Title:
Skeleton construction of sponges: the simple and accordingly robust mechanisms underlying both their plastic growth and phenotypic plasticity

 

Speaker:
Noriko Funayama
Laboratory of Molecular Developmental Biology
Department of Biophysics, Graduate School of Science, Kyoto University

 

Abstract:
Animal bodies are shaped by skeletons. Thus, determining the mechanisms of how a skeleton forms is one of the important issues for understanding how the body forms. In all of the well-studied examples of skeleton construction of animals, such as in vertebrates, echinoderms and arthropods, skeletons’ shapes are a direct reflection of the pattern of skeleton-producing cells. Although it was known that internal skeletons of sponges consist of spicules assembled into large pole-and-beam structures with a variety of morphologies, before our study, almost nothing was known about the spicule-assembly-process (i.e., how spicules become held up and connected basically in staggered tandem). Our work revealed that sponges have a fundamentally different mode of skeleton construction that enables them to construct their skeleton to adjust and link it to their plastic and indeterminate growth. Fine skeletal elements (spicules) are dynamically carried from where they are produced by transport cells, which we discovered and identified, and the spicules are then held up or connected to the spicule-constructing skeleton one by one. As the result of the iterations of sequential physical reactions of player cells (in situation A, do B), spiculous skeleton is self-organized. As sponges are sessile organisms, their morphology varies among individuals and also differs depending on their environment. The advantages of this fundamentally new mechanism of skeleton construction for plastic growth and phenotypic plasticity of sponges will be discussed together with our new experimental approaches.

 

References:
Nakayama et al. Current Biology 25:1-6 (2015)
Alie et al. Proc. Natl. Acad. Sci. 112（5）：E7093-E7100（2015）
Funayama N. Dev. Genes. Evol. 223:23-38 (2013)