Using drift nets to capture early life stages and monitor spawning of the Yangtze River Chinese sturgeon (Acipenser sinensis)

P>A sampling system for capturing sturgeon eggs using a D-shaped bottom anchored drift net was used to capture early life stages (ELS) of Chinese sturgeon, Acipenser sinensis, and monitor annual spawning success at Yichang on the Yangtze River, 1996-2004, before and just after the Three Gorges Dam began operation. Captured were 96 875 ELS (early life stages: eggs, yolk-sac larvae = eleuthero embryos, and larvae); most were eggs and only 2477 were yolk-sac larvae. Most ELS were captured in the main river channel and inside the bend at the Yichang spawning reach. Yolk-sac larvae were captured for a maximum of 3 days after hatching began, indicating quick dispersal downstream. The back-calculated day of egg fertilization over the eight years indicated a maximum spawning window of 23 days (20 October-10 November). Spawning in all years was restricted temporally, occurred mostly at night and during one or two spawning periods, each lasting several days. The brief temporal spawning window may reduce egg predation by opportunistic predators by flooding the river bottom with millions of eggs. During 1996-2002, the percentage of fertilized eggs in an annual 20-egg sample was between 63.5 to 94.1%; however, in 2003 the percentage fertilized was only 23.8%. This sudden decline may be related to the altered environmental conditions at Yichang caused by operation of the Three Gorges Dam. Further studies are needed to monitor spawning and changes in egg fertilization in this threatened population.

Seasonal changes, life cycle, and production of a psychrophilic chironomid (Propsilocerus akamusi) in a Chinese Lake

Seasonal changes, life cycle, and production of a psychrophilic Chironomidae species, Propsilacerus akamusi (Tokunage), were studied in eutrophic Lake Donghu. The P akamusi population was characterized by a single annual reproduction period during late November to December, and the larval growth mainly occurred in winter. Most of P akamusi were univoltine, while some of them came to emergence in two years or more. The average density and biomass were 318.9 ind./m(2) and 0.57 g dry weight /m(2) during January 1998 to June 2000, respectively, but these values did not include any summer measurement,; since the larvae aestivated in the deep sediment layer and could not be sampled routinely in summer. The annual production of P akamusi was 2.73g dry weight/m(2), and the corresponding production/biomass ratio was 4.60.

Life history and production of Sphaerium lacustre (Mollusca : Sphaeriidae) in a shallow subtropical Chinese lake

A fingernail clam, Sphaerium lacustre, was studied in subtropical Lake Donghu from June 1999 to May 2000. The S. lacustre population was characterized by a single annual reproduction period starting in March and ending in October; the population comprised three size groups, of which the 1999 cohort was dominant. The annual average density and biomass were 100.2 ind./m(2) and 12.11 g/m(2), respectively The annual production was 43.02 wet weight g/m(2), and the corresponding annual production/biomass ratio was 3.55.

Extension of life span and improvement of vitality of Drosophila melanogaster by long-term supplementation with different molecular weight polysaccharides from Porphyra haitanensis

Polysaccharides isolated from Porphyra (porphyran) have been known to have diverse biological activities, including immunomodulatory and antioxidant activities. The molecular weight-antiaging activity relationship of degraded porphyrans was examined in this study. Natural porphyran was extracted from P. haitanensis, and then was degraded into different molecular weight fractions, P1 molecular weight 49 kDa, P2 molecular weight 30 kDa, P3 molecular weight 8.2 kDa, by free radical. The influence on life span and vitality of porphyrans were carried out on Drosophila melanogaster. We found that all the degraded porphyrans and natural porphyran (P), added daily to the diet, can significantly increase the life span of D. melanogaster, except for P3. Among them, P1 exhibited the most prolonging life span activity. Furthermore, vitality of middle-aged flies (assessed by measuring their mating capacity) receiving porphyrans was increased considerably in comparison with the controls. Finally, in the heat-stress test, we observed a remarkable increase in survival time, especially in P3-diet groups. These results suggest that porphyrans may be effective in reducing the rate of the aging process and molecular weight has important influence on the effects. It seems that P1 and P2, possessed higher molecular weight, may be more useful in normal metabolic condition and P3, possessed the lowest molecular weight, may be more beneficial for D. melanogaster in stress condition. (C) 2007 Elsevier Ltd. All rights reserved.