On the Occurrence and Structure of Choanocyte-like Cells in Some Echinoderms

Abstract

Choanocyte‐like cells with a collar of regularly arranged cylindrical microvilli around the base of the flagellum were observed in the ciliary bands of the Brachiolaria larva of Asterias rubens. The ambulacral ampullae and coelomic epithelia of adult Asterias and coelomic epithelia of Mesothuria contain similar cells with radial lamellae instead of cylindrical microvilli. Other similar but more modified types of cells, in which the inner edges of the radiating lamellae could be recognized as longitudinal ridges in the wall of a cylindrical flagellar pit, were found in ambulacral ampullae of Porania and in coelomic epithelia of Stichopus. Distinct indications of phagocytosis were seen in most of these cells. The present report together with previously published data lend support to the idea, that the choanocyte is a fundamental cell type in metazoans, probably derived phylogenetically from some flagellate ancestor.

Water flow analysis and particle capture in ciliary suspension-feeding scallops (Pectinidae)

“…From Owen & McCrae (1976) MATERIALS AND METHODS SEM observations. The structure of the ciliary systems was studied on scanning electron micrographs (SEM) of gill fragments dissected out of small specimens of Palliolium furtivum (Lovén) (Pecten furtivus) and Aequipecten opercularis (Linnaeus) (Pecten opercularis), obtained from the Marine Biological Laboratory, Helsingør (Denmark), quick-frozen by liquid N 2 (-210°C, in an attempt to preserve ciliary metachronic waves) and subsequently fixed in 2% OsO 4 , and further prepared according to the freeze-drying technique described by Nørrevang & Wingstrand (1970).…”

Bacterial Influences on Animal Origins

“…Epithelial cells, which are conserved in all animal lineages, may also be related to the ancient bacteria-eating collar cells of the Urmetazoan. The apical-basal polarity of epithelial cells, their possession of an apical primary cilium surrounded by microvilli, and phagocytic activity provide parallels to some of the most diagnostic features of collar cells (Norrevang 1964;Nerrevang and Wingstrand 1970;Walker 1979;Martinez et al 1991;Singla and Reiter 2006).…”

“…The notion that the first animals used a filter-feeding collar cell to capture bacteria provides a useful starting point for reconstructing bacterial influences on animal origins. Although collar cells were once thought to be restricted to choanoflagellates and sponges, collar cells have now been documented in cnidarians (Lyons 1973;Goldberg and Taylor 1989b;Peterson 2004), echinoderms (Nerrevang and Wingstrand 1970;Walker 1979;Martinez et al 1991), ascidians (Milanesi 1971), and hemichordates (Norrevang 1964). In cnidarians, some presumptive collar cells act as phagocytic feeding cells in the gastrodermis (Lyons 1973).…”

The microvilli and hyaline layer of embryonic asteroid epithelial collar cells: A sensory structure to determine the position of locomotory cilia?

“…They are found in many diverse species of marine and aquatic invertebrates such as adult sponges (Fjerdingstad, 19611, adult and larval cnidarians (Goreau and Philpot, 1956;Bilbaut and Pavons de CeCatty, 1971;Lyons, 1973a,b;Clark and Dewel, 1974;Chia and Crawford, 1977;Goldberg and Taylor, 1989a,b), ascidians (Milanisi, 1971), enteropneusts (Norrevang, 19641, and molluscs (Stauffacher, 1898;Schneider, 1902). They have also been reported in the epithelial cells of larvae of echinoids and asteroids (Wolpert and Mercer, 1963;Lyons et al, 1964;Norrevang and Wingstrand, 1970;Immers and Lundgren 1972;Lundgren, 1973;Schemkel, 1975;Walker, 1979;Anstrom, 1992) review see Walker, 1979) (Martinez et. al., 1991).…”