Abstract
We review the evolutionary ecology and genetics of telomeres in taxa that cannot elevate their body temperature to a preferred level through metabolism but do so by basking or seeking out a warm environment. This group of organisms contains all living things on earth, apart from birds and mammals. One reason for our interest in this synthetic group is the argument that high, stable body temperature increases the risk of malignant tumours if long, telomerase-restored telomeres make cells ‘live forever’. If this holds true, ectotherms should have significantly lower cancer frequencies. We discuss to what degree there is support for this ‘anti-cancer’ hypothesis in the current literature. Importantly, we suggest that ectothermic taxa, with variation in somatic telomerase expression across tissue and taxa, may hold the key to understanding ongoing selection and evolution of telomerase dynamics in the wild. We further review endotherm-specific effects of growth on telomeres, effects of autotomy (‘tail dropping’) on telomere attrition, and costs of maintaining sexual displays measured in telomere attrition. Finally, we cover plant ectotherm telomeres and life histories in a separate ‘mini review’.This article is part of the theme issue ‘Understanding diversity in telomere dynamics'.
Highlights
In a lecture on ‘Endothermy versus Ectothermy’ at University of Washington (2005), the distinguished physiologist and former ‘Evolution’ Editor Prof
This breadth should constrain how much could be said per taxon in a short review; there is a real dearth of research on the evolutionary ecology, genetics and physiology of ectotherm telomeres
The non-coding DNA telomere sequences that are shielded by a protein complex are gradually lost with cellular age in many organisms [3] but are partly restored by telomerase [4], the reverse transcriptase coupled to an RNA template replacing the telomeric sequence
Summary
In a lecture on ‘Endothermy versus Ectothermy’ at University of Washington (2005), the distinguished physiologist and former ‘Evolution’ Editor Prof. As opposed to ectotherms, telomerase repression in somatic tissue, and telomere length distributions, have been suggested to be an evolutionary response to the risk of tumour development because of endotherms’ higher metabolic rate and cellular replication. There appears to be an increasing acceptance and awareness that there is no single, universal pattern of telomere erosion and that our understanding has been restricted by studying primarily laboratory mammal models and humans with little or no telomerase production in somatic tissue. The use of telomerase knock-down mutants provides a potentially powerful way to understand the role of telomerase in telomere dynamics, ageing and disease processes in both ectotherms and endotherms. We focus on (a) life history and telomeric covariation, (b) telomere links to personality, predation and proliferation, and (c) telomere length: selection and heritability
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