Summary
A specialized structure of tunic cord inPolyandrocarpa misakiensis is investigated by electron microscopy. The tunic cord is a cord-like coiled structure of 5–30 μm in diameter and 0.1–9.0 mm in length. The tunic cords originate and elongate from the dorsal tunic, and their termini have a swollen and ornamented structure. Scanning and transmission electron micrographs and the electron diffractogram show that the tunic cords are composed of bundled microfibrils of cellulose I with high crystallinity. The tunic cord is completely surrounded by single-layered epidermal cells, which have been found as the site of cellulose biosynthesis. A number of tunic cords are connected to the internal tunic of the siphon by forming “eyelet” structures at their termini. These observations suggest that the tunic cords act as a connector between dorsal and internal tunic of the siphon.
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Kimura, S., Itoh, T. A new cellulosic structure, the tunic cord in the ascidianPolyandrocarpa misakiensis . Protoplasma 204, 94–102 (1998). https://doi.org/10.1007/BF01282297
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DOI: https://doi.org/10.1007/BF01282297