Worm Breeder's Gazette 2(2): 13
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 process of fertilization requires the interaction of gametes that must have specialized macromolecules on their surface that promote cell adhesion and penetration. By studying fertilization in detail and by isolating mutants blocked in fertilization, our laboratory hopes to investigate the genetic control of the cell surface architecture of the gametes. We have begun by studying the normal process of fertilization in C. elegans and the morphology of the sperm with light and electron microscopy. In the hermaphrodite, sperm accumulate in the spermatheca. They first contact an oocyte in the oviduct as the oocyte matures adjacent to the spermatheca. When the oocyte is mature, contractions of the oviduct wall push into the spermatheca where it contacts many sperm. It is then squeezed into the uterus through a constriction at the end of the spermatheca. Supernumerary sperm carried into the uterus on the oocyte abruptly migrate back through the constriction to the spermatheca so that every sperm can fertilize an oocyte. When males mate with hermaphrodites they deposit their sperm in the region of the vulva and these sperm migrate past the zygotes in the uterus to the spermatheca. When the male sperm arrive at the spermatheca they preferentially fertilize the subsequent oocytes even though hermaphrodite sperm are still present. The sperm are ameboid cells with a specialized pseudopodial region that is extended from the cell while the sperm is migrating. The sperm contain specialized membraneous vesicles that can fuse with the plasma membrane. In one fertilization defective mutant this fusion does not occur, in another the vesicles have altered fine structure. Sperm extracted into buffer from males or hermaphrodites initially appear as irregular round cells 5-7 m in diameter, but after a few minutes they begin to extend long filamentous processes that can grow to as long as 40 m. Such processes are not seen on sperm inside the hermaphrodite and their origin and role in fertilization is unclear.