Observations of metal concentrations in tilapia (Oreochromis mossambicus)in reservoirs of South Sri Lanka

Samples of the muscle and liver of tilapia (Oreochromis mossambicus) obtained from the five reservoirs in four catchments in southern Sri Lanka in 1998 were analyzed for 16 elements: As, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, and Zn by inductively coupled plasma emission spectrophotometry, and Hg by atomic absorption spectrophotometry. The concentrations of Cr, Ni, and Pb were below the detection limits of the instrumental techniques employed in all samples. The elements As, Ca, Co, Cu, Fe, Hg, K, Mg, Mn, Na, Sr, and Zn were detected in the muscle and liver tissue, with Cd detected in some liver samples. There were no statistically significant differences between the individual concentrations of any of the metals and the site from which the tilapia were collected (P>0.05). Furthermore, no statistically significant correlations were found between total length of fish and metal concentration. No elements were found at concentrations of toxicological concern. However, a principal component analysis suggests that the populations of tilapia in the reservoirs may be exposed to different regimes of metals, possibly associated with different catchment land-use patterns.

Effect of elevated lipid concentrations on human skeletal muscle gene expression

Dietary fatty acids regulate the abundance and activity of various proteins involved in the regulation of fat oxidation by functioning as regulators of gene transcription. To determine whether the transcription of key lipid metabolic proteins necessary for fat metabolism within human skeletal muscle are regulated by acute elevations in circulating free fatty acid (FFA) concentrations, 7 healthy men underwent 3 randomized resting infusions of Intralipid (20%) with heparin sodium, saline and heparin sodium, or saline only for 5 hours. These infusions significantly elevated plasma FFA concentrations by 15-fold (to 1.67 ± 0.13 mmol/L) in the Intralipid infusion trial, with modest elevations observed in the saline and heparin sodium and saline alone infusion groups (0.67 ± 0.09 and 0.49 ± 0.087 mmol/L, P < .01 both vs Intralipid infusion). Analysis of messenger RNA (mRNA) concentration demonstrated that pyruvate dehydrogenase kinase isoform 4 (PDK4) mRNA, a key negative regulator of glucose oxidation, was increased in all trials with a 24-fold response after Intralipid infusion, 15-fold after saline and heparin infusion, and 9-fold after saline alone. The PDK4 increases were not significantly different between the 3 trials. The mRNA concentration of the major uncoupling protein within skeletal muscle, uncoupling protein 3, was not elevated in parallel to the increased plasma FFA as similar (not, vert, similar2-fold) increases were evident in all trials. Additional genes involved in lipid transport (fatty acid translocase/CD36), oxidation (carnitine palmitoyltransferase I), and metabolism (1-acylglycerol-3-phosphate O-acyltransferase 1, hormone-sensitive lipase, and peroxisomal proliferator-activated receptor-γ coactivator-1α) were not altered by increased circulating FFA concentrations. The present data demonstrate that of the genes analyzed that encode proteins that are key regulators of lipid homeostasis within skeletal muscle, only the PDK4 gene is uniquely sensitive to increasing FFA concentrations after increased plasma FFA achieved by intravenous lipid infusion.

Observations on the effects of caged carp culture on water and sediment metal concentrations in Lake Kasumingaura, Japan

The concentrations of 24 elements in the sediment and associated water column were monitored at two sites, one an area of intensive cage culture of carp, the other a wild site far from known cage culture areas, in Lake Kasumigaura, Japan, between September 1994 and September 1995. The concentrations of most elements in Lake Kasumigaura are mostly sub-parts per billion, except those for Ca, Fe, K, Mg, Na, P, and Si. The concentrations of Cd, Co, Cu, Mn, Ni, Pb, V, and Fe in Lake Kasumigaura are higher than the values in Lake Mashu, Lake Shikotsu, and Lake Biwa, and comparable to the levels in open ocean. Statistically significant differences in metal concentrations were observed between the culture and wild sites, with metal concentrations consistently higher at the culture site. Although cage culture of carp in the Lake Kasumigaura system may be causing localized increase in metal concentrations in the sediments, we must treat the results with caution, since the concentrations of metals observed in the sediments in 1995 were lower than those observed in 1979 for all metals at both sampling sites. In conclusion, further study of the concentrations of metals in the lake as a whole must be undertaken before the differences between the culture and wild sites can be proved, or disproved, to be the result of carp culture.

