Gametogenesis in placental and non-placental ovicellate cheilostome Bryozoa



Oogenesis is compared in two cheilostome bryozoans with contrasting reproductive strategies. from southern Britain: Chartella papyracea (Ellis & Solander) is a non–placental ovicellate brooder, whereas Bugula flabellata (Thompson in Gray) is a placental brooder. The ovarian cycles are similar, and each oocyte develops in tandem with a single nurse cell. Eggs of both species are telolecithal, However, those of B. flabellata are less than 20% the volume of those of the other species, and there are considerable differences in the ultra-structure of oogenesis. In both cases, spermatogenesis has the typical bryozoan pattern. Precocious insemination of the oocyte occurs in both species.