Search

Assessing the carbon footprint of marine bivalve aquaculture demands an accurate estimation of the CO 2 release associated to capital goods and aquaculture operations but also to the metabolic CO 2 budget of the cultured species. Nowadays, there are discrepancies on the processes to include in that budget, how to estimate them, and which scale should be applied, from individual to ecosystem. Site-specific environmental conditions and culture methods also affect significantly the estimates. Here, we have gathered environmental, biochemical and metabolic data from published scientific articles, reports and existing databases to present the metabolic CO 2 budget for mussel aquaculture in the coastal inlets of the Northwest Iberian upwelling. We analyse the contribution of mussel flesh and shell production jointly and separately. At the individual scale, the shell CO 2 budget is estimated from CO 2 removal by shell matrix protein synthesis and CO 2 release during calcification and respiration to support shell maintenance. Organic carbon in mussel flesh and CO 2 released by respiration to support flesh maintenance contribute to the flesh CO 2 budget. Only calcification and respiration processes are considered when estimating the metabolic carbon footprint of individual mussels because organic carbon in mussel flesh and shell returns to the atmosphere as CO 2 in a relatively short period. While the metabolic carbon footprint associated to mussel shell remains constant at 365 kg CO 2 per ton of shell, it varies from 92 to 578 kg CO 2 per ton of mussel flesh. This large variability depends on mussel seeding time and harvesting size, due to the differential seasonal growth patterns of flesh and shell. Inclusion of the CO 2 potentially immobilised in mussel faeces buried in the sediments would lead to a reduction of the metabolic carbon footprint estimates by up to 6 % compared with the individual estimates., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Forecasting of climate change impacts on marine aquaculture production has become a major research task, which requires taking into account the biases and uncertainties arising from ocean climate models in coastal areas, as well as considering culture management strategies. Focusing on the suspended mussel culture in the NW Iberian coastal upwelling system, we simulated current and future mussel growth by means of a multistructural net production Dynamic Energy Budget (DEB) model. We considered two scenarios and three ocean climate models to account for climate uncertainty, and applied a bias correction to the climate models in coastal areas. Our results show that the predicted impact of climate change on mussel growth is low compared with the role of the seeding time. However, the response of mussels varied across climate models, ranging from a minor growth decline to a moderate growth increase. Therefore, this work confirms that an accurate forecasting of climate change impacts on shellfish aquaculture should take into account the variability linked to both management strategies and climate uncertainty., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Determining the magnitude and causes of intrinsic variability is a main issue in the analysis of bivalve growth. Inter-individual variability in bivalve growth has been attributed to differences in the physiological performance. This hypothesis has been commonly tested comparing the physiological rates of fast and slow growers after size differentiation has occurred. This experimental design may detect a link between growth and physiological performance, but we cannot interpret the posterior physiological performance as a driver for the prior growth variability. Considering these limitations, this work introduces a new methodological framework for the analysis of bivalve growth variability. We have conducted sequential measurements of size and physiological performance (feeding, digestion and metabolic rates) in even-sized mussels growing under homogeneous environmental conditions. This experimental design allows us to distinguish between changes over time within individuals, i.e. growth and trends in the physiological rates, from differences between individuals with respect to a baseline level. In addition, Functional Data Analysis provides powerful tools to summarize all the information obtained in the exhaustive sampling scheme and to test whether differences in the physiological performance enhance growth dispersion. Our results report an increasing dispersion in both size and physiological performance over time. Although mussels grew during the experiment, it is difficult to detect any increasing or decreasing temporal pattern in their feeding, digestion and metabolic rates due to the large inter-individual variability. Comparison between the growth and physiological patterns of mussels with final size above (fast growers) and below (slow growers) the median found that fast growers had larger feeding and digestion rates and lower metabolic expenditures during the experimental culture than mussels with slow growth, which agrees with the hypothesis of a physiological basis for bivalve growth variability., Competing Interests: The authors have declared that no competing interests exist.

