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The Journal of Experimental Biology Apr 2022The venom glands of reptiles, particularly those of front-fanged advanced snakes, must satisfy conflicting biological demands: rapid synthesis of potentially labile and... (Review)
Review
The venom glands of reptiles, particularly those of front-fanged advanced snakes, must satisfy conflicting biological demands: rapid synthesis of potentially labile and highly toxic proteins, storage in the gland lumen for long periods, stabilization of the stored secretions, immediate activation of toxins upon deployment and protection of the animal from the toxic effects of its own venom. This dynamic system could serve as a model for the study of a variety of different phenomena involving exocrine gland activation, protein synthesis, stabilization of protein products and secretory mechanisms. However, these studies have been hampered by a lack of a long-term model that can be propagated in the lab (as opposed to whole-animal studies). Numerous attempts have been made to extend the lifetime of venom gland secretory cells, but only recently has an organoid model been shown to have the requisite qualities of recapitulation of the native system, self-propagation and long-term viability (>1 year). A tractable model is now available for myriad cell- and molecular-level studies of venom glands, protein synthesis and secretion. However, venom glands of reptiles are not identical, and many differ very extensively in overall architecture, microanatomy and protein products produced. This Review summarizes the similarities among and differences between venom glands of helodermatid lizards and of rear-fanged and front-fanged snakes, highlighting those areas that are well understood and identifying areas where future studies can fill in significant gaps in knowledge of these ancient, yet fascinating systems.
Topics: Animals; Exocrine Glands; Lizards; Salivary Glands; Snake Venoms; Snakes
PubMed: 35363854
DOI: 10.1242/jeb.227348 -
The Veterinary Clinics of North... Jan 2020Renal disease accounts for a considerable amount of morbidity and mortality in reptiles, in part owing to inadequate husbandry practices, such as inappropriate... (Review)
Review
Renal disease accounts for a considerable amount of morbidity and mortality in reptiles, in part owing to inadequate husbandry practices, such as inappropriate temperature, humidity, and access to water. Inappropriate husbandry practices may lead to subclinical dehydration that can specifically impact the renal system, which relies on vascular perfusion to function. This article aims to highlight urinary pathophysiology and summarize infectious and noninfectious causes of renal disease in reptiles as a guide for differential diagnoses to consider during clinical evaluation.
Topics: Animals; Diagnosis, Differential; Gout; Kidney Diseases; Reptiles
PubMed: 31759443
DOI: 10.1016/j.cvex.2019.08.006 -
Genes Aug 2019In this contribution, the aspects of reptile and amphibian speciation that emerged from research performed over the past decade are reviewed. First, this study assesses... (Review)
Review
In this contribution, the aspects of reptile and amphibian speciation that emerged from research performed over the past decade are reviewed. First, this study assesses how patterns and processes of speciation depend on knowing the taxonomy of the group in question, and discuss how integrative taxonomy has contributed to speciation research in these groups. This study then reviews the research on different aspects of speciation in reptiles and amphibians, including biogeography and climatic niches, ecological speciation, the relationship between speciation rates and phenotypic traits, and genetics and genomics. Further, several case studies of speciation in reptiles and amphibians that exemplify many of these themes are discussed. These include studies of integrative taxonomy and biogeography in South American lizards, ecological speciation in European salamanders, speciation and phenotypic evolution in frogs and lizards. The final case study combines genomics and biogeography in tortoises. The field of amphibian and reptile speciation research has steadily moved forward from the assessment of geographic and ecological aspects, to incorporating other dimensions of speciation, such as genetic mechanisms and evolutionary forces. A higher degree of integration among all these dimensions emerges as a goal for future research.
Topics: Amphibians; Animals; Ecosystem; Evolution, Molecular; Genetic Speciation; Reptiles; Selection, Genetic
PubMed: 31455040
DOI: 10.3390/genes10090646 -
Journal of Experimental Zoology. Part... Jan 2021Research on the thermal ecology and physiology of free-living organisms is accelerating as scientists and managers recognize the urgency of the global biodiversity... (Review)
Review
Research on the thermal ecology and physiology of free-living organisms is accelerating as scientists and managers recognize the urgency of the global biodiversity crisis brought on by climate change. As ectotherms, temperature fundamentally affects most aspects of the lives of amphibians and reptiles, making them excellent models for studying how animals are impacted by changing temperatures. As research on this group of organisms accelerates, it is essential to maintain consistent and optimal methodology so that results can be compared across groups and over time. This review addresses the utility of reptiles and amphibians as model organisms for thermal studies by reviewing the best practices for research on their thermal ecology and physiology, and by highlighting key studies that have advanced the field with new and improved methods. We end by presenting several areas where reptiles and amphibians show great promise for further advancing our understanding of how temperature relations between organisms and their environments are impacted by global climate change.
