Validating osteological correlates for the hepatic piston in the American alligator ().

Unlike the majority of sauropsids, which breathe primarily through costal and abdominal muscle contractions, extant crocodilians have evolved the hepatic piston pump, a unique additional ventilatory mechanism powered by the diaphragmaticus muscle. This muscle originates from the bony pelvis, wrapping around the abdominal viscera, extending cranially to the liver. The liver then attaches to the caudal margin of the lungs, resulting in a sub-fusiform morphology for the entire "pulmo-hepatic-diaphragmatic" structure.

Exposure to ecologically relevant estrogen levels do not influence morphology or immune parameters in hatchling American alligators (Alligator mississippiensis).

Human activity has increased concentrations of endocrine-disrupting contaminants (EDCs) in many ecological systems. Many EDCs are xenoestrogens, which imitate naturally derived estrogen like estradiol 17-β (E2). These pollutants can critically affect a broad range of biological functions, particularly in organisms inhabiting aquatic environments.

Hypoxic incubation at 50% of atmospheric levels shifts the cardiovascular response to acute hypoxia in American alligators, Alligator mississippiensis.

We designed a series of studies to investigate whether hypoxia (10% O) from 20% of incubation to hatching, or from 20 to 50% of incubation, affects cardiovascular function when juvenile American alligators reached an age of 4-5 years compared to juveniles that were incubated in 21% O. At this age, we measured blood flows in all the major arteries as well as heart rate, blood pressure, and blood gases in animals in normoxia and acute hypoxia (10% O and 5% O). In all three groups, exposure to acute hypoxia of 10% O caused a decrease in blood O concentration and an increase in heart rate in 4-5-year-old animals, with limited effects on blood flow in the major outflow vessels of the heart.

Exposure to hypoxia during embryonic development affects blood flow patterns and heart rate in juvenile American alligators during digestion.

The developmental environment can alter an organism's phenotype through epigenetic mechanisms. We incubated eggs from American alligators in 10% O (hypoxia) to investigate the functional plasticity of blood flow patterns in response to feeding later in life. Digestion is associated with marked elevations of metabolism, and we therefore used the feeding-induced stimulation of tissue O demand to determine whether there are lasting effects of developmental hypoxia on the cardiovascular response to digestion later in life.

A rare case of partial skull and brain duplication in a hatchling Alligator mississippiensis.

Errors in development occur in all vertebrates. When severe, these anomalies are lethal and frequently escape attention. In rare cases, animals with profound malformations are born and can provide a glimpse into structures and their respective function that would otherwise go unnoticed.

Xenobiotic estradiol-17ß alters gut microbiota of hatchling American alligators (Alligator mississippiensis).

Environmental oestrogens pose serious concerns for ecosystems through their effects on organismal survival and physiology. The gut microbiome is highly vulnerable to environmental influence, yet the effects of oestrogens on gut homeostasis are unknown because they are poorly studied in wildlife populations. To determine the influence of environmental oestrogens (i.

Developmental oxygen preadapts ventricular function of juvenile American alligators, .

Developmental oxygen is a powerful stressor that can induce morphological and functional changes in the cardiovascular systems of embryonic and juvenile vertebrates. This plasticity has been ascribed, at least in part, to the unique status of the developing cardiovascular system, which undergoes organogenesis while meeting the tissue oxygen demands of the embryo. We have previously reported an array of functional and morphological changes in embryonic American alligators that persist into juvenile life.

Ontogeny of the trigeminal system and associated structures in Alligator mississippiensis.

From the appearance of the vertebrate head, the trigeminal system has played a role in behavioral and ecological adaptation. The trigeminal nerve is the primary cranial somatosensory nerve, also innervating the jaw muscles. In crocodylians, the trigeminal nerve plays a role in modulating the high bite force and unique integumentary sensation.

The developing bird pelvis passes through ancestral dinosaurian conditions.

Living birds (Aves) have bodies substantially modified from the ancestral reptilian condition. The avian pelvis in particular experienced major changes during the transition from early archosaurs to living birds. This stepwise transformation is well documented by an excellent fossil record; however, the ontogenetic alterations that underly it are less well understood.

Ontogeny of the nasolacrimal apparatus and nasal sensory systems of the American alligator (Alligator mississippiensis).

The nasolacrimal apparatus (NLA) is a feature common to many sauropsid amniotes. It consists of an orbital Harderian gland (HG)whose secretions drain into the nasal cavity, in the vicinity of the vomeronasal organ (VNO), an accessory olfactory organ derived from the olfactory epithelium, and a connecting nasolacrimal duct (NLD). Though not all features are present in all posthatchling sauropsids (i.

Tissue Distribution of Mercury in the Bodies of Wild American Alligators (Alligator mississippiensis) from a Coastal Marsh in Louisiana (USA).

Total mercury (THg) concentrations were measured in wild alligators inhabiting a coastal marsh in southern Louisiana, to determine the tissue distribution of THg among various body organs and tissue compartments. Concentrations of THg in claws and dermal tail scutes were compared to those in blood, brain, gonad, heart, kidney, liver, and skeletal muscle to determine if the former tissues, commonly available by non-lethal sampling, could be used as measures of body burdens in various internal organs. Mercury was found in all body organs and tissue compartments.

Ontogeny of the American alligator (Alligator mississippiensis) prenatal head: A morphometric approach.

Variation in vertebrate cranial morphology is both extensive and functionally significant. Morphometric analysis attempts to explain such variation in form in evolutionary and functional contexts. Developmental morphometric analyses of vertebrate crania are less common, and many taxa are underrepresented.

