Ageing in Reptiles

Abstract

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.

Species Selection in Comparative Studies of Aging and Antiaging Research

“…Species like Blanding's turtle (Emydoidea blandingii) and the painted turtle (Chrysemys picta) have been reported not to show signs of aging in studies lasting decades (Congdon et al, 2001(Congdon et al, , 2003). An increased reproductive output with age was also reported, in accordance with reports of de novo oogenesis in adult reptiles (Finch, 1990;Patnaik, 1994). Understanding the physiological basis of this phenomenon, also termed negligible senescence (Finch, 1990), has tremendous implications for gerontology but has so far been neglected.…”

“…Increased reproductive output with age has also been reported in other reptiles apart from turtles, such as in the northern fence lizard (Sceloporus undulatus) and in king snakes (Lampropeltis getulus), as well as other species (Finch, 1990;Patnaik, 1994). With the exception of turtles, the longest-lived reptile is the tuatara (Sphenodon punctatus), which lives at least 77 years, but possibly much longer (Patnaik, 1994). Tuataras are the only living descendants from the Rhynchocephalia order and thus have no closely related species.…”

“…The ability to regenerate oocytes in adulthood is crucial to avoid reproductive senescence and, according to evolutionary models, essential for the emergence of negligible senescence. Increased reproductive output with age has also been reported in other reptiles apart from turtles, such as in the northern fence lizard (Sceloporus undulatus) and in king snakes (Lampropeltis getulus), as well as other species (Finch, 1990;Patnaik, 1994). With the exception of turtles, the longest-lived reptile is the tuatara (Sphenodon punctatus), which lives at least 77 years, but possibly much longer (Patnaik, 1994).…”

“…Nonetheless, while some short-lived reptiles show signs of aging, other long-lived reptilian species may be of interest. For example, de novo oogenesis has been reported in different reptiles, including alligators and lizards, plus the aforementioned turtles (Patnaik, 1994). The ability to regenerate oocytes in adulthood is crucial to avoid reproductive senescence and, according to evolutionary models, essential for the emergence of negligible senescence.…”

Ressignificação existencial do pretérito e longevidade humana

“…O segundo tipo apresenta uma senescência gradual, com um tempo de vida definido, podendo variar de 2 a 100 anos, aproximadamente, que é o tipo que ocorre na maioria dos lagartos e cobras e no próprio homem. E, por último, a senescência considerada desprezível, ou seja, a de animais que apresentam um processo de envelhecimento muitíssimo lento, quase imperceptível, como é o caso de tartarugas e crocodilos (Cooper, 1994;Patnaik, 1994). Envelhecer é, portanto, uma etapa pela qual todos os indivíduos passarão após atingirem uma determinada idade.…”