves through small tubes (parabronchi) in one direction; ...201020377411
heavy metal and selenium concentrations in liver tissue from wild american alligator (alligator mississippiensis) livers near charleston, south carolina.liver samples from 33 wild american alligators (alligator mississippiensis) livers from the charleston, south carolina, area were analyzed for arsenic (as), cadmium (cd), cobalt (co), chromium (cr), mercury (hg), nickel (ni), lead (pb), and selenium (se) concentrations. alligators are top predators and are considered a good biomonitoring species for various toxins, including heavy metals. alligators from other areas in the us have shown high concentrations of mercury and other heavy metals, but ...201020966273
influences of sex, incubation temperature, and environmental quality on gonadal estrogen and androgen receptor messenger rna expression in juvenile american alligators (alligator mississippiensis).gonadal steroid hormone receptors play a vital role in transforming ligand signals into gene expression. we have shown previously that gonads from wild-caught juvenile alligators express greater levels of estrogen receptor 1 (esr1) than estrogen receptor 2 (esr2). furthermore, sexually dimorphic esr2 mrna expression (female > male) observed in animals from the reference site (lake woodruff, fl, usa) was lost in alligators from the contaminated lake apopka (fl, usa). we postulated that environmen ...201019759368
isolation of faecal coliform bacteria from the american alligator (alligator mississippiensis).to determine whether american alligators (alligator mississippiensis) are an unrecognized poikilothermic source of faecal coliform and/or potential pathogenic bacteria in south carolina's coastal waters.201019735329
maternal investment and nutrient use affect phenotype of american alligator and domestic chicken hatchlings.maternal investment by oviparous amniotes, in the form of yolk and albumen, and the mechanisms by which embryos use available energy and nutrients have a profound effect on embryo and, consequently, hatchling phenotype. nutrient provisioning and uptake vary within and among oviparous taxa, avian and non-avian reptiles, due to differences and similarities in environment, behavior, and phylogeny. eggs of crocodilians, the closest extant relatives to modern birds, are ideal models for examining mod ...201020580852
material properties of mandibular cortical bone in the american alligator, alligator mississippiensis.this study reports the elastic material properties of cortical bone in the mandible of juvenile alligator mississippiensis obtained by using an ultrasonic wave technique. the elastic modulus, the shear modulus, and poisson's ratio were measured on 42 cylindrical alligator bone specimens obtained from the lingual and facial surfaces of 4 fresh alligator mandibles. the data suggest that the elastic properties of alligator mandibular cortical bone are similar to those found in mammals and are ortho ...201019922820
comparative development of the crocodylian interclavicle and avian furcula, with comments on the homology of dermal elements in the pectoral apparatus.the pectoral apparatus (shoulder girdle plus sternum) of amniotes plesiomorphically includes an unpaired element of dermal origin. in crocodylians, lepidosaurs, and nontherian synapsids (monotremes and their ancestors) this element is identified as the interclavicle, in testudines (turtles and tortoises) as the entoplastron, and in aves as the furcula. we investigated embryonic development of the interclavicle in alligator mississippiensis (american alligator) and of the furcula in gallus gallus ...201020422674
detection of west nile virus rna in mosquitoes and identification of mosquito blood meals collected at alligator farms in louisiana.since 2001, alligator farms in the united states have sustained substantial economic losses because of west nile virus (wnv) outbreaks in american alligators (alligator mississippiensis). once an initial infection is introduced into captive alligators, wnv can spread among animals by contaminative transmission. some outbreaks have been linked to feeding on infected meat or the introduction of infected hatchlings, but the initial source of wnv infection has been uncertain in other outbreaks. we c ...201020695278
calcified cartilage shape in archosaur long bones reflects overlying joint shape in stress-bearing elements: implications for nonavian dinosaur locomotion.in nonavian dinosaur long bones, the once-living chondroepiphysis (joint surface) overlay a now-fossilized calcified cartilage zone. although the shape of this zone is used to infer nonavian dinosaur locomotion, it remains unclear how much it reflects chondroepiphysis shape. we tested the hypothesis that calcified cartilage shape reflects the overlying chondroepiphysis in extant archosaurs. long bones with intact epiphyses from american alligators (alligator mississippiensis), helmeted guinea fo ...201021046673
