A new species of Austrodecus Hodgson, 1907 (Arthropoda, Pycnogonida, Austrodecidae) from the Southwest Indian Ridge.
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ABSTRACT:
SUBMITTER: Wang JJ
PROVIDER: S-EPMC3837406 | biostudies-literature | 2013
REPOSITORIES: biostudies-literature
Similar Datasets
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Project description:We describe Hedgpethia spinosasp. n. based on a single male specimen obtained from 197-207 m depth, south of Yaku Island, Kagoshima Prefecture, Japan. Among 15 previously known congeners, the new species resembles Hedgpethia bicornis (Losina-Losinsky & Turpaeva, 1958), Hedgpethia chitinosa (Hilton, 1943), and probably Hedgpethia brevitarsis (Losina-Losinsky & Turpaeva, 1958), in having a mid-dorsal tubercle on the posterior rim on each trunk segment. The new species, however, is distinguishable from those by a pair of horns on the anterior margin of the cephalic segment, spines on the first coxae, and denticulate spines on the strigilis. The new species represents the fifth member of the genus so far known from Japanese waters, in addition to Hedgpethia brevitarsis (Losina-Losinsky & Turpaeva, 1958), Hedgpethia chitinosa (Hilton, 1943), Hedgpethia dofleini (Loman, 1911), and Hedgpethia elongata Takahashi, Dick & Mawatari, 2007.
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Project description:A new species of pycnogonid collected by the Chinese research vessel, R/V HY IV, during deep sea cruises to the South China Sea in 2013, is described. The new species, Hemichela nanhaiensis, obtained from more than 1300 m depth, is distinguished from the other two species in the genus by the characters of the chela dactylus with 12 denticulations on the inner margin and by the presence of taller tubercles on the lateral processes.
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Project description:Dorvilleids were collected from hydrothermal vents on the Southwest Indian Ridge by manned submersible Jiaolong. These represent a new species of Ophryotrocha that is here described as Ophryotrocha jiaolongisp. n. This is the first dorvilleid described from vents on the Southwest Indian Ridge. It most closely resembles another vent species, Ophryotrocha akessoni Blake, 1985 from the Galapagos Rift, but can be distinguished by its antennae, palps, jaw structure. The new species has particularly distinctive mandibles, which allow it to be easily identified.
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Project description:The existence of ancient rocks in present mid-ocean ridges have long been observed but received less attention. Here we report the discovery of zircons with both reasonably young ages of about 5?Ma and abnormally old ages of approximate 180?Ma from two evolved gabbroic rocks that were dredged from the Southwest Indian Ridge (SWIR) in the Gallieni fracture zone. U-Pb and Lu-Hf isotope analyses of zircons were made using ion probe and conventional laser abrasion directly in petrographic thin sections. Young zircons and their host oxide gabbro have positive Hf isotope compositions (?Hf?=?+15.7-+12.4), suggesting a highly depleted mantle beneath the SWIR. The spread ?Hf values (from-2.3 to-4.5) of abnormally old zircons, together with the unradiogenic Nd-Hf isotope of the host quartz diorite, appears to suggest an ancient juvenile magmatism along the rifting margin of the southern Gondwana prior to the opening of the Indian Ocean. A convincing explanation for the origin of the unusually old zircons is yet to surface, however, an update of the theory of plate tectonics would be expected with continuing discovery of ancient rocks in the mid-oceanic ridges and abyssal ocean basins.
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Project description:Southwest Indian Ridge Plume and Background metagenome Metagenome
| PRJNA527615 | ENA
Project description:Sea spiders (Pycnogonida) are a widespread and phylogenetically important group of marine arthropods. However, their biology remains understudied, and detailed information about their feeding ecology is difficult to find. Observations on pycnogonid feeding are scattered in the literature, often in older sources written in various languages, and have never been comprehensively summarized. Here we provide an overview of all information on feeding in pycnogonids that we have been able to find and review what is known on feeding specializations and preferences in the various pycnogonid taxa. We deduce general findings where possible and outline future steps necessary to gain a better understanding of the feeding ecology of one of the world's most bizarre animal taxa.
