Physiology and Ecology of Marine Bryozoans

Abstract

Publisher Summary This chapter reviews the physiology and ecology of marine bryozoans and presents the latest research in these fields to marine biologists generally rather than to bryozoologists particularly. Three classes are recognized: Phylactolaemata, Stenolaemata, and Gymnolaemata. The first of these is confined to fresh water; the second comprises those bryozoans with slender, tubular, calcified walls; the third is the dominant and most diverse marine class. A new bryozoan colony normally arises from a sexually produced larva. In stenolaemates the larva metamorphoses into the proancestrula, a hemispherical body that later elongates to form a tubular extension housing the polypide. Colony form in erect, branching species is known to be labile. Harmelin has studied the relationships between the branching pattern of the cyclostomes “Idmonea” atlantica and environmental factors. The chapter discusses the reproduction, larvae and metamorphosis of marine bryozoans. The larval organization completely breaks down during metamorphosis and, in Electra, a new structure, the ancestrula or primary zooid of the colony, arises in its place. During metamorphosis, which has been described by Atkins, there is a reversal of internal polarity: the distal end of the polypide and the blastogenic face of the ancestrula correspond to the posterior of the larva. The geographical distribution of marine bryozoans is discussed in the chapter.