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.M. Navarro et al. J. Exp. Mar. Biol. Ecol. 247 2000 67 –83
supplemented with carbohydrates. The energy expended in oxygen uptake and ammonia excretion was very similar in the different experimental diets and temperatures. Scope for growth in A
. purpuratus appears mainly affected by the diet and not by temperature. While the lower SFG
seems to be associated with diets composed of pure microalgae and microalgae 1 carbohydrates, the highest values being found for a diet rich in lipids. The data were in agreement with the
reproductive conditioning of A . purpuratus, where the highest percentage of ripe scallops occurred
in individuals fed with a diet of microalgae supplemented with lipids at both temperatures. Similarly the highest larval survival rate was obtained from gametes released by scallops
conditioned with the diet containing lipids.
2000 Elsevier Science B.V. All rights reserved.
Keywords : Scallop; Reproduction; Diet; Temperature; Feeding; Scope for growth
1. Introduction
The scallop Argopecten purpuratus is naturally distributed between central Chile and northern Peru, but the commercial interest in this species has led to its introduction to
southern Chile with the objective of developing a major aquaculture industry. Natural production of juvenile A
. purpuratus has been highly variable during recent decades in the north of Chile, although seed production has not been successful with the introduced
scallops to the south of Chile, mainly due to the low environmental temperatures. These have been the main constraints to a sustained development of A
. purpuratus culture in Chile, and the development of fisheries and aquaculture for A
. purpuratus will be highly dependent on the hatchery production of juveniles.
Most of the studies on A . purpuratus have been related to its culture Padilla, 1979;
Hojas, 1983; 1984; Illanes, 1987, but only a few have concerned to reproduction and ´
´ ´
physiology Dıaz and Martınez, 1992; Martınez et al., 1992, 1995; Navarro and Gonzalez, 1998. Temperature and diet have been shown to be environmental factors
playing an important role on the scope for growth energy available for allocation to growth and or reproduction of marine bivalves Bayne and Newell, 1983; MacDonald
and Thompson, 1986; Bayne and Hawkins, 1990. But no studies combining the effects of temperature and food have been carried out on A
. purpuratus during reproductive conditioning. These variables must be considered when raising juveniles in the hatchery,
because the nutrient content and size of the eggs, the size and survivorship of the larvae and growth of the spat have been associated with the reproductive conditioning of the
broodstock Sastry, 1966, 1968; Uki and Kikuchi, 1984; Grant and Cranford, 1989; Robinson, 1992. Diet composition alone has also been considered highly relevant to
development and biochemical changes of the gonad. According to Gabbott 1975 the gametogenic cycle of marine bivalves is coupled to synthesis of lipid during vit-
ellogenesis at the expense of stored glycogen. Helm et al. 1991 observed that survival of larvae of Ostrea edulis was related to the lipid content of the larvae at the time of
release. Other authors Thompson, 1977; Gallager and Mann, 1986; Robinson, 1992; Coutteau et al., 1996 have also reported lipids as playing a significant role in the
development of gonad, larvae and juveniles. On the other hand Ward et al. 1992 demonstrated the capacity of chemoreception in the sea scallop Placopecten magel-
J .M. Navarro et al. J. Exp. Mar. Biol. Ecol. 247 2000 67 –83
69
lanicus, species which increases its clearance and ingestion rates in response to specific metabolites from the diatom Chaetoceros muelleri. This knowledge on the chemorecep-
tory capacity of bivalves is important to understand the feeding behaviour of bivalves in nature as well as under laboratory conditions.
The main objective of the present study was to evaluate the interactive effect of diet and temperature by measuring the scope for growth and gonad maturation of the scallop
Argopecten purpuratus during reproductive conditioning, under the hypothesis that both diet and temperature are key factors influencing potential for production and gameto-
genesis in this species.
2. Material and methods
