Scallop Argopecten Purpuratus Research Articles

Effect of increasing salinity on physiological response in juvenile scallops Argopecten purpuratus at two rearing temperatures

Argopecten purpuratus can be cultivated using Recirculating Aquaculture Systems (RAS) as a method to increase production. In order to determine physiological response of A. purpuratus under different salinities and temperature conditions, two groups of juvenile scallops (small: h = 6.5 mm and large: h = 25.5 mm) were acclimated and close-cultured at salinities of 34, 38, and 42 g/l, at 16 and 22 °C and fed on Isochrysis galbana and Chaetoceros calcitrans. Survival, shell growth and scope for growth were determined at the end of the trials. Survival showed an inverse relationship with temperature and ammonia levels. In small scallops an increase in salinity at 16 °C increased survival. However, this relationship was not evident at 22 °C. On the other hand, salinity did not affect survival of large juveniles. Small juveniles had a lower survival (approximately 40%) than larger scallops (up to 85%) throughout the trials. Oxygen consumption was not affected by salinity. Small scallops showed similar oxygen consumption at 16 and 22 °C but in large juveniles higher values were registered at 22 °C. In large juveniles routine consumption at 16 °C was higher (up to 35%) than standard consumption. This pattern was not evident at 22 °C, suggesting that oxygen demand is higher regardless of feeding condition. NH 4 +–N excretion rate is inversely related to salinity. Only small juveniles showed a higher NH 4 +–N excretion rate at 22 °C. Scope for growth was positive in all treatments, although the upper limit of salinity should not be based only in this index. Higher scope for growth values at 38 and 42 g/l was related with a reduction in ammonia excretion and high absorption efficiency. In addition, an increase in salinity produced a reduction in NH 3–N proportion and under hypersaline conditions scallops tended to decrease excretion as a way of osmoconformation. This explains our findings of higher survival rates at higher salinities. Even though the scope for growth is positive at 42 g/l, the osmotic stress reduces the survival chances. The data obtained can be considered useful information for A. purpuratus culture under controlled conditions.

Modificación de los parámetros inmunitarios hemolinfáticos en el ostión del norte (Argopecten purpuratus Lamarck, 1819) afectados por el cuadro de retracción del manto

The scallop Argopecten purpuratus is characterized by variations in some immunity parameters of the hemolymph when faced with the pathology known as mantle retraction. A relationship between the hemocytic reaction of encapsulation and this pathology was established with light and electronic transmission microscopy. The quantita- tive comparison of the number of hemocytes, the phagocytic capacity of these cells in the presence of yeasts, and the cytotoxicity of the hemolymph in specimens with and without mantle retraction showed that the hemocytes and serum of scallops with mantle retraction respond differently. When mantle retraction is observed, the number of circular he- mocytes decreases. In exchange, the serum increases its cytotoxic capacity when faced with erythrocytes. On the other hand, when the yeasts were previously incubated in this serum, the phagocytic capacity of the hemocytes decreased. The results show that the pathology known as mantle retraction in the scallop determines a significant variation in cellular immunity and the humoral components of the hemolymph, and an encapsulation response in the presence of coalescent bodies in the mantle.

Artificial collection and early growth of spat of the scallop <i>Argopecten purpuratus</i> (Lamarck, 1819), in La Rinconada Marine Reserve, Antofagasta, Chile

Artificial collection of early juveniles (“spat”) of the scallop Argopecten purpuratus in Japanese-type collectors was evaluated between January 2001 and July 2002 in the La Rinconada Marine Reserve, Antofagasta, Chile. This area of Antofagasta Bay has in the past been noted for the retention of scallop larvae by local gyres, in which their numbers can vary between 89 and 34175 larvae m -3 , producing larval sets of 400 to 15340 post-larvae (spat) per collector. The results showed no quantitative relationship between larval abundance in the water and the spat density collected per day in the collectors, although high settlement rates were associated with high numbers of umboned larvae in the water. Allowing collectors to remain in situ for extended periods of 88 and 159 days resulted in a severe loss of seed which had settled in the collectors during the first 28 to 40 days of immersion. These losses varied between 50.9 and 99.6% of the spat collected, and were more prejudicial for the smaller cohorts that had settled in the collectors at the end of the first immersion period. The growth rates measured among different cohorts for each immersion period varied between 81.3 and 235.2 mm/day for the first cohort (C 1 ) and between 64.0 and 167.4 mm/day for the second cohort (C 2 ). The highest growth rates occurred in collectors containing the lowest numbers of spat after the occurrence of spat losses during the long periods of immersion. Occurrence of intraspecific competition within the collectors is discussed as potentially responsible for the decreases in spat numbers and the variations observed in their growth rates.

