Ovarian growth in the crab Chasmagnathus
granulata induced by hormones and neuroregulators throughout the year.
In vivo and in vitro studies
V. Zapata, L.S. López Greco, D. Medesani and E.M.
Rodríguez-2003
Aquaculture, 224(1-4): 339-352
Abstract:
The hormones 17α-hydroxyprogesterone and
juvenile hormone III (JHIII), as well as the dopaminergic antagonist
spiperone, were assayed both in vivo and in vitro on adult females of the
estuarine crab Chasmagnathus granulata at different times of the
year. All the chemicals were administered both by injection and by
incorporation into the food. Each of these in vivo assays lasted 1 month,
and they were done during three different periods of the year, in accordance
with the reproductive cycle of this crab (pre-, post- and reproductive
periods). Spiperone and progesterone were always administered at a dose of
10-8 mol/crab, while JHIII at 10-7 mol/crab. The
assays done during the reproductive period (spring and summer) yielded a
significantly higher gonadosomatic index (GSI) than that of the concurrent
control for all the chemicals assayed, whether injected or incorporated into
the food. During the pre-reproductive period (winter), only progesterone and
JHIII increased the GSI, while for the post-reproductive period (autumn),
only spiperone and progesterone did so. These differences may be related to
the phases of the annual reproductive cycle that is synchronized by both
external and internal stimuli. In vitro assays that involved a 24-h
incubation of isolated pieces of ovary from females sampled during the
reproductive period were also done. A significant increase of leucine uptake
by the ovary fragments was observed by merely adding either progesterone or
JHIII to the incubation medium, but a similar effect of spiperone was only
observed when thoracic ganglion (TG) was also added. Spiperone was also able
to reverse the inhibitory effect caused by eyestalk tissue (ET) added to
medium. The results of these in vitro assays support the hypothesis,
previously suggested, about the inhibitory role of dopamine in crustacean
reproduction acting on neuroendocrine organs such as TG and ET.
(Animal Physiology Laboratory, Department of
Biodiversity and Experimental Biology, FCEyN, University of Buenos Aires,
Ciudad Universitaria, Pab. II, C1428EGA, Buenos Aires, Argentina, e-mail of
E.M. Rodriguez: enrique@bg.fcen.uba.ar)