Under the influence of the Western Iberian upwelling system, the Iberian Atlantic coast holds important hatcheries and recruitment areas for Octopus vulgaris . Recently identified as an octopus hatchery, the Ría de Vigo harbors an important mesozooplankton community that supports O. vulgaris paralarvae during the first days of their planktonic stage. This study represents a preliminary approach to determine the nutritional link between wild O. vulgaris hatchlings, paralarvae and their zooplankton prey in the Ría de Vigo, by analyzing their lipid class content and fatty acid profiles. The results show that octopus hatchlings are richer in structural lipids as phospholipids and cholesterol, while the zooplankton is richer in reserve lipids like triacylglycerol and waxes. Zooplankton samples are also particularly rich in C18:1n9 and 22:6n3 (DHA), that seem to be successfully incorporated by O. vulgaris paralarvae thus resulting in a distinct fatty acid profile to that of the hatchlings. On the other hand, content in C20:4n6 (ARA) is maintained high through development, even though the zooplankton is apparently poorer in this essential fatty acid, confirming its importance for the development of O. vulgaris paralarvae. The content in monounsaturated fatty acids, particularly C18:1n7, and the DHA: EPA ratio are suggested as trophic markers of the diet of O. vulgaris paralarvae.

Understanding biological processes, such as growth, is crucial to development management and sustainability plans for bivalve populations. Von Bertalanffy and Gompertz models have been commonly used to fit bivalve growth. These models assume that individual growth is only determined by size, overlooking the effects of environmental and intrinsic conditions on growth patterns. The comparison between classical models and nonparametric GAM (generalized additive models) fits conducted in this work shows that the latter provide a more realistic approach of mussel growth measured in terms of shell length, and dry weight of hard and soft tissues. GAM fits detected a reduction in growth during the cold season, under unfavourable nutritional conditions. These fits also captured the decoupling between hard and soft tissue growth, widely addressed in the literature but not incorporated in growth models. In addition a GAM fit of condition index allowed us to explain annual changes in resources allocation, identifying the asymptotic growth of shell and the effects of the reproductive cycle on soft tissue fluctuations., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Identifying the environmental factors driving larval settlement processes is crucial to understand the population dynamics of marine invertebrates. This work aims to go a step ahead and predict larval presence and intensity. For this purpose we consider the influence of solar irradiance, wind regime and continental runoff on the settlement processes. For the first time, we conducted a 5-years weekly monitoring of Mytilus galloprovincialis settlement on artificial suspended substrates, which allowed us to search for interannual variability in the settlement patterns. Comparison between the seasonal pattern of larval settlement and solar irradiance, as well as the well-known effect of solar irradiance on water temperature and food availability, suggest that solar irradiance indirectly influences the settlement process, and support the use of this meteorological variable to predict settlement occurrence. Our results show that solar irradiance allows predicting the beginning and end of the settlement cycle a month in advance: Particularly we have observed that solar irradiance during late winter indirectly drives the timing and intensity of the settlement onset, Finally, a functional generalise additive model, which considers the influence of solar irradiance and continental runoff on the settlement process, provides an accurate prediction of settlement intensity a fortnight in advance.

Mussel seed (Mytilusgalloprovincialis) gathered from the intertidal and subtidal environments of a Galician embayment (NW, Spain) were maintained in the laboratory during five months to select fast (F) and slow (S) growing mussels. The physiological basis underlying inter-individual growth variations were compared for F and S mussels from both origins. Fast growing seemed to be a consequence of greater energy intake (20% higher clearance and ingestion rate) and higher food absorption rate coupled with low metabolic costs. The enhanced energy absorption (around 65% higher) resulted in 3 times higher Scope for Growth in F mussels (20.5±4.9 J h(-1)) than S individuals (7.3±1.1 J h(-1)). The higher clearance rate of F mussels appears to be linked with larger gill filtration surface compared to S mussels. Intertidal mussels showed higher food acquisition and absorption per mg of organic weight (i.e. mass-specific standardization) than subtidal mussels under the optimal feeding conditions of the laboratory. However, the enhanced feeding and digestive rates were not enough to compensate for the initial differences in tissue weight between mussels of similar shell length collected from the intertidal and subtidal environments. At the end of the experiment, subtidal individuals had higher gill efficiency, which probably lead to higher total feeding and absorption rates relative to intertidal individuals.

