The presence of females in the cross numbers 6 and
9, which were expected to produce all-male offspring
was not surprising.Sagi and Cohen (1990)also found
0.92% female offspring in one of the two crosses
between the neofemales and normal male freshwater
prawn.Malecha et al. (1992)also reported the skewed
sex ratio towards femaleness (1M:1.29F) in offspring
from seven control crosses and one cross produced
1M:2.22F. In the present study 4 of 10 normal crosses
produced more female offspring than the males while
the expected all-male offspring (arising from ZZ-neofemale×ZZ-normal male) contained some females.
These may indicate the presence of modifying genes on
sex determination and a selective mortality upon male
(Malecha et al., 1992). The additional explanation
particularly applied for our study would be misidenti-fication of a male as a female. We could not rule out this
explanation because we identified sexes of the post-larvae at very early stage (10mm CL) based on a
presence of gonopore complexes and the appendixes
masculina in males hence late differentiated males could
have been misidentified as females