. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 3. (A) Cross section through several attached ctenidial fila- ments. Nearly the entire filament consists of bacteriocytes (arrowheads). The ventral edge (*) contains a wide hemocoelic vessel; the dorsal edge is attached to the mantle (azan-stained paraffin section, light micro- graph). Scale 1 mm. (B) Details of filament, median cross section, show- ing the two layers of bacteriocytes (b) separated by the middle lamella (ml). Scale 100 fjm. (C) Scanning electron micrograph of bacteriocytes with cell wall peeled open s
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 3. (A) Cross section through several attached ctenidial fila- ments. Nearly the entire filament consists of bacteriocytes (arrowheads). The ventral edge (*) contains a wide hemocoelic vessel; the dorsal edge is attached to the mantle (azan-stained paraffin section, light micro- graph). Scale 1 mm. (B) Details of filament, median cross section, show- ing the two layers of bacteriocytes (b) separated by the middle lamella (ml). Scale 100 fjm. (C) Scanning electron micrograph of bacteriocytes with cell wall peeled open showing the dense packing of bacteria (b). Scale 5 ^m. layers (width varying between 2 and 15 /jm) harbors mus- cles, nerves, connective tissue, hemocoel with hemocytes, and additional extracellular material. At the distal, ventral edge of the filament the two layers of extracellular mate- rial become very thick (50 pm) and join, enclosing a wide hemocoelic vessel that extends all along the lower edge of the ctenidial length. In fixed material the hemocoelic space appears more or less empty, containing only some granular material, possibly remnants of the blood fluid (Fig. 5A). At the boundary walls, very flat cells are abun- dant (Fig. 5C). Each cross section through a filament (dorsal to ventral, see Fig. 2) can be subdivided into six zones, five of which represent the symbiont-free parts, the remaining large one the symbiont-containing median part of the ctenidial fil- ament (for numbering see Fig. 4). Zones 1-4 form the lower (ventral) axis of the filament, zone 6 the upper (dorsal) edge. Symbiont-free parts. The five zones that lack symbionts are described below. Zone 1—the ventral edge of the filament (Fig. 5A). It consists of a ciliated epithelium with cells having a height of 10 to 20/jm and containing large nuclei (5 /jm long). Externally, they are covered by ^m long microvilli and by several 5 pm long cilia. Glandular cells are abundant and contain electron-luce
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
