New perspective on the origin of endothermy

Book ChapterA new hypothesis for the origin of endothermy in birds is discussed. I suggest extensive parental care provided the initial impetus for the evolution of endothermy. Among extant animals one of the most important functions of an endothermic metabolism is the incubation of embryos. Furthermore, I propose that extensive parental care is a key innovation that greatly influenced much of the homoplasy observed in extant birds and mammals, including their extraordinary ability to sustain vigorous exercise and their parasagittal postures

Integration of ventilation and locomotion in archosaurs

Journal ArticleMovements of the pelvis have recently been found to contribute to ventilation in both crocodilians and birds. Alligators have a kinetic pelvis in which the ischiopubic and ischiotruncus muscles rotate the pubic bones ventrally to increase abdominal volume and thereby facilitate inspiration. In birds, the entire pelvis rocks on the axial skeleton to produce ventilation. Although the mechanisms of pelvic aspiration are very different in crocodilians and birds, it is unusual among vertebrates for the pelvic musculoskeletal system to play an active role in inspiration. This observation raises the possibility that the pelvic musculoskeletal system may have played an important role in the ventilation of basal archosaurs. Based on the mechanism of pelvic aspiration in crocodilians and the structure of gastralia in basal archosaurs, we suggest that an ischiotruncus muscle pulled the medial aspect of the gastralia caudally, and thereby helped to produce inspiration by increasing the volume of the cuirassal basket. The proposed mechanism of cuirassal breathing in non-avian theropods leads us to suggest that the phase relationship of the ventilatory and locomotor cycles in running theropods was the opposite of that observed in running birds. Furthermore, we suggest that the ventilatory cycle of flying pterosaurs was entrained to the locomotor cycle with a phase relationship that was the opposite of that observed during flight in modern birds

The provenance of alveolar and parabronchial lungs: insights from paleoecology and the discovery of cardiogenic, unidirectional airflow in the American alligator (Alligator mississippiensis)

Journal ArticleBirds 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 his 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; in mammals, air flows tidally into and out of the alveoli. Here, I present a scenario for the origin of both the alveolar and parabronchial lungs that explains when and how they could have arisen by a gradual sequence of steps. I argue that (1) the alveolar lung evolved in the late Paleozoic, when high levels of atmospheric oxygen relaxed selection for a thin blood-gas barrier within the lungs; (2) unidirectional flow originated in the ectothermic ancestral archosaur, the forerunner of birds and crocodilians, to enable the heart to circulate pulmonary gases during apnea. This hypothesis would be supported by a demonstration of unidirectional flow in the lungs of crocodilians, the extant sister taxon of birds. Airflow in the lungs of juvenile alligators was measured during apnea using dual thermistor flowmeters, and cardiac activity was measured with electrocardiography. Coincident with each heartbeat, a pulse of air flowed in the pulmonary conduit under study with a bias in the direction of movement, yielding a net unidirectional flow. These data suggest the internal structures requisite for unidirectional flow were present in the common ancestors of birds and crocodilians and may have preadapted the lungs of archosaurs to function advantageously during the oxygen-poor period of the early Mesozoic

Reproduction: the adaptive significance of endothermy

Journal ArticleA central theme raised by Angilletta and Sears is that the energetic cost of endothermy is too enormous to be offset by the benefits that thermogenesis could provide for reproduction. Angilletta and Sears suggest that parents would have been better off producing additional offspring with the energy used for incubation or minimizing their risk of predation by minimizing foraging efforts. However, these views overlook the fact that a defining characteristic of both birds and mammals is high investment in relatively few offspring

Parental care: the key to understanding endothermy and other convergent features in birds and mammals

Journal ArticleBirds and mammals share a number of features that are remarkably similar but that have evolved independently. One of these characters, endothermy, has been suggested to have played a cardinal role in avian and mammalian evolution. I hypothesize that it is parental care, rather than endothermy, that is the key to understanding the amazing convergence between mammals and birds. Endothermy may have arisen as a consequence of selection for parental care because endothermy enables a parent to control incubation temperature. The remarkable ability of many birds and mammals to sustain vigorous exercise may also have arisen as a consequence of selection for parental care because provisioning of offspring often requires sustained vigorous exercise. Because extensive parental care encompasses a wide range of behaviors, morphology, and physiology, it may be a key innovation that accounts for the majority of convergent avian and mammalian characters

Dendrobates auratus (green and black poison dart frog). Larval Predation

Journal ArticleDendrobates auratus was intentionally introduced onto the island of O'ahu, Hawai'i in 1932 from Taboga Island, Panama for mosquito control. Phelsuma laticauda was accidentally introduced from Madagascar in 1996 to the University of Hawaii at Manoa. Both species are well established in the Manoa Valley

