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

   https://doi.org/10.1098/rsbl.2019.0354  

   Codd, Jonathan R.; Rose, Kayleigh A.; Tickle, Peter G.; Sellers, William I.; Brocklehurst, Robert J.; Elsey, Ruth M.; Crossley, Dane A. (July 2019, Biology Letters)
2. Rib kinematics during lung ventilation in the American alligator ( Alligator mississippiensis ): an XROMM analysis

   https://doi.org/10.1242/jeb.156166  

   Brocklehurst, Robert J.; Moritz, Sabine; Codd, Jonathan; Sellers, William I.; Brainerd, Elizabeth L. (September 2017, The Journal of Experimental Biology)
3. The influence of incubation temperature on offspring traits varies across northern and southern populations of the American alligator ( Alligator mississippiensis )

   https://doi.org/10.1002/ece3.10915  

   Smaga, Christopher R; Bock, Samantha L; Johnson, Josiah M; Rainwater, Thomas; Singh, Randeep; Deem, Vincent; Letter, Andrew; Brunell, Arnold; Parrott, Benjamin B (February 2024, Ecology and Evolution)

   Abstract Maternal provisioning and the developmental environment are fundamental determinants of offspring traits, particularly in oviparous species. However, the extent to which embryonic responses to these factors differ across populations to drive phenotypic variation is not well understood. Here, we examine the contributions of maternal provisioning and incubation temperature to hatchling morphological and metabolic traits across four populations of the American alligator (Alligator mississippiensis), encompassing a large portion of the species' latitudinal range. Our results show that whereas the influence of egg mass is generally consistent across populations, responses to incubation temperature show population‐level variation in several traits, including mass, head length, head width, and residual yolk mass. Additionally, the influence of incubation temperature on developmental rate is greater at northern populations, while the allocation of maternal resources toward fat body mass is greater at southern populations. Overall, our results suggest that responses to incubation temperature, relative to maternal provisioning, are a larger source of interpopulation phenotypic variation and may contribute to the local adaptation of populations. 

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4. Developmental oxygen preadapts ventricular function of juvenile American alligators, Alligator mississippiensis

   https://doi.org/10.1152/ajpregu.00059.2022  

   Crossley, Janna L.; Lawrence, Tyler; Tull, Melissa; Elsey, Ruth M.; Wang, Tobias; Crossley, Dane A. (November 2022, American Journal of Physiology-Regulatory, Integrative and Comparative Physiology)

   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. Most notably, cardiac enlargement as well as functional parameters of anesthetized juvenile alligators remains after embryonic hypoxic exposure. Because the effects of developmental oxygen in crocodilians have only been investigated in anesthetized animals, we explored the pressure dynamics of both ventricles as well as systemic pressure in response to stressors of acute hypoxia and swimming. Our current findings demonstrate that developmental programming of cardiac function (intraventricular pressure and heart rate) does persist into juvenile life, but it is chamber-specific and depends on the experimental manipulation. Acute hypoxic exposure revealed that juvenile alligators that had experienced 10% O 2 as embryos maintain right ventricle function and increase left ventricle function during exposure. Finally, the data indicate blood flow in the left aorta must originate from the left ventricle during acute hypoxia and swimming. 

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5. Anatomy and Ontogeny of the Mandibular Symphysis in Alligator mississippiensis

   https://doi.org/10.1002/ar.24116  

   Lessner, Emily J.; Gant, Cortaiga A.; Hieronymus, Tobin L.; Vickaryous, Matthew K.; Holliday, Casey M. (April 2019, The Anatomical Record)

   ABSTRACT Crocodylians evolved some of the most characteristic skulls of the animal kingdom with specializations for semiaquatic and ambush lifestyles, resulting in a feeding apparatus capable of tolerating high biomechanical loads and bite forces and a head with a derived sense of trigeminal‐nerve‐mediated touch. The mandibular symphysis accommodates these specializations being both at the end of a biomechanical lever and an antenna for sensation. Little is known about the anatomy of the crocodylian mandibular symphysis, hampering our understanding of form, function, and evolution of the joint in extant and extinct lineages. We explore mandibular symphysis anatomy of an ontogenetic series ofAlligator mississippiensisusing imaging, histology, and whole mount methods. Complex sutural ligaments emanating about a midline‐fused Meckel's cartilage bridge the symphysis. These tissues organize during days 37–42 ofin ovodevelopment. However, interdigitations do not manifest until after hatching. These soft tissues leave a hub and spoke‐like bony morphology of the symphyseal plate, which never fuses. Interdigitation morphology varies within the symphysis suggesting differential loading about the joint. Neurovascular canals extend throughout the mandibles to alveoli, integument, and bone adjacent to the symphysis. These features suggest theAlligatormandibular symphysis offers compliance in an otherwise rigid skull. We hypothesize a fused Meckel's cartilage offers stiffness in hatchling mandibles prior to the development of organized sutural ligaments and mineralized bone while offering a scaffold for somatic growth. The porosity of the dentaries due to neurovascular tissues likely allows transmission of sensory and proprioceptive information from the surroundings and the loaded symphysis. Anat Rec, 302:1696–1708, 2019. © 2019 American Association for Anatomy 

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