Marine Oil from C. finmarchicus Enhances Glucose Homeostasis and Liver Insulin Resistance in Obese Prediabetic Individuals.

The intermediate state between normal glucose tolerance and overt type 2 diabetes mellitus is associated with micro- and macrovascular diseases, requiring safe and cost-effective treatment measures interventions. A novel source of LC n-3 FAs is Calanus finmarchicus Oil, which showed promising effects on glucose homeostasis in preclinical studies due to anti-obesity effects and/or anti-inflammatory properties. In total, 43 obese patients (BMI: 31.7 ± 5.2 kg/m2) were allocated in the following two groups: (1) Calanus oil group (2 g CO/day) and (2) placebo group (2 g paraffin oil/day). Markers of glucose metabolism, body composition and energy intake were measured at the beginning (t0), after 12 weeks (t12) and 16 weeks (t16). Overall, parameters reflecting abnormal glucose homeostasis and insulin resistance in the liver, including fasting insulin (-2.9 mU/L ± 4.10, p < 0.05), HOMA-IR (-0.9 ± 1.28, p < 0.05) and hepatic insulin resistance index (-1.06 ± 1.72 × 106, p < 0.05) significantly enhanced after a 12-week CO-intervention, while no differences were observed in HbA1c, AUC0-2h Glucose, AUC0-2h Insulin, 2 h plasma glucose and muscle insulin sensitivity index. Our results indicate that Calanus oil causes beneficial effects on glucose metabolism and insulin resistance in obese patients, with clinical relevance to be verified in further studies. In addition, the possible active compounds and their mechanisms of action should be elucidated.

Intake of Calanus finmarchicus oil for 12 weeks improves omega-3 index in healthy older subjects engaging in an exercise programme.

The n-3 PUFA, EPA and DHA, play an important role in human health. As the intake of EPA and DHA from the diet is often inadequate, supplementation of those fatty acids is recommended. A novel source of n-3 PUFA is Calanus finmarchicus oil (CO) which contains fatty acids mainly bound in wax esters. To date, no data are available on the effects of long-term intake of this marine oil on n-3 PUFA blood levels. Therefore, the aim of this study was to evaluate the effect of CO on the n-3 PUFA blood levels using the omega-3 index (O3I). The data originate from a larger randomised controlled trial. For this analysis, samples from seventy-two participants (59·2 (sd 6·2) years, BMI 27·7 (sd 5·28) kg/m2) were analysed. Of those, thirty-six performed 2×/week exercise and received 2 g of CO, which provided 124 mg stearidonic acid (SDA), 109 mg EPA and 87 mg DHA daily (EXCO group), while the other group performed exercise only (EX group) and served as a control for this analysis. The O3I increased from 6·07 (sd 1·29) % at baseline to 7·37 (sd 1·10) % after 12 weeks within the EXCO group (P < 0·001), while there were no significant changes in the EX group (6·01 (sd 1·26)-6·15 (sd 1·32) %, P = 0·238). These data provide first evidence that wax ester-bound n-3 PUFA from CO can significantly increase the O3I despite relatively low EPA + DHA amounts. Further, the effects of exercise could be excluded.

Effects of Exercise Combined with a Healthy Diet or Calanus finmarchicus Oil Supplementation on Body Composition and Metabolic Markers-A Pilot Study.

Aging is accompanied by a progressive decline in muscle mass and an increase in fat mass, which are detrimental changes associated with the development of health conditions such as type-2 diabetes mellitus or chronic low-grade inflammation. Although both exercise as well as nutritional interventions are known to be beneficial in counteracting those age-related changes, data to which extent untrained elderly people may benefit is still sparse. Therefore, a randomized, controlled, 12-week interventional trial was conducted in which 134 healthy untrained participants (96 women and 38 men, age 59.4 ± 5.6 years, body mass index (BMI) 28.4 ± 5.8 kg/m2) were allocated to one of four study groups: (1) control group with no intervention (CON); (2) 2×/week aerobic and resistance training only (EX); (3) exercise routine combined with dietary counseling in accordance with the guidelines of the German Nutrition Society (EXDC); (4) exercise routine combined with intake of 2 g/day oil from Calanus finmarchicus (EXCO). Body composition (bioelectrical impedance analysis), as well as markers of glucose metabolism and blood lipids, were analyzed at the beginning and the end of the study. The highest decreases in body fat were observed within the EXCO group (-1.70 ± 2.45 kg, p < 0.001), and the EXDC (-1.41 ± 2.13 kg, p = 0.008) group. Markers of glucose metabolism and blood lipids remained unchanged in all groups. Taken together results of this pilot study suggest that a combination of moderate exercise and intake of oil from Calanus finmarchicus or a healthy diet may promote fat loss in elderly untrained overweight participants.

