Size and shape control dynamics in an early diverging animal

Animals have traditionally been characterized as clonal cell populations with complex tissue architectures which have specific developmental programs that guide the morphogenesis of organs and in turn whole animals. On the other hand, very early diverging metazoans display simple tissue architecture with a lesser division of labour that allows high plasticity and scalability. High plasticity in such tissues allows dynamic shape changes at time scales of ~five minutes and a scalable tissue architecture allows size variation of over two orders of magnitude. For such tissues, size and shape are deeply interdependent due to physical constraints. Using high throughput long term scanning microscopy, we collect datasets on shape and size variation in lab culture conditions and quantify their temporal trajectories. Using perturbations to these 'natural' trajectories, we decouple size and shape parameters to decipher the principles that the system uses to exercise control over growth. Utilizing large datasets and growth-based models, our study provides abstract principles that would have governed size and shape control in very primitive `animal-like' multicellular clusters.