Reproduction

Abstract

The vastness of the hydrosphere and environmental uncertainties characteristic of a pelagic existence favor specialized adaptive mechanisms in planktonic organisms to enhance survival and promote sufficient reproductive success to ensure continuity of the species. Planktonic foraminifera do not possess locomotory organelles, and under the best of circumstances seem to be able only to regulate their position vertically within the water column. Thus, they are particularly vulnerable to the uncertainties of water currents, turbulence, and other hydrodynamic events that may cause widespread dispersal or reduction in numbers of the individuals within a locale in the ocean. Massive motion of water (e.g., downwelling, upwelling or strong advective processes) as occurs in high energy regions of the ocean may disperse individuals of a population over a considerable volume of water. Widespread dispersal of individuals is not particularly problematic for asexual or monoecious sexual organisms as the offspring produced from a single parent are more likely to survive in a hospitable environment where competition by other members of the species is low. Sexually reproducing, dioecious organisms (gametes from different parent organisms must combine to form a zygote), however, require propinquity of gametes from the parent organisms to ensure zygote formation and production of the next generation.