Irina M. Drobysheva
Zoological Institute, Russian Academy of Sciences, Universitetskaya nab.1, St. Petersburg, 199034, Russia
Mitotic activity was studied in two polyclads Notoplana humilis (Stimpson, 1857) and Prosthiostomum ostreae Kato 1937 by means of the (3H)thymidine and colchicine. The intact embryos and larvae of N. humilis (direct development) and Cycloporus japonicus Kato 1944 (development with Müller's larva) were examined to calculate the mitotic figures and to determine their disposition. The present investigation suggests that in polyclads the formation of the definitive epidermis is associated with disappearance of the mitotic cells in the integument which occurs on different stages of the morphogenesis. The time of this disappearance seems to depend on the development type of the polyclad. Instead, the formation of the definitive gastrodermis is linked with the appearance of the mitotic cells in the intestine isolating itself from the parenchyma. The current study has shown that the polyclad with the Müller's larva present the first example of a "turbellarian" with ectodermal mitotic activity at the late stages of morphogenesis.
Valentin P. Semyanov & Nina P. Vagina
Zoological Institute, Russian Academy of Sciences, Universitetskaya nab., 1, St. Petersburg, 199034, Russia
Adult H.sedecimnotata beetles possessed a well pronounced trophic diapause; no photoperiodic diapause was found. In contrast to constantly ovipositing females, a strong increase fecundity (93%) was found in females fed on aphids after a 30-day long trophic diapause. The state of the trophic diapause itself had a little affect on part of females (14%) longevity.