Worm Breeder's Gazette 6(1): 24

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.

A Mutation Affecting Gamete Differentiation

L. Edgar

In the spermatogenesis mutant B245, spermatogenesis appears to be 
suppressed during growth at restrictive temperature, and normal 
oocytes appear at the developmental age at which sperm would be made.  
Pulse-up experiments on worms hatched within a one hour period show 
that the temperature sensitive period occurs between 6 and 16 hours 
post-hatching (25 C age). Pulse-down experiments show the same 
discrete time period during which worms are fertile if shifted to 
permissive temperature.  This tsp occurs during the late L1-early L2 
somatic gonad divisions.  At a given age during the tsp, the fraction 
of sterile worms increases exponentially with increasing time at 25 C, 
with sterile worms appearing after as little as 15 minutes at high 
temperature.  A 2-hour pulse was used to determine an age curve for 
the temperature sensitivity and gave a bell-shaped curve between 6 and 
16 hours with a peak at 12 hours.  Individual worms from such an 
experiment examined by Feulgen staining show three classes.  Worms are 
either fertile (approximate 160 sperm per gonad arm), sterile (0 sperm 
per gonad arm); or semi-sterile (160 sperm in one gonad arm, and none 
in the other).  Either gonad arm may be sterile, although the 
posterior arm is more sensitive at any time.  Thus, the hermaphrodite 
spermatogenesis pathway seems to be controlled independently for each 
arm of the gonad during a short period close to the time of the L1 
Spontaneous B245 males have been isolated, although a fertile male 
stock has not been obtained.  Him-5 B245 and him-1 B245 strains have 
also been constructed, and him-5 B245 males are fertile.  Males of all 
three types show the same phenotype: at 16 C they produce sperm 
normally, but when shifted to 25 C, even as adults, they produce 
oocytes.  Mature oocytes with typical premeiotic chromosomes are found 
by about 24 hours after the shift up, but so appear to degenerate.  In 
males given ten hour pulses of high temperature, the switch to oocyte 
production will occur only for pulses beginning 15 hours post-hatching 
or later.  This corresponds to the time when the hermaphrodite tsp 
ends.  After such pulses, sperm production does not resume with the 
shift to permissive temperature.
B245 maps to linkage group III, approximately 7 map units from dpy-1.
It complements tra-1 giving fertile heterozygous hermaphrodites at 
25 C.