Effect of Calanus Oil Supplementation and 16 Week Exercise Program on Selected Fitness Parameters in Older Women.

We investigated changes in functional fitness after an exercise program in combination with Calanus oil supplementation, a novel source of bioactive lipids rich in wax esters with omega-3 polyunsaturated fatty acid (n-3 PUFA). Fifty-five healthy sedentary women aged 65-80 (mean age 70.9 ± 3.9 years, BMI 27.24 ± 3.9 kg m-2, VO2peak 19.46 ± 3.7 ml kg-1 min-1) were enrolled in the study. The participants were divided into two groups: exercise training plus Calanus Oil supplementation (n = 28) or exercise plus placebo (sunflower oil) supplementation (n = 27). The exercise intervention program was completed by 53 participants and contained functional circuit training (twice a week, 45 min plus 15 min of stretching and balance training) and Nordic walking (once a week, 60 min) for 16 weeks. Senior fitness test, exercise stress test on bicycle ergometer, hand-grip, and body composition were evaluated before and after the program. Our results show that functional fitness and body composition improved following the interventional exercise program, but for most of the parameters there was no synergic effect of supplementing n-3 PUFA-rich Calanus oil. In comparison to the placebo group, the group with Calanus supplementation experienced significantly higher improvement of functional strength of lower body which was evaluated by the chair stand test. Supplementation with Calanus may have a synergic effect with exercise on functional strength of the lower body in the elderly.

Calanus oil in the treatment of obesity-related low-grade inflammation, insulin resistance, and atherosclerosis.

Calanus oil (COil) is a natural product extracted from marine zooplankton Calanus finmarchicus found in the North Atlantic Ocean. This oil is rich in wax esters of polyunsaturated fatty acids (PUFAs) and has been projected as the best alternative to fish oil because its production cannot keep pace with the demands from the growing markets. The COil is the only commercially available marine source of wax esters, whereas classic ω-3 PUFAs comes from triglycerides, ethyl esters, and phospholipids. It has, in recent decades, been seen that there is an unprecedented rise in the use of PUFA-rich oil in the aquaculture industry. A simultaneous rise in the demand of PUFAs is also observed in the health care industry, where PUFAs are suggested preventing various disorders related to lifestyles such as obesity, diabetes mellitus, chronic low-grade inflammation, atherosclerosis, and brain and cardiovascular disorders (CVDs). In this review, we will explore the metabolic aspects related to the use of COil as an antioxidant, anticholesterinemic, and anti-inflammatory dietary source and its impact on the prevention and therapy of obesity-related metabolic disorders.

Wax Ester Rich Oil From The Marine Crustacean, Calanus finmarchicus, is a Bioavailable Source of EPA and DHA for Human Consumption.

Oil from the marine copepod, Calanus finmarchicus, which contains >86 % of fatty acids present as wax esters, is a novel source of n-3 fatty acids for human consumption. In a randomized, two-period crossover study, 18 healthy adults consumed 8 capsules providing 4 g of Calanus(®) Oil supplying a total of 260 mg EPA and 156 mg DHA primarily as wax esters, or 1 capsule of Lovaza(®) providing 465 mg EPA and 375 mg DHA as ethyl esters, each with an EPA- and DHA-free breakfast. Plasma EPA and DHA were measured over a 72 h period (t = 1, 2, 4, 6, 8, 10, 12, 24, 48, and 72 h). The positive incremental area under the curve over the 72 h test period (iAUC0-72 h) for both EPA and DHA was significantly different from zero (p < 0.0001) in both test conditions, with similar findings for the iAUC0-24 h and iAUC0-48 h, indicating the fatty acids were absorbed. There was no difference in the plasma iAUC0-72 h for EPA + DHA, or DHA individually, in response to Calanus Oil vs the ethyl ester condition; however, the iAUC0-48 h and iAUC0-72 h for plasma EPA in response to Calanus Oil were both significantly increased relative to the ethyl ester condition (iAUC0-48 h: 381 ± 31 vs 259 ± 39 µg*h/mL, p = 0.026; iAUC0-72 h: 514 ± 47 vs 313 ± 49 µg*h/mL, p = 0.009). These data demonstrate a novel wax ester rich marine oil is a suitable alternative source of EPA and DHA for human consumption.

