nauplii per spawn (24,400 nauplii vs 8,500
nauplii). The number of half-sib families produced
with the single spermatophore technique also
increased. The ratio of full-sib families to number
of sires was 1.7 for the single spermatophore
technique, whereas the ratio of full-sib families
to number of dams was 1.2 for the double
spermatophore technique. In addition, the time it
took to produce 80 families decreased from 14 d
to 9 d. In a recent breeding run using only the
single spermatophore technique, the mean number
of viable nauplii per spawn was 36,500, spawning
success was 87%, and the half-sib ratio was 1.7.
An important distinction between the two
AI techniques described above is that, in the single
spermatophore technique, the sperm sac is
ruptured thereby liberating the sperm mass from
the chitinous spermatophore. Also, in this
procedure, the sperm is separated from a sheath
of glutinous material surrounding the
spermatophore that may interfere with
fertilization. Using forceps to apply the sperm
mass inside the thelycum allows for more effective
fertilization of eggs and increases the number of
viable nauplii. In addition, using a single
spermatophore per female is a more efficient use
of male gametes and increases the number of halfsib
families because it precludes the need for a
specific female to spawn twice in a 2-wk period.
One advantage of producing an increased
number of viable nauplii in a shorter time is that
potential confounding environmental effects are
minimized. Increasing the number of half-sib
families is advantageous to a breeding program
because it allows for more accurate estimates of
genetic parameters, such as heritability and
genetic correlations. Heritability describes the
percentage of phenotypic variance that is inherited
in a predictable manner and is used to determine
the potential response to selection. Heritability
estimates may be used to estimate progress in a
breeding program, whereas phenotypic and
genotypic correlations may reveal an indirect
response, either positive or negative, to a breeding
plan. Use of the single spermatophore AI
technique and production of paternal half-sib
families has improved the efficiency of the
breeding program at OI and should be considered
in other shrimp breeding programs.