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A world dataset on the geographic distributions of Solenidae razor clams (Mollusca: Bivalvia)
(2019)
Background: Using this dataset, we examined the global geographical distributions of Solenidae species in relation to their endemicity, species richness and latitudinal ranges and then predicted their distributions under future climate change using species distribution modelling techniques (Saeedi et al. 2016a, Saeedi et al. 2016b). We found that the global latitudinal species richness in Solenidae is bi-modal, dipping at the equator most likely derived by high sea surface temperature (Saeedi et al. 2016b). We also found that most of the Solenidae species will shift their distribution ranges polewards due to global warming (Saeedi et al. 2016a). We also provided a comprehensive review of the taxon to test whether the latitudinal gradient in species richness was uni-modal with a peak in the tropics or northern hemisphere or asymmetric and bimodal as proposed previously (Chaudhary et al. 2016).
New information: This paper presents an integrated global geographic distribution dataset for 77 Solenidae taxa, including 3,034 geographic distribution records. This dataset was compiled after a careful data-collection and cleaning procedure over four years. Data were collected using field sampling, literature and from open-access databases. Then all the records went through quality control procedures such as validating the taxonomy of the species by examining and re-identifying the specimens in museum collections and using taxonomic and geographic data quality control tools in the World Register of Marine Species (WoRMS) and the r-OBIS package (Provoost and Bosch 2017). This dataset can thus be further used for taxonomical and biogeographical studies of Solenidae.
A review was done on all species of the genus Talassia (family Vanikoridae Gray, 1840), which are known from an upper bathyal depth range in the Atlantic Ocean. Four new species are proposed: Talassia mexicana sp. nov. from the Gulf of Mexico, T. laevapex sp. nov. and T. flexisculpta sp. nov. from off Mauritania and T. rugosa sp. nov. from off Angola. Empty shells of the new species were found in sediment samples collected in habitats associated with deep-water corals. The new species were compared with the type species Talassia coriacea (Manzoni, 1868) and the deep-water species T. tenuisculpta (R.B. Watson, 1873), T. dagueneti (de Folin, 1873) and T. sandersoni (A.E. Verrill, 1884). Particularly the shape and sculpture of the protoconch show regional differences. Other specific characteristics are macro- and micro-sculpture of the teleoconch.
A bibliography (including an author index) of the literature on the land and freshwater molluscs of the Cape Verde Islands is presented, encompassing 81 entries, of which 61 are directly related to land and freshwater molluscs, while another 20 deal with marine Pulmonata and/or brackish and saltwater inhabiting Hydrobiidae. A historical synopsis of the exploration of the land and freshwater mollusc fauna of the Cape Verde archipelago is presented. An annotated check-list of the land-bound gastropods of the Cape Verde Islands is also included, differentiating between freshwater, land and marine species and completed by a list of taxa that have been erroneously mentioned for the archipelago due to misidentification or confusion about the location of origin.
Background: Until recently, read lengths on the Solexa/Illumina system were too short to reliably assemble transcriptomes without a reference sequence, especially for non-model organisms. However, with read lengths up to 100 nucleotides available in the current version, an assembly without reference genome should be possible. For this study we created an EST data set for the common pond snail Radix balthica by Illumina sequencing of a normalized transcriptome. Performance of three different short read assemblers was compared with respect to: the number of contigs, their length, depth of coverage, their quality in various BLAST searches and the alignment to mitochondrial genes. Results: A single sequencing run of a normalized RNA pool resulted in 16,923,850 paired end reads with median read length of 61 bases. The assemblies generated by VELVET, OASES, and SeqMan NGEN differed in the total number of contigs, contig length, the number and quality of gene hits obtained by BLAST searches against various databases, and contig performance in the mt genome comparison. While VELVET produced the highest overall number of contigs, a large fraction of these were of small size (< 200bp), and gave redundant hits in BLAST searches and the mt genome alignment. The best overall contig performance resulted from the NGEN assembly. It produced the second largest number of contigs, which on average were comparable to the OASES contigs but gave the highest number of gene hits in two out of four BLAST searches against different reference databases. A subsequent meta-assembly of the four contig sets resulted in larger contigs, less redundancy and a higher number of BLAST hits. Conclusion: Our results document the first de novo transcriptome assembly of a non-model species using Illumina sequencing data. We show that de novo transcriptome assembly using this approach yields results useful for downstream applications, in particular if a meta-assembly of contig sets is used to increase contig quality. These results highlight the ongoing need for improvements in assembly methodology. Keywords: next generation sequencing; short read assembly; Mollusca
Empty shells (thanatocoenoses) have been reviewed of species in the genus Granulina (Gastropoda: Granulinidae) from the lower shelf and upper bathyal zones off Mauritania and Western Sahara. We encountered nine species of which four were already known from off Mauritania. Four new species are proposed herein: Granulina reginae sp. nov., G. ronaldi sp. nov., G. sandrae sp. nov. and G. sigridae sp. nov. These four sympatric new species lack labial denticles and they probably form a phyletic clade with a common ancestor. Most hitherto known species in Granulina from the NE Atlantic Ocean and the Mediterranean possess labial denticles. One additional new species with denticles was left in open nomenclature because the material available was considered inadequate. Species in Granulina from Mauritania and Western Sahara have not been found off NW Morocco or the Canary Islands, and the species known from NW Morocco and the Canary Islands have not been found off Mauritania and Western Sahara. The southern extents of the distributions of the Mauritanian species are currently uncertain as additional sampling would be required off Senegal or further South. A key to Mauritanian species in Granulina is given.