Ontogenetic changes in limb posture, kinematics, forces and joint moments in American alligators (Alligator mississippiensis).

As animals increase in size, common patterns of morphological and physiological scaling may require them to perform behaviors such as locomotion while experiencing a reduced capacity to generate muscle force and an increased risk of tissue failure. Large mammals are known to manage increased mechanical demands by using more upright limb posture. However, the presence of such size-dependent changes in limb posture has rarely been tested in animals that use non-parasagittal limb kinematics.

Correlations between environmental salinity levels, blood biochemistry parameters, and steroid hormones in wild juvenile American alligators (Alligator mississippiensis).

American alligators (Alligator mississippiensis) inhabit freshwater wetlands that are vulnerable to salinization caused by anthropogenic alterations to freshwater flow, in addition to storm surges, sea level rise, and droughts. Salinization of coastal freshwater habitats is a growing concern in a changing climate due to increased frequency and intensity of storm surges and drought conditions. This study opportunistically sampled juvenile male and female wild alligators in various salinities each month excluding November, December, and January for one year at Rockefeller Wildlife Refuge in coastal Louisiana.

Scaling of axial muscle architecture in juvenile Alligator mississippiensis reveals an enhanced performance capacity of accessory breathing mechanisms.

Quantitative functional anatomy of amniote thoracic and abdominal regions is crucial to understanding constraints on and adaptations for facilitating simultaneous breathing and locomotion. Crocodilians have diverse locomotor modes and variable breathing mechanics facilitated by basal and derived (accessory) muscles. However, the inherent flexibility of these systems is not well studied, and the functional specialisation of the crocodilian trunk is yet to be investigated.

Arterial wall thickening normalizes arterial wall tension with growth in American alligators, Alligator mississippiensis.

Arterial wall tension increases with luminal radius and arterial pressure. Hence, as body mass (M) increases, associated increases in radius induces larger tension. Thus, it could be predicted that high tension would increase the potential for rupture of the arterial wall.

Anatomical and histological analyses reveal that tail repair is coupled with regrowth in wild-caught, juvenile American alligators (Alligator mississippiensis).

Reptiles are the only amniotes that maintain the capacity to regenerate appendages. This study presents the first anatomical and histological evidence of tail repair with regrowth in an archosaur, the American alligator. The regrown alligator tails constituted approximately 6-18% of the total body length and were morphologically distinct from original tail segments.

Modest Regulation of Digestive Performance Is Maintained through Early Ontogeny for the American Alligator, .

The American alligator, , is an opportunistic carnivore that experiences an ontogenetic shift in food and feeding habits with an increase in body size. Alligators frequently feed on invertebrates and small fish as neonates and transition to feeding less frequently on larger vertebrates as they grow. We hypothesized that alligators experience an ontogenetic shift in the regulation of intestinal performance-modest regulation with frequent feeding early in life and wider regulation with less frequent feeding as they increase in body size.

The ecological importance of crocodylians: towards evidence-based justification for their conservation.

Large-bodied predators are well represented among the world's threatened and endangered species. A significant body of literature shows that in terrestrial and marine ecosystems large predators can play important roles in ecosystem structure and functioning. By contrast, the ecological roles and importance of large predators within freshwater ecosystems are poorly understood, constraining the design and implementation of optimal conservation strategies for freshwater ecosystems.

Growing up gator: a proteomic perspective on cardiac maturation in an oviparous reptile, the American alligator (Alligator mississippiensis).

We recently described lasting changes in the cardiac proteome of American alligators (Alligator mississippiensis) reared under hypoxic conditions, that resemble what embryos encounter in natural nests. While these changes were consistent with functional differences in cardiac performance induced by developmental hypoxia, the magnitude of this response was dwarfed by a much greater effect of development alone (76% of the total differentially abundant proteins). This means that substantial differences in relative steady-state protein expression occur in the hearts of alligators as they mature from egg-bound embryos to 2-year-old juveniles, and this developmental program is largely resistant to variation in nest conditions.

Embryonic developmental oxygen preconditions cardiovascular functional response to acute hypoxic exposure and maximal β-adrenergic stimulation of anesthetized juvenile American alligators ().

The effects of the embryonic environment on juvenile phenotypes are widely recognized. We investigated the effect of embryonic hypoxia on the cardiovascular phenotype of 4-year-old American alligators (). We hypothesized that embryonic 10% O preconditions cardiac function, decreasing the reduction in cardiac contractility associated with acute 5% O exposure in juvenile alligators.

A novel accessory respiratory muscle in the American alligator ( Alligator mississippiensis).

The muscles that effect lung ventilation are key to understanding the evolutionary constraints on animal form and function. Here, through electromyography, we demonstrate a newly discovered respiratory function for the iliocostalis muscle in the American alligator ( Alligator mississippiensis). The iliocostalis is active during expiration when breathing on land at 28°C and this activity is mediated through the uncinate processes on the vertebral ribs.

Hypoxia-induced reprogramming of the cardiac phenotype in American alligators (Alligator mississippiensis) revealed by quantitative proteomics.

Hypoxic exposure during development can have a profound influence on offspring physiology, including cardiac dysfunction, yet many reptile embryos naturally experience periods of hypoxia in buried nests. American alligators experimentally exposed to developmental hypoxia demonstrate morphological and functional changes to the heart that persist into later life stages; however, the molecular bases of these changes remain unknown. We tested if targeted and persistent changes in steady-state protein expression underlie this hypoxic heart phenotype, using isobaric tags for relative and absolute quantitation (iTRAQ) proteomics.