Worm Breeder's Gazette 12(1): 50 (September 1, 1991)
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.
The ultimate fate of the anchor cell has been a puzzle for some time. As originally described by Judith Kimble, the anchor cell cytoplasmic boundary becomes indistinct in the latter part of the L4 stage and the nucleus drifts off to one side. We think that we may have solved this mystery from our EM reconstructions of the developing hermaphrodite gonad. A reconstruction was made of an animal that was fixed about twenty minutes after the terminal divisions of the vulval precursor cells. This was compared with another reconstruction that was done of an animal that was fixed at a later stage when the anchor cell cytoplasmic boundary had become indistinct but the nucleus was clearly identifiable on the dorsal extremity of the vulva primordium.
In the first reconstruction the anchor cell was a distinctive single cell. It had conspicuous ruffles in its plasma membrane adjacent to the F cells of the vulva primordium. The vulva primordium appeared to adhere to other cells in the uterus (probably the uv1 cells) as well as to the anchor cell at this stage. No basal lamina could be seen between the vulva primordium or the developing uterus, however a continuous basal lamina was seen adjacent to the vulva/uterus junction, suggesting that the vulva and uterus were bounded by a single basal lamina at this stage.
In the second reconstruction the anchor cell nucleus could be unambiguously identified from its position, yet it was clear that the anchor cell no longer existed as a single cell, but rather had fused with the use to form a thin hymen-like sheet that separates the uterine lumen from the vulval lumen. In the adult the use cell functions to attach the uterus laterally to the seam cells. The use cell has nine nuclei, four on the left and five on the right; the extra nucleus on the right presumably originates from the anchor cell. Although the anchor cell is in intimate contact with the developing vulva primordium for most of the period of its existence as a single cell, the use cell is not directly attached to the vulva, this attachment being made via the four mononucleate uv1 uterine cells.