论山东、辽宁寒武系炒米店组底部(古丈阶顶部)小凤凰虫(Fenghuangella Yang in Zhou et al.,1977)北大核心

本文对在山东济南市钢城区九龙山和辽宁东部大连市白家山寒武系炒米店组底部报道的小凤凰虫,进行了详细的描述及修订。根据与小凤凰虫共生的三叶虫对于华北地台区苗岭统与芙蓉统的界线进行了深入探讨,将产有小凤凰虫的Liostracina simesi-Placosema convexa组合带作为华北地台区苗岭统古丈阶最上部的一个化石带,而将Prochuangia mansuyi的首现作为华北地台区芙蓉统排碧阶的底界,对于华南斜坡相区和华北地台区苗岭统和芙蓉统之间界线划分和对比具有重要意义。     

Ultrastructural Features of the Oral Region of Amicronucleate Paramecium tetraurelia in Autogamy1

ABSTRACT Amicronucleate Paramecium tetraurelia fails to develop an oral apparatus but resorbs the pre-existing one in the sexual cycle. Previous cytological studies have revealed the presence of a shallow, oral depression with a few scattered basal bodies after autogamy or conjugation. The present ultrastructural study of the ectoplasm beneath the oral depression revealed only the presence of a disorganized filamentous reticulum and small blocks of cytopharyngeal ribbons. In addition, beneath the oral depression, a large number of discoidal vesicles were found, similar to but larger in diameter than those normally associated with the cytopharynx of vegetative cells. The oral structures found in amicronucleates in autogamy might be remnants of the pre-existing oral apparatus, but the possibility that they were newly developed was not excluded. The morphogenetic interest of these structures was discussed. It is evident that amicronucleates in autogamy do not develop an extensive oral ultrastructural organization.     

Comparing genetic variants detected in the 1000 genomes project with SNPs determined by the International HapMap Consortium

Single-nucleotide polymorphisms (SNPs) determined based on SNP arrays from the international HapMap consortium (HapMap) and the genetic variants detected in the 1000 genomes project (1KGP) can serve as two references for genomewide association studies (GWAS). We conducted comparative analyses to provide a means for assessing concerns regarding SNP array-based GWAS findings as well as for realistically bounding expectations for next generation sequencing (NGS)-based GWAS. We calculated and compared base composition, transitions to transversions ratio, minor allele frequency and heterozygous rate for SNPs from HapMap and 1KGP for the 622 common individuals. We analysed the genotype discordance between HapMap and 1KGP to assess consistency in the SNPs from the two references. In 1KGP, 90.58% of 36,817,799 SNPs detected were not measured in HapMap. More SNPs with minor allele frequencies less than 0.01 were found in 1KGP than HapMap. The two references have low discordance (generally smaller than 0.02) in genotypes of common SNPs, with most discordance from heterozygous SNPs. Our study demonstrated that SNP array-based GWAS findings were reliable and useful, although only a small portion of genetic variances were explained. NGS can detect not only common but also rare variants, supporting the expectation that NGS-based GWAS will be able to incorporate a much larger portion of genetic variance than SNP arrays-based GWAS.     

Borrelia burgdorferi infection in Ixodes ricinus from habitats in Denmark

A total of 2647 ticks of the genus Ixodes was sampled by flagging the vegetation in thirty-one sites in eastern Jutland, Denmark. All ticks were identified as Ixodes ricinus Linnaeus. A total of 317 ticks (202 nymphs and 115 adults) from three different sites were examined for the spirochaete Borrelia burgdorferi Johnson et al. by indirect fluorescent antibody staining; the frequency of infection varied from 7% to 22%. It is concluded that I. ricinus, known to be the most common tick in Denmark, is the vector largely responsible for the transmission of B. burgdorferi in this country.     

Phyllotaxis in the Oil Palm: Arrangement of Male/Female Spikelets on the Inflorescence Stalk

The geometry of spikelet arrangement along the massive maleand female inflorescences of this monoecious palm is investigatedthrough techniques of phyllotaxis measurement (Equivalent phyllotaxisindex or E.P.I. Essentially there is little apparent differencewhether E.P.I. values from male inflorescences or female areconsidered. In both sexes E.P.I. estimates vary in a curvilinearmanner along the inflorescence length, higher values being obtainedtoward the broad base. Based on this pattern one value-over-allinflorescence E.P.I. is suggested to compare bunches emanatingfrom different treatment or genetic sources. It is also shownthat over-all bunch (inflorescence) E.P.I. varies systematicallywith palm age, being low in young palms and rising to asymptoticlevels in c. 11-year-old palms. Some physiological explanationsfor this latter observation are put forward, and some possibleapplications in cultural and genetic studies are suggested.Attention is also given to describing the results in terms ofFibonacci contact parastichy systems.     

