. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 104 P. EMSCHERMANN *^ T UA Q * -* 'f '1 • K'l;^. Figure 8. a: Lime-twig thread, fixed during discharge hut before its total unfolding, hidden under adhering masses of secretion vesicles except at the top right. Visible at the bottom (arrow head) is the rim of the capsular extrusion opening; at the top right (*), between the secretion masses, the distal-most coiled part of the lime-twig thread is visible, b: Electron microscopic section through a loop of an ejected lime-twig thread; the cuticular core (arrows) is still covere
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 104 P. EMSCHERMANN *^ T UA Q * -* 'f '1 • K'l;^. Figure 8. a: Lime-twig thread, fixed during discharge hut before its total unfolding, hidden under adhering masses of secretion vesicles except at the top right. Visible at the bottom (arrow head) is the rim of the capsular extrusion opening; at the top right (*), between the secretion masses, the distal-most coiled part of the lime-twig thread is visible, b: Electron microscopic section through a loop of an ejected lime-twig thread; the cuticular core (arrows) is still covered by partly empty secretion vesicles (*): inset: Part of an extruded lime-twig thread at higher light microscopic magnification (a and inset in b Nomarski contrast; scale bars: a: 100 urn; b and inset: 10 ^m). ithelial cells can be found (Figs. 3, 5, 6, 1 Ib). Like the mucous cells of unknown function that occur in all lox- osomatids(Emschermann, 1982; 1994) and are scattered between the normal, uniform epidermal cells in the ten- tacles and the periatrial fold (Fig. 1 la), these paracapsular cells in L. brochobola are characterized by large, tightly packed vacuoles full of an electron-dense, granular mu- copolysaccharide material and by well-developed rough ER and Golgi complexes in the narrow plasmatic domains between them. Such epidermal mucous cell clusters in the vicinity of discharged capsules quite probably give rise to replacement lime-twig organs. I have found different developmental stages of lime- twig capsules in most of the specimens examined. Capsule differentiation starts from a rosette of four enlarged epi- dermal cells (Fig. 9c, inset) bulging out slightly below the underside of the epidermal layer. They contain the same large electron-dense vacuoles as the mucous cells men- tioned above (Fig. 9a). Judging from their arrangement, these clusters each seem to arise from single "mother- ; probably the above epidermal mucous cells. The ejectible t
Size: 1739px × 1437px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
