Short report

Demographic analysis reveals gradual senescence in the flatworm Macrostomum lignano

Stijn Mouton¹ , Maxime Willems¹ , Patricia Back² , Bart P Braeckman² and Gaetan Borgonie¹

¹  Nematology Unit, Department of Biology, Ghent University, Ledeganckstraat 35, 9000 Ghent, Belgium

²  Research Group for Aging Physiology and Molecular Evolution, Department of Biology, Ghent University, Ledeganckstraat 35, 9000 Ghent, Belgium

author email corresponding author email

Frontiers in Zoology 2009, 6:15doi:10.1186/1742-9994-6-15

Published:	30 July 2009

Abstract

Free-living flatworms ("Turbellaria") are appropriate model organisms to gain better insight into the role of stem cells in ageing and rejuvenation. Ageing research in flatworms is, however, still scarce. This is partly due to culture difficulties and the lack of a complete set of demographic data, including parameters such as median lifespan and age-specific mortality rate. In this paper, we report on the first flatworm survival analysis. We used the species Macrostomum lignano, which is an emerging model for studying the reciprocal influence between stem cells, ageing and rejuvenation. This species has a median lifespan of 205 ± 13 days (average ± standard deviation [SD]) and a 90^th percentile lifespan of 373 ± 32 days. The maximum lifespan, however, is more than 745 days, and the average survival curve is characterised by a long tail because a small number of individuals lives twice as long as 90% of the population. Similar to earlier observations in a wide range of animals, in M. lignano the age-specific mortality rate increases exponentially, but levels off at the oldest ages. To compare the senescence of M. lignano with that of other ageing models, we determined the mortality rate doubling time, which is 0.20 ± 0.02 years. As a result, we can conclude that M. lignano shows gradual senescence at a rate similar to the vertebrate ageing models Rattus norvegicus and Mus musculus. We argue that M. lignano is a suitable model for ageing and rejuvenation research, and especially for the role of stem cells in these processes, due to its accessible stem cell system and regeneration capacity, and the possibility of combining stem cell studies with demographic analyses.