Differential absorption of biochemical food components by the scallop Argopecten purpuratus exposed to different salinities and food concentrations

The scallop Argopecten purpuratus is naturally distributed between central Chile and northern Peru. The objective of the present study was to determine some key acute and acclimated responses of A. purpuratus under a range of salinity and food conditions. The differential absorption of different biochemical components of the diet of this scallop was studied over short time periods (1,3, and 7 days), varied salinity (24, 27, and 30%c), and varied food availability (1.03 and 2.99 mg suspended matter litre‐1). The results showed that variation in salinity explained most of the variance in the food ingestion rate, absorption efficiency, and absorption rates of dietary biochemical components. At high food levels, A. purpuratus acclimatised its absorption efficiency for proteins and carbohydrates after 7 days, but only at salinities of 27 and 30‰. Lipid absorption at 24‰ salinity was negative, with a tendency to show lower values over time. At salinities of 27 and 30‰ the absorption efficiency of lipid was negative for the first 3 days, followed by recuperation with positive values after 7 days of acclimation. However the acclimation process was not complete, as values of absorption at high food levels were significantly lower than those obtained by A. purpuratus at low food levels at the same salinities.

Reproductive and larval cycle of the scallop Argopecten purpuratus (Ostreoida: Pectinidae), during El Niño-La Niña events and normal weather conditions in Antofagasta, Chile

Seasonality, amplitude, and magnitude of spawning events were determined for Argopecten purpuratus in the La Rinconada marine reserve, Antofagasta, Chile, between December 1995 and January 2004. During the same period, samples of scallop larvae were obtained in vertical plankton hauls recovered within this reserve in an area routinely exposed to circular, gyre-like currents which helped retain the larvae within the bay. The reproduction of this population in normal or cool (e.g. "La Niña", 1998-2000) years occurred throughout the year, with a more active period between September and April, declining in June and August; this contrasted with the warmer "El Niño" oceanographic period of 1997-98 in which reproductive activity was more intense and prolonged throughout the entire year. The reproductive events in this population were mostly synchronous, although one asynchronous period occurred each year following the more intense March to May spawnings. This reproductive activity generated a continuous presence of larvae in the area in which no strict relation could be found between the intensities of spawning and numbers of larvae in the water. Larval presence was, however, generally correlated with active spawning periods. Important increases in larval numbers recorded at the end of 1999 and the beginning of 2003 were correlated with census data showing a higher percentage presence of broodstock over 90 mm in shell length during these years. An adequate stock of this size class is needed for a successful seed capture program in the reserve (for mass culture).

Will providing a filamentous substratum in the water column and shell litter on the bottom increase settlement and post-larval survival of the scallop Argopecten purpuratus?

The marked variability in the natural recruitment of Argopecten purpuratus, a common characteristic for many marine invertebrates with a pelagic larval stages, with important consequences for community functioning, is a problem for the fishery on this species. We ran experiments in the subtidal zone in Tongoy Bay, Chile, to test whether providing a filamentous settlement substratum in the water column and shell litter on the bottom would increase the settlement and post-larval survival of scallops. We placed collectors made of Netlon® 50 cm above the sand and mud bottoms, and three and a half months later there were significantly more scallop spat on the bottom under the collectors (38.5 ind m − 2 ), than in areas without collectors (0 ind m − 2 ), or in controls where collectors were installed but a bag around the collector prevented the juveniles from falling to the bottom (4.8 ind m − 2 ). Also, the addition of either entire or broken scallop shells to the bottom resulted in increased settlement of juveniles on the bottom (33.7 ind m − 2 with entire shells and 48.1 ind m − 2 with broken shells), compared to plots where no shell debris was added (0 ind m − 2 ). The 2 week survival rate of juveniles (< 3 mm shell height) added to plots covered with entire scallop shells (12.4%) and to plots covered with broken shells (15.1%) was greater than in plots where we did not add shells (3.5%). These results suggest that substrate availability explains spatial variability of recruitment for this species, while temporal variability (between years) is mainly the consequence of larval supply. The manipulation of substrates can locally increase settlement, but will not remove the temporal variability. Whereas our experiments provide useful insights into strategies for managing or establishing local scallop populations, experiments over a longer term and at a large scale are needed to further understand the community functioning in order to develop a strategy for managing this fishery resource.