detection of prodynorphin end products in lizard, turtle, and alligator brain extracts.heterologous radioimmunoassays (rias) for the mammalian prodynorphin end products, alpha-neo-endorphin, dynorphin a(1-17), dynorphin a(1-8), and dynorphin b(1-13) were used to screen brain extracts obtained from representatives of the major surviving orders of reptiles: chelonia (pseudemys scripta), squamata (anolis carolinensis), and crocodylia (alligator mississippiensis). methanol/acid extracts of whole brains obtained from each species were separately fractionated by gel filtration chromatog ...20101355904
hypoxic alligator embryos: chronic hypoxia, catecholamine levels and autonomic responses of in ovo alligators.hypoxia is a naturally occurring environmental challenge for embryonic reptiles, and this is the first study to investigate the impact of chronic hypoxia on the in ovo development of autonomic cardiovascular regulation and circulating catecholamine levels in a reptile. we measured heart rate (f(h)) and chorioallantoic arterial blood pressure (map) in normoxic ('n21') and hypoxic-incubated ('h10'; 10% o(2)) american alligator embryos (alligator mississippiensis) at 70, 80 and 90% of development. ...201121798363
Computed tomography of granulomatous pneumonia with oxalosis in an American alligator (Alligator mississippiensis) associated with Metarhizium anisopliae var anisopliae.An 18-yr-old, male, albino, American alligator (Alligator mississippiensis) was evaluated for decreased appetite and abnormal buoyancy. Computed tomography (CT) of the coelomic cavity showed multifocal mineral and soft tissue attenuating pulmonary masses consistent with pulmonary fungal granulomas. Additionally, multifocal areas of generalized, severe emphysema and pulmonary and pleural thickening were identified. The alligator was euthanized and necropsy revealed severe fungal pneumonia associa ...201122204066
morphology and histochemistry of juvenile male american alligator (alligator mississippiensis) phallus.phalli of male crocodilians transfer sperm to female cloaca during sexual intercourse, resulting in internal fertilization. for over a century there have been scientific descriptions of crocodilian phallus morphologies; however, little work has presented detailed cellular-level analyses of these structures. here we present a histological investigation of the complex functional anatomy of the juvenile male american alligator phallus, including fibrous and vascular erectile structures, a variety o ...201122190479
role of the left aortic arch and blood flows in embryonic american alligator (alligator mississippiensis).all embryonic and fetal amniotes possess a ductus(i) arteriosus(i) that allows blood to bypass the pulmonary circulation and the non-functional lungs. the central hemodynamic of embryonic reptiles are unique, given the additional systemic aorta that allows pulmonary circulatory bypass, the left aorta (lao). the lao exits in the right ventricle or 'pulmonary side' of reptilian hearts in both embryos and adults, but its functional significance in ovo is unknown. this study investigated the role of ...201121053004
evaluation of an 18-micron filter for use in reptile blood transfusions using blood from american alligators (alligator mississippiensis).blood transfusions are a common therapeutic procedure in small animal medicine and have been investigated in some exotic species but little information is available about their safety and efficacy in reptiles. in human pediatrics and small animal practice, the hemo-nate18-micro filter is used to prevent embolic clots and particulate waste from entering the recipient during a transfusion. the goal of this study was to determine the hemolytic effect of an 18-micro hemo-nate filter for whole blood ...201122946400
does variation in movement tactics and trophic interactions among american alligators create habitat linkages?1. highly mobile top predators are hypothesized to spatially and/or temporally link disparate habitats through the combination of their movement and feeding patterns, but recent studies suggest that individual specialization in habitat use and feeding could keep habitats compartmentalized. 2. we used passive acoustic telemetry and stable isotope analysis to investigate whether specialization in movement and feeding patterns of american alligators (alligator mississippiensis) in an oligotrophic s ...201121418209
sex steroid and thyroid hormone receptor expressions in the thyroid of the american alligator (alligator mississippiensis) during different life stages.the expression of estrogen receptors, esr1 (erα) and esr2 (erβ), and androgen receptors (ar) in the thyroid gland has been reported in few vertebrate species other than a few mammals. this study reports the presence of sex steroid hormone receptors and thyroid receptors (erα, erβ, ar, trα, and trβ) in the thyroid gland of the american alligator at several life stages. it provides a semiquantification and distribution of erα in the thyroid follicle cells using an immunohistochemical approach as w ...201121308728
