Taxonomy and Biology ofPelosina Arborescenswith Comparative Notes onAstrorhiza Limicola(Foraminiferida)

Abstract

The diagnosis of Pelosina arborescens Pearcey, 1914 is amended: only the Scottish specimens of the original description are now included in the species. Factors like water current, aquarium conditions, bioturbation and rough sampling and handling may cause a wide morphological variation which earlier caused uncertainty about the identity of the species. "It was studied on the Swedish west coast, where it may reach 60 mm in length. It occurs below the halocline on bottoms with little bioturbation. It is a suspension feeder. The granuloreticulopodia are extended in the water, where they collect planktonic algae and detritus. It adapts its form according to the prevailing water current. The erect form allows it to penetrate the viscous sublayer and reach the turbulent boundary layer, where food is more plentiful. Studies of the functional biology of P. arborescens suggest that the shape and size of the test are adaptations that also protect against bioturbation and predation but may restrict the respiratory surface. Field observations and laboratory experiments under anoxic conditions show that P. arboresens can live anaerobically. Histological analysis of the protoplasm revealed large amounts of glycogen which may be used during anoxic periods. Some aspects of the biology are compared with Astrorhiza limicola.