Critical assessment of various techniques for the extraction of carotenoids and co-enzyme Q10 from the Thraustochytrid strain ONC-T18

A variety of techniques for extracting carotenoids from the marine Thraustochytrium sp. ONC-T18 was compared. Specifically, the organic solvents acetone, ethyl acetate, and petroleum ether were tested, along with direct and indirect ultrasonic assisted extraction (probe vs bath) methods. Techniques that used petroleum ether/acetone/water (15:75:10, v/v/v) with 3 h of agitation, or 5 min in an ultrasonic bath, produced the highest extraction yields of total carotenoids (29−30.5 μg g^-1). Concentrations up to 11.5 μg g^-1 of canthaxanthin and 17.5 μg g^-1 of β-carotene were detected in extracts stored for 6 weeks. Astaxanthin and echinenone were also detected as minor compounds. Extracts with and without antioxidants showed similar carotenoid concentration profiles. However, total carotenoid concentrations were approximately 8% higher when antioxidants were used. Finally, an easy-to-perform and inexpensive method to detect co-enzymes in ONC-T18 was also developed using silica gel TLC plates. Five percent methanol in toluene as a mobile phase consistently eluted co-enzyme Q10 standards and could separate the co-enzyme fractions present in ONC-T18.

Seasonal stress physiology and body condition differ among co-occurring tropical finch species.

Seasonal changes in avian hormonal stress responses and condition are well known for common species found at temperate and arctic latitudes, but declining and tropical species are poorly studied. This study compares stress and condition measures of co-occurring declining and non-declining tropical grass finch species in Australia. We monitored declining Gouldian finches (Erythrura gouldiae) and non-declining long-tailed and masked finches (Poepila acuticauda and P. personata) during two seasons that are potentially stressful: peak breeding (early dry season when food is plentiful) and moult (late dry to early wet season when food may be scarce). We measured body condition (muscle and fat), haematocrit, and stress response to capture using plasma corticosterone and binding globulin concentrations. All species had higher muscle and lower fat indices during breeding than moult. Haematocrit did not consistently differ between seasons. Long-tailed finches had higher stress responses during breeding than moult, similar to other passerines studied. Masked finches showed no seasonal changes in stress response. Gouldian finches had stress response patterns opposite to those of long-tailed finches, with higher stress responses during moult. However, seasonal trends in Gouldian and long-tailed finch stress responses sometimes differed between years or sites. The differences in stress response patterns between species suggest that the declining Gouldian finch is more sensitive to recent environmental changes which are thought to further reduce grass seed food resources during the late dry to early wet season. Retention of stress responsiveness during a protracted moult could increase the survival potential of Gouldian finches. This study highlights the utility of stress and condition indices to determine the sensitivity of co-occurring species to environmental conditions.

Climate change as an unexpected co-factor promoting coral eating seastar (Acanthaster planci) outbreaks

Coral reefs face a crisis due to local and global anthropogenic stressors. A large proportion of the ~50% coral loss on the Great Barrier Reef has been attributed to outbreaks of the crown-of-thorns-seastar (COTS). A widely assumed cause of primary COTS outbreaks is increased larval survivorship due to higher food availability, linked with anthropogenic runoff . Our experiment using a range of algal food concentrations at three temperatures representing present day average and predicted future increases, demonstrated a strong influence of food concentration on development is modulated by temperature. A 2°C increase in temperature led to a 4.2–4.9 times (at Day 10) or 1.2–1.8 times (Day 17) increase in late development larvae. A model indicated that food was the main driver, but that temperature was an important modulator of development. For instance, at 5000 cells ml−1 food, a 2°C increase may shorten developmental time by 30% and may increase the probability of survival by 240%. The main contribution of temperature is to ‘push’ well-fed larvae faster to settlement. We conclude that warmer sea temperature is an important co-factor promoting COTS outbreaks.