Egg activation in the black
tiger shrimp Penaeus monodon
P. Pongtippatee-Taweepreda, J. Chavadej, P. Plodpai,
B. Pratoomchart, P. Sobhon, W. Weerachatyanukul, B. Withyachumnarnkul-2004
Aquaculture, 234(1-4): 183-198
Abstract:
This report describes morphological changes in the
eggs in the black tiger shrimp Penaeus monodon upon contact with
seawater, the process known as egg activation. Eggs from wild P. monodon
broodstock were collected at 15-s intervals post-spawning during the first
15 min, and at 15-min intervals thereafter for 2 h. The samples were fixed
and processed for light, scanning and transmission electron microscopy. As
soon as the egg was released into seawater, the cortical rods began to
emerge from the crypts on the periphery of the egg, and elevated the thin
investment coat that covered the surface of the egg. Sperm in the first
phase of the acrosome reaction were observed on both the egg and the surface
of the investment coat. The rods protruded from the surface and were
completely expelled out within 45 s. Immediately after complete extrusion,
the cortical rods began to break up and formed the jelly layer around the
egg. By this time, the interaction between the sperm at the second phase of
the acrosome reaction and egg began. The hatching envelope had started
formation at 1-min post-spawning, and was completed within 13–15-min
post-spawning. The first and second polar bodies extruded from the egg at
3–5- and 10–15-min post-spawning, respectively. It was apparent that
after the hatching envelop had formed, additional sperm could not enter the
egg. This study suggests that the critical period for the egg–sperm
interaction in P. monodon is within 45-s post-spawning.
(Department of Anatomy, Faculty of Science, Mahidol
University, Bangkok 10400, Thailand, e-mail of B. Withyachumnarnkul: boonsirm@asianet.co.th)