free body analysis, beam mechanics, and finite element modeling of the mandible of alligator mississippiensis.the mechanical behavior of mammalian mandibles is well-studied, but a comprehensive biomechanical analysis (incorporating detailed muscle architecture, accurate material properties, and three-dimensional mechanical behavior) of an extant archosaur mandible has never been carried out. this makes it unclear how closely models of extant and extinct archosaur mandibles reflect reality and prevents comparisons of structure-function relationships in mammalian and archosaur mandibles. we tested hypothe ...201121567445
thermal acclimation, mitochondrial capacities and organ metabolic profiles in a reptile (alligator mississippiensis).reptiles thermoregulate behaviourally, but change their preferred temperature and the optimal temperature for performance seasonally. we evaluated whether the digestive and locomotor systems of the alligator show parallel metabolic adjustments during thermal acclimation. to this end, we allowed juvenile alligators to grow under thermal conditions typical of winter and summer, providing them with seasonally appropriate basking opportunities. although mean body temperatures of alligators in these ...201120680297
chronic hypoxic incubation blunts a cardiovascular reflex loop in embryonic american alligator (alligator mississippiensis).hypoxia is a naturally occurring environmental challenge for embryonic non-avian reptiles, and this study is the first to investigate the impact of chronic hypoxia on a possible chemoreflex loop in a developing non-avian reptile. we measured heart rate and blood pressure in normoxic and hypoxic-incubated (10% o(2)) american alligator embryos (alligator mississippiensis) at 70 and 90/95% of development. we hypothesized that hypoxic incubation would blunt embryonic alligators' response to a reflex ...201121445563
the impact of bone and suture material properties on mandibular function in alligator mississippiensis: testing theoretical phenotypes with finite element analysis.the functional effects of bone and suture stiffness were considered here using finite element models representing three different theoretical phenotypes of an alligator mississippiensis mandible. the models were loaded using force estimates derived from muscle architecture in dissected specimens, constrained at the 18th and 19th teeth in the upper jaw and 19th tooth of the lower jaw, as well as at the quadrate-articular joint. stiffness was varied systematically in each theoretical phenotype. th ...201121091693
ontogeny of the alligator cartilago transiliens and its significance for sauropsid jaw muscle evolution.the cartilago transiliens is a fibrocartilaginous structure within the jaw muscles of crocodylians. the cartilago transiliens slides between the pterygoid buttress and coronoid region of the lower jaw and connects two muscles historically identified as m. pseudotemporalis superficialis and m. intramandibularis. however, the position of cartilago transiliens, and its anatomical similarities to tendon organs suggest the structure may be a sesamoid linking a single muscle. incompressible sesamoids ...201121949795
subglottal pressure and fundamental frequency control in contact calls of juvenile alligator mississippiensis.vocalization is rare among non-avian reptiles, with the exception of the crocodilians, the sister taxon of birds. crocodilians have a complex vocal repertoire. their vocal and respiratory system is not well understood but appears to consist of a combination of features that are also found in the extremely vocal avian and mammalian taxa. anatomical studies suggest that the alligator larynx is able to abduct and adduct the vocal folds, but not to elongate or shorten them, and is therefore lacking ...201121865521
seasonal androgen cycles in adult male american alligators (alligator mississippiensis) from a barrier island population.the seasonal patterns of two primary plasma androgens, testosterone (t) and dehydroepiandrosterone (dhea), were assessed in adult male alligators from the merritt island national wildlife refuge, a unique barrier island environment and home to the kennedy space center in florida. samples were collected monthly from 2008 to 2009, with additional samples collected at more random intervals in 2007 and 2010. plasma t concentrations peaked in april, coincident with breeding and courtship, and decline ...201121816848
ultrastructure of the spermatozoon of the american alligator, alligator mississippiensis (reptilia: alligatoridae).this study details the ultrastructure of the spermatozoa of the american alligator, alligator mississippiensis. american alligator spermatozoa are filiform and slightly curved. the acrosome is tapered at its anterior end and surrounded by the acrosome vesicle and an underlying subacrosomal cone, which rests just cephalic to the nuclear rostrum. one endonuclear canal extends from the subacrosomal cone through the rostral nucleus and deep into the nuclear body. the neck region separates the nucleu ...201121688296
