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Demographic analysis reveals gradual senescence in the flatworm Macrostomum lignano.

Mouton S, Willems M, Back P, Braeckman BP, Borgonie G - Front. Zool. (2009)

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nematology Unit, Department of Biology, Ghent University, Ledeganckstraat 35, 9000 Ghent, Belgium. stijn.mouton@ugent.be.

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 90th 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.

No MeSH data available.


Survival curve of Macrostomum lignano. The grey curves are the survival curves of the separate replicate cohorts. The black, bold curve represents the average overall survival curve of the three replicate cohorts.
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Figure 1: Survival curve of Macrostomum lignano. The grey curves are the survival curves of the separate replicate cohorts. The black, bold curve represents the average overall survival curve of the three replicate cohorts.

Mentions: The data presented here were obtained in three replicate cohorts, maintained under controlled culture conditions. In M. lignano, the average (± SD) median lifespan is 205 ± 13 days, the 90th percentile lifespan 373 ± 32 days, and the maximum lifespan more than 745 days (2.04 years). While all individuals in replicate 1 and 2 were already dead at this age, 4% of the individuals in replicate 3 are still alive (figure 1). The lifespan data of the separate replicates are listed in table 1, and individuals of four, 27 and 76 weeks old are presented in figure 2 to illustrate the morphological changes as a function of age. The maximum lifespan here observed is considerably longer than 42 weeks (0.8 year), which was previously reported by Egger et al. [8]. These authors noted, however, that culture limitations like bacteria or parasites may have shortened the lifespan of the specimens. It is remarkable that the maximum lifespan of 745 days is twice as long as the 90th percentile lifespan, which is visualised by the long tail in the survival curve (figure 1), and more than three times the median lifespan, indicating a levelling off of the mortality rate acceleration at advanced ages (see below). This phenomenon was previously described in large medfly cohorts by Carey et al. [5]. Furthermore, these authors concluded that medflies appear not to have a characteristic lifespan, because they observed different maximum lifespans in the several cohorts. Because the maximum lifespan is based on only one individual in the cohort, it results in a great variability which can also be observed in M. lignano (table 1). Therefore it is better to use more reliable statistics such as the median lifespan and 90th percentile when demographic data are compared among laboratories, or in experiments studying lifespan extension and rejuvenation.


Demographic analysis reveals gradual senescence in the flatworm Macrostomum lignano.

Mouton S, Willems M, Back P, Braeckman BP, Borgonie G - Front. Zool. (2009)

Survival curve of Macrostomum lignano. The grey curves are the survival curves of the separate replicate cohorts. The black, bold curve represents the average overall survival curve of the three replicate cohorts.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2724480&req=5

Figure 1: Survival curve of Macrostomum lignano. The grey curves are the survival curves of the separate replicate cohorts. The black, bold curve represents the average overall survival curve of the three replicate cohorts.
Mentions: The data presented here were obtained in three replicate cohorts, maintained under controlled culture conditions. In M. lignano, the average (± SD) median lifespan is 205 ± 13 days, the 90th percentile lifespan 373 ± 32 days, and the maximum lifespan more than 745 days (2.04 years). While all individuals in replicate 1 and 2 were already dead at this age, 4% of the individuals in replicate 3 are still alive (figure 1). The lifespan data of the separate replicates are listed in table 1, and individuals of four, 27 and 76 weeks old are presented in figure 2 to illustrate the morphological changes as a function of age. The maximum lifespan here observed is considerably longer than 42 weeks (0.8 year), which was previously reported by Egger et al. [8]. These authors noted, however, that culture limitations like bacteria or parasites may have shortened the lifespan of the specimens. It is remarkable that the maximum lifespan of 745 days is twice as long as the 90th percentile lifespan, which is visualised by the long tail in the survival curve (figure 1), and more than three times the median lifespan, indicating a levelling off of the mortality rate acceleration at advanced ages (see below). This phenomenon was previously described in large medfly cohorts by Carey et al. [5]. Furthermore, these authors concluded that medflies appear not to have a characteristic lifespan, because they observed different maximum lifespans in the several cohorts. Because the maximum lifespan is based on only one individual in the cohort, it results in a great variability which can also be observed in M. lignano (table 1). Therefore it is better to use more reliable statistics such as the median lifespan and 90th percentile when demographic data are compared among laboratories, or in experiments studying lifespan extension and rejuvenation.

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nematology Unit, Department of Biology, Ghent University, Ledeganckstraat 35, 9000 Ghent, Belgium. stijn.mouton@ugent.be.

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 90th 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.

No MeSH data available.