We traced the food sources of mussel Mytilus galloprovincialis cultured in suspension in Ría Ares-Betanzos (N.W. Spain) by means of fatty acid (FA) biomarkers. The FA profile of seston, mussels' mantle, digestive gland and feces was analyzed during five seasons. Due to the proximity of a fish farm to the bivalve aquaculture site, we also tested if mussels and seston situated 170 m distant from the fish cages incorporated fish feed FA markers compared with samples obtained 550 m away. The principal FA in the mussels' organs were 16:0, 16:1ω7, EPA (20:5ω3) and DHA (22:6ω3), while 16:0 predominated in the feces. Seasonal fluctuations in the seston composition were mirrored in the FA signature of mussels' organs and feces, although the digestive gland had the closest resemblance to the seston FA profile. In general, diatom and bacteria derived-biomarkers predominated in mussels' organs and feces during the upwelling period (spring-summer), while dinoflagellates were the dominant dietary source during downwelling (autumn-winter). The higher concentration of EPA and DHA in both organs and the feces compared with the seston suggested a preferential accumulation of these ω3 FA in the mussels' tissues. The results showed a lack of assimilation of fish feed FA biomarkers in the seston and mussel samples. This might be due to the dispersion of uneaten feed particles by high current velocity, substantial distance between the fish and mussel culture, the limited amount of nutrient waste released by the fish farm and dilution of feed particles in the large mussel standing stock., (Copyright © 2014 Elsevier Inc. All rights reserved.)

We examined the influence of the reproductive cycle and environmental variables on the gonadal fatty acid profile in the tropical scallop Nodipecten nodosus. Individuals from a natural population in north-eastern Venezuela (Caribbean Sea) were sampled monthly during one year. The gonadosomatic index (GSI) and a visual assessment of gonadic status are also reported. The environmental conditions characterized by chlorophyll a, temperature and seston concentration were measured in parallel. The highest reproductive activity, with a GSI of 13-18%, was observed from November 2003 to April 2004, and a decrease in GSI, taken as an indication of three spawning periods, was recorded in October, January and May-June. The GSI was 5-8% outside these intervals. A similar trend was observed in maturity stage frequency. Statistical analysis (MDS-ANOSIM) established two different periods; one dominated by upwelling (January to July) and the other characteristic of non-upwelling conditions (August to December). The fatty acids 16:0, 22:6n-3, 20:5n-3 and 16:1n-7 were responsible for the differences between two periods and explained 50% of the observed variance. Accordingly, during the upwelling period, fatty acids such as 22:6n-3 were positively correlated with temperature, organic seston and bivalves in the spent sexual stage and inversely related to the GSI. Furthermore, individuals in the ripe sexual stage were positively related to 20:5n-3 and 18:3n-3, whereas chlorophyll a was directly related to 18:1n-7 and 16:1n-7. In the non-upwelling period, a significant and positive correlation was obtained between fatty acids such as 20:5n-3 and 22:6n-3 and the GSI and the bivalves in the ripe sexual stage, whereas these acids were inversely correlated with the spent sexual stage. In addition, chlorophyll a was positively related to 18:1n-9 and 18:2n-6. Changes in the gonadal fatty acid profile of N. nodosus were influenced by the environmental variables (exogenous factors) during the upwelling and non-upwelling periods and by reproductions (endogenous factors)., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Trophic interactions between Mytilus chilensis and the toxic dinoflagellate Alexandrium catenella were studied over a 21-day period to determine the absorption kinetics of biochemical components and the enzymatic activity of the digestive gland (i.e. amylase, cellulase complex, laminarinase and protease). For the duration of the experiment, logarithmic relationships were established for the assimilatory balance and carbohydrase activities (amylase, laminarinase and cellulase) of the mussels fed with a toxic diet. The study shows that M. chilensis was able to develop mechanisms which allow exploitation of the toxic microalgae as a food source, despite that its feeding and digestive processes were affected during the first days of contamination.

