Memory and obesity affect the population dynamics of asexual freshwater planarians.
Asexual reproduction in multicellular organisms is a complex biophysical process that is not yet well understood quantitatively. Here, we report a detailed population study for the asexual freshwater planarian Schmidtea mediterranea, which can reproduce via transverse fission due to a large stem cell contingent. Our long-term observations of isolated non-interacting planarian populations reveal that the characteristic fission waiting time distributions for head and tail fragments differ significantly from each other. The stochastic fission dynamics of tail fragments exhibits non-negligible memory effects, implying that an accurate mathematical description of future data should be based on non-Markovian tree models. By comparing the effective growth of non-interacting planarian populations with those of self-interacting populations, we are able to quantify the influence of interactions between flatworms and physical conditions on the population growth. A surprising result is the non-monotonic relationship between effective population growth rate and nutrient supply: planarians exhibit a tendency to become 'obese' if the feeding frequency exceeds a critical level, resulting in a decreased reproduction activity. This suggests that these flatworms, which possess many genes homologous to those of humans, could become a new model system for studying dietary effects on reproduction and regeneration in multicellular organisms.
Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, UK. j.dunkel@damtp.cam.ac.uk
Jörn
J
Dunkel
Jared
J
Talbot
Eva-Maria
EM
Schötz
D000818:Animals; D005523:Food Supply; D056145:Freshwater Biology; D019083:Mediterranean Region; D008568:Memory; D023421:Models, Animal; D009765:Obesity; D010932:Planarians / Q000254:growth & development / Q000502:physiology*; D011157:Population Dynamics; D012100:Reproduction, Asexual