51 research outputs found
Species diversity of the deep-water gulper sharks (Squaliformes: Centrophoridae: Centrophorus) in North Atlantic waters - current status and taxonomic issues
The gulper sharks (genus Centrophorus) are a group of deep-water benthopelagic sharks with a worldwide distribution. The alpha taxonomy of the group has historically been problematic and the number of species included in the genus has varied considerably over the years and is still under debate. Gulper sharks are routinely caught in mid- and deep-water fisheries worldwide and some have shown a considerable decline in abundance in the last few decades. Clear and consistent species discrimination of Centrophorus is essential for an efficient and sustainable management of these fisheries resources. Our study used molecular cytochrome oxidase subunit I (COI) and 16S ribosomal RNA gene sequences and morphometric data to re-evaluate the diversity of Centrophorus in North Atlantic waters, including the Gulf of Mexico, the Caribbean, and the Mediterranean Seas. Molecular data separated North Atlantic Centrophorus into five well-supported groups whereas morphometric data separated these same five groups and suggested three additional groups for which no molecular data were available. Four of the five groups identified in the North Atlantic also occur in the Indian and/or Pacific Oceans, thus extending the reported range of some species considerably. A species identification key for North Atlantic Centrophorus is provided based on our findings. (c) 2014 The Linnean Society of Londo
Advancements towards restoration of the endangered limpet Patella ferruginea Gmelin, 1791 through controlled reproduction
The ferruginous limpet is one of the most threatened invertebrate species in the Mediterranean Sea. Its controlled reproduction has been considered one of the potentially most effective strategies for the production of juveniles for population restocking or for recolonization of areas where the species was brought to extinction by human pressure but is now under protection (e.g., MPAs). This approach has been pursued for at least two decades but with partial results: at most, some juveniles have been obtained and have reached adult stage, yet not starting from spawning induction but through sacrifice of female specimens (lethal approach), additionally resulting in low genetic diversity of the juveniles produced. Herein, we describe, for the first time, positive results of the spawning induction in P. ferruginea. The fertilizations made after these experiences allow describing the larval development of the species from its early stages to its metamorphosis. The fertilization rate in these spawning events was much higher (>97%) than in previous studies that were based on the extraction of oocytes by dissection. The rate of non-anomalous larvae after 15 hours was not negligible but variable, depending perhaps on the quality of the sperm available at each fertilization. The timing of larval development of the species and its variability, particularly regarding metamorphosis, are described. Settlement ability is reached at 3\u20134 days after fertilization, depending on water temperature, while a large variability is observed in metamorphosis, occurring between 7 and 32 days (probably up to 40 days), although inducing factors are still unknown
Trends in anthropogenic CO2 in water masses of the Subtropical North Atlantic Ocean
12 pĂĄginas, 4 figuras,1 tabla.-- Proyecto CarbochangeThe variability in the storage of the oceanic anthropogenic CO2 (Cant) on decadal timescales is evaluated within the main water masses of the Subtropical North Atlantic along 24.5°N. Inorganic carbon measurements on five cruises of the A05 section are used to assess the changes in Cant between 1992 and 2011, using four methods (ÎCâ, TrOCA, ÏCT0, TTD). We find good agreement between the Cant distribution and storage obtained using chlorofluorocarbons and CO2 measurements in both the vertical and horizontal scales. Cant distribution shows higher concentrations and greater decadal storage rates in the upper layers with both values decreasing with depth. The greatest enrichment is obserbed in the central water masses, with their upper limb showing a mean annual accumulation of about 1 ÎŒmol kgâ1 yrâ1 and the lower limb showing, on average, half that value. We detect zonal gradients in the accumulation of Cant. This finding is less clear in the upper waters, where greater variability exists between methods. In accordance with data from time series stations, greater accumulation of Cant is observed in the upper waters of the western basin of the North Atlantic Subtropical Gyre. In intermediate and deep layers, the zonal gradient in the storage of Cant is more robust between methods. The much lower mean storage rates found along the section (<0.25 ÎŒmol kgâ1 yrâ1) become more obvious when longitudinal differences in the Cant accumulation are considered. In particular, west of 70°W the ventilation by the Labrador Sea Water creates a noticeable accumulation rate up to âŒ0.5 ÎŒmol kgâ1 yrâ1 between 1000 and 2500 dbar. If a Transient Stationary State of the Cant distributions is considered, significant bi-decadal trends in the Cant storage rates in the deepest North Atlantic waters are detected, in agreement with recent estimations.We acknowledge funding from the Spanish Ministry of Economy and Competitiveness through Grants CSD2008-00077 (Circumnavigation Expedition MALASPINA 2010 Project), CTM2009-08849 (ACDC Project) and CTM2012-32017 (MANIFEST Project). We also acknowledge funding from the EU FP7 project CARBOCHANGE under Grant Agreement No. 264879 and by the Marine Biogeochemistry and Global Change research group (Generalitat de Catalunya, 2014SGR1029). E.F. Guallart was funded through a JAE-Pre grant that was financed by the Spanish National Research Council Agency (Consejo Superior de Investigaciones CientĂficas, CSIC) and by the European Social Fund.Peer reviewe
Benchmarking the performance of a low-cost Magnetic Resonance Control System at multiple sites in the open MaRCoS community
Purpose: To describe the current properties and capabilities of an
open-source hardware and software package that is being developed by many sites
