Worm Breeder's Gazette 2(2): 6

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.

Post-embryonic Lineages of the Somatic Structures of the Gonad in Hermaphrodites and Males

J. Kimble

The post-embryonic lineages of both the hermaphrodite and the male 
gonads have been determined by direct observation in living worms.  
Although the adult male and hermaphrodite gonads are quite different 
from each other, their lineages have a number of common features.  
Both male and hermaphrodite gonads arise from a gonadal primordium 
consisting of four cells (named 1, 2, 3 and 4 from anterior to 
posterior).  Two of these cells (1 and 4) are somatic, and two (2 and 
3) are germ line precursor cells.  In each sex, the lineage of the 
somatic cells proceeds according to a nearly invariant pattern with 
respect to the number of cell divisions, cell migrations, and the 
final fates of specific daughter cells.  The lineage of the germ line 
cells is invariable.  In each sex, the somatic precursor cells undergo 
an early period of cell divisions (late L1-early L2).  These early 
divisions give rise to 10 cells in the male and 12 cells in the 
hermaphrodite.  These cells do not divide again until early L3 when 
they divide extensively to generate all the cells present in the adult 
somatic structures.  The hermaphrodite somatic structures include the 
anterior sheath, the anterior spermatheca, the uterus, the posterior 
spermatheca, and the posterior sheath.  The male somatic structures 
include the seminal vesicle, and vas deferens.  In the hermaphrodite, 
the quiescent period during L2 is characterized by a migration of the 
cells.  The cells of the male migrate during the early period of cell 
division and simply grow larger during L2.  In both males and 
hermaphrodites there seems to be a general rule that a clone of cells 
does not define a given structure.  Instead, both cell 1 and cell 4 
contribute some daughters to each structure.  The anterior and 
posterior sheaths are the only exception since each is comprised 
exclusively of daughters of cell 1 (anterior) or cell 4 (posterior).  
Finally, there is an indication in the hermaphrodite lineage of an 
effect of position on the lineage pattern.  At the L2-L3 stage in 
hermaphrodites the cells that will give rise to the ventral uterus and 
anchor cell assume one of two different configurations (3L or 3R).  
The cells follow one lineage pattern from the 3L configuration, and a 
different lineage from the 3R configuration.  The two alternative 
lineages, however, give rise to equivalent structures.