Inhibition of byssal formation in Semimytilus algosus (Gould, 1850) by a film-forming bacterium isolated from biofouled substrata in northern Chile

Semimytilus algosus is a small mussel species that fouls artificial culture systems of the scallop Argopecten purpuratus (Lamarck, 1819) in the north of Chile. Since biofouling organisms are a serious problem in culture, competing with the scallops for food and oxygen, environmentally- friendly methods are required to mitigate the effects of this fouling in the culture systems. The present study reports the evaluation of the inhibitory effect of biofilms and extracellular products (EP) of the bacterium Alteromonas strain Ni1-LEM on the byssal formation of S. algosus juveniles. Laboratory bioassays were carried out to determine the reattachment, exploratory behaviour and/or byssal thread production of the mussel in plastic Petri dishes containing bacterial biofilms, different dilutions of EP, and EP incorporated in a test substratum. It was concluded from the results that culture supernatants of the Alteromonas tested had an inhibitory effect on reattachment by S. algosus.

Copper accumulation by bacteria and transfer to scallop larvae

A bacterial copper-resistant strain was isolated from a hatchery-conditioned adult of the scallop Argopecten purpuratus and was identified as Vibrio sp. according to its physiological characteristics. The lowest concentration of Cu 2+ required for its complete inhibition in VNSS medium was 50 μg ml −1. The Vibrio strain was found to accumulate copper, exhibiting cellular and loosely bound copper levels of 201.14 and 493.21 μg g −1 dry weight, respectively, after 24 h of incubation in VNSS medium supplemented with 15 μg ml −1 of Cu 2+, with cellular concentration factors of 10.17 and 14.35 after 12 and 24 h of exposure. When a scallop larvae culture was exposed to a concentration of 6.46 × 10 2 CFU ml −1 of Cu-enriched Vibrio, they accumulated 20.42 ± 1.12 and 30.96 ± 1.85 μg Cu 2+ g −1 dry weight after 12 and 24 h, respectively. This study suggests that bacterial copper accumulation could be very active in marine environments increasing the occurrence of copper transfer to marine food chains.

Domestication reduces the capacity to escape from predators

Phenotypic plasticity in response to variations in predatory pressure frequently occurs in wild populations, but it may be more evident and critical in species subjected to high exploitation rates and aquaculture. The Chilean scallop Argopecten purpuratus is becoming a domesticated species and the production of hatchery-reared scallops (closed environment), has implied the development of successive generations of individuals deprived of several stimuli normally present in their natural habitats (e.g. predators). We compared the escape capacities between wild and cultured A. purpuratus and also evaluated the effect of reproductive investment on the escape response capacities. Wild and cultured scallops, at different reproductive stages (maturing, mature and spawned), were stimulated to escape with the predatory sea star Meyenaster gelatinosus. We recorded: (1) the time to reaction, (2) the total number of claps, the duration of the clapping response and the clapping rate until exhaustion, (3) the time they spent closed after exhaustion, and (4) the proportion of claps recovered, the duration of the clapping response and the clapping rate after 20 min of recuperation. We found that wild A. purpuratus (1) reacted earlier when contacted by their natural predator, (2) escaped faster (greater clapping rates), (3) spent less time with their valves closed when exhausted, and (4) most of their escape capacities (i.e. claps number; clapping time; capacity of recuperation) were less affected by the energetic requirements imposed by gonad maturation and/or spawning than in cultured scallops. We considered that all these aspects of the escape response would make wild scallops less vulnerable to predation than cultured scallops, thus decreasing predation risk. Given the reduction of escape performance in cultured scallops, we suggest that this aspect should be considered for the success of culture-based restocking programs.

