The sea urchin is the material of choice for studying many early devel
opmental events. Methods to extend the viability of sea urchin gametes
have not received much attention, but it is well known that the eggs
are easily damaged by freezing. This study was designed to extend the
viability of Lytechinus pictus eggs and sperm without freezing. Gamete
viability measurements were based on relative numbers of fertilized v
s unfertilized eggs, percentage fertilization, and on observations of
embryonic development. Results indicate that gametes can be stored lon
ger and at lower temperatures than previously described. Sperm were co
nsistently kept viable for at least 12 days with little decrease in vi
ability when stored in glass test tubes or plastic petri dishes and su
bmerged in ice inside a refrigerator at 0 +/- 1 degrees C. In one expe
riment, sperm stored in glass test tubes on ice remained viable up to
20 days after extraction. Eggs were maintained from 1 to 7 days, rathe
r than the 1 day or so previously reported, when stored in glass test
tubes submerged in ice in a refrigerator at 0 +/- 1 degrees C. Results
of egg and sperm experiments varied at different times in the season.
Such variations may be caused by seasonal cytoplasmic changes, popula
tion differences, or the time mature individuals were maintained unfed
in aquaria prior to use. Results from this study should be useful for
a variety of research, mariculture, and teaching applications in whic
h sea urchin supplies are limited or when the same gamete population i
s required for subsequent experiments. (C) 1995 Academic Press, Inc.