This study evaluates the effect of temperature, coupled with ingestion rate, on the dynamics of biochemical components and lipid classes in R. philippinarum. The data are discussed with regard to sexual development and energy balance. Experimental protocol developed in the present study used two groups of the clam R. philippinarum: L (temperatures of 14 degrees C and 18 degrees C) and H (temperatures of 18 degrees C and 22 degrees C). The intra-group ingestion level was similar, although the ingestion level of the clams in the group H was 2.4 times higher than group L. We observed that R. philippinarum conditioned at 18 degrees C (18L) shows higher protein content, furthermore an important loss of organic weight was observed after 48 days. In such a situation, the clams use their own reserves (carbohydrates and glycogen) for sexual development while in situations without food stress (positive energy balance) and low temperature (14 degrees C) an accumulation of reserves is produced. Strikingly dissimilar behaviour in biochemical composition was observed for the 18H and 22H treatments, both with a positive energy balance. Despite similar protein content, the highest levels of carbohydrates were observed at the lower temperature (18 degrees C). Glycogen was also higher for the 18 degrees C treatment, although the differences were significant only in the males. Although the total lipids in R. philippinarum showed no significant differences in any treatment, they became apparent and related to sex when considering the individual lipid classes. There was no variation in lipid classes in the males between the 14L and 22H treatments despite the large disparity in the degree of sexual development. However, in the females significant differences in lipid classes (phospholipids, triglycerides) were observed. The results of this study show that a positive energy balance permits R. philippinarum gonadal development and accumulation of reserves both in low and high temperature conditions. In low temperature situations, gonadal development is slower and the energy reserves are accumulated in the form of carbohydrates. When the clams are conditioned at high temperatures, gonadal development is fast and complete, carbohydrates are consumed and lipids are accumulated.

The biochemical composition (proteins, carbohydrates, glycogen, total lipids and lipid classes) of the mussel Mytilus galloprovincialis was investigated during an experimental culture using mussel seed from areas with different degree of exposure to the Prestige oil spill. The aim of the study was to identify alterations in the biochemical composition of mussel seed from natural populations commonly used in Galicia for mussel raft culture that might be linked to previous oil exposure. We have selected three mussel seed populations from Pindo, Miranda and Redes, that were characterised in a previous study according to the oil exposure three months after the spill. These populations were transplanted to a raft culture system in the Ría de Ares-Betanzos where our experimental culture followed standard commercial techniques from March 2003 to February 2004. Mussels from Pindo (characterised as the most affected area by the oil spill) showed marked differences in lipid composition with regard to other populations in the content of triacylglycerols, (P<0.001), free fatty acids (P<0.001) and phospholipids (P<0.05) at the onset of the culture. Although these differences in lipid composition might reflect their previous exposition to hydrocarbons, this pattern did not last longer most likely due to depuration of hydrocarbons stored in the tissues or by the development of certain tolerance to PAHs. These significant differences were not detected between Miranda (designed as hardly affected area) and Redes (designed as reference area) which may reflect that Miranda mussels were not affected or only hardly affected by the spill. With the exception of the onset of the culture, biochemical composition showed similar patterns in all mussel populations. Then, the fact of being cultured in a common environment seemed to be more responsible for the long-term variability in the energetic reserve than the origin of the populations or their previous biochemical status.

