Hormonal and environmental
control of finfish reproduction
Aquaflow Technical Leaflet 2002-99
European Network for the Dissemination of Aquaculture
RTD Information (Q5CA-2000-30105) and previously FAIR-3837, URL: http://www.aquaflow.org/
The main objectives of this research, studying the
effects of the photoperiod on sex differentiation, the onset of puberty and
the spawning season changes in sea bass (Dicentrarchux labrax L),
were as follows:
To determine the stimulatory and inhibitory effects
of different photoperiods on the characteristics and the physiological
response of the cerebrum-pituitary-gonadal axis of the sea bass.
To investigate the action of luminous signals on the
cerebrum-pituitary-gonadal axis and to determine how the onset of the
reproduction process is controlled and its development through time.
To establish new tools and environmental control
techniques for reproduction.
Initial experiments were carried out with sexually
immature sea bass (4 months old) over a period of four uninterrupted years.
The hormonal analyses made during these early ontogeny phases show the
important role played by sex steroids (testosterone) in sex differentiation,
which in this species takes place around the ninth month of life. However,
it was not possible to establish any influence of photoperiod on the sex
ratio. The action of photoperiod was more related to the increment in
somatic (cell) growth, the disturbance of the sex differentiation date, the
advance or delay of the onset of puberty and, above all, to the appearance
of ‘advanced’ fish (i.e. those reaching sexual maturity (spermiation) in
the first year, rather than the second as is normal).
The spawning season of adult fish clearly changes
with the photoperiod regime. Compressed photoperiods of 6 months, or short
constant photoperiods (9L:15D, light:darkness), interrupted during one month
with long constant photoperiod (15L:9D) applied before the summer solstice,
advanced the spawning season by several months compared with the control
groups. However, expanded photoperiods of 18 months, or long constant
photoperiods (15L:9D), delayed the spawning season by several months
compared with controls. Furthermore, a reliable, quick and friendly method
(micro-plates) to assess both the spawn quality and the survival of eggs and
larvae, has been developed.
Studies of circadian variations in sex steroids and
the characterisation of a regulatory peptide involved in the reproduction
and ingesta of sea-bass (neuropeptide Y) have been undertaken. The cloning
of the vitelogenine and estradiol receptors has also been started, in order
to produce useful molecular tools to further study how sea-bass reproductive
mechanism are disturbed by exposure to different photoperiods.
The two main applications of this research (related
to the environmental control of reproduction and to the micro-plates method
to assess the spawn quality) have been transferred to a company for
industrial usage.
For more information:
CARRILLO
ESTEVEZ Manuel
Instituto de Acuicultura de Torre la Sal (CSIC)
12595 – Torre la Sal (Castellon)
Spain
Phone : +34 964 319500
Fax : +34 964 319509
E-mail :
carrillo@iats.csic.es