Worm Breeder's Gazette 11(3): 74
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
Reconstruction of the cellular organization of the vulva and uterus from electron micrographs is often difficult in the adult due to the presence of unfixed eggs in the gonad and the tissue stretching and distortion that occurs following vulva eversion at the L4 moult. We have found that late L4 animals are much easier to reconstruct and have undertaken a serial section reconstruction of the vulval and uterus. The L4 vulval primordium is made up of a stack of seven, multi- nuclear toroidal epidermal cells designated A, B1, B2, C, D, E & F ( the figure shows a transverse view of these cells to one side of the mid-line of the vulval orifice). They are attached to each other by desmosomes with their interior apical faces making up the lumen of the vulva. Cells B1 and B2 are fused in the adult into a single toroid ( designated B). The ventral-most cell in the stack (A) is attached by desmosomes to the adjacent syncytial epidermal cell (hyp-7) and the dorsal-most cell (F) to the uv1 cells of the uterus. The anterior and posterior regions of each toroidal cell contain the nuclei and are considerably thicker than the lateral regions. The lateral regions of A, B, & C become particularly thin after vulva eversion and in some cases may part. It seems likely that there are some local specializations between the vulval cells: E sends out lateral extensions and is attached to the seam cells on either side of the animal; the vm1 vulval muscles attach at the junction of C and D; D also seems to form a hinge point during vulval eversion, forming the rim to the vulval orifice in the adult. The vm2 vulval muscles are attached distally to seam cells in the same region as the lateral attachment of the E vulva cell. They are attached proximally to the junction of the F vulval cell and the uv1 cells of the uterus. The vm1 vulval muscles are attached distally to hyp-7, in a sub-ventral location between body muscle cells. They are attached proximally to the junction of the C and D vulval cells. The vulval muscles have well-defined myofilaments in the L4, but in contrast, the uterine muscles have a very different appearance at this stage with a very prominent ER and no obvious myofilaments. [See Figure 1]