Adult specimens of two species of clams, Ruditapes decussatus and Venerupis pullastra, were starved for 84 days to determine the effect of starvation on their metabolism. The energy cost of metabolism in starvation was assessed using the oxygen consumption rates (respiration rates) of the clams and assessing the type of fuel used to provide this energy by analyzing their biochemical composition. Respiration rates decreased in both species after 15 days of starvation and remained at basal levels throughout the rest of the experimental period. Both during the first period and also after the metabolism had slowed down, the amount of energy consumed in respiration was higher in V. pullastra than in R. decussatus. The energy needed to maintain vital functions in both species is obtained from catabolism of body components, with a reduction in dry mass of the specimens, and consequently their energy content, in both species. This reduction was greater in V. pullastra given that energy demand is higher in this species. In both species carbohydrates made the largest contributions to energy output, followed by lipids in males and proteins in females. However, the energy contribution of each biochemical component differs according to species: R. decussatus obtains its energy from the catabolism of carbohydrates and proteins in equal proportion, while V. pullastra obtains it from proteins and lipids. In both species, albeit to a greater extent in R. decussatus, we observed that female specimens conserved their lipids until the later stages of the period of starvation (day 70), after which they started to metabolise their lipid components more intensely. The interspecific differences are interpreted in relation to the different habitat occupied by the two species.

Variability of taurine (2-aminoethane sulfonic acid) was studied as a function of size in the mussel Mytilus galloprovincialis and tissue specificity. Isometric and/or allometric relationships were established with regard to total soft mass of the mussels between 20 and 60 mm shell length. Relative amounts of taurine dropped significantly with increasing mass of whole soft tissues with an allometric coefficient value of -0.15. The inverse relationship between taurine and increasing size of mussels was confirmed for gill epithelium and labial palp (allometric coefficient values of -0.16 and -0.10, respectively), tissues that, in turn, represented isometric functions with regard to total soft mass. Although relative amounts of taurine were significantly different in digestive gland, mantle and foot, relationships with increasing size of mussels remained unchanged in these tissues. Gill area of mussels was related to soft mass with an allometric coefficient of 0.70 by 2D Image Analysis, but increased to 0.85 when introducing a third dimension, i.e. gill thickness. Results are discussed according to gill structure analysis and taurine functionality.

This study investigates the influence of the lipid composition of microalgal and commercial flour diets on the lipid classes and fatty acids of Ruditapes philippinarum spat. Aspects of the nutritional role of the diets and the feeding ration are discussed with regard to previously published spat growth data. Our results demonstrated that clams showed the best growth rates when fed with diets that supplied a larger quantity of lipids, further characterised by a high content of phospholipids and triacylglycerols. We observed a significant correlation between the amount of triacylglycerols (r=0.929, p<0.05) and phospholipids (r=0.781, p<0.05) supplied and spat growth. In addition, R. phillipinarum spat reached the highest percentages of triacylglycerols (about 12%) and the lowest percentages of phospholipids (about 60%) and sterols (about 4%) with these growth-promoting diets. Spat fed with the other diets and/or rations showed lower growth rates and significantly lower quantities of triacylglycerols. In the present study, the alternative essentiality of 20:5n-3 and/or 22:6n-3 is confirmed. The diminishing supply of 22:6n-3 without an increase of 20:5n-3 has an effect on the growth of the spat. The dietary composition of fatty acids influenced the fatty acid profiles in bivalves. The results of our study would suggest that R. philippinarum is incapable of transforming 18:3n-3 to 20:5n-3 and then to 22:6n-3. Accordingly, although diets contained 18:3n-3, the spat reflected the low content of 20:5n-3 of the diets. With respect to 22:6n-3, given that this fatty acid is present in high quantities in Isochrysis, the spat content of this fatty acid was relative to its content in the diet. This study showed that clams with the lowest growth rates presented an increase in 20:4n-6. In the spat fed with the microalgal diets, 18:2n-6 scarcely reached 2% whereas in spat fed with wheat germ 18:2n-6 amounted to 18% of the total fatty acids. This fatty acid, by means of elongation, transforms to 20:2n-6, which also appeared in important quantities in the lipids of the spat fed totally or partially by wheat germ. We note that 20:2n-6 did not originate from the diet since it is absent in the microalgae and the flour. The desaturation of 20:2n-6 to 20:3n-6 has not been observed (low levels of 20:3n-6 in all cases) and therefore it can be assumed that the observed levels of 20:4n-6 were diet-related.