Fruit Ripening in the Oil-palm Elaeis guineensis

Some gross morphological, biochemical, and quantitative sizechanges of the fruit which occur during the 150 or 80 days fromfertilization to ripeness for this species are described. Threemain phases of development are discernible. For the first 15days little activity may be noted. This is followed by a differentiationperiod of 60 to 70 days during which the fruit develops to almostmaximum size and the embryo, endosperm, mesocarp, and epicarpare virtually completely differentiated. The last period ofripening is considered a maturation period during which timethe embryo becomes viable, the tissues become consolidated intofinal forms, and oil formation in the endosperm and mesocarptakes place. These processes are described quantitatively withgrowth curves.     

Phyllotaxis in the Oil Palm: Applications in Selection of Interspecific Hybrids

The main purpose of the investigation was to determine whethermeasures associated with or dependent on the differences inphyllotaxis organization of the stem, fronds, and inflorescencesof three families of oil palms which differ considerably ingrowth habit and genetic background could be associated with,or allow prediction of their yield differences. Two of the familiesused are interspecific crosses between Elaeis guineensis andE. melanococca and these hybrids yield almost double that ofthe third ‘family’ (a group of E. guineensis selections)and have about twice the individual frond areas, inflorescencevolume, and surface area and about half the rate of verticalgrowth; they have, however, a slightly slower rate of frondand inflorescence production. One of the views expressed isthat the phyllotaxis organization which determines the measuredreduction of stem volume in the interspecific crosses is associatedwith the greater development of more productive reproductiveelements. Further, it is suggested that measurements of frond(even in the juvenile stage) and both male and female inflorescenceorganization could be used in yield prediction for these familiesand possibly other genetic groups-and thus increase the speedand efficiency of genetic selection.     

Phylogeographic structure in mitochondrial DNA of a South-east Asian freshwater fish, Hemibagrus nemurus (Siluroidei; Bagridae) and Pleistocene sea-level changes on the Sunda shelf

We postulated that the biogeographical history of South-east Asia contributed to extensive admixture during Pleistocene low sea levels of genetic groups of an obligate freshwater fish (the river catfish, Hemibagrus nemurus) isolated during periods of high sea levels. During Pleistocene glacial maxima, the sea level was lower than at present and the islands of the Sunda shelf (Sumatra, Borneo and Java) and the Asian mainland were connected by lowlands traversed by rivers. Restriction fragment length polymorphisms in mitochondrial DNA were documented for 140 putative H. nemurus analysed from 13 sampling sites resulting in the definition of 35 haplotypes. The high level of haplotype differentiation (mean P × 100 = 2.22, SD = 1.33) indicates that the subdivision of the ancestral H. netnurus group was extensive and probably occurred early in the Pleistocene. The occurrence of some genetically divergent groups of the H. netnurus complex occurring in sympatry in widely separated locations supports the proposition that low sea levels aided the dispersion and mingling of genetic groups. Based on both genetic and morphological evidence, the main H. nemurus line gave rise to three regional groups: (1) a morphologically distinct ‘Indochinese’ group composed of two mtDNA clades overlapping in east peninsular Malaysia; (2) a ‘Sundaic’ group composed of various lineages of differing morphology and genetic identity; (3) a genetically distinct ‘Sarawak’ group in west Borneo, similar in morphology to the ‘Sundaic’ and ‘Indochinese’ groups, but including a small, golden colour morph as a distinct dade. The morphologically similar Sundaic forms from west Java, Sumatra and west Borneo show some degree of genetic divergence, but their phylogenetic relationships are poorly resolved. The most genetically and morphologically distinct Sundaic dade, assigned to H. hoevenii, colonized the Kapuas river (west Borneo), east Sumatra and south peninsular Malaysia. Contrary to our original hypothesis and present biogeographical theory, little exchange of genetic groups has apparently occurred between the mainland and the Sunda Islands during recent glaciations.