HAUSSMANN,M.F.*; VLECK,C.M.; BRENNER,S.A.: Aging animals using telomere length – a novel approach.

Field biologists often must work with animals for which there is no prior history. A physiological marker of an animal’s age would offer insight into how age and experience affect reproductive success and other life history parameters. The length of telomeres, theprotective caps on the ends of chromosomes, has been shown to shorten with age in humans. Our objective was to determine if telomere restriction fragments cleaved from blood cell DNA would shorten as birds aged, thus providing a relatively non-invasive way to estimate ages of animals. We took blood samples from fourteen zebra finches placed in three age groups, juvenile (< 2 months old, n=5), young (12 to 13 months old, n=5) and old (> 24 months, n=4). The DNA was extracted from isolated erythrocyte nuclei, digested, and separated on a nondenaturing agarose gel. The gel was dried and hybridized with ³²P-labeled (C₃TA₂)₄ oligonucleotides and telomere restriction fragments were than visualized using a phosphor screen. Mean telomere length was determined using densitometry. Telomere length decreased with age in the zebra finches (ANOVA, F_2,11 = 7.18, P = .01) Juvenile birds had longer telomere fragments than old birds (juvenile = 7190 � 207 bp, old = 6008 � 232 bp; Tukey-Kramer HSD, P < .05). In young birds, telomere length (6675 � 232) was intermediate to that of juveniles and adults. To our knowledge, this is the first demonstration in a non-human study, of a change in telomere length with age. It may be possible, in the field, to estimate ages of animals with nucleated erythrocytes once the relationship between telomere length and age has been determined. This would allow the incorporation of age into estimates of factors affecting life history parameters in cases where previous histories of animals in the population are unknown.