Dietary Calanus oil antagonizes angiotensin II-induced hypertension and tissue wasting in diet-induced obese mice.

BACKGROUND: We have recently shown that Calanus oil, which is extracted from the marine copepod Calanus finmarchicus, reduces fat deposition, suppresses adipose tissue inflammation and improves insulin sensitivity in high fat-fed rodents. This study expands upon our previous observations by examining whether dietary supplementation with Calanus oil could antagonize angiotensin II (Ang II)-induced hypertension and ventricular remodeling in mice given a high fat diet (HFD). METHODS: C57BL/6J mice were initially subjected to 8 weeks of HFD with or without 2% (w/w) Calanus oil. Thereafter, animals within each group were randomized for the administration of either Ang II (1µg/kg/min) or saline for another two weeks, while still on the same dietary regimen. RESULTS: Ang II caused a marked decline in body and organ weights in mice receiving non-supplemented HFD, a response which was clearly attenuated in mice receiving Calanus oil supplementation. Furthermore, Ang II-induced elevation in blood pressure was also attenuated in the Calanus oil-supplemented group. As expected, infusion of Ang II produced hypertrophy and up-regulation of marker genes (mRNA level) of both hypertrophy and fibrosis in cardiac muscle, but this response was unaffected by dietary Calanus oil. Fibrosis and inflammation were up-regulated also in the aorta following Ang II infusion. However, the inflammatory response was blocked by Calanus oil supplementation. A final, and unexpected, finding was that dietary intake of Calanus oil caused a robust increase in the level of O-GlcNAcylation in cardiac tissue. CONCLUSION: These results suggest that dietary intake of oil from the marine copepod Calanus finmarchicus could be a beneficial addition to conventional hypertension treatment. The compound attenuates inflammation and the severe metabolic stress caused by Ang II infusion. Although the present study suggests that the anti-hypertensive effect of the oil (or its n-3 PUFAs constituents) is related to its anti-inflammatory action in the vessel wall, other mechanisms such as interaction with intracellular calcium mechanisms or a direct antagonistic effect on Ang II receptors should be examined.

Clinical safety evaluation of marine oil derived from Calanus finmarchicus.

Marine oils are rich in polyunsaturated fatty acids (PUFAs), including docosahexaenoic and eicosapentaenoic acid. These PUFAs are associated with health benefits and additional sustainable sources of marine oils are desirable. One of the source organisms is Calanus finmarchicus, a copepod endemic to the North Atlantic. PUFAs in the lipid fraction of this organism are largely in the form of wax esters. To assess the safety of these wax esters as a source of PUFAs, a randomized, double-blinded, placebo-controlled clinical trial was conducted whereby 64 subjects consumed 2 g Calanus oil in capsule form daily for a period of one year. A group of 53 subjects consumed placebo capsules. At baseline, 6-, and 12-months, series of evaluations were conducted, including: vital signs, clinical chemistry and hematological evaluations, and adverse event reporting. Food intake and physical exercise were controlled by means of a questionnaire. There were no effects on Calanus oil treatment on any of the safety parameters measured. A slight increase in the incidence of eczema was reported in the Calanus oil group, but the response was minor in nature, not statistically significant after controlling for multiple comparisons, and could not be attributed to treatment.

Characterisation of iron regulatory protein 1A and 1B in the blood-feeding copepod Lepeophtheirus salmonis.

