Effects of the dinoflagellate Alexandrium tamarense on early development of the scallop Argopecten irradians concentricus

The effects of Alexandrium tamarense (strain ATHK) on early development of the bay scallop Argopecten irradians concentricus were studied under laboratory conditions. The algal culture was verified by HPLC to produce paralytic shellfish poisoning (PSP) at a level of 37.48 fmol/cell. Survival of the scallop larvae was not affected when they were grown with A. tamarense at concentrations of 500-10,000 cells/ml for 48 h. However, the activity of D-shape larvae was inhibited after 48-h exposure to A. tamarense at the algal cell density of 10,000 cells/ml. Scallop growth was inhibited significantly by A. tantarense during a 14-day exposure starting at the eye-spot larval stage. The size of juvenile scallops in the group of 10,000 cells/ml was only about 32% of that of the controls, although no obvious effect of A. tamarense was found on the rate of larval metamorphosis. All juvenile scallops survived in algal concentrations of 600-2400 cells/ml, however, attachment rates were significantly lower than control values after a 5-h exposure to A. tamarense at concentrations >600 cells/ml, while they were not obviously reduced after only 1 h of exposure. At concentrations >600 cells/ml, the climbing ability of juveniles was clearly reduced by exposure to A. tamarense after only 1 h. The climbing rate and height were only 55% and 45%, respectively, of those of the controls, when exposed to A. tantarense at a concentration of 600 cells/ml. The results indicated that A. tamarense blooms may have detrimental impacts on shellfish at early life stages, therefore, special attention should be paid to the toxic algal blooms in shellfish breeding area. (C) 2003 Elsevier Science B.V. All rights reserved.

Inhibition of egg hatching success and larvae survival of the scallop, Chlamys farreri, associated with exposure to cells and cell fragments of the dinoflagellate Alexandrium tamarense

We report an apparently novel toxic effect of the dinoflagellate Alexandrium tamarense, manifested by inhibition of the egg hatching success of the scallop, Chlamys farreri. The hatching rate of C. farreri approached only 30% of controls when its fertilised eggs were exposed for 36 h to A. tamarense cells or cellular fragments at a concentration of 100 cells/ml, and the hatching rate was just 5% after exposure to A. tamarense of 500 cells/ml. Similar exposures of the fertilised scallop eggs to two other algal species, the diatom Phaeodactylum tricornutum and the raphidophyte Heterosigma carterae, resulted in no such toxicity or inhibitory effects.. Likewise, exposure of eggs to standard STX toxin. as well as to A. tamarense cell contents (supernant of re-suspended algal cells following ultrasonication and centrifugation), did not elicit this inhibitory response. However, exposure of the scallop eggs to cell cultures, intact algal cells, or cell fragments of A. tamarense produced marked toxicity. The alga also influenced larvae at early D-shape stage of scallop. The survival rates began to decrease significantly after exposed for 6 days at concentration of 3000 cells/ml and above: no larvae could survive after 14-day exposure to A. tamarense at 10,000 cells/ml or 20-day at 5000 cells/ml. The results indicated the production of novel substances from A. tamarense which can cause adverse effects on egg hatching and survival of the scallop larvae, The experiment also found that the developmental stages before blastula was the developmental period most sensitive to the A. tamarense toxin(s) and the alga at early exponential stage had the strongest effect on egg hatching comparing with other growth phases. The adverse effect of A. tamarense on early development of scallops may cause decline of shellfish population and may have further impact on marine ecosystem. (C) 2001 Elsevier Science Ltd. All rights reserved.

Immune responses of the scallop Chlamys farreri after air exposure to different temperatures

The present study examined the influence of air exposure at different temperatures: a common perturbation associated with aquaculture handling practices, on immune responses in zhikong scallop Chlamys farreri. Scallops were exposed to air for 2 h, 6 h, 12 h and 24 h at 5 degrees C, 17 degrees C and 25 degrees C respectively. Thereafter, a recovery period of 24 h at 17 degrees C was applied. Haemocyte mortality, phagocytosis and reactive oxygen species (ROS) production of haemocytes, acid phosphatase (ACP) and superoxide dismutase (SOD) activity in haemocyte lysates were chosen as immumomarkers of anoxic stress. The results showed that an increase of haemocyte mortality and a decrease of phagocytosis and ACP activity were observed after 2 h of air exposure for all temperatures tested. Moreover, a significant increase of ROS production occurred following 2 h of air exposure at 25 degrees C and 24 h of air exposure at 17 degrees C. Significant differences were also observed in haemocyte mortality, percentage of phagocytic cells and ACP and SOD activity depending on the temperature of air exposure. Finally, after 24 h of recovery at 17 degrees C, percentage of phagocytic haemocytes and ACP activity did not return to initial values. ROS production was significantly higher than before the recovery period and initial values for scallops subjected to air exposure at 5 degrees C. In our study, scallops showed a relative low anoxia tolerance under a high temperature. All the scallops air exposed to 25 degrees C died after the 6 h sampling. In conclusion, air exposure associated to aquaculture practices was demonstrated to strongly affect functional immune activities of scallop haemocytes, and high temperature air exposure caused reduced survival of scallops. (c) 2007 Elsevier B.V. All rights reserved.