HISTOLOGICAL STUDY OF GONADS IN TRIPLOID SCALLOPS, ARGOPECTEN PURPURATUS

Abstract It is expected that in triploid organisms the energy normally used for reproduction would be allocated to growth. However, not all triploid molluscs are completely sterile, and in some cases even gametes are produced. The aim of this study is to assess the gonadal development in the native scallop Argopecten purpuratus induced to triploidy. Argopecten purpuratus Lamarck 1819, is a functional hermaphrodite, the male portion of the gonad being creamy-white, located proximal to the foot, and the distal female gonadal portion is bright orange-red. They were induced to triploidy with 6-dimethylaminopurine (6-DMAP). Treated (=induced) and control scallops were processed for histology using routine methods. At the age of 11 mo, when the control scallops were mature, some treated scallops had a gonad, which showed a uniform brown color. These were true triploids, assessed by chromosome counts. They showed the tendency of reducing the “ripeness” of the female gonad, only few acini with oocytes were observ...

Extracellular Ca2+ requirement for serotonin-induced release and meiosis reinitiation from prophase in oocytes of the scallop Argopecten purpuratus

Summary The requirement for Ca2+in the external medium for the release and reinitiation of meiosis in the scallop Argopecten purpuratus was examined. In vitro experiments demonstrated that the serotonin-induced release of oocytes is inhibited in a calcium-free medium. Caffeine (10 and 20 mM), a known activator of ryanodine channels, increased oocyte release by gonadal pieces and 50 μM ryanodine inhibited this release and blocked the serotonin-induced effect. The number of oocytes released under control conditions was not affected when ryanodine was used in concentrations in the nanomolar range. Germinal vesicle breakdown, indicative of meiosis reinitiation, was inhibited in gonadal pieces incubated in calcium-free normal or artificial seawater and serotonin does not overcome this inhibition in the same conditions. An increase in fluorescence on adding serotonin (10−5 M, final concentration) was detected under the confocal microscope when oocytes charged with the calcium fluorescent dye Fluo-3 AM were studied. We postulate that there is a rise in cellular calcium in the serotonin-induced spawning process and that the source for the increase is influx from the external medium and release from internal stores. We suggest that this calcium rise plays a role in germinal vesicle breakdown and in the contraction of gonadal smooth muscle.

GENOME SIZE ESTIMATION IN TWO POPULATIONS OF THE NORTHERN CHILEAN SCALLOP, ARGOPECTEN PURPURATUS, USING FLUORESCENCE IMAGE ANALYSIS

Abstract Genome size (the C-value) is known to vary considerably among organisms, but is relatively constant among individuals of the same species. To determine the genome size in the Northern Chilean scallop Argopecten purpuratus, two populations were analyzed by measuring the fluorescence signal in hemocyte nuclei stained with DAPI. The fluorescence intensity was measured during a fluorescence-fading period by image analysis (fluorescence fading method). The area under the curve during a fading period was associated with the genome size, thus we determined the C-value in the Arica population as 1.057 ± 0.057 pg of DNA and 1.139 ± 0.066 pg of DNA for the Tongoy population. The interindividual variation was smaller that 6% for both populations. Variance analysis was performed to detect the effects of organisms and population in the genome size of A. purpuratus. Significant differences were detected between Arica and Tongoy populations (P = 0.0011). The genome size of Tongoy population was larger statistic...

Role of second messenger IP3 in the reproductive process of Argopecten purpuratus

Summary Levels of IP3 in the female gonadal portion of the functional hermaphrodite scallop Argopecten purpuratus were measured at different times during an induced spawning and at different times of the gonadal recovery period following this process. The IP3 content in the tissue samples was determined by a radioreceptor analysis. The amounts of IP3 remained unchanged during the intermediate stages of spawning and increased when the release of gametes had just been completed. The content of this compound in the gonads decreased as the gonadal maturation proceeded. IP3 does not appear to be significantly involved in the process of gametogenesis but may be involved in the mechanism of spawning. We postulate that IP3 acts as a second messenger that increases the Ca2+ concentration which would be necessary for gamete release or for gonadal recovery.