altered gonadal expression of tgf-β superfamily signaling factors in environmental contaminant-exposed juvenile alligators.environmental contaminant exposure can influence gonadal steroid signaling milieus; however, little research has investigated the vulnerability of non-steroidal signaling pathways in the gonads. here we use american alligators (alligator mississippiensis) hatched from field-collected eggs to analyze gonadal mrna transcript levels of the activin-inhibin-follistatin gene expression network and growth differentiation factor 9. the eggs were collected from lake woodruff national wildlife refuge, a s ...201121251980
molecular cloning of anti-müllerian hormone from the american alligator, alligator mississippiensis.anti-müllerian hormone (amh) plays an important role in male sex differentiation in vertebrates. amh produced by sertoli cells of the fetal testis induces regression of the müllerian duct in mammalian species. in alligators, sexual differentiation is controlled by the temperature during egg incubation, termed temperature-dependent sex determination (tsd). the tsd mechanism inducing sex differentiation is thought to be unique and different from that of genetic sex determination as no gene such as ...201121187121
effects of intrapulmonary co2 and airway pressure on pulmonary vagal afferent activity in the alligator.the effects of airway co2 and pressure on pulmonary vagal afferent fibers were studied in seven anesthetized alligators alligator mississippiensis, at room temperature (24 degrees c). of 49 receptors which fired in phase with ventilation, 13 behaved like mammalian rapidly adapting pulmonary stretch receptors, 19 like mammalian slowly adapting pulmonary stretch receptors (psr), and 17 like avian intrapulmonary co2-sensitive chemoreceptors (ipc). psr and ipc were positively localized to the lung b ...20113146784
gender differences in haemogregarine infections in american alligators (alligator mississippiensis) at savannah river, south carolina, usa.we report a host gender bias in haemogregarine infection characteristics in the american alligator (alligator mississippiensis) at the savannah river site, south carolina, usa. prevalence and severity in female alligators was higher than it was in males. the reason for this pattern is not clear.201122102683
quantitative rt-pcr analyses of five evolutionary conserved genes in alligator brains during development.gene expression was investigated in the major brain subdivisions (telencephalon, diencephalon, midbrain and hindbrain) in a representative reptile, alligator mississipiensis, during the later stages of embryonic development. the following genes were examined: voltage-gated sodium channel isoforms: nav1.1 and nav1.2; synaptic vesicle 2a (sv2a); synaptophysin; and calbindin 2. with the exception of synaptophysin, which was only expressed in the telencephalon, all genes were expressed in all brain ...201122379598
seasonal variation in plasma thyroid hormone concentrations in coastal versus inland populations of juvenile american alligators (alligator mississippiensis): influence of plasma iodide concentrations.thyroid hormones, essential for normal growth and health, are associated with changes in temperature, photoperiod, and reproduction. iodide, a necessary element for thyroid hormone production, varies in diet, and is more abundant in estuarine environments, which could alter thyroid hormone variation. however, associations between thyroid hormone concentrations in animals from marine versus freshwater environments, which could become more pertinent with rising sea levels associated with global cl ...201121986089
histology-based morphology of the neurocentral synchondrosis in alligator mississippiensis (archosauria, crocodylia).morphology of the neurocentral synchondroses--thin cartilaginous layers between centra and neural arches--are documented in the extant crocodilian, alligator mississippiensis (archosauria, crocodylia). examination of dry skeletons demonstrates that neurocentral suture closure occurs in very late postnatal ontogeny (after reaching sexual maturity and/or body size ca. 40% from the upper range). before sexual maturity (body length (bl) ≥ ca. 1.80 m), completely fused centra and neural arches are re ...201222095938
technique for the collection of clear urine from the nile crocodile (crocodylus niloticus).urine samples can be a very useful diagnostic tool for the evaluation of animal health. in this article, a simple technique to collect urine from the nile crocodile (crocodylus niloticus) was described, based on a similar unpublished technique developed for the american alligator (alligator mississippiensis) using a canine urinary catheter. with this technique, it was possible to collect relatively clean urine samples from nile crocodiles of different sizes using canine urinary catheters or smal ...201223327128