During its parasitic life stages, the marine ectoparasitic copepod Lepeophtheirus salmonis ingests large amounts of host blood, which contains high amounts of iron. Iron is an essential micronutrient, but also toxic in high dosages, and blood-feeding parasites like the salmon louse must thus possess an efficient system to handle the excess iron. Iron regulatory protein 1 and 2 (IRP1 and IRP2) are known to play crucial roles in this process, by regulating several proteins involved in iron transport and storage, depending on the cellular iron concentration. To gain knowledge about the regulation of the iron metabolism in salmon lice, two IRP homologues (LsIRP1A and LsIRP1B) were identified by sequence and predicted structure similarity to known IRPs in other species. In situ hybridisation revealed that LsIRP1A and LsIRP1B mRNAs were expressed in the ovaries, oviducts and vitellogenic oocytes of adult females. Transcription levels of LsIRP1A and LsIRP1B mRNAs did not differ significantly between the different developmental stages of the salmon louse. Adults in the absence of blood as a feed source had decreased levels of LsIRP1A, but not LsIRP1B mRNA. RNA binding experiments indicated the presence of functioning IRP in salmon lice. In order to explore the biological functions of LsIRP1A and LsIRP1B, the mRNAs of both proteins were knocked down by RNA interference (RNAi) in preadult females. The knockdown was confirmed by qRT-PCR. LsIRP1B knockdown lice produced less offspring than control lice due to slightly shorter egg strings and had decreased levels of transcripts involved in egg development. Knockdown of both LsIRP1A and LsIRP1B caused increased expression of a salmon louse Ferritin (LsFer). These results confirm that salmon lice have two IRP1 homologues, LsIRP1A and LsIRP1B, and might suggest a function in cellular iron regulation in the reproductive organs and eggs.

Oil droplet ingestion and oil fouling in the copepod Calanus finmarchicus exposed to mechanically and chemically dispersed crude oil.

The rates of ingestion of oil microdroplets and oil fouling were investigated in the zooplankton filter-feeder Calanus finmarchicus (Gunnerus, 1770) at 3 concentrations of oil dispersions ranging from 0.25 mg/L to 5.6 mg/L. To compare responses to mechanically and chemically dispersed oil, the copepods were exposed to comparable dispersions of micron-sized oil droplets made with and without the use of a chemical dispersant (similar oil droplet size range and oil concentrations) together with a constant supply of microalgae for a period of 4 d. The filtration rates as well as accumulation of oil droplets decreased with increasing exposure concentration. Thus the estimated total amount of oil associated with the copepod biomass for the 2 lowest exposures in the range 11 mL/kg to 17 mL/kg was significantly higher than the approximately 6 mL/kg found in the highest exposure. For the 2 lowest concentrations the filtration rates were significantly higher in the presence of chemical dispersant. Furthermore, a significant increase in the amount of accumulated oil in the presence of dispersant was observed in the low exposure group.

Molecular characterisation of the salmon louse, Lepeophtheirus salmonis salmonis (Krøyer, 1837), ecdysone receptor with emphasis on functional studies of female reproduction.

The salmon louse Lepeophtheirus salmonis (Copepoda, Caligidae) is an important parasite in the salmon farming industry in the Northern Hemisphere causing annual losses of hundreds of millions of dollars (US) worldwide. To facilitate development of a vaccine or other novel measures to gain control of the parasite, knowledge about molecular biological functions of L. salmonis is vital. In arthropods, a nuclear receptor complex consisting of the ecdysone receptor and the retinoid X receptor, ultraspiracle, are well known to be involved in a variety of both developmental and reproductive processes. To investigate the role of the ecdysone receptor in the salmon louse, we isolated and characterised cDNA with the 5'untranslated region of the predicted L. salmonis EcR (LsEcR). The LsEcR cDNA was 1608 bp encoding a 536 amino acid sequence that demonstrated high sequence similarities to other arthropod ecdysone receptors including Tribolium castaneum and Locusta migratoria. Moreover, in situ analysis of adult female lice revealed that the LsEcR transcript is localised in a wide variety of tissues such as ovaries, sub-cuticula and oocytes. Knock-down studies of LsEcR using RNA interference terminated egg production, indicating that the LsEcR plays important roles in reproduction and oocyte maturation. We believe this is the first report on the ecdysone receptor in the economically important parasite L. salmonis.

Wax esters from the marine copepod Calanus finmarchicus reduce diet-induced obesity and obesity-related metabolic disorders in mice.