Metazoan parasites and commensals of the northern Chilean scallop Argopecten purpuratus (Lamarck, 1819) as tools for stock identification

Abstract The value of parasites and commensals of the northern scallops Argopecten purpuratus as biological tags for stock discrimination is assessed. Six-hundred and eighty-six specimens obtained from four wild populations in northern Chile (El Fraile, La Rinconada, Caldera and Tongoy) were analyzed. Eleven species (four parasites and seven commensals) were obtained. A canonical multivariate analysis suggests that scallops from northern Chile comprise four stocks. Identification of stocks is largely based on significant differences in the mean intensity of infection of Rhinebothrium sp. (Cestoda) and Dodecaceria sp. and Polydora sp. (Polychaeta)

Congelamiento de espermatozoides de Argopecten pupuratus Congelamiento de espermatozoides del ostión del norte Argopecten purpuratus mediante congelador mecánico

The freezing of spermatozoa is a technique used in aquaculture which permits the storage of excess spermatozoa from natural or induced spawning, and saves them for use in subsequent procedures. The cryopreservation process requires gradual, controlled lowering of temperature in order to reduce osmotic shock injury or ice crystal formation in the cells. This is difficult to accomplish in the field, where appropriate automatic equipment is not available. This study describes a portable manually operated device usable for accurately repeating required freezing protocols. The device includes a Dewar container for liquid nitrogen, a system of graduated pulleys, an acrylic sample carrier, and a low temperature thermocouple. To test the freezing system, pieces of male gonad of the scallop Argopecten purpuratus were frozen at different rates (1.1, 2.2, 4.6, 6.5, 8.8, 12.9, 19.2, 32.2 and 96.5oC·min -1 ). The cryoprotective mixture used was composed of lyophilized skim milk, ME 2 SO, and sucrose, with a thawing rate of 573oC·min -1 . The optimum freezing rate was 8.8oC·min -1 , obtaining 51.3 ± 6.6% motile sperm. The mechanical freezer was efficient in cryopreservation of A.purpuratus spermatozoa at different freezing rates, since it permitted regulation of the lowering of the samples into the liquid nitrogen vapor at different speeds.

Diet and prey selection dynamics of Cancer polyodon in three different habitat types in Tongoy Bay, Chile

Feeding dynamics of Cancer polyodon was studied, by comparing the diets of three size-classes of the crab to environmental abundance of prey species in three habitats in Tongoy Bay, Chile (30°S). In the sea grass and sand–gravel habitats cannibalism was observed, the small C. polydon being actively selected as the main prey in spite of their lower abundance compared with other crustaceans. In the mud habitat the scallop Argopecten purpuratus was the most important prey, being actively selected although occurring at low relative abundance. Cancer polyodon showed plasticity in feeding habits, adapting to differential prey availability, but always selecting certain species independently of their abundance in each habitat. Accessibility, more than the abundance of the prey, seem to be the main factors influencing prey selection.

Population estimates, extraction, and translocation of the pectinid &lt;i&gt;Argopecten purpuratus&lt;/i&gt; within Mejillones Bay, Chile

SUMMARY: The population of the scallop Argopecten purpuratus in Mejillones Bay, Chile (23°S) was estimated using diving-quadrat techniques between July and August 1999. The population, distributed over an area of 255 ha, was estimated at about 18 * 106 individuals, having a mean length of about 68 mm. Of this number, about 16 * 106 individuals were aggregated into a core area of 51 ha. A subsequent controlled harvest carried out in 33.5 ha of this area in November 2000 produced only 2 * 105 individuals, strongly suggesting that large scale clandestine (illegal) harvesting had occurred since the original population survey. Reseeding of collected scallops was carried out in an interior area of the bay which had low densities of scallops but highly similar physical and chemical seawater characteristics. Post-seeding mortality of the translocated scallops, determined two weeks after the transfer, was 12.5%, with a mean of 2.5 indiv./m 2 in an 8.2 ha area. The low initial mortality, compared with values in the literature, suggested that the methods of retrieval, transport, and restocking the scallops could serve as a viable repopulation strategy in other areas in the future.

