Donna and Tito-
Actually, ascidian "smooth" muscle can come very close to conventional striated muscle. Terakado & Obinata 1987 (cited by Burighel and Cloney in Ch 4 of Vol 15 of Microscopic Anatomy of Invertebrates 1997) show recognizable sarcomeres in Halocynthia with thick filaments defining the A zone, thin filaments and "dense bodies" ( equivalent to Z bands) defining the I zone. The EM pictures are quite convincing I think. Burighel and Cloney say the muscle has "intermediate characteristics" between smooth and striated but to me it looks like striated muscle in which the sarcomeres are not perfectly in register laterally. Sveva.
__________________________________________________________________
Get your own FREE, personal Netscape Webmail account today at http://webmail.netscape.com/
|