Effect of different
temperature regimes on reproductive conditioning in the scallop Argopecten
purpuratus
G. Martínez, H. Pérez-2001
Aquaculture, 228(1-4): 153-167
Abstract:
Adult Argopecten purpuratus were conditioned
under four different temperature regimes and their gonadal development and
quality of the resulting offspring evaluated. Biochemical composition of
muscle and gonad, during laboratory conditioning at the different
treatments, was also examined. Spawned-out individuals were obtained from
commercial culture centers for experimentation. Test groups of scallops were
independently maintained at: (a) 15 °C, (b) 19 °C, (c) 15 °C in the first
stage, raised to 19 °C in the second stage, and (d) 19 °C in the first
stage decreasing to 15 °C in the second stage. Scallops were maintained in
seawater which was changed daily, provided with aeration, and were
continuously fed a diet consisting of 50% Isochrysis galbana (var.
T-iso) and 50% Chaetoceros gracilis. The daily ration was equivalent
to 6% of the dry biomass of the scallops. Animals were maintained under a
constant photoperiod of 12-h light and 12-h dark. Progress of gonadal
recovery was followed by periodic determination of gonadosomatic index (GSI)
and histological analysis. The highest percentage of scallops attaining
spawning condition and highest values for GSI was obtained from animals
conditioned under the constant 15 °C regime. The group started at 15 °C
and raised to 19 °C showed the most variable pattern of maturation. Of the
major biochemical components of the adductor muscle, lipids and proteins
changed most during conditioning under any of the temperature regimes;
changes in carbohydrate levels in this tissue were only detected for
scallops maintained at a constant temperature. Changes in protein levels,
depending on the time and temperature of conditioning, were detected in the
gonad. Based on quality indicators used in this study, including fecundity,
egg size, biochemical composition, and "D" larvae survival, the
best physiological conditioning for the reproductive process was obtained in
scallops, which were conditioned at a constant temperature of 15 °C, and at
an initial temperature of 19 °C and then decreased to 15 °C. Results
showed an inverse relationship between temperature and conditioning success
and the importance of maintaining stable temperatures during the laboratory
conditioning process which permitted adequate accumulation and use of
nutritional reserves required to produce highly viable larvae.
(Departamento de Biología Marina, Universidad Católica
del Norte, Larrondo 1281, Coquimbo, Chile, e-mail: gmartine@ucn.cl)