Argopecten purpuratus is a bivalve filter feeder inhabiting protected areas of the Peruvian coastline and northern and central Chile. The species is commercially valuable and the natural stocks are over-exploited in Chile, mainly in the central region. Expansion of aquaculture farms to the geographically protected coastline of southern Chile is a potential solution to this problem. So, the objective of the present study was to determine the acute feeding and digestive response of A. purpuratus in relation to short acclimation periods (1, 3 and 7 days) and exposure to variable salinity (24 per thousand, 27 per thousand and 30 per thousand) with two different diets. The feeding behaviour of A. purpuratus follows that described for other species of bivalves whereby the decrease in salinity produces a reduction in the clearance and ingestion rates. This behaviour is not affected by the diet type or the 7 day acclimation period. Lower values of absorption efficiency are associated with increasing food concentration. The response of the AE at 24 per thousand salinity and low organic content diet indicates that the interaction of low salinity and low organic content diet reduces the AE to values approaching zero. The enzymatic investment of A. purpuratus at low salinity (24 per thousand) is similar for both diets and more reduced than for 30 per thousand and 27 per thousand salinity. The results show that osmotic stress leads to a reduction of the enzymatic response capacity. The multiple regression analysis indicates that different responses are observed as a function of the enzymatic activity and the organ. A reduction of the carbohydrase activities in the digestive gland was observed to low salinity (24 per thousand), specifically amylase and celullase. The results of this study are ecophysiologically relevant and highlight a relationship between digestive enzymatic activity and salinity, and may explain the possible differences in the energetic balance of A. purpuratus in response to changes in salinity.

Fatty acid profiles of seeds of the mussel Mytilus galloprovincialis originating from two habitats (rocky shore and subtidal) were compared after transfer to the same habitat (subtidal). The objective was to study the initial levels of different fatty acids of metabolic importance and, furthermore, the variability of these fatty acids over the experimental period. The results show that of all fatty acids identified in both seed groups, the polyunsaturated fatty acids (PUFA) is the group with highest percentage. Within this group, the C20:5n-3 and C22:6n-3 fatty acids show the highest levels. Additionally, the mussels of subtidal origin presented higher initial levels than the rocky shore mussels with regard to fatty acids characterised by energetic-type functions, such as the C14:0, C16:0, and the C20:5n-3 fatty acids, among others. Fatty acids characterised by structural-type functions, e.g. C18:0, C22:6n-3 and non-methylene interrupted dienoic (NMID) with 20 and 22 carbons in rocky shore mussels presented higher levels than those of the subtidal mussels. However, it has not been ruled out that aside from influences relating to the functional aspects of the different fatty acids, the initial differences were also associated with the quantitative and qualitative differences of the available food in both habitats. Nevertheless, 22 days into the experiment (in the majority of cases) the initial differences disappear in the different fatty acids with metabolic importance. On the basis of these results, the influence that mussel origin could exercise on the variability of the fatty acid profiles of recognised metabolic importance is discussed.