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Project description:UNLABELLED:Sulfur is an important element in sustaining microbial communities present in hydrothermal vents. Sulfur oxidation has been extensively studied due to its importance in chemosynthetic pathways in hydrothermal fields; however, less is known about sulfate reduction. Here, the metagenomes of hydrothermal chimneys located on the ultraslow-spreading Southwest Indian Ridge (SWIR) were pyrosequenced to elucidate the associated microbial sulfur cycle. A taxonomic summary of known genes revealed a few dominant bacteria that participated in the microbial sulfur cycle, particularly sulfate-reducing Deltaproteobacteria. The metagenomes studied contained highly abundant genes related to sulfur oxidation and reduction. Several carbon metabolic pathways, in particular the Calvin-Benson-Bassham pathway and the reductive tricarboxylic acid cycles for CO2 fixation, were identified in sulfur-oxidizing autotrophic bacteria. In contrast, highly abundant genes related to the oxidation of short-chain alkanes were grouped with sulfate-reducing bacteria, suggesting an important role for short-chain alkanes in the sulfur cycle. Furthermore, sulfur-oxidizing bacteria were associated with enrichment for genes involved in the denitrification pathway, while sulfate-reducing bacteria displayed enrichment for genes responsible for hydrogen utilization. In conclusion, this study provides insights regarding major microbial metabolic activities that are driven by the sulfur cycle in low-temperature hydrothermal chimneys present on an ultraslow midocean ridge. IMPORTANCE:There have been limited studies on chimney sulfides located at ultraslow-spreading ridges. The analysis of metagenomes of hydrothermal chimneys on the ultraslow-spreading Southwest Indian Ridge suggests the presence of a microbial sulfur cycle. The sulfur cycle should be centralized within a microbial community that displays enrichment for sulfur metabolism-related genes. The present study elucidated a significant role of the microbial sulfur cycle in sustaining an entire microbial community in low-temperature hydrothermal chimneys on an ultraslow spreading midocean ridge, which has characteristics distinct from those of other types of hydrothermal fields.
| S-EPMC3903282 | biostudies-literature
Project description:Continuous tow investigations have shown that the present vent field inventory along fast to intermediate spreading ridges may be underestimated by at least 3-6 times, while the limited towed line investigations of venting sites along slow to ultra-slow spreading ridges make it impossible to determine their distribution. The Chinese Dayang cruise has conducted detailed towed line surveys of hydrothermal activity on segment 27 of the ultra-slow spreading southwest Indian ridge in 2015. The results have identified as many as 9 hydrothermal fields along 85-km-long segment, including one confirmed hydrothermal field, three inferred hydrothermal fields and five suspected fields. Hydrothermal activities are not only limited along-axis but also found approximately 10 km away from the axis. These vent fields are likely powered by a seismically identified axial magma chamber, including melt migration along normal faults to flank areas. The calculated hydrothermal activity frequency on segment 27 is approximately 3.6-8 times higher than that calculated from the Interridge database, suggesting that careful system exploration can reveal more hydrothermal activities even on ultra-slow spreading ridges effected by hotspot.
| S-EPMC6614410 | biostudies-other
Project description:BackgroundMitochondrial genomes form units of genetic information replicating indepentently from nuclear genomes. Sequence data (most often from protein-coding genes) and other features (gene order, RNA secondary structure) of mitochondrial genomes are often used in phylogenetic studies of metazoan animals from population to phylum level. Pycnogonids are primarily marine arthropods, often considered closely related to chelicerates (spiders, scorpions and allies). However, due to their aberrant morphology and to controversial results from molecular studies, their phylogenetic position is still under debate.ResultsThis is the first report of a complete mitochondrial genome sequence from a sea spider (Nymphon gracile, class Pycnogonida). Gene order derives from that of other arthropods so that presumably 10 single tRNA gene translocations, a translocation of the mitochondrial control region, and one large inversion affecting protein-coding genes must have happened in the lineage leading to Nymphon gracile. Some of the changes in gene order seem not to be common to all pycnogonids, as those were not found in a partial mitochondrial genome of another species, Endeis spinosa. Four transfer RNAs of Nymphon gracile show derivations from the usual cloverleaf secondary structure (truncation or loss of an arm). Initial phylogenetic analyses using mitochondrial protein-coding gene sequences placed Pycnogonida as sister group to Acari. However, this is in contrast to the majority of all other studies using nuclear genes and/or morphology and was not recovered in a second analysis where two long-branching acarid species were omitted.ConclusionExtensive gene rearrangement characterizes the mitochondrial genome of Nymphon gracile. At least some of the events leading to this derived gene order happened after the split of pycnogonid subtaxa. Nucleotide and amino acid frequencies show strong differences between chelicerate taxa, presumably biasing phylogenetic analyses. Thus the affinities between Pycnogonida and Acari (mites and ticks), as found in phylogenetic analyses using mitochondrial genes, may rather be due to long-branch attraction and independently derived nucleotide composition and amino acid frequency, than to a real sister group relationship.
| S-EPMC1636051 | biostudies-literature