BV12 focused on the three patterns of aging in biology: 1) Increasing mortality rate over age in human, mammals and birds; 2) Flat mortality rate over age in freshwater polyp Hydra vulgaris; 3) Decreasing mortality rate over age in tortoise Gopherus agassizii and many reptiles, amphibians, fish, and plants.
BV12 discussed Baudisch12Gerontology, where Baudisch discussed various models. It was mentioned that enhanced repair and maintenance can lead to flat or decreasing mortality rate over age. Increasing reproductive potential with age was also mentioned.
Estep 2010 argues that decline asexual reproduction is an indicator of senescence in hydra.
I thought a plausible way to explain the decreasing mortality rate in tortise is to use the parasites or viruses argument: older individuals are more resistant to pathogens.
I had a discussion with Adam Reitzel, UNC Charlotte about hydra aging at SMBE2013. We discussed whether hydra has an more active repair/renewal mechanism than other organisms. This lead me to wonder about the aging pattern in planarian. I found one article, Mouton11, that reported lack of metabolic aging in Schmidtea polychora.
References:
Turner FB, Berry KH, Randall DC, White GC. Report No. 87-RD-81”. Southern California Edison Company; 1987. “Population ecology of the desert tortoise at Goffs, California, 1983-1986.
(I did not find online sources for this reference).
MartÃnez DE. Exp. Gerontol. 1998;33:217
Estep, Exp Gerontol. 2010 Sep;45(9):645-6. doi: 10.1016/j.exger.2010.03.017. mm
Declining asexual reproduction is suggestive of senescence in hydra: comment on Martinez, D., "Mortality patterns suggest lack of senescence in hydra." Exp Gerontol 33, 217-25
Mouton S, Willems M, Houthoofd W, Bert W, Braeckman BP. Exp Gerontol. 2011 Sep;46(9):755-61. doi: 10.1016/j.exger.2011.04.003. Epub 2011 Apr 23. Lack of metabolic ageing in the long-lived flatworm Schmidtea polychroa.
Declining asexual reproduction is suggestive of senescence in hydra: comment on Martinez, D., "Mortality patterns suggest lack of senescence in hydra." Exp Gerontol 33, 217-25
Mouton S, Willems M, Houthoofd W, Bert W, Braeckman BP. Exp Gerontol. 2011 Sep;46(9):755-61. doi: 10.1016/j.exger.2011.04.003. Epub 2011 Apr 23. Lack of metabolic ageing in the long-lived flatworm Schmidtea polychroa.
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