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https://www.readbyqxmd.com/read/27853556/relations-between-morphology-buoyancy-and-energetics-of-requiem-sharks
#1
Gil Iosilevskii, Yannis P Papastamatiou
Sharks have a distinctive shape that remained practically unchanged through hundreds of millions of years of evolution. Nonetheless, there are variations of this shape that vary between and within species. We attempt to explain these variations by examining the partial derivatives of the cost of transport of a generic shark with respect to buoyancy, span and chord of its pectoral fins, length, girth and body temperature. Our analysis predicts an intricate relation between these parameters, suggesting that ectothermic species residing in cooler temperatures must either have longer pectoral fins and/or be more buoyant in order to maintain swimming performance...
October 2016: Royal Society Open Science
https://www.readbyqxmd.com/read/27794535/convergence-in-thunniform-anatomy-in-lamnid-sharks-and-jurassic-ichthyosaurs
#2
Theagarten Lingham-Soliar
Among extinct ichthyosaurs the Jurassic forms Ichthyosaurus and Stenopterygius share a number of anatomical specializations with lamnid sharks, characterized in the white shark, Carcharodon carcharias These features allow their inclusion within the mode of high-speed thunniform swimming to which only two other equally distinctive phylogenetic groups belong, tuna and dolphins-a striking testaments to evolutionary convergence. Jurassic ichthyosaurs evolved from reptiles that had returned to the sea (secondarily adapted) about 250 million years ago (MYA) while lamnid sharks evolved about 50 MYA from early cartilaginous fishes (originating ca...
October 29, 2016: Integrative and Comparative Biology
https://www.readbyqxmd.com/read/27783634/whale-shark-rhincodon-typus-seasonal-occurrence-abundance-and-demographic-structure-in-the-mid-equatorial-atlantic-ocean
#3
Bruno C L Macena, Fábio H V Hazin
Whale sharks are generally associated with environmental factors that drive their movements to specific locations where food availability is high. Consequently, foraging is believed to be the main reason for the formation of whale shark aggregations. Feeding aggregations occur mainly in nearshore areas and are composed primarily of immature individuals. Conversely, aggregations of mature adults are rarely observed, and their occurrence is correlated with oceanic environments. Despite an increase in the number of whale shark studies, information on mating and parturition grounds is still lacking...
2016: PloS One
https://www.readbyqxmd.com/read/27774596/a-novel-field-method-to-distinguish-between-cryptic-carcharhinid-sharks-australian-blacktip-shark-carcharhinus-tilstoni-and-common-blacktip-shark-c-limbatus-despite-the-presence-of-hybