Ovarian growth in the crab Chasmagnathus granulata, induced by hormones and neuroregulatrs throughout the year. In vivo and in vitro studies.

ZAPATA, V.; LÓPEZ GRECO, L.S.; RODRÍGUEZ, E.M.

AQUACULTURE

ELSEVIER SCIENCE BV

Año: 2003 vol. 224 p. 339 - 352

0044-8486

The hormones 17a-hydroxyprogesterone and juvenile hormone III (JHIII), as well as thedopaminergic antagonist spiperone, were assayed both in vivo and in vitro on adult females of theestuarine crab Chasmagnathus granulata at different times of the year. All the chemicals wereadministered both by injection and by incorporation into the food. Each of these in vivo assayslasted 1 month, and they were done during three different periods of the year, in accordance withthe reproductive cycle of this crab (pre-, post- and reproductive periods). Spiperone andprogesterone 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.