Digestive enzyme activities (amylase, cellulase, laminarinase and protease) were analysed in mussels (Mytilus chilensis) from intertidal and subtidal habitats in Yaldad Bay, Chiloé, Chile. In order to analyse the effects of the past-feeding history (origin) and new nutritional conditions (habitat) on these enzymatic activities, a cross-over transplant was carried out and the analysis performed after a 7-day acclimation period. Crystalline styles showed higher carbohydrase and lower protease activities than digestive glands, with the highest differences recorded for subtidal mussels. Cellulase is the enzyme with the highest activity in both the digestive gland and crystalline style in all the experimental conditions. Intertidal mussels transplanted to a subtidal habitat showed enzyme resources significantly higher than in their original habitat. In the inverse case, mussels transferred from an original subtidal habitat to an intertidal one, a significant decrease in carbohydrase and protease activities was observed. The "past feeding history' is involved in the specific and total carbohydrase and protease activities, with a highly significant effect on amylase and cellulase activities in both the crystalline style and the digestive gland. Laminarinase activity can be interpreted considering the habitat (trophic regime), either individually or interacting with mussels' origin, in relation with the feeding periods. The results establish that in M. chilensis, an investment in enzyme resources is one of the mechanisms employed to optimise the acclimated response in terms of energy gains when variations in the food regime occur.

The influence of both the lipid composition of microalgal diets and commercial flours on the lipid classes and fatty acids of Ruditapes decussatus spat was studied. These aspects of the nutritional value of the diets were discussed in relation to the growth of the spat. Four diets were tested; Diet A, composed of 100% of the daily food ration of microalgae; Diet B, composed of 100% of wheatgerm; Diet C, composed of 50% of microalgae and 50% of wheatgerm; and Diet D, composed of 25% of microalgae and 75% of wheatgerm. The microalgal cells present a higher lipid content than that for wheatgerm. Tahitian Isochrysis cells have phospholipids and triacylglycerols as majority lipids, whereas in the wheatgerm particles, the lipids more abundant are triacylglycerols. Fatty acid content was higher in the microalgal cells than in the wheatgerm particles. The n-3 fatty acids were the most abundant acids in the microalgae, whereas the n-6 fatty acids were in the wheatgerm. The n-3 PUFA were not detected in wheatgerm. Phospholipids were the main lipids present in the clam spat, followed by triacylglycerols. Other lipid classes, detected in significantly lower amounts, included free fatty acids, sterols, and sterol ester + waxes. The composition of fatty acids in the spat was influenced by the fatty acid composition of the diet. Highest spat growth rates were observed with those diets that present a higher phospholipid/triacylglycerol relation. A negative correlation in the relation n-6/n-3 vs. growth has also been observed, with better growth rates in diets with a lower ratio. If the fatty acid 20:5n-3 and 22:6n-3 considered "essential" for marine animals were not present in the diet, they were not present in the spat either. Desaturation and elongation capabilities of R. decussatus spat were also discussed.

The effects of the storage temperature (-18 degrees C and -40 degrees C) and the addition of butylhydroxytoluene (BHT) on the different classes of lipids (phospholipids, triacylglycerides, free fatty acids, sterols and sterol esters plus waxes) and the fatty acid composition of minced (8 and 12 mm) and whole rayfish wing muscle stored for 1 year in the frozen state were studied. The phospholipid content decreased significantly and the free fatty acid content increased significantly at both storage temperatures, but more pronounced, at -18 degrees C. Significant differences were found between phospholipid and free fatty acid contents of the minced and the whole samples, which again were more pronounced at -18 degrees C. A significant increase of the major fatty acids (22:6n-3 and 16:0) was observed after 1 year in the frozen state. Significant differences were also obtained between the samples stored at -18 degrees C and at -40 degrees C; the lower the storage temperature, the higher their content. The polyunsaturated fatty acid (PUFA) content increased significantly in all the samples. Significant differences were found between the samples stored at -18 degrees C and at -40 degrees C. The lower the temperature, the higher the PUFA content. Non-significant differences were observed between the 8-mm and the 12-mm minced samples. Non-significant differences were found between the samples stored in the presence and in the absence of BHT. Mincing hastened hydrolytic and oxidative processes, which were slowed down at the lower storage temperature. Nonetheless, non-significant differences were found between both particle sizes.