Lastly, teleost fishes comprise about half of all vertebrate species 12, making them a crucial part of understanding vertebrate evolution and life history. Second, fish can be accurately aged using hard internal structures (e.g., otoliths), a convenience not offered by many other vertebrates (e.g., mammals, birds, and amphibians). First, long-lived fishes possess some of the longest lifespans observed within vertebrates 11, suggesting slow rates of senescence. Long-lived fishes are excellent candidates for studying senescence in free-living vertebrates. Age-related changes in mortality and fecundity inform us about general rates of senescence, but understanding the underlying mechanisms requires studies of age-related changes in physiological systems. However, because senescence is a complex phenotype, quantifying age-related changes within different physiological systems in wild populations can help us better understand the progression of senescence. Few studies have examined how multiple physiological systems change with age. However, a clear decline in immune resistance to parasites was found in late-life in Soay sheep ( Ovis aries) 10. For example, studies in long-lived seabirds have found little evidence of a decline in immunity 6, 7, stress response 7, reproduction 8, or metabolism 9. Age-related changes to physiological systems appear inconsistent across vertebrates and may depend upon the system that is examined. Studies on senescence often focus on age-related changes in mortality and fecundity without quantifying changes in the function of physiological systems, and the physiological systems that contribute to differences in senescence patterns are not well understood, especially in long-lived vertebrates. Species that exhibit extremely slow senescence reveal the notable variation that exists in pace of senescence and highlight the value of studying senescence in slow-aging species. In addition, some turtle species display no sign of increased mortality or loss of vigor in old age and older females lay more eggs and have more consistent reproduction than younger females 4 (although see Warner et al. For example, captive naked mole-rats display minimal changes in physiology or morphology while living more than 28 years, approximately 9 times longer than mice of similar size, and females show no decline in fertility even near the end of their lifespan 3. Some organisms have extremely slow rates of aging. Although evidence for senescence is accumulating, there is considerable variation in the rate of senescence among and even within species 2. Research in a wide range of species has demonstrated declines in diverse life-history traits in old age consistent with senescence (reviewed by Nussey et al. Senescence is characterized by age-related changes that adversely affect physiological function and ultimately reduce fitness 1. Taken together, these findings suggest that bigmouth buffalo exhibit negligible senescence in multiple physiological systems despite living for nearly a century. There was no significant effect of age on telomeres, but individuals that may be more stressed had shorter telomeres. Instead, older fish appeared to be less stressed and had greater immunity than younger fish, suggesting age-related improvements rather than declines in these systems. Contrary to expectation, we did not find any evidence for age-related declines in these physiological systems. In this study we examined the potential relationship between age and multiple physiological systems including: stress levels, immune function, and telomere length in individuals ranging in age from 2 to 99 years old in bigmouth buffalo ( Ictiobus cyprinellus), the oldest known freshwater teleost fish. Long-lived bony fish (i.e., Class Osteichthyes) are a particularly useful model for studies of senescence because they can readily be aged and exhibit some of the longest lifespans among vertebrates. Although the pace of senescence varies considerably, the physiological systems that contribute to different patterns of senescence are not well understood, especially in long-lived vertebrates.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |