Thiamin requirement of juvenile shrimp (Penaeus monodon)

Dietary choline requirement of juvenile grass shrimp (Penaeus monodon)

A feeding trial was conducted to determine the dietary choline requirement of juvenile grass shrimp, Penaeus monodon. Purified basal diets were formulated using vitamin-free casein (containing 370 mg choline per kg) as the protein source. Graded levels (0, 300, 600, 1000, 2000, 4000, 7000, and 10 000 mg choline per kg diet) of choline chloride were added to the basal diet, resulting in eight dietary treatments in the experiment. Each diet was given to three replicate groups of shrimp initially averaging 1·18 (s.d. 0·01) g for 8 weeks. Weight gain was highest in shrimp given the diets supplemented with 7000 and 4000 mg choline per kg diet, followed by the groups given 2000 mg/kg, then 1000 and 600 mg/kg, and finally 300 mg/kg and the unsupplemented control group (P < 0·05). Shrimp given diets supplemented with 7000 and 4000 mg choline per kg diet had significantly higher food efficiency and survival than those given diet with 300 mg choline per kg or the control diet. Higher body crude protein and choline concentrations were recorded in shrimp given diets supplemented with 4000 and 7000 mg choline per kg diet than shrimp given diets with ≤600 mg choline/kg and ≤2000 mg choline per kg, respectively. Analysis by polynomial regression of weight gain and body choline concentration for P. monodon gave a maximum at about 6000 mg/kg. Taking into account the choline concentration of the unsupplemented basal diet, the optimal dietary choline requirement for growing P. monodon is about 6200 mg/kg.

The importance of dietary calcium consumption in two species of semi-terrestrial grapsoid crabs

Calcium (Ca) is essential for crustaceans, due to calcium carbonate (CaCO3) deposition in the new exoskeleton to harden it. The purpose of this work was to study short term Ca balance in terms of dietary Ca ingestion in two phylogenetically related crabs (Superfamily Grapsoidea) showing different degrees of terrestrial adaptations: Sesarma rectum Randall, 1840 and Neohelice granulata (Dana, 1851). Dietary Ca ingestion was studied using purified diets with different Ca concentrations (0, 2.2 and 6.66 % Ca), together with measurements of Ca excretion and Ca hemolymph levels. The results showed that both crabs had the same response to foods containing different levels of Ca, with both species eating more of the high Ca diet. However, S. rectum consumed more per mg body mass at all Ca concentrations (6 mg.g-1 for S. rectum against 3 mg.g-1 for N. granulata). Both species excreted/egested Ca differently: S. rectum excreted Ca proportionally to ingestion, whereas N. granulata maintained constant faecal Ca output at all dietary Ca levels. Moreover, Ca hemolymph levels for crabs fed the different diets were independent of dietary Ca. In conclusion, both S. rectum and N. granulata seem to regulate the consumption of diets containing more Ca, which suggests a fine balance for Ca intake.

Density-dependent patterns of thiamine and pigment production in the diatom Nitzschia microcephala

In the present study we investigate how intraspecific (density-dependent) competition for nutrients by the diatom Nitzschia microcephala affects the level of oxidative stress in the algal cells as well as their production of pigments and thiamine. N. microcephala was grown in three different densities until the stationary growth phase was reached. Throughout the experiment, growth rate was negatively related to cell density. Superoxide dismutase activity, protein thiol, and diatoxanthin concentrations indicated increasing oxidative stress with increasing cell density, which was most probably caused by nutrient depletion of the medium. Pigment contents per cell (except for diatoxanthin) decreased with increasing cell density. N. microcephala was able to synthesize thiamine and its thiamine content per cell increased in concert with cell density. In comparison, the dinoflagellate Amphidinium carterae was unable to synthesize thiamine. These results suggest that cells of N. microcephala subjected to higher competition and lower growth rates have a lower carotenoid content and a higher thiamine content. If such responses would occur in nature as well, eutrophication (higher cell densities) may alter the quality of microalgae as food items for higher trophic levels not only by species shifts in the phytoplankton, but also by changes in the cellular nutritional value within species.

Dietary pantothenic acid requirement of juvenile grass shrimp, Penaeus monodon

A feeding trial was conducted to estimate the minimal dietary pantothenic acid (PA) requirement for juvenile grass shrimp, Penaeus monodon. Purified diets with seven levels (0, 20, 40, 60, 120, 240, and 480 mg/kg) of supplemental PA were fed to P. monodon (mean weight 0.88 +/- 0.01 g) for 8 wk. The level of PA detected in the unsupplemented diet was 0.02 mg/kg. Each diet was fed to three replicate groups of shrimp. Feed efficiencies (FE) and protein efficiency ratios were highest in shrimp fed the diets supplemented with 120, 240, and 480 mg PA/kg diet, followed by the groups fed 60 mg/kg, then 40 mg/kg, and finally the unsupplemented control group (P < 0.05). Shrimp fed diets supplemented with PA had significantly higher survival percentages and lower hepatopancreatic lipid concentration than those fed the unsupplemented, control diets. Broken-line regression analyses of weight gain percentage and hepatopancreatic CoA and PA concentrations of the shrimp indicated that the adequate dietary PA concentration in growing P. monodon is 101-139 mg/kg.