Feeding behaviour of the asteroid Meyenaster gelatinosus in response to changes in abundance of the scallop Argopecten purpuratus in northern Chile

Between winter 1996 and autumn 1997, the prey spectrum and feeding behaviour of the sea star Meyenaster gelatinosus (MEYEN, 1834) and the seasonal abundance of the dominant benthic macrofauna were analysed in: (1) a shore-fringing seagrass meadow and (2) an adjacent sand-gravel benthic system of Tongoy Bay (central-north Chile). Of 524 sea stars collected, 130 (25 %) had food in their stomachs or were feeding on the scallop Argopecten purpuratus (LAMARCK, 1819), snails Calytraea trochiformis (BORN, 1778), Tegula luctuosa (ORBIGNY, 1841), and T. eryomphala (JONES, 1844), and small epifauna constituted by the polyplacophora Chiton spp., gastropods such as Nassarius gayi (KIENER, 1835), Nucula pisum (SOWERBY, 1835), Turritela cingulata (SOWERBY, 1825) and Mitrella unifasciata (SOWERBY, 1832). The scallop A. purpuratus suffered an intensive commercial harvest during the study period which decreased significantly its abundance in both habitats. Before harvesting. A. purpuratus constituted the principal prey for M. gelatinosus in the seagrass habitat, whereas all prey types were equally distributed in the sea star's diet in the sand-gravel habitat. After harvesting, the frequency of occurrence of the scallop in the stomachs of the sea star in the seagrass habitat decreased and was substituted by small epifauna. Furthermore, in the seagrass habitat after harvesting, the breadth of the feeding-niche of the sea star increased. indicating that the sea star became more of a generalist feeder. In the sand-gravel habitat alter harvesting, the diet composition remained unaltered, but M. gelatinosus showed an inverse tendency, specialising on the scallop. Additionally, M. gelatinosus increased its feeding preferences on A. purpuratus in both habitats (especially in sand-gravel) when the abundance of the scallop declined. M. gelatinosus feeds on a wide size-range (4 to 14cm) of the scallop with a marked dominance of larger size classes. Our results confirm, in part, the observations of local fishermen of Puerto Aldea regarding the possible negative impact of M. gelatinosus on the standing stock of the commercially exploited scallop.

Polyunsaturated fatty acids in total lipid and phospholipids of chilean scallop Argopecten purpuratus (L.) larvae: effects of diet and temperature

The composition of lipids and fatty acids of larval scallop Argopecten purpuratus were determined when cultured at one of two temperatures and using one of the three algal diets. Larvae grown at 12 °C had the lowest values of phosphatidylcholine (PC) and highest values of cholesterol and steryl esters (SE). The ratio of triacylglycerol (TAG)/cholesterol was affected by temperature but not by diet and the lowest values were observed in larvae grown at 12 °C. By using the ratio of TAG/cholesterol as an index of larval condition, the best condition was observed at the begining of the experiment, before feeding, with values of 3.9 and 2.9 in eggs and D-larvae, respectively. The best culture conditions for larval scallop from this point of view was a temperature of 19 °C and a diet of Isochrysis galbana grown at 25 °C while the poorest condition was observed in larvae cultured at 12 °C and 19 °C and fed the mixture of Isochrysis aff galbana (clone T- Iso) high-protein and Chaetoceros neogracile high-protein (IH/GH diet). However, no significant differences in the growth rate and survival of larvae fed different diets were detected. I. galbana grown at 25 °C had no detectable percentage of arachidonic acid (ARA; 20:4 n−6), but larvae grew well and ARA was detected in PC and phosphatidylethanolamine (PE) in similar quantities to other diets. This suggests ARA may not be essential during early life stages of larval Chilean scallops. Total lipids and PC of larvae were affected by the diet in their ratio of docosahexaenoic acid (DHA; 22:6 n−3)/eicosapentaenoic acid (EPA; 20:5 n−3), but PE composition was highly conserved and was unaffected by diet. DHA/EPA ratio in total lipid and in PC showed highest values when larvae were fed I. galbana grown at 25 °C. Temperature affected the total highly unsaturated fatty acids (HUFA) in total lipids, PC and PE of larvae. In all cases values were lowest when larvae were cultured at 12 °C. In addition, increased temperature increased the ratio of EPA/ARA in PC and decreased the ratio of monounsaturated fatty acids (MUFA)/saturated fatty acids in PE. The ratio of n−6/ n−3 PUFA was constant in total lipid, PE and PC of larval scallops regardless of temperature or diet.

Effect of different temperature regimes on reproductive conditioning in the scallop Argopecten purpuratus

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.