Fatty acids and stable isotopes as indicators of early-life feeding and potential maternal resource dependency in the bull shark Carcharhinus leucas

The degree of reliance of newborn sharks on energy reserves from maternal resource allocation and the timescales over which these animals develop foraging skills are critical factors towards understanding the ecological role of top predators in marine ecosystems. We used muscle tissue stable carbon isotopic composition and fatty acid analysis of bull sharks Carcharhinus leucas to investigate early-life feeding ecology in conjunction with maternal resource dependency. Values of δ13C of some young-of-the-year sharks were highly enriched, reflecting inputs from the marine-based diet and foraging locations of their mothers. This group of sharks also contained high levels of the 20:3ω9 fatty acid, which accumulates during periods of essential fatty acid deficiency, suggesting inadequate or undeveloped foraging skills and possible reliance on maternal provisioning. A loss of maternal signal in δ13C values occurred at a length of approximately 100 cm, with muscle tissue δ13C values reflecting a transition from more freshwater/estuarine-based diets to marine-based diets with increasing length. Similarly, fatty acids from sharks >100 cm indicated no signs of essential fatty acid deficiency, implying adequate foraging. By combining stable carbon isotopes and fatty acids, our results provided important constraints on the timing of the loss of maternal isotopic signal and the development of foraging skills in relation to shark size and imply that molecular markers such as fatty acids are useful for the determination of maternal resource dependency.

Relationship of Omega-3 Fatty Acids on C-Reactive Protein and Homocysteine in Haitian and African Americans with and without Type 2 Diabetes

Background: Omega-3 fatty acids (n-3) may be protective of cardiovascular risk factors for vulnerable populations. The purpose of this study was to assess the association between n-3 with, C-reactive protein (CRP), and homocysteine (HCY) in Black minorities with and without type 2 diabetes. Methods: A cross-sectional study was conducted with 406 participants: Haitian Americans (HA): n=238. African Americans (AA): n=172. Participants were recruited from a randomly generated mailing lists, local diabetes educators, community health practitioners and advertisements from 2008-2010. Sociodemographics and anthropometrics were collected and used to adjust analyses. All dietary variables were collected using the semi-quantitative food frequency questionnaire (FFQ) and used to quantify vitamin components. Blood was collected to measure CVD risk factors (blood lipids, HCY, and CRP). Results: African Americans had higher waist circumferences and C-reactive protein and consumed more calories as compared to Haitian Americans. Omega 3 fatty acid intake per calorie did not differ between these ethnicities, yet African Americans with low n-3 intake were three times more likely to have high C-reactive protein as compared to their counterparts [OR=3. 32 (1. 11, 9. 26) p=0.031]. Although homocysteine did not differ by ethnicity, African Americans with low omega 3 intake (<1 g/day) were four times as likely to have high homocysteine (>12 mg/L) as compared to their counterparts, adjusting for confounders [OR=4.63 (1.59, 12.0) p=0.004]. Consumption of n-3 by diabetes status was not associated with C-reactive protein or homocysteine levels. Conclusions: Consumption of n-3 may be protective of cardiovascular risk factors such as C-r

Stoichiometry, growth, and fecundity responses to nutrient enrichment by invertebrate grazers in sub-tropical turtle grass (Thalassia testudinum) meadows

Although the effectiveness of herbivores in mitigating the effects of nutrient enrichment is well documented, few studies have examined the effects of nutrient enrichment on components of consumer fitness. Enclosures were deployed in shallow turtle grass (Thalassia testudinum) beds in Florida Bay, Florida in fall 2003, spring 2004, and fall 2004 to measure the effects of nitrogen and phosphorous enrichment on the growth, fecundity, and stoichiometry of three invertebrate epiphyte grazers commonly associated with T. testudinum. The gastropod Turbo castanea exhibited significantly greater wet weight gain and lower C:P and N:P in enriched than in ambient treatments. Although nutrient enrichment did not have any significant effects on the growth of caridean shrimp (treatment consisted of several different caridean shrimp species), their C:N was significantly lower in enriched treatments. The final size and stoichiometry of the hermit crab Paguristes tortugae was not significantly affected by nutrient enrichment, nor did nutrient enrichment significantly affect the fecundity of P. tortugae, the only grazer in which gravid individuals or egg masses were present. Our study demonstrated that nutrient enrichment of primary producers can positively affect the growth of marine invertebrate grazers and alter their stoichiometry; however, these effects were species-specific and may be dependent upon the life stage, specific diets, and/or compensatory feeding habits of the grazers.