We showed previously that dietary supplementation with oil from the marine zooplankton Calanus finmarchicus (Calanus oil) attenuates obesity, inflammation, and glucose intolerance in mice. More than 80% of Calanus oil consists of wax esters, i.e., long-chain fatty alcohols linked to long-chain fatty acids. In the present study, we compared the metabolic effects of Calanus oil-derived wax esters (WE) with those of purified eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) ethyl esters (E/D) in a mouse model of diet-induced obesity. C57BL/6J mice received a high-fat diet (HFD; 45% energy from fat). After 7 wk, the diet was supplemented with either 1% (wt:wt) WE or 0.2% (wt:wt) E/D. The amount of EPA + DHA in the E/D diet was matched to the total amount of n-3 (ω-3) polyunsaturated fatty acids (PUFAs) in the WE diet. A third group was given an unsupplemented HFD throughout the entire 27-wk feeding period. WE reduced body weight gain, abdominal fat, and liver triacylglycerol by 21%, 34%, and 52%, respectively, and significantly improved glucose tolerance and aerobic capacity. In abdominal fat depots, WE reduced macrophage infiltration by 74% and downregulated expression of proinflammatory genes (tumor necrosis factor-α, interleukin-6, and monocyte chemoattractant protein-1), whereas adiponectin expression was significantly upregulated. By comparison, E/D primarily suppressed the expression of proinflammatory genes but had less influence on glucose tolerance than WE. E/D affected obesity parameters, aerobic capacity, or adiponectin expression by <10%. These results show that the wax ester component of Calanus oil can account for the biologic effects shown previously for the crude oil. However, these effects cannot exclusively be ascribed to the content of n-3 PUFAs in the wax ester fraction.

Oil from the marine zooplankton Calanus finmarchicus improves the cardiometabolic phenotype of diet-induced obese mice.

The aim of the present study was to investigate the effects of oil extracted from the zooplankton Calanus finmarchicus (Calanus oil) on diet-induced obesity and obesity-related disorders in mice. C57BL/6J mice fed a high-fat diet (HFD, 45% energy from fat) exhibited increased body weight and abdominal fat accumulation as well as impaired glucose tolerance compared with mice fed a normal chow diet (10% energy from fat). Supplementing the HFD with 1.5% (w/w) Calanus oil reduced body-weight gain, abdominal fat accumulation and hepatic steatosis by 16, 27 and 41%, respectively, and improved glucose tolerance by 16%. Calanus oil supplementation reduced adipocyte size and increased the mRNA expression of adiponectin in adipose tissue. It also reduced macrophage infiltration by more than 70%, accompanied by reduced mRNA expression of pro-inflammatory cytokines (TNF-α, IL-6 and monocyte chemotactic protein-1). The effects of Calanus oil were not only preventive, but also therapeutic, as the oil proved to be beneficial, regardless of whether the supplementation was started before or after the onset of obesity and glucose intolerance. Although the present study cannot pinpoint the active component(s) of the oil, there is reason to believe that the n-3 fatty acids EPA and DHA and/or antioxidants are responsible for its beneficial effects. It should be noted that the concentration of n-3 fatty acids in the Calanus oil diet was considerably lower than the concentrations used in similar studies reporting beneficial effects on obesity and obesity-related abnormalities.

A wax ester and astaxanthin-rich extract from the marine copepod Calanus finmarchicus attenuates atherogenesis in female apolipoprotein E-deficient mice.

The aim of this study was to investigate the effect of dietary supplementation with an oil extracted from the zooplankton copepod Calanus finmarchicus [calanus oil (CO)] on atherosclerosis in apoE-deficient (apoE(-/-)) mice. Thirty 6-wk-old female apoE(-/-) mice (n = 10/group) were fed: 1) a Western-type, high-fat diet (HFD); 2) HFD supplemented with 1% (wt:wt) CO; or 3) HFD supplemented with 0.88% (wt:wt) corn oil + 0.12% (wt:wt) EPA+DHA ethyl esters (EPA+DHA) for 13 wk. Dietary CO supplementation lowered total aorta atherogenesis by 36.5% compared to the HFD (P < 0.01), whereas the reduction in the lesion prone aortic arch was 34.8% (P < 0.01). The degree of aortic atherogenesis was intermediate in mice fed EPA+DHA compared to those fed HFD and CO. The effect on atherogenesis was paralleled by reduced expression of hepatic genes for the proinflammatory cytokines, Ccl2, Icam1, Il1b, and Nfkb1, in mice fed CO compared to those fed HFD. For mice fed EPA+DHA, gene expression did not differ compared to those fed CO or HFD. Plasma concentrations of total cholesterol, TG, and cytokines did not differ between the groups at the end of the study. However, mice fed CO gained more weight compared to those fed HFD but not compared to those fed EPA+DHA. In conclusion, dietary CO supplementation attenuated atherosclerotic lesion formation in female apoE(-/-) mice and may be an effective and safe dietary intervention to reduce the development of atherosclerosis. However, further studies are warranted to elucidate the underlying physiological and molecular mechanisms.