internationally with the aim of providing an inexpensive yet flexible platform
for low-cost MRI. Methods: This paper describes three different setups from 50
to 360 mT in different settings, all of which used the MaRCoS console for
acquiring data, and different types of software interfaces (custom-built GUI or
PulSeq overlay) to acquire the data. Results: Images are presented from both
phantoms and in vivo from healthy volunteers to demonstrate the image quality
that can be obtained from the MaRCoS hardware/software interfaced to different
low-field magnets. Conclusions: The results presented here show that a number
of different sequences commonly used in the clinic can be programmed into an
open-source system relatively quickly and easily, and can produce good quality
images even at this early stage of development. Both the hardware and software
will continue to develop, and it is an aim of this paper to encourage other
groups to join this international consortium.Comment: 9 pages, 10 figures, comments welcom
Portable magnetic resonance imaging of patients indoors, outdoors and at home
Mobile medical imaging devices are invaluable for clinical diagnostic
purposes both in and outside healthcare institutions. Among the various imaging
modalities, only a few are readily portable. Magnetic resonance imaging (MRI),
the gold standard for numerous healthcare conditions, does not traditionally
belong to this group. Recently, low-field MRI start-up companies have
demonstrated the first decisive steps towards portability within medical
facilities, but these are so far incompatible with more demanding use cases
such as in remote and developing regions, sports facilities and events, medical
and military camps, or home healthcare. Here we present in vivo images taken
with a light, home-made, low-field extremity MRI scanner outside the controlled
environment provided by medical facilities. To demonstrate the true portability
of the system and benchmark its performance in various relevant scenarios, we
have acquired images of a volunteer's knee in: i) an MRI physics laboratory;
ii) an office room; iii) outside a campus building, connected to a nearby power
outlet; iv) in open air, powered from a small fuel-based generator; and v) at
the volunteer's home. All images have been acquired within clinically viable
times, and signal-to-noise ratios (SNR) and tissue contrast suffice for 2D and
3D reconstructions with diagnostic value, with comparable overall image quality
across all five situations. Furthermore, the volunteer carries a fixation
metallic implant screwed to the femur, which leads to strong artifacts in
standard clinical systems but appears sharp in our low-field acquisitions.
Altogether, this work opens a path towards highly accessible MRI under
circumstances previously unrealistic.Comment: 17 pages, 4 figures, comments welcom
Acidification response of Mediterranean Sea temperate and cold-water corals from mid- to long-term experiments
Call me by my name: unravelling the taxonomy of the gulper shark genus Centrophorus in the Mediterranean Sea through an integrated taxonomic approach
The current shift of fishery efforts towards the deep sea is raising concern about the vulnerability of deep-water sharks, which are often poorly studied and characterized by problematic taxonomy. For instance, in the Mediterranean Sea the taxonomy of genus Centrophorus has not been clearly unravelled yet. Since proper identification of the species is fundamental for their correct assessment and management, this study aims at clarifying the taxonomy of this genus in the Mediterranean Basin through an integrated taxonomic approach. We analysed a total of 281 gulper sharks (Centrophorus spp.) collected from various Mediterranean, Atlantic and Indian Ocean waters. Molecular data obtained from cytochrome c oxidase subunit I (COI), 16S ribosomal RNA (16S), NADH dehydrogenase subunit 2 (ND2) and a portion of a nuclear 28S ribosomal DNA gene region (28S) have highlighted the presence of a unique mitochondrial clade in the Mediterranean Sea. The morphometric results confirmed these findings, supporting the presence of a unique and distinct morphological group comprising all Mediterranean individuals. The data strongly indicate the occurrence of a single Centrophorus species in the Mediterranean, ascribable to C. cf. uyato, and suggest the need for a revision of the systematics of the genus in the area.En prens
Reproductive Strategy of the Giant Electric Ray in the Southern Gulf of California
The objective of the present study was to describe and characterize macroscopic and microscopic aspects of the reproductive biology of the Giant Electric Ray Narcine entemedor, a viviparous elasmobranch targeted by commercial fishers in Mexico. A total of 305 individual rays were captured (260 females, 45 males); all males were sexually mature. The median size at maturity for females was estimated to be 58.5 cm TL, the median size at pregnancy was 63.7 cm TL, and the median size at maternity was 66.2 cm TL. The range of ovarian follicles recorded per female was 1â69; the maximum ovarian fecundity of fully grown vitellogenic oocytes was 17, and uterine fecundity ranged from 1 to 24 embryos per female. The lengths of the oblong ovarian follicles varied significantly among months, and the largest ovarian follicles were found in July, August, and September. Median embryo size was largest in August, and the size at birth was between 12.4 and 14.5 cm TL. Histological evidence of secretions from the glandular tissue of the uterine villi indicate that this species probably has limited histotrophy as a reproductive mode. Vitellogenesis in the ovary occurred synchronously with gestation in the uterus. The Giant Electric Ray has a continuous annual reproductive cycle; a period of ovulation occurs between May and September and two peaks of parturition, one in January and one in August, occur, suggesting that embryonic diapause occurs in some individuals. These results provide useful information for the management of this important commercial species in BahĂa de La Paz, Mexico, and will allow possible modification of the current Mexican regulations to enable better protection of this species
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