Topics: Amphibians; Animals; Body Temperature; Ecosystem; Embryo, Nonmammalian; Monitoring, Physiologic; Reptiles
PubMed: 32638552
DOI: 10.1002/jez.2396 -
Biological Psychology May 2023The polyvagal theory (PT), offered by Porges (2021), proposes that the autonomic nervous system (ANS) was repurposed in mammals, via a "second vagal nerve", to suppress... (Review)
Review
The polyvagal theory (PT), offered by Porges (2021), proposes that the autonomic nervous system (ANS) was repurposed in mammals, via a "second vagal nerve", to suppress defensive strategies and support the expression of sociality. Three critical assumptions of this theory are that (1) the transition of the ANS was associated with the evolution of 'social' mammals from 'asocial' reptiles; (2) the transition enabled mammals, unlike their reptilian ancestors, to derive a biological benefit from social interactions; and (3) the transition forces a less parsimonious explanation (convergence) for the evolution of social behavior in birds and mammals, since birds evolved from a reptilian lineage. Two recently published reviews, however, provided compelling evidence that the social-asocial dichotomy is overly simplistic, neglects the diversity of vertebrate social systems, impedes our understanding of the evolution of social behavior, and perpetuates the erroneous belief that one group-non-avian reptiles-is incapable of complex social behavior. In the worst case, if PT depends upon a transition from 'asocial reptiles' to 'social mammals', then the ability of PT to explain the evolution of the mammalian ANS is highly questionable. A great number of social behaviors occur in both reptiles and mammals. In the best case, PT has misused the terms 'social' and 'asocial'. Even here, however, the theory would still need to identify a particular suite of behaviors found in mammals and not reptiles that could be associated with, or explain, the transition of the ANS, and then replace the 'asocial' and 'social' labels with more specific descriptors.
Topics: Animals; Humans; Biological Evolution; Autonomic Nervous System; Vagus Nerve; Mammals; Social Behavior; Reptiles
PubMed: 37094735
DOI: 10.1016/j.biopsycho.2023.108569 -
The Veterinary Clinics of North... Sep 2022Monitoring blood lactate concentrations with a handheld, point-of-care (POC) meter is an efficient and inexpensive method of monitoring critically ill or anesthetized... (Review)
Review
Monitoring blood lactate concentrations with a handheld, point-of-care (POC) meter is an efficient and inexpensive method of monitoring critically ill or anesthetized exotic patients. Serial monitoring of lactate allows early recognition of hypoperfusion, allowing for prompt implementation of resuscitative efforts. Reference ranges for exotic animals are currently sparse and often gathered from field studies of wild animals. In the absence of reference ranges, extrapolations can be made regarding mammals and birds, but may be more difficult in reptiles and amphibians.
Topics: Amphibians; Animals; Animals, Exotic; Lactic Acid; Mammals; Point-of-Care Systems; Reptiles
PubMed: 36122941
DOI: 10.1016/j.cvex.2022.05.006 -
Biological Reviews of the Cambridge... Apr 2022Sleep is ubiquitous in the animal kingdom and yet displays considerable variation in its extent and form in the wild. Ecological factors, such as predation, competition,... (Review)
Review
Sleep is ubiquitous in the animal kingdom and yet displays considerable variation in its extent and form in the wild. Ecological factors, such as predation, competition, and microclimate, therefore are likely to play a strong role in shaping characteristics of sleep. Despite the potential for ecological factors to influence various aspects of sleep, the ecological context of sleep in non-avian reptiles remains understudied and without systematic direction. In this review, we examine multiple aspects of reptilian sleep, including (i) habitat selection (sleep sites and their spatio-temporal distribution), (ii) individual-level traits, such as behaviour (sleep postures), morphology (limb morphometrics and body colour), and physiology (sleep architecture), as well as (iii) inter-individual interactions (intra- and inter-specific). Throughout, we discuss the evidence of predation, competition, and thermoregulation in influencing sleep traits and the possible evolutionary consequences of these sleep traits for reptile sociality, morphological specialisation, and habitat partitioning. We also review the ways in which sleep ecology interacts with urbanisation, biological invasions, and climate change. Overall, we not only provide a systematic evaluation of the conceptual and taxonomic biases in the existing literature on reptilian sleep, but also use this opportunity to organise the various ecological hypotheses for sleep characteristics. By highlighting the gaps and providing a prospectus of research directions, our review sets the stage for understanding sleep ecology in the natural world.
