ArticleLiterature Review

Reptile geriatrics.

Authors:
  • Toronto Zoo
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Abstract

Although basic notions, such as life expectancy, and thus what constitutes old age, remain to be determined in the vast majority of reptile species, there is a tendency at least for captive reptiles to live longer now than in the past. Clinicians are expected to recognize signs of senescence or old age in reptile patients, to acquire a heightened index of suspicion for diseases likely to affect older individuals of a given species or taxon, and to provide sound advice on geriatric care of such patients. Reptiles are stoic and show few signs of aging, but subtle changes in behavior, mobility, reproduction, weight, or appetite may all signal the onset of senescence to the vigilant caregiver. Serial, for example, yearly or biannual physical examination, blood sampling, and imaging initiated at maturity or earlier are probably the most powerful tools in diagnosing, monitoring, and managing geriatric issues.

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Chapter
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Chapter
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Chapter
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Book
Contents Specialization in Reptile Medicine SECTION I: ADVANCES IN REPTILE MEDICINE 1. Current Herpetological Husbandry and Products 2. Common Pathology and Diseases Seen in Pet Store Reptiles 3. Clinical Aspects of Evolution in Reptile Medicine 4. Molecular Infectious Disease Diagnostics 5. Clinical Virology 6. Updates on Fungal Infections in Reptiles 7. Therapeutics 8. Clinical Pathology 9. CT and MRI 10. Ultrasonography 11. Conditioning and Behavioral Training in Reptiles SECTION II: ADVANCES IN ANESTHESIA, SURGERY AND ANALGESIA 12. Anesthesia 13. Diagnostic Endoscopy 14. Endosurgery 15. Vacuum Assisted Wound Closure in Chelonians 16. New Techniques in Chelonian Shell Repair 17. Video Telescopic Operating Microscope: A Recent Development in Reptile Microsurgery 18. Analgesia 19. Reptiles and Amphibians in Laboratory Animal Medicine SECTION III: ADVANCES IN AMPHIBIAN MEDICINE 20. Amphibian Therapy 21. Amphibian Diversity in a New Era of Amphibian Taxonomy 22. Exhibiting Amphibians 23. Infectious Diseases of Amphibians: It Isn't Just Redleg Anymore 24. Chytridiomycosis 25. Short Tongue Syndrome and Hypovitaminosis A 26. Ranaviruses SECTION IV: ADVANCES IN BIOLOGY, CONSERVATION, LEGAL AND RESEARCH 27. Conservation Issues 28. Invasive and Introduced Reptiles and Amphibians 29. Techniques for Working with Wild Reptiles 30. Forensics in Reptile Investigation APPENDICES Appendix 1: Developing your Reptile Medicine IQ: Learning How to Get the Most Out of and Contribute to the Herpetologic Literature Appendix 2: Drug Formulary and Laboratory Normals
Book
The online form of this book can be accessed at: http://www.demogr.mpg.de/longevityrecords/
Article
Many reptiles live relatively long lives wherein senescence is postponed to an advanced age. Altering nutrition, reproduction, temperature, and other physiological parameters may favorably contribute to increased life spans. But life spans are also evolved characteristics of populations, and the distinctive longevities also result from selective regimes arising within particular environments. Aging is not favored directly by evolution as a way to clear a population of senescent individuals. Instead, aging is probably an indirect byproduct of selection for early physical vitality. Senescence may result from delayed appearance of deleterious genes later in life (mutation accumulation) or from multiple effects of single genes with overriding favorable effects early but coupled deleterious effects later in life (antagonistic pleiotropy). Both physiological and evolutionary causes contribute to species or even population-specific aging characteristics. Separating environmentally imposed mortality from that attributable to senescence has been aided by compiling maximum life spans of captive reptiles. Further understanding the underlying aging biology of reptiles would be aided by following mortalities of age cohorts, identifying differences in aging between populations, documenting the effects, favorable or not, of husbandry practices, and by characterizing senescence not just by mortality, but also by changes in age-related performance. Theoretical issues, inspired by experimental results in rattlesnakes, suggest conditions under which the chance mortalities of young rattlesnakes together with continued growth of adults might favor late appearance of beneficial genes and thereby account for postponed senescence in some reptiles. © 1996 Wiley-Liss, Inc.
Article
