Biomedical subjects

S C France

Publications and source records attributed to S C France.

4 recordsLinked to original sources

PubMed1999

Phylogenetic relationships within the class Anthozoa (phylum Cnidaria) based on nuclear 18S rDNA sequences.

Taxonomic relationships within the corals and anemones (Phylum Cnidaria: Class Anthozoa) are based upon few morphological characters. The significance of any given character is debatable, and there is little fossil record available for deriving evolutionary relationships. We analyzed complete 18S ribosomal sequences to examine subclass-level and ordinal-level organization within the Anthozoa. We suggest that the Subclass Ceriantipatharia is not an evolutionarily relevant grouping. The Order Corallimorpharia appears paraphyletic and closely related to the Order Scleractinia. The 18S rRNA gene may be insufficient for establishing robust phylogenetic hypotheses concerning the specific relationships of the Corallimorpharia and the Ceriantharia and the branching sequence for the orders within the Hexacorallia. The 18S rRNA gene has sufficient phylogenetic signal, however, to distinguish among the major groupings within the Class Anthozoa, and we use this information to suggest relationships for the enigmatic taxa Dactylanthus and Dendrobrachia.

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PubMed1999

Genetic structure of harbour porpoise Phocoena phocoena populations in the northwest Atlantic based on mitochondrial and nuclear markers.

The harbour porpoise, Phocoena phocoena, experiences high levels of nonnatural mortality owing to interactions with commercial fisheries throughout its range. To accurately evaluate the significance of this bycatch, information on population structure is required. We have examined the population structure of this species in the northwest Atlantic Ocean using mitochondrial DNA (mtDNA) sequence and nuclear microsatellite data. Samples from four previously proposed summer breeding populations--the Gulf of Maine, eastern Newfoundland, the Gulf of St Lawrence and West Greenland--were analysed. Control-region sequences revealed a significant partitioning of genetic variation among most of these summer populations, indicating that northwest Atlantic harbour porpoises should not be considered one panmictic population. Analysis of females alone yielded the highest levels of population subdivision, suggesting that females are more philopatric than males. At least three management units may be defined for harbour porpoises in the northwest Atlantic based on these data. Analysis of six microsatellite loci failed to detect significant population subdivision. Male-mediated gene flow may maintain homogeneity among nuclear loci, while female philopatry is sufficient to produce a signal of population subdivision in the maternally inherited mtDNA genome. mtDNA analyses also indicate that winter aggregations of harbour porpoises along the US mid-Atlantic states comprise animals from more than one summer breeding population.

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PubMed1996

DNA sequence variation of mitochondrial large-subunit rRNA provides support for a two-subclass organization of the Anthozoa (Cnidaria).

We have sequenced a portion of the mitochondrial 16S rRNA gene from 29 species of Anthozoa, representing six orders of the subclasses Ceriantipatharia, Hexacorallia, and Octocorallia, with the focus on deep-seamount corals (> 500-m depth). We have detected significant length variation in the gene, with homologous gene fragments ranging from 545 bp in a shallow-water scleractinian coral to 911 bp in a deep-sea antipatharian black coral. The aligned sequences were divided into five regions: three high-identity sequence blocks (HSBs) and two highly variable blocks of insertions/deletions (INDELs). Most of the length variation among species occurred as varying numbers of nucleotides in the two INDELs. Little or no intraspecific sequence variation was detected over spatial scales of up to approximately 150 km. Interspecific sequence variation was lowest among the octocorals and greatest among the ceriantipatharians. Our data indicate that the orders Ceriantharia and Antipatharia are highly divergent, and a phylogenetic reconstruction provides support for the two-subclass system of the class Anthozoa (Hexacorallia and Octocorallia).

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PubMed1996

DNA sequencing of formalin-fixed crustaceans from archival research collections.

Marine invertebrate collections have historically been maintained in ethanol following fixation in formalin. These collections may represent rare or extinct species or populations, provide detailed time-series samples, or come from presently inaccessible or difficult-to-sample localities. We tested the viability of obtaining DNA sequence data from formalin-fixed, ethanol-preserved (FFEP) deep-sea crustaceans, and found that nucleotide sequences for mitochondrial 16S rRNA and COI genes can be recovered from FFEP collections of varying age, and that these sequences are unmodified compared with those derived from frozen specimens. These results were repeatable among multiple specimens and collections for several species. Our results indicate that in the absence of fresh or frozen tissues, archived FFEP specimens may prove a useful source of material for analysis of gene sequence data by polymerase chain reaction (PCR) and direct sequencing.

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