Fatty acid utilisation and metabolism in caecal enterocytes of rainbow trout (Oncorhynchus mykiss) fed dietary fish or copepod oil.

A combined fatty acid metabolism assay was employed to determine fatty acid uptake and relative utilisation in enterocytes isolated from the pyloric caeca of rainbow trout. In addition, the effect of a diet high in long-chain monoenoic fatty alcohols present as wax esters in oil derived from Calanus finmarchicus, compared to a standard fish oil diet, on caecal enterocyte fatty acid metabolism was investigated. The diets were fed for 8 weeks before caecal enterocytes from each dietary group were isolated and incubated with [1-14C]fatty acids: 16:0, 18:1n-9, 18:2n-6, 18:3n-3, 20:1n-9, 20:4n-6, 20:5n-3, and 22:6n-3. Uptake was measured over 2 h with relative utilisation of different [1-14C]fatty acids calculated as a percentage of uptake. Differences in uptake were observed, with 18:1n-9 and 18:2n-6 showing the highest rates. Esterification into cellular lipids was highest with 16:0 and C18 fatty acids, accounting for over one-third of total uptake, through predominant incorporation in triacylglycerol (TAG). The overall utilisation of fatty acids in phospholipid synthesis was low, but highest with 16:0, the most prevalent fatty acid recovered in intracellular phosphatidylcholine (PC) and phosphatidylinositol (PI), although exported PC exhibited higher proportions of C20/C22 polyunsaturated fatty acids (PUFA). Other than 16:0, incorporation into PC and PI was highest with C20/C22 PUFA and 20:4n-6 respectively. Recovery of labelled 18:1n-9 in exported TAG was 3-fold greater than any other fatty acid which could be due to multiple esterification on the glycerol 'backbone' and/or increased export. Approximately 20-40% of fatty acids taken up were beta-oxidised, and was highest with 20:4n-6. Oxidation of 20:5n-3 and 22:6n-3 was also surprisingly high, although 22:6n-3 oxidation was mainly attributed to retroconversion to 20:5n-3. Metabolic modification of fatty acids by elongation-desaturation was generally low at <10% of [1-14C]fatty acid uptake. Dietary copepod oil had generally little effect on fatty acid metabolism in enterocytes, although it stimulated the elongation and desaturation of 16:0 and elongation of 18:1n-9, with radioactivity recovered in longer n-9 monoenes. The monoenoic fatty acid, 20:1n-9, abundant in copepod oil as the homologous alcohol, was poorly utilised with 80% of uptake remaining unesterified in the enterocyte. However, the fatty acid composition of pyloric caeca was not influenced by dietary copepod oil.

Modeling selenium bioaccumulation through arthropod food webs in San Francisco Bay, California, USA.

Trophic transfer is the main process by which upper trophic level wildlife are exposed to selenium. Transfers through lower levels of a predator's food web thus can be instrumental in determining the threat of selenium in an ecosystem. Little is known about Se transfer through pelagic, zooplankton-based food webs in San Francisco Bay ([SFB], CA, USA), which serve as an energy source for important predators such as striped bass: A dynamic multipathway bioaccumulation model was used to model Se transfer from phytoplankton to pelagic copepods to carnivorous mysids (Neomysis mercedis). Uptake rates of dissolved Se, depuration rates, and assimilation efficiencies (AE) for the model were determined for copepods and mysids in the laboratory. Small (73-250 microm) and large (250-500 microm) herbivorous zooplankton collected from SFB (Oithona/Limnoithona and Acartia sp.) assimilated Se with similar efficiencies (41-52%) from phytoplankton. Mysids assimilated 73% of Se from small herbivorous zooplankton; Se AE was significantly lower (61%) than larger herbivorous zooplankton. Selenium depuration rates were high for both zooplankton and mysids (12-25% d(-1)), especially compared to bivalves (2-3% d(-1)). The model predicted steady state Se concentrations in mysids similar to those observed in the field. The predicted concentration range (1.5-5.4 microg g(-1)) was lower than concentrations of 4.5 to 24 microg g(-1) observed in bivalves from the bay. Differences in efflux between mysids and bivalves were the best explanation for the differences in uptake. The results suggest that the risk of selenium toxicity to predators feeding on N. mercedis would be less than the risk to predators feeding on bivalves. Management of selenium contamination should include food webs analyses to focus on the most important exposure pathways identified for a given watershed.