Lipid composition of Ruditapes philippinarum spat: effect of ration and diet quality

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.     

Contrasting Physiological Responses of Two Populations of the Razor Clam Tagelus dombeii with Different Histories of Exposure to Paralytic Shellfish Poisoning (PSP)

This study describes the physiological performance of two populations of the razor clam Tagelus dombeii from two geographic areas with different histories of exposure to paralytic shellfish poisoning (PSP) linked to the toxic dinoflagellate Alexandrium catenella. Clams from Melinka-Aysén, which are frequently exposed to PSP, were not affected by the presence of toxins in the diet. However, clams from Corral-Valdivia, which have never been exposed to PSP, exhibited significantly reduced filtration activity and absorption, affecting the energy allocated to scope for growth (SFG). Ammonia excretion and oxygen uptake were not affected significantly by the presence of A. catenella in the diet. Measurements of energy acquisition and expenditure were performed during a 12-day intoxication period. According to three-way repeated measure ANOVAs, the origin of the clams had a highly significant effect on all physiological variables, and the interaction between diet and origin was significant for the clearance and absorption rates and for the scope for growth. The scope for growth index showed similar positive values for both the toxic and non-toxic individuals from the Melinka-Aysén population. However, it was significantly reduced in individuals from Corral-Valdivia when exposed to the diet containing A. catenella. The absence of differences between the physiological response of the toxic and non-toxic clams from Melinka-Aysén may be related to the frequent presence of A. catenella in the environment, indicating that this bivalve does not suffer negative consequences from PSP. By contrast, A. catenella has a negative effect on the physiological performance, primarily on the energy gained from the environment, on T. dombeii from Corral-Valdivia. This study supports the hypothesis that the history of PSP exposure plays an important role in the physiological performance and fitness of filter feeding bivalves.     

Dynamics of biochemical components, lipid classes and energy values on gonadal development of R. philippinarum associated with the temperature and ingestion rate

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.     

Response of two species of clams, Ruditapes decussatus and Venerupis pullastra, to starvation: physiological and biochemical parameters

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.     

Association of Sepsis-Related Mortality with Early Increase of TIMP-1/MMP-9 Ratio

Objective

Higher circulating levels of tissue inhibitor of matrix metalloproteinases (TIMP)-1 at the time of severe sepsis diagnosis have been reported in nonsurviving than in surviving patients. However, the following questions remain unanswered: 1) Does TIMP-1/MMP-9 ratio differ throughout the first week of intensive care between surviving and non-surviving patients? 2) Is there an association between TIMP-1/MMP-9 ratio and sepsis severity and mortality during such period? 3) Could TIMP-1/MMP-9 ratio during the first week be used as an early biomarker of sepsis outcome? 4) Is there an association between TIMP-1/MMP-9 ratio and coagulation state and circulating cytokine levels during the first week of intensive care in these patients? The present study sought to answer these questions.

Methods

Multicenter, observational and prospective study carried out in six Spanish Intensive Care Units (ICUs) of 295 patients with severe sepsis. Were measured circulating levels of TIMP-1, MMP-9, tumour necrosis factor (TNF)-alpha, interleukin (IL)-10 and plasminogen activator inhibitor (PAI)-1 at day 1, 4 and 8. End-point was 30-day mortality.

Results

We found higher TIMP-1/MMP-9 ratio during the first week in non-surviving (n = 98) than in surviving patients (n = 197) (p<0.01). Logistic regression analyses showed that TIMP-1/MMP-9 ratio at days 1, 4 and 8 was associated with mortality. Receiver operating characteristic (ROC) curves showed that TIMP-1/MMP-9 ratio at days 1, 4 and 8 could predict mortality. There was an association between TIMP-1/MMP-9 ratio and TNF-alpha, IL-10, PAI-1 and lactic acid levels, SOFA score and platelet count at days 1, 4 and 8.

Conclusions

The novel findings of our study were that non-surviving septic patients showed persistently higher TIMP-1/MMP-9 ratio than survivors ones during the first week, which was associated with severity, coagulation state, circulating cytokine levels and mortality; thus representing a new biomarker of sepsis outcome.     

