Willenz, P; Van de Vyver, G. (1982). Endocytosis of Latex Beads by the Exopinacoderm in the Fresh Water Sponge Ephydatia fluviatilis an in Vitro and in Situ Study in SEM and TEM. Journal of Ultrastructure Research. 79: 294-306.
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Willenz, P; Van de Vyver, G.
1982
Endocytosis of Latex Beads by the Exopinacoderm in the Fresh Water Sponge <i>Ephydatia fluviatilis</i> an in Vitro and in Situ Study in SEM and TEM
Endocytosis capability of the dermal membrane of Ephydatia fluviatilis has been demonstrated in vitro and in situ using two different sizes of calibrated Latex beads. After a preliminary adhesion to the cell coat, 5.7- and 0.109-/~m beads were endocytized by exopinacocytes. Some ingestion mechanisms appeared to depend upon particle size. In vitro, with 0.109-/zm beads, the exopinacocyte cell surface creased, forming ruffles in the central area of the cells. In vitro and in situ, 0.109-/zm beads were observed to slip through gaps in the dermal membrane. In addition to their conventional role as an inhalent pore, porocytes were shown to possess a particle retention ability, which remained even in the case of complete closure of the ostia. Endocytosis, occurring on the whole sponge surface, points out the importance of exopinacocytes in particle retention, bypassing the choanocytes in their capture role.