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.

Fertilization in C. elegans

S. Ward, G. Korman, J. Carrel

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.