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Figure 4 | Frontiers in Zoology

Figure 4

From: Ultrastructure of book gill development in embryos and first instars of the horseshoe crab Limulus polyphemus L. (Chelicerata, Xiphosura)

Figure 4

A complex outgrowth of cells (C) from the base of the genital operculum after the third embryonic molt (stage 20). Limulus polyphemus. TEM. Such somewhat erratic outgrowths may be helpful for gas exchange, and they result in a knobby outer wall as commonly occurs for opisthosomal appendages at this stage (Figures 2A, B and 3). As described in more detail below, a thin cuticle (Cu) is secreted by these cells. Scale, 5 μm.

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