Regeneration and Morphogenesis in the Feather Star Arm

The regeneration of the arm of the crinoid Antedon mediterranea has been studied by means of LM, TEM, and SEM techniques as regards the development of both the external form and the internal anatomical organization. According to the timing and the modalities of development of the different structures and their reciprocal interactions, three main stages can be recognized in the morphogenesis of the whole arm: 1) a coelom-dependent stage, 2) a nervous system-dependent stage and 3) a skeleton-dependent stage. Moreover, using histofluorescence and immunohistochemical methods to visualize catecholamines and indolamines, it has been possible to reveal the presence of dopamine and serotonin and follow the fluctuations and the different involvements of these neuro-trasmitters during the regeneration process.