Unidirectional pulmonary airflow patterns in the savannah monitor lizard

pre-printThe unidirectional airflow patterns in the lungs of birds have long been considered a unique and specialized trait associated with the oxygen demands of flying, their endothermic metabolism1 and unusual pulmonary architecture2,3. However, the discovery of similar flow patterns in the lungs of crocodilians indicates that this character is probably ancestral for all archosaurs-the group that includes extant birds and crocodilians as well as their extinct relatives, such as pterosaurs and dinosaurs4-6. Unidirectional flow in birds results from aerodynamic valves, rather than from sphincters or other physical mechanisms7,8, and similar aerodynamic valves seem to be present in crocodilians4-6. The anatomical and developmental similarities in the primary and secondary bronchi of birds and crocodilians suggest that these structures and airflow patterns may be homologous4-6,9. The origin of this pattern is at least as old as the split between crocodilians and birds, which occurred in the Triassic period10. Alternatively, this pattern of flow may be even older; this hypothesis can be tested by investigating patterns of airflow in members of the outgroup to birds and crocodilians, the Lepidosauromorpha (tuatara, lizards and snakes). Here we demonstrate region-specific unidirectional airflow in the lungs of the savannah monitor lizard (Varanus exanthematicus). The presence of unidirectional flow in the lungs of V. exanthematicus thus gives rise to two possible evolutionary scenarios: either unidirectional airflow evolved independently in archosaurs and monitor lizards, or these flow patterns are homologous in archosaurs and V. exanthematicus, having evolved only once in ancestral diapsids (the clade encompassing snakes, lizards, crocodilians and birds). If unidirectional UU IR Author Manuscript UU IR Author Manuscript University of Utah Institutional Repository Author Manuscript Page 2 of 14 airflow is plesiomorphic for Diapsida, this respiratory character can be reconstructed for extinct diapsids, and evolved in a small ectothermic tetrapod during the Palaeozoic era at least a hundred million years before the origin of birds

Right-to-left shunt of crocodilians serves digestion

Journal ArticleAll amniotes except birds and mammals have the ability to shunt blood past the lungs, hut the physiological function of this ability is poorly understood. We studied the role of the shunt in digestion in juvenile American alligators in the following ways. First, we characterized the shunt in fasting and postprandial animals and found that blood was shunted past the lungs during digestion. Second, we disabled the shunt by surgically sealing the left aortic orifice in one group of animals, and we performed a sham surgery in another

The pulmonary anatomy of alligator mississippiensis and its similarity to the avian respiratory system

ManuscriptUsing 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 the cervical, interclavicular, anterior thoracic, posterior thoracic, and abdominal air sacs. Furthermore, we suggest that many of the features that alligators and birds share are homologous and that some of these features are important to the aerodynamic valve and are likely plesiomorphic for Archosauria

Implementation of the Ebola Virus Persistence in Ocular Tissues and Fluids (EVICT) study: Lessons learned for vision health systems strengthening in Sierra Leone.

BACKGROUND: Following the West African Ebola virus disease (EVD) outbreak of 2013-2016 and more recent EVD outbreaks in the Democratic Republic of Congo, thousands of EVD survivors are at-risk for sequelae including uveitis, which can lead to unremitting inflammation and vision loss from cataract. Because of the known risk of Ebola virus persistence in ocular fluid and the need to provide vision-restorative, safe cataract surgery, the Ebola Virus Persistence in Ocular Tissues and Fluids (EVICT) Study was implemented in Sierra Leone. During implementation of this multi-national study, challenges included regulatory approvals, mobilization, community engagement, infection prevention and control, and collaboration between multiple disciplines. In this report, we address the multifacted approach to address these challenges and the impact of implementation science research to address an urgent clinical subspecialty need in an outbreak setting. METHODOLOGY/PRINCIPAL FINDINGS: Given the patient care need to develop a protocol to evaluate ocular fluid for Ebola virus RNA persistence prior to cataract surgery, as well as protocols to provide reassurance to ophthalmologists caring for EVD survivors with cataracts, the EVICT study was designed and implemented through the work of the Ministry of Health, Sierra Leone National Eye Programme, and international partnerships. The EVICT study showed that all 50 patients who underwent ocular fluid sampling at 19 and 34 months, respectively, tested negative for Ebola virus RNA. Thirty-four patients underwent successful cataract surgery with visual acuity improvement. Here we describe the methodology for study implementation, challenges encountered, and key issues that impacted EVD vision care in the immediate aftermath of the EVD outbreak. Key aspects of the EVICT study included defining the pertinent questions and clinical need, partnership alignment with key stakeholders, community engagement with EVD survivor associations, in-country and international regulatory approvals, study site design for infection prevention and control, and thorough plans for EVD survivor follow-up care and monitoring. Challenges encountered included patient mobilization owing to transportation routes and distance of patients in rural districts. Strong in-country partnerships and multiple international organizations overcame these challenges so that lessons learned could be applied for future EVD outbreaks in West and Central Africa including EVD outbreaks that are ongoing in Guinea and Democratic Republic of Congo. CONCLUSIONS/SIGNIFICANCE: The EVICT Study showed that cataract surgery with a protocol-driven approach was safe and vision-restorative for EVD survivors, which provided guidance for EVD ophthalmic surgical care. Ophthalmologic care remains a key aspect of the public health response for EVD outbreaks but requires a meticulous, yet partnered approach with international and local in-country partners. Future efforts may build on this framework for clinical care and to improve our understanding of ophthalmic sequelae, develop treatment paradigms for EVD survivors, and strengthen vision health systems in resource-limited settings