Elektronenmikroskopische Untersuchungen anAnaitides mucosa (Annelida, Polychaeta). Cuticula und Cilien, Schleimzellen und Schleimextrusion

Abstract

Electron microscopical studies on Anaiffdes mucosa (Annelida, Polychaeta). Cuticle and cilia, mucous cells and mucus extrusion. Two components, a basal cuticle and an epicuticle, make up the cuticle of A. mucosa. The basal cuticle consists of collagen fibrils, which are arranged in about 20 layers. The orientation of the fibrils changes rectangularly from one layer to the next. Fine filaments interweave the basal cuticle. The epicuticle, which is covered by a layer of electron dense material, is composed of irregularly arranged thin filaments. Branched microvilli of the epidermal cells penetrate the cuticle. Bacteria are found in the basal cuticle. Dorsally each segment has a band of densely packed smooth cilia. Laterally and partly ventrally aggregates of cilia are observed. These cilia exhibit apically artificial swellings. At least six different mucous cells are observed in the epidermis, morphologically distinguishable by the structure of the secretion products. Mucus is secreted via exocytosis through cuticular pores. During this process the mucus might expand. The secreted mucus consists of filamentous subunits. EINLEITUNG

Ultrastructural observations on feeding appendages and gills ofAlvinella pompejana (Annelida, Polychaeta)

“…Their function, however, remains to be elucidated. In AnaitJdes mucosa, Hausmann (1982) found many kinds of mucous cells, but could not explain their function. On sectional preparations, one cannot even see whether they, in fact, correspond to different cell types, or whether they merely represent different phases of maturation of one cell type.…”

“…Findings on Ampharetidae are lacking. Mucous cells have been investigated by Bielakoff et al (1975), Dorsett & Hyde (1969), Hausmann (1982), Hilbig (1986), Kryvi (1972), Martin (1978), Storch & Welsch (1972), again excluding the aforementioned family.…”

Comparative structure of the epidermis in polychaetes (Annelida)

“…Several ultrastructural descriptions of secretory cells reflect the high structural diversity of the secretions from compact material to fine filamentous or granular material packed in vesicles of various sizes or in sometimes highly ordered arrangements, which seemingly may lack a surrounding membrane (Dorsett & Hyde, 1970a, b;Kryvi, 1972;Storch & Welsch, 1972;Hausmann, 1982;Welsch et al, 1984;Hilbig, 1986b;Storch, 1988;Gardiner, 1992b). Histochemical investigations revealed that epidermal cells can secrete many different substances including glycosaminoglycans like hyaluronic acid, different mucopolysaccharids, mucoproteins, proteins, enzymes, phenols, and varying inorganic components (Dorsett & Hyde, 1970a, b;Defretin, 1971;Kryvi, 1971;Moermans, 1974;Bielakoff et al, 1975;Vovelle, 1979;Vovelle & Gaill, 1986;Vovelle et al, 1994).…”

“…1E, F) and a lot of microtubules may occur in the cell apex of secretory cells. Both structures are discussed to assist in controlling the secretion process (Storch & Welsch, 1972;Richards, 1978;Hausmann, 1982;Storch, 1988). In certain secretory cells of Spiochaetopterus typicus the opening is surrounded by kinocilia (Storch, 1988).…”

Complex epidermal organs of Phascolion (Sipuncula): insights into the evolution of bimodal secretory cells in annelids

“…muco‐polysaccharids, proteins, enzymes, phenols) to inorganic compounds (e.g. Dorsett and Hyde ,b; Defretin ; Kryvi , ; Storch and Welsch ; Moermans ; Anctil ; Vovelle ; Hausmann ; Welsch et al . ; Hilbig ,b; Vovelle and Gaill ; Storch ; Gardiner ; Vovelle et al .…”