the pulmonary anatomy of alligator mississippiensis and its similarity to the avian respiratory system.using gross dissections and computed tomography we studied the lungs of juvenile american alligators (alligator mississippiensis). our findings indicate that both the external and internal morphology of the lungs is strikingly similar to the embryonic avian respiratory system (lungs + air sacs). we identified bronchi that we propose are homologous to the avian ventrobronchi (entobronchi), laterobronchi, dorsobronchi (ectobronchi), as well as regions of the lung hypothesized to be homologous to t ...201222344783
sequencing three crocodilian genomes to illuminate the evolution of archosaurs and amniotes.the international crocodilian genomes working group (icgwg) will sequence and assemble the american alligator (alligator mississippiensis), saltwater crocodile (crocodylus porosus) and indian gharial (gavialis gangeticus) genomes. the status of these projects and our planned analyses are described.201222293439
the evolution, development and skeletal identity of the crocodylian pelvis: revisiting a forgotten scientific debate.unlike most tetrapods, in extant crocodylians the acetabulum is formed by only two of the three skeletal elements that constitute the pelvis, the ilium, and ischium. this peculiar arrangement is further confused by various observations that suggest the crocodylian pelvis initially develops from four skeletal elements: the ilium, ischium, pubis, and a novel element, the prepubis. according to one popular historical hypothesis, in crocodylians (and many extinct archosaurs), the pubis fuses with th ...201222821815
towards an understanding of the evolution of the chorioallantoic placenta: steroid biosynthesis and steroid hormone signaling in the chorioallantoic membrane of an oviparous reptile.amniotes, mammals, reptiles, and birds form common extraembryonic membranes during development to perform essential functions, such as protection, nutrient transfer, gas exchange, and waste removal. together with the maternal uterus, extraembryonic membranes of viviparous (live-bearing) amniotes develop as an endocrine placenta that synthesizes and responds to steroid hormones critical for development. the ability of these membranes to synthesize and respond to steroid hormone signaling has trad ...201222811568
isolation and determination of the primary structure of a lectin protein from the serum of the american alligator (alligator mississippiensis).mass spectrometry in conjunction with de novo sequencing was used to determine the amino acid sequence of a 35kda lectin protein isolated from the serum of the american alligator that exhibits binding to mannose. the protein n-terminal sequence was determined using edman degradation and enzymatic digestion with different proteases was used to generate peptide fragments for analysis by liquid chromatography tandem mass spectrometry (lc ms/ms). separate analysis of the protein digests with multipl ...201222085437
pharmacokinetics of tetracycline after single-dose oral administration in the american alligator (alligator mississippiensis).the major objective of the study was to assess the pharmacokinetics of tetracycline administered orally to fasted and nonfasted american alligators (alligator mississippiensis) at 50 mg/kg. plasma levels of tetracycline were determined using high-performance liquid chromatography with ultraviolet detection. the concentration versus time curve was analyzed using a compartmental modeling technique. a one-compartment model with first-order absorption and elimination, as well as a lag time to absorp ...201223272354
a test of the validity of range of motion studies of fossil archosaur elbow mobility using repeated-measures analysis and the extant phylogenetic bracket.recent studies have presented range of motion (rom) data in degrees for dinosaur forelimb joints, usually via physical manipulation of one individual. using these data, researchers have inferred limb orientations, postures, gaits, ecological functions and even phylogenetic trends within clades. however, important areas of concern remain unaddressed; for example, how does rom at a forelimb joint change after soft tissues are lost in archosaurs? and are fossil rom methodologies amenable to reprodu ...201222623191
effects of dehydration on cardiovascular development in the embryonic american alligator (alligator mississipiensis).effects of dehydration on reptilian embryonic cardiovascular function are unknown. here, we present the first morphological and physiological data quantifying the cumulative effects of four acute dehydration events on the embryonic american alligator, alligator mississipiensis. we hypothesized that dehydration would alter embryonic morphology, reduce blood volume and augment the response to angiotensin ii (ang ii), a key osmotic and blood volume regulatory response element in adult vertebrates. ...201222484708
