. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. _^' Perioslrocum """^ Prismatic layer Nocerous layer Proto-nocre formation Proto-prism formation Periostracol groo»e. Shell Mantle cavity Figure 1. Formation of an intracellular proto-prisms (pp). Subunits (sit) with an outer coating attach to the iniracelliilar organelle (here shown with the vacoiile membrane removed) tire condensed and incorpor- ated into the structure of the prolo-prism (si). To the right of the la- beled proto-prisin has the vacuo/e membrane intact, (ca ). Figure 2. \acreous proto-p
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. _^' Perioslrocum """^ Prismatic layer Nocerous layer Proto-nocre formation Proto-prism formation Periostracol groo»e. Shell Mantle cavity Figure 1. Formation of an intracellular proto-prisms (pp). Subunits (sit) with an outer coating attach to the iniracelliilar organelle (here shown with the vacoiile membrane removed) tire condensed and incorpor- ated into the structure of the prolo-prism (si). To the right of the la- beled proto-prisin has the vacuo/e membrane intact, (ca ). Figure 2. \acreous proto-platelel slack being transported through the cell surface into the space between the mantle layer and perioslracum. The platelet is composed of several layers composed oj condensing subunits which are larger at the margin that in the central region. The surface of the eel! is covered with microvilli that contain subunits sized particles (arrow). It is proposed that the \nbiinits are released from the microvilli to cement the proto-p/ate/ets and proto-prisms into sheets of either interior nacreous shell (illustrated here! or the outer layer of prismatic shell. (;.) Figure 3. Groups ot pinto-plalelels emerging from the mantle MII/,ice /msl into the space between the perioslracum and mantle The platelets are fused together to jorm a commons sheet which eventually fuses with the prismatic to form the embryonic shell (ca. 1000X). Figure 4. Diagram of the mantle edge showing the proposed scheme of shell formation, through the mantle cell surface where they are assembled into the adult shell composed of prismatic and nacreous layers. The first figure shows the formation of a proto-prism from subunits. These subunits have two components: a core about ^m in diameter, and an outer coating that appears to be lost when the subunits form the shell. Figure 1 shows a proto-prism forming within a cell at the periostracal groove. On the surface the sub- units are large and less den
Size: 2074px × 1205px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
