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RESEARCH PRODUCT

Ingestion, digestion, and egestion in Spongilla lacustris (Porifera, Spongillidae) after pulse feeding with Chlamydomonas reinhardtii (Volvocales)

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description

The route followed by food particles in Spongilla lacustris was clarified by light and electron microscopic examination of sponges fed with Chlamydomonas reinhardtii. The algal cells are phagocytosed by prosendopinacocytes and choanocytes. After some time they are transferred to archaeocytes, amoebocytes, and lophocytes. Changes in algal structure during digestion were observed and the egestion of algal remnants was documented in life for the first time. In light micrographs, digestion of the algal cells is manifest first in shrinkage of the cells, then in disintegration to form several spherical green fragments 2–3 μm in diameter, and finally, after 12–18 h, in a reddish brown discoloration of the fragments. Signs of the digestive process in electron micrographs include disappearance of the cell-wall layers, the flagella, and the pyrenoid and its starch sheath, as well as a progressive increase in the density of the cytoplasm and karyoplasm.