Reptile longevity is even more complex than we imagined – study
In the 2003 movie “Finding Nemo,” protagonist Marlin, a clownfish, asks Crush, a sea turtle how old is he. Crush yells, “One hundred and fifty, man! And still young!
This California troll surfer turtle reminds viewers that turtles are amazing in part because of their longevity, even though they look like shrunken old men from birth. Despite this, herpetologists (those who study reptiles and amphibians) know relatively little about the longevity of reptiles, especially compared to their mammalian counterparts.
Reptiles are often offbeat, both as favorite animals and as scientific specimens. “There will always be more people who like cuddly, fluffy, or soft things than those who like scaly, slimy things like reptiles and amphibians,” says Alexandre Pyron, an evolutionary biologist at George Washington University who focuses on these very scaly, slimy things. A recent survey of reptile species found that one in five of these creatures are endangered, a higher figure than expected because reptiles are often left out of data sets.
Now, a new study is trying to figure out exactly how a turtle can be 150 years old and still be young. This paper, published today in the review Scienceexamines the aging rates and longevity of dozens of species of reptiles and amphibians.
What’s new – The largest reptile longevity study to date examines four hypotheses behind the group’s remarkable lifespan. Dozens of researchers from around the world have collected data on 107 populations of 77 species of reptiles and amphibians.
The creatures examined are known in the reptile world as “herpes”, according to lead author Beth Reinke, professor of biology at Northeastern Illinois University. Herpes are cold-blooded or ectothermic reptiles. Fish, for example, are also ectotherms, but they are not herpes and were not included in the analysis. Reinke expected to find a bunch of examples like Crush – herpes that, perhaps because they aren’t expending energy regulating their own body temperature in a state called thermoregulatory mode, have on average a longer life. long than warm-blooded or endothermic creatures. Instead, she discovered that herpes may actually have a longer or shorter lifespan than endotherms.
“Based on a prior assumption of aging, we would expect ectotherms to age more slowly than endotherms and probably the thermoregulatory mode is the reason. However, since this is not the model we have found, it meant there was a lot more going on,” she said. Reverse.
“Their range of aging and longevity extends beyond what we know for endotherms in either direction, which was really surprising.”
Crush apparently represents popular anecdotal evidence that turtles box live to be super old. There are grumps like Jonathan the Seychelles Giant Tortoise which reach a whopping 190, but herpetologists haven’t contextualized these delightful anecdotes into larger data. This study gives a better idea of how often herpes lives on for centuries and why this might be the case. The study researchers also adjusted the size of reptiles and amphibians, so a creature may have a shorter lifespan, but for its size, it may be significantly aged.
Although this is the most comprehensive study of its kind to date, the size of this sample is only a drop in the ocean. “This is a sampling of tiny tiny fractions and it reflects the difficulty and intensity of collecting this data,” said Pyron of George Washington University, who was not involved in the current research. . Reverse. The sample represents less than one percent of the 10,000 known reptile species.
Why is it important – Although not all herpes have found the secret to longevity, those who have can help us better understand aging. Reinke says she and her team have found evidence in some species of a principle called negligible senescence, or aging. Negligible senescence means that throughout a creature’s lifetime, its chance of mortality does not change much. For example, Crush is no more likely to die of natural causes at age 150 than he was at age 30. His body hasn’t aged much, so his chances of mortality mostly come from his environment. This phenomenon illustrates the difference between a person’s chronological age – his age in years – and biological age – the aging of the body.
Pyron also points out that the great variability of reptiles makes them worthy of in-depth study. Looking at the magnificent variance between species can tell us how evolution has changed. Pyron says that, for example, although there are thousands of species of birds, there is not much difference between them – most of them have wings, feathers, beaks and the ability to take flight. Herpes, on the other hand, can come in all shapes and sizes, even within a family.
“From sea snakes to flying snakes, to flying lizards, to burrowing lizards, to legless lizards, to snakes that live in deserts, to snakes that live in the high Himalayas, in Tibet, in hot springs,” says- he. There is greater variation in a factor called functional diversity, which are traits acquired from different adaptations.
Dig into the details — Reinke and his massive team explored the evidence behind four factors that may contribute to herpes longevity:
- Ambient temperature
- Protective phenotypes
- life history rhythm
The idea is that ectotherms do not expend as much energy constantly warming their internal body temperature as endotherms. Therefore, they can devote more energy to other functions. Reinke and his team came up with the surprising finding while examining thermoregulation that ectotherms had a greater variance in lifespan than endotherms.
Looking at environmental temperature, the team concludes that the rate of aging increased in reptiles, but decreased in amphibians when looking at average temperature. With warming waters due to climate change, this theory deserves some consideration.
Protective phenotypes refer to the natural protection of a reptile or amphibian, such as armor or venom. Those with protection aged more slowly than those without protection. Additionally, those with physical protection like a shell outlasted those with chemical defenses, like venom or skin toxins.
The rhythm of life history examines biological aging versus chronological aging. In particular, this team examined aging in relation to mating practices. In reptiles, slower rates of aging corresponded to first reproduction at a later age. On the other hand, amphibians showed slower aging rates with longer annual breeding seasons.
And after – Pyron wants to see clade-specific analyses; that is, more detailed examinations of small groups. He often works with lungless salamanders, which are one of the most diverse groups of reptiles on a fine ecological scale. Thus, comparing aging between different types of these salamanders could provide even more accurate data.
“They could take it a step further and start to unravel very small-scale processes or mechanisms that determine rates of aging or longevity, like temperature or water balances or different elevation changes,” he says.
Reinke sees two main directions in which this research could go, one of which is already underway. This one might consider how sex differences affect aging, and the other goes along the lines of what Pyron wants to see. The researchers looked at some geographically different populations of the same species and found that the rate of aging and longevity varied between them. “What’s driving this?” How drastic is this variation? Which species have it, and are there any species that don’t have this variation? said Reinke.
Reptiles and amphibians may not get the same love as warm-blooded creatures, but maybe they can teach us how to reach 150 while surfing the East Australian Current in style.