Bidirectional mass selection for naupliar length was
practised in Artemia franciscana fromGreat Salt Lake,
UT, USA, with the aim of developing two divergent
lines, namely small naupliar size (SNS) and bigger
naupliar size (BNS). A random-bred control line was
also maintained to quantify the environmental
e¡ects. The mean naupliar length in the base
population was 486.9972.11 mm in males and
490.5871.82 mm in females. Six generations of selection
for smaller naupliar size in the SNS line resulted
in a phenotypic response of ^45.32 mmand ^37.52mm
decreases in naupliar size in males and females respectively. In the BNS line, responses (increase in
size) from ¢ve generations of selection for bigger size
were 8.59 mmand 35.80 mmrespectively.The cumulative
genetic gain in males and females of the SNS
were ^41.72 mm and ^38.76mm compared with
12.64 mmand 39.48 mm, respectively, in the BNS line
