Spatio-temporal variability of phytoplankton assemblages and its controlling factors in spring and summer in the Subei Shoal of Yellow Sea, China

The Subei Shoal is a special coastal area with complex physical oceanographic properties in the Yellow Sea.In the present study,the distribution of phytoplankton and its correlation with environmental factors were studied during spring and summer of 2012 in the Subei Shoal of the Yellow Sea.Phytoplankton species composition and abundance data were accomplished by Utermohl method.Diatoms represented the greatest cellular abundance during the study period.In spring,the phytoplankton cell abundance ranged from 1.59×10^3 to 269.78×10^3 cell/L with an average of 41.80×10^3 cell/L,and Skeletonema sp.and Paralia sulcata was the most dominant species.In summer,the average phytoplankton cell abundance was 72.59×10^3 cell/L with the range of 1.78×10^3 to 574.96×10^3 cell/L,and the main dominant species was Pseudo-nitzschia pungens,Skeletonema sp.,Dactyliosolen fragilissima and Chaetoceros curvisetus.The results of a redundancy analysis(RDA)showed that turbidity,temperature,salinity,pH,dissolved oxygen(DO),the ratio of dissolved inorganic nitrogen to silicate and SiO4-Si(DIN/SiO4-Si)were the most important environmental factors controlling phytoplankton assemblages in spring or summer in the Subei Shoal of the Yellow Sea.

Karyological observations of Ulva linza chromosomes

Abstract Ulva linza is one of the species that causes green tides in the Yellow Sea,China.Due to the diffi culties in chromosomal preparation,the large numbers of chromosomes,and their relatively small sizes,there have been no reported studies on Ulva macroalgae chromosomes.The karyotypes and chromosomes in U.linza were observed after a series of treatments.The chromosomes were pretreated with 0.1%colchicine for 12 h and then mixed with enzymes.The samples were dropped from 30 cm height onto glass slides,which spread out the surface coat.These pretreatments were the optimal chromosomes preparation treatments.The prepared chromosomes were stained with 4',6-diamidino-2-phenylindole(DAPI),which is a fl uorescent probe sensitive and specifi c to DNA.The chromosome number in the haploid male and female gametophytes was n=9,and was 2 n=18 in the diploid sporophytes.The female gametophyte chromosomes were between 0.804 and 2.292μm in size,the male gametophyte chromosomes were between 0.917 and 2.916μm,and the sporophyte chromosomes were between 0.912 and 2.167μm.The relative sizes of the chromosomes were used to analyze the karyotypes of the female and male gametophyte chromosomes.The results provide a solid foundation for the basic technique that can be used to localize molecular markers of Ulva chromosomes.

Equivalent intensity but differential dominance of sodium channel blocker insecticide resistance conferred by F1845Y and V1848l mutations of the voltage-gated sodium channel in Plutella xylostella

Two point mutations(F1845Y and V1848I)in the voltage-gated sodium channel gene of Plutella xylostella are involved in the target-site resistance to sodium channel blocker insecticides(SCBIs).The contribution of the individual mutations to the SCBI resistance and the associated inheritance modes is as yet unclear.Through 2 rounds of single-pair crossing and marker-assisted selection,2 P xylostella strains(1845Y and 18481)bearing homozygous F1845Y or V18481 mutant alleles were successfully established from a field-collected population,and the contribution of each mutation to SCBI resistance,as well as associated inheritance patterns,was determined.When compared with the susceptible SZPS strain,each of the mutations individually conferred equally high-level resistance to indoxacarb(378 and 313 fold)and metaflumizone(734 and 674 fold),respectively.However,dominance levels of resistance to SCBIs were significantly different between the 2 resistant strains.Resistance of the 1845Y strain to indoxacarb and metaflumizone was inherited as an autosomal and incompletely dominant trait(D values ranged from 0.43 to 0.76).In contrast,that of the 1848I strain followed an autosomal but incompletely recessive to semidominant mode(D values:-0.24 to 0.09).Our findings enriched the current understanding of inheritance and mechanisms of SCBI resistance in P.xylostella,and will help develop resistance management programs for P:xylostella and othereconomic pests.