structure, innervation and response properties of integumentary sensory organs in crocodilians.integumentary sensory organs (isos) are densely distributed on the jaws of crocodilians and on body scales of members of the families crocodilidae and gavialidae. we examined the distribution, anatomy, innervation and response properties of isos on the face and body of crocodilians and documented related behaviors for an alligatorid (alligator mississippiensis) and a crocodylid (crocodylus niloticus). each of the isos (roughly 4000 in a. mississippiensis and 9000 in c. niloticus) was innervated ...201223136155
molecular cloning and characterization of the corticoid receptors from the american alligator.steroid hormones are essential for health in vertebrates. corticosteroids, for example, have a regulatory role in many physiological functions, such as osmoregulation, respiration, immune responses, stress responses, reproduction, growth, and metabolism. although extensively studied in mammals and some non-mammalian species, the molecular mechanisms of corticosteroid hormone (glucocorticoids and mineralocorticoids) action are poorly understood in reptiles. here, we have evaluated hormone recepto ...201323127802
establishment of transactivation assay systems using fish, amphibian, reptilian and human thyroid hormone receptors.thyroid hormones are essential for the regulation of a wide range of biological processes associated with normal development and metabolism in vertebrates. for the screening of chemicals with a potential thyroid hormone and anti-thyroid hormone activities, we have established transient transactivation assay systems using thyroid hormone receptors (trα and trβ) from three frog species (xenopus laevis, silurana tropicalis and rana rugosa), a fish (oryzias latipes), an alligator (alligator mississi ...201323112079
using the american alligator and a repeated-measures design to place constraints on in vivo shoulder joint range of motion in dinosaurs and other fossil archosaurs.using the extant phylogenetic bracket of dinosaurs (crocodylians and birds), recent work has reported that elbow joint range of motion (rom) studies of fossil dinosaur forearms may be providing conservative underestimates of fully fleshed in vivo rom. as humeral rom occupies a more central role in forelimb movements, the placement of quantitative constraints on shoulder joint rom could improve fossil reconstructions. here, we investigated whether soft tissues affect the more mobile shoulder join ...201322972888
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
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
in vivo bone strain and finite element modeling of the mandible of alligator mississippiensis.forces experienced during feeding are thought to strongly influence the morphology of the vertebrate mandible; in vivo strain data are the most direct evidence for deformation of the mandible induced by these loading regimes. although many studies have documented bone strains in the mammalian mandible, no information is available on strain magnitudes, orientations or patterns in the sauropsid lower jaw during feeding. furthermore, strain gage experiments record the mechanical response of bone at ...201323855772
a 3d interactive model and atlas of the jaw musculature of alligator mississippiensis.modern imaging and dissemination methods enable morphologists to share complex, three-dimensional (3d) data in ways not previously possible. here we present a 3d interactive model of the jaw musculature of the american alligator (alligator mississippiensis). alligator and crocodylian jaw musculature is notoriously challenging to inspect and interpret because of the derived nature of the feeding apparatus. using iodine-contrast enhanced microct imaging, a segmented model of jaw muscles, trigemina ...201323762228
feeding mechanics in spinosaurid theropods and extant crocodilians.a number of extant and extinct archosaurs evolved an elongate, narrow rostrum. this longirostrine condition has been associated with a diet comprising a higher proportion of fish and smaller prey items compared to taxa with broader, more robust snouts. the evolution of longirostrine morphology and a bulbous anterior rosette of premaxillary teeth also occurs in the spinosaurid theropod dinosaurs, leading to suggestions that at least some members of this clade also had a diet comprising a notable ...201323724135
sex-biased expression of sex-differentiating genes foxl2 and fgf9 in american alligators, alligator mississippiensis.across amniotes, sex-determining mechanisms exhibit great variation, yet the genes that govern sexual differentiation are largely conserved. studies of evolution of sex-determining and sex-differentiating genes require an exhaustive characterization of functions of those genes such as foxl2 and fgf9. foxl2 is associated with ovarian development, and fgf9 is known to play a role in testicular organogenesis in mammals and other amniotes. as a step toward characterization of the evolutionary histor ...201323689672
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