Regeneration of oral siphon pigment organs in the ascidian Ciona intestinalis Hélène Auger1, Yasunori Sasakura2, Jean-Stéphane Joly1, and William R. Jeffery3, 4 1INRA MSNC Group, DEPSN, Institut A. Fessard, CNRS, 1 Avenue de la Terrasse, 91198 Gif- Sur-Yvette, France, 2Shimoda Marine Research Center, University of Tsukuba, Shimoda, Shizuoka, Japan, 3 Marine Biological Laboratory, Woods Hole, MA 02543 USA, and 4 Department of Biology, University of Maryland, College Park, MD 20742, USA. Running title: Siphon pigment organ regeneration in Ciona Address for Correspondence: William R. Jeffery Department of Biology University of Maryland College Park, MD 20742 USA
[email protected] 1-301-405-5202 (Telephone) 1-302-314-9358 (Fax) 1 Abstract Ascidians have powerful capacities for regeneration but the underlying mechanisms are poorly understood. Here we examine oral siphon regeneration in the solitary ascidian Ciona intestinalis. Following amputation, the oral siphon rapidly reforms oral pigment organs (OPO) at its distal margin prior to slower regeneration of proximal siphon parts. The early stages of oral siphon reformation include cell proliferation and re-growth of the siphon nerves, although the neural complex (adult brain and associated organs) is not required for regeneration. Young animals reform OPO more rapidly after amputation than old animals indicating that regeneration is age dependent. UV irradiation, microcautery, and cultured siphon explant experiments indicate that OPOs are replaced as independent units based on local differentiation of progenitor cells within the siphon, rather than by cell migration from a distant source in the body. The typical pattern of eight OPOs and siphon lobes is restored with fidelity after distal amputation of the oral siphon, but as many as sixteen OPOs and lobes can be reformed following proximal amputation near the siphon base.