Response of the diatom flora in Jiaozhou Bay, China to environmental changes during the last century

The diatom flora in a 164 cm long sediment core obtained from Jiaozhou Bay (Yellow Sea, China) was analyzed in order to trace the response of diatoms to environmental changes over the past 100 years. The sediment core was dated by Pb-210 and Cs-137 and represented approximately 100 years (1899-2001 A.D.). The flora was mainly composed of centric diatoms (59-96%). The concentration of diatoms declined sharply above 30 cm (after similar to 1981 A.D.), while the dominant species changed from Thalassiosira anguste-lineatus, Thalassiosira eccentria, Coscinodiscus excentricus, Coscinodiscus concinnus and Diploneis gorjanovici to Cyclotella stylorum and Paralia sulcata. Species richness decreased slightly, and the cell abundance of warm-water species increased. We argue that these floral changes were probably caused by climate change in combination with eutrophication resulting from aquaculture and sewage discharge. (c) 2007 Elsevier B.V. All rights reserved.

Evolution of the black muntjac (Muntiacus crinifrons) karyotype revealed by comparative chromosome painting

The black muntjac (Muntiacus crinifrons) has an unusual karyotype of 2n = 8 in females and 2n = 9 in males. We have studied the evolution of this karyotype by hybridising chromosome-specific paints derived from flow-sorted chromosomes of the Chinese muntjac (M. reevesi, 2n = 46) to chromosomes of the black muntjac. The hybridisation pattern allowed us to infer chromosomal homologies between these two species. Tandem and centromeric fusions, reciprocal translocations, and insertions are involved in the reduction of the diploid number from 2n = 46 to 2n = 8, 9. The painting patterns further show complex chromosomal rearrangements in the male black muntjac which involve more than half the karyotype, including both sex chromosomes. Since early meiosis is reported to be normal without any visible inversion loops of the synaptonemal complex, the observed chromosomal rearrangements would lead to heterosynapsis and, therefore, leave a large fraction of the male black muntjac karyotype balanced between the two sexes.

An approach to prediction of the South China Sea summer monsoon onset

In the present paper, correlation between the South China Sea summer monsoon (SCSSM) onset and heat content in the upper layer of the warm pool in the western Pacific Ocean is examined using the Scripps Institution of Oceanography dataset for the period of 1955-1998 and an approach to prediction the SCSSM onset is proposed. Correlation showes that there exists interdecadal variability of the SCSSM onset demarcated by 1970 with the largest correlation coefficient in the area west of the center of the warm pool rather than near its centers, implying certain effect from other factors involved besides ENSO. As the correlation is poor for the period before 1970, the heat content anomaly of the warm pool after 1970 is used to indicate early or late onset of the SCSSM beforehand. An ideal representative area (1A degrees x1A degrees) for the warm pool heat content was determined with its center at 3A degrees N/138A degrees E. The nearest TAO (TAO-Tropical Atmosphere Ocean-array) mooring to the center is at 2A degrees N/137A degrees E, and chosen to calculate the heat content for prediction. It is suggested that the TAO mooring at 2A degrees N/137A degrees E could be used to predict the SCSSM onset with the heat content in the upper layer, if the correlation between the SCSSM onset and the heat content of the warm pool runs like that of after 1970. On the other hand, if the situation does like the one before 1970, the representative station is determined at 13A degrees S/74A degrees E with relatively poor correlation, meaning that the warm pool in the western Pacific Ocean plays more important role in the SCSSM onset than the Indian Ocean.

Highly sensitive determination of the methylated p16 gene in cancer patients by microchip electrophoresis

The p16 tumor suppressor gene is inactivated by promoter region hypermethylation in many types of tumor. Recent studies showed that aberrant methylation of the p16 gene is an early event in many tumors, especially in lung cancer, and may constitute a new biomarker for early detection and monitoring of prevention trials. We detected tumor-associated aberrant hypermethylation of the p16 gene in plasma and tissue DNA from 153 specimens using a modified semi-nested methylation-specific PCR (MSP) combining plastic microchip electrophoresis or slab gel electrophoresis, respectively. Specimens were from 79 lung cancer patients, 15 abdominal tumor patients, 30 positive controls and 30 negative controls. The results showed that the positive rate obtained by microchip electrophoresis was more than 26.6% higher and the same speciticity was kept when compared with slab gel electrophoresis. The microchip electrophoresis can rapidly and accurately analyze the PCR products of methylated DNA and obviously improve the positive rate of diagnosis of cancer patients when compared with gel electrophoresis. This method with the high assay sensitivity might be used for detection of methylation of p16 gene and even to facilitate early diagnosis of cancer patients. (C) 2004 Elsevier B.V. All rights reserved.