Serum Levels of Caspase-Cleaved Cytokeratin-18 and Mortality Are Associated in Severe Septic Patients: Pilot Study

Objective

Apoptosis is increased in sepsis. Cytokeratin 18 (CK-18), a protein of the intermediate filament group present in most epithelial and parenchymal cells, is cleaved by the action of caspases and released into the blood as caspase-cleaved CK (CCCK)-18 during apoptosis. Circulating levels of CCCK-18 have scarcely been explored in septic patients. In one study with 101 severe septic patients, the authors reported higher serum CCCK-18 levels in non-survivors than in survivors; however, the sample size was too small to demonstrate an association between serum CCCK-18 levels and early mortality and whether they could be used as a biomarker to predict outcomes in septic patients. Thus, these were the objectives of this study with a large series of patients.

Methods

We performed a prospective, multicenter, observational study in six Spanish Intensive Care Units with 224 severe septic patients. Blood samples were collected at the time that severe sepsis was diagnosed to determine serum levels of CCCK-18, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6 and IL-10. The end point was 30-day mortality.

Results

Non-surviving patients (n = 80) showed higher serum CCCK-18 levels (P<0.001) than survivors (n = 144). Multiple logistic regression analysis showed that serum CCCK-18 levels>391 u/L were associated with 30-day survival (Odds ratio = 2.687; 95% confidence interval = 1.449–4.983; P = 0.002), controlling for SOFA score, serum lactic acid levels and age. Kaplan-Meier survival analysis showed that the risk of death in septic patients with serum CCCK-18 levels >391 u/L was higher than in patients with lower values (Hazard Ratio = 3.1; 95% CI = 1.96–4.84; P<0.001). Serum CCCK-18 levels were positively associated with serum levels of IL-6 and lactic acid, and with SOFA and APACHE scores.

Conclusions

The major novel finding of our study, the largest cohort of septic patients providing data on circulating CCCK-18 levels, was that serum CCCK-18 levels are associated with mortality in severe septic patients.     

Enzymatic and feeding behaviour of Argopecten purpuratus under variation in salinity and food supply

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.     

Feeding behavior and differential absorption of biochemical components by the infaunal bivalve Mulinia edulis and the epibenthic Mytilus chilensis in response to changes in food regimes

We measured changes in the feeding rate and food absorption efficiency of two suspension feeding bivalves, cross-trasplanted between habitats with special emphasis on their capacity for differential absorption of biochemical components from their food supply. Mulinia edulis were moved from the intertidal zone to the subtidal zone, and Mytilus chilensis from the subtidal to the intertidal zone for a period of 7 days, and then compared with animal that had not been transplanted. Experimentally prepared diets similar to those available in the two different environments were offered to the bivalves, and their rates of feeding and differential uptake of biochemical components were determined and statistically compared. The two species did not achieve complete acclimation of their feeding behaviour during the transplant period since the highest ingestion rates for biochemical components occurred under dietary conditions that reflected their habitats of origin. Absorption efficiency showed greater acclimation than the other physiological parameters measured, indicating the capacity of these species to modulate their enzymatic-digestive activity depending on food composition. We conclude that both Mytilus and Mulinia have a certain degree of physiological plasticity in their feeding behaviour and assimilatory balance of biochemical components, being greater in Mytilus. When both species encounter ambient food conditions characteristic of their normal habitats, they show maximum values of food absorption, while under conditions where their typical diets are exchanged (Mytilus in intertidal and Mulinia in subtidal), the energy absorbed declines in each, but in ways very different between the two species. Thus, Mytilus exposed to high concentrations of low quality seston reduced the energy absorbed by 31.7% compared to its normal habitat, while Mulinia exposed to low concentrations of high-quality food reduced their energy absorption by 64%.     

Enzymatic digestive activity in Mytilus chilensis (Hupé 1854) in response to food regimes and past feeding history

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.     

Fatty acid profiles of Mytilus galloprovincialis (Lmk) mussel of subtidal and rocky shore origin

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.