Like in fishes, the reptiles appear to show three types of senescence. The African skink, Mabuya buettneri, shows rapid senescence similar to death at mating observed in Salmon and marsupial mouse. Most of the lizards and snakes undergo gradual senescence comparable to the pattern exhibited by a majority of vertebrates. On the other hand, turtles, tortoises and crocodiles continue to grow throughout life and are thus credited with slow or negligible senescence. Evidences and mechanisms of rapid or negligible senescence in reptiles are still fragmentary and unclear. Findings in a few species of lizards (Calotes versicolor) and snakes (Natrix natrix) showing gradual senescence support the concept of commonalities in ageing phenomena in vertebrates. An age-related increase in the stability of collagen and accumulation of altered enzyme molecules, a decrease in metabolism and response to stress-enhanced anti-oxidative defence mechanisms and the nature of responses to hormones, restricted diet and lower environmental temperature corroborate the concept. On the other hand neither the increase in mortality rate and accumulation of lipofuscin nor the reproductive senility have been shown conclusively in ageing reptile populations. It is likely that there are multiple mechanisms of senescence in reptiles. Further studies on selected species from among the 6,000 living species are necessary to unravel the phenomena.
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After a brief recall of the classical meaning of the concept of longevity, the first part of this chapter describes and summarises the main current technique for the estimation of age in reptiles. Among them, sclerochronology is primarily taken into account. The cautious analysis of seasonal growth cycles recorded in hard tissues, although not as rigorous as the mark-release-recapture method of animals in their natural conditions, now appears as a rapid and reliable chronological tool already successfully used in individuals of many reptile species. Sclerochronology is especially efficient for the comparison of several populations, and it is the only method for fossils. The second part presents a synthetic review of known longevities and records in the different groups of reptiles. A short discussion about the significance of longevity shows that for reptiles, because of their thermic metabolism (ectothermy), the physiological longevity must be strongly distinguished from the chronological longevity, especially for a comparison with that known for birds and most mammals.
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Two criteria have been proposed for the demonstration of negligible senescence. These include (1) no increase in age-related mortality and (2) negligible functional impairments with age. Although researchers have suspected turtles to exhibit negligible senescence, this has been largely based on the former rather than the latter criteria for which scant evidence is available. Using a long-term study on a population of three-toed box turtles (Terrapene carolina triunguis) in Cole County, Missouri, I combine known minimum age ranges and reproductive evidence to demonstrate their apparent escape from senescence. During 1998 and 1999, eight females >60 years of age were found gravid. The oldest of these is estimated to be at least 65-74 years of age. Of females >60 years, the mean clutch size and the proportion gravid were greater, although not significantly different, when compared to females <60 years. These findings indicate that the reproductive function in these turtles does not become impaired with age, thus supporting the second criteria for demonstrating negligible senescence.
Article
There are many ecological advantages to attaining a large body size as fast as possible (such as reduced risks of being caught by predators or increased reproductive success). However, studies in several taxa indicate that fast growth in itself can have negative as well as positive effects. There appears to be a link between accelerated growth and lifespan: rapid growth early in life is associated with impaired later performance and reduced longevity. In this review we assess the evidence for such within individual trade-offs between growth rate and lifespan, and the potential physiological mechanisms that might underlie them. We discuss the fitness implications of any reduction in lifespan, and point out that certain environmental circumstances may favour a 'grow fast and die young' strategy if this increases overall reproductive success. However, investigation of the intra-specific relationships among growth rate, lifespan and fitness is not straightforward; few studies have controlled for confounding variables such as adult body size or duration of the growth period, and none to date have measured fitness in an appropriate ecological setting. We suggest a number of experimental approaches that might allow the true relationships between growth rate and future performance to be elucidated.
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