• colonial ascidian;
  • tunicate;
  • Botryllus;
  • regeneration;
  • serotonin;
  • nervous system;
  • muscle


Botryllus schlosseri is a colonial ascidian, and the closest relative to vertebrates that can completely regenerate its entire body, including all somatic and germline tissues, using an asexual developmental pathway called blastogenesis. This regenerative potential exhibited by Botryllus and other colonial ascidians does not exist in any other chordate and makes B. schlosseri a promising model to investigate the cellular and molecular basis of regeneration. In this report, we describe postembryonic myogenesis and characterized the development of the neural system during blastogenic development. α-Tubulin immunoreactivity revealed a high correlation with previous studies on the motor nervous system. The pattern of the serotoninergic system in the adult reflects that observed in solitary ascidians, but in early blastogenesis suggests a morphogenic role of this monoamine. In summary, this study provides the morphological framework to dissect the mechanisms underlying the ability to regenerate entire organ systems as an adult in a chordate model. Developmental Dynamics 238:2081–2094, 2009. © 2009 Wiley-Liss, Inc.