Mira-Jover, A., Rodríguez-Caro, R.C., Noguera, J.C., Fritz, U., Kehlmaier, C., García de la Fuente, M.I., Giménez, A. and Graciá, E. (2024). Shorter telomeres are related to shell anomalies in a long-lived tortoise. Journal of Zoology, vol. 323, pp. 67-75. https://doi.org/10.1111/jzo.13154
Scientifically, telomeres are repeated sequences of DNA positioned on the finish of chromosomes with the operate of defending the genome in opposition to oxidative injury, recombination errors or different mobile stressors. Telomere size (TL) is a time period used to outline the amount of DNA that these buildings include (the extra base pairs (A, C, T, G)they’ve, the longer they’re). Telomere depletion is the method of base pair misplaced (the construction turns into shorter). This loss may be thought-about a “give up” of base pairs in favour of genome safety. Subsequently, figuratively talking, our telomeres are an armed knight who protects our chromosomes from exterior injury, however they received’t stay without end. When telomeres shorten till a important threshold, the cell dies and organismal decline begins.
The lack of our knight’s armour (or telomere shortening) is usually related to growing older, at the very least for many taxa. Telomere size is anticipated to scale back after delivery as a symptom of senescence (gradual deterioration with age). Because of this, telomere depletion is intently associated to longevity or mortality threat and in addition ailments, most cancers and different well being situations. Nevertheless, there does exist mechanisms to restore (and even elongate) telomeres, such because the enzyme telomerase. Like if we had been capable of refresh the warrior’s spirit of battle. Nevertheless, telomerase works in another way in endotherms and ectotherms, as they differ significantly by way of their metabolism and physiology. Telomerase exercise is related to elevated most cancers threat in endotherms, nonetheless bugs, fish and reptiles are able to repairing somatic telomeres all through their life with much less drastic penalties.
Moreover “time-effects” over telomere size, life-history traits or particular person traits could modulate telomere size. Research on lizards, alligators and snakes have explored the results of intercourse, progress charges and reproductive funding over telomere size. Telomere shortening or elongation generally is a consequence of environmental stress, self-maintenance or different key pressures in ecological phrases, which have a powerful affect on telomere dynamics over particular person health. Nevertheless, in the midst of that mess, how telomere dynamics range all through the life span in reptiles is just not utterly clear, since telomere patterns differ throughout species, people and even tissues, cell sorts and life phases (for instance amphibian metamorphosis or tail regeneration in lizards). Moreover, understanding how all these processes happen within the wild stays an open query, particularly for non-model organisms.
In our examine, we carried out a telomere size evaluation with a extremely fascinating examine system: a long-lived reptile, the spur-thighed tortoise (Testudo graeca). This little chelonian has been described a slow-life species with excessive grownup survival charges, lengthy technology occasions and low replica patterns. We needed to learn the way particular person traits (intercourse, age, progress charge, physique situation index and presence of shell anomalies) relate to telomere size. Moreover, we carried out longitudinal sampling (capture-recapture) to check the impact of time over the tortoise’s telomeres. Despite the fact that tortoises appear simple to catch, longitudinal capture-recapture research are time-consuming and recapture of people is just not all the time simple.
We report for the primary time the connection between TL and the presence of shell anomalies, though we didn’t discover any relationship between TL and intercourse, particular person progress charge, or physique situation. People with shell anomalies (deviation of the standardized scute sample) had much less chromosome safety than those which had a “good” carapace. In reptiles, asymmetries and anomalies are attributable to environmental elements, ontogenetic growth and in addition by inbreeding or genetics. Anomalies are ceaselessly used as health proxies, and our outcomes counsel a hyperlink between developmental instability and telomere size.
The connection of telomere size with age on this tortoise species stays unclear, probably because of the complicated dynamics of TL over time. To elucidate the absence of telomere shortening, we recommend {that a}) these tortoises are able to restoring or elongating their telomeres (everlasting and all the time good armor for his or her genome-protecting knights) and/or b) there’s a choice strain in opposition to people with shorter telomeres (the “longest” knight stays in court docket).
We conclude that learning these ‘knights of the chromosomes’ provides a possible framework to deduce ontogenetic points for tortoises. In the meantime, the usage of telomere size as a organic marker of age appears to be restricted for these lengthy and gradual life organisms.
Andrea Mira-Jover