Topics: Animals; Biological Evolution; Ecology; Ecosystem; Predatory Behavior; Reptiles; Sleep
PubMed: 34708504
DOI: 10.1111/brv.12808 -
The Veterinary Clinics of North... Jan 2023Advances in reptile cognitive research would help to (1) better qualify behavioral responses to pain experiences, (2) monitor welfare impacts, and (3) model analgesic... (Review)
Review
Advances in reptile cognitive research would help to (1) better qualify behavioral responses to pain experiences, (2) monitor welfare impacts, and (3) model analgesic studies with ecologically relevant insight to better qualify interventional responses. The focus of future analgesic studies in reptiles require the continued elucidation of the opiate systems and the given variations across taxa in efficacy in nociceptive tests.
Topics: Animals; Pain; Reptiles; Analgesics
PubMed: 36402486
DOI: 10.1016/j.cvex.2022.09.004 -
Brain, Behavior and Evolution 2022The author previously worked extensively on the broad problem of the evolution of the vertebrate pallium. He proposed various Bauplan models covering at least...
The author previously worked extensively on the broad problem of the evolution of the vertebrate pallium. He proposed various Bauplan models covering at least gnathostomes, based in the definition of a set of pallial sectors with topologically invariant positional relationships and distinct molecular profiles. Out of one of these models, presented as the "updated tetrapartite pallium model," a modified definition of the earlier lateral pallium sector (LPall) concept emerged, characterizing it in mammals as an unitary claustro-insular transitional (mesocortical) complex intercalated between the neocortex or dorsal pallium (DPall) above and olfactory cortex or ventral pallium (VPall) underneath. A distinctive molecular marker of the early-born deep claustral component of the LPall was found to be the transcription factor Nr4a2, which is not expressed significantly in the overlying insular cortex or in adjoining cortical territories. Given that earlier comparative studies had identified molecularly and topologically comparable VPall, LPall, and DPall sectors in the avian pallium, an avian Nr4a2 probe was applied, aiming to identify the reportedly absent avian claustro-insular complex. An early-born superficial subpopulation of the avian LPall that expresses this marker selectively through development was indeed found. This was proposed to be a claustrum homolog, whereas the remaining Nr4a2-negative avian LPall cells were assumed to represent a possible insular homolog. This last notion was subsequently supported by comparable selective expression of the mouse insular marker Cyp26b, also found restricted to the avian LPall. Some published data suggested that similar molecular properties and structure apply at the reptilian LPall. This analysis was reviewed in Puelles et al. [The pallium in reptiles and birds in the light of the updated tetrapartite pallium model. 2017]. Four years on, the present commentary discusses some international publications accrued in the interval that touch on the claustro-insular homology hypothesis. Some of them are opposed to the hypothesis whereas others corroborate or support it. This raises a number of secondary issues of general interest.
Topics: Animals; Birds; Mammals; Mice; Reptiles; Transcription Factors
PubMed: 34753135
DOI: 10.1159/000520742 -
Biology Letters Apr 2022In amniotes, daily rates of dentine formation in non-ever-growing teeth range from less than 1 to over 25 μm per day. The latter value has been suggested to represent...
In amniotes, daily rates of dentine formation in non-ever-growing teeth range from less than 1 to over 25 μm per day. The latter value has been suggested to represent the upper limit of odontoblast activity in non-ever-growing teeth, a hypothesis supported by the lack of scaling between dentine apposition rates and body mass in Dinosauria. To determine the correlates and potential controls of dentine apposition rate, we assembled a dataset of apposition rates, metabolic rates and body masses for 80 amniote taxa of diverse ecologies and diets. We used phylogenetic regression to test for scaling relationships and reconstruct ancestral states of daily dentine apposition across Amniota. We find no relationship between body mass and daily dentine apposition rate (DDAR) for non-ever-growing teeth in Amniota as a whole or within major clades. Metabolic rate, the number of tooth generations, diet and habitat also do not predict or correspond with DDARs. Similar DDARs are found in large terrestrial mammals, dinosaurs and marine reptiles, whereas primates, cetaceans and some smaller marine reptiles independently evolved exceptionally slow rates. Life-history factors may explain the evolution of dentine apposition rates, which evolved rapidly at the origin of major clades.
Topics: Animals; Dentin; Dinosaurs; Mammals; Phylogeny; Reptiles; Tooth
PubMed: 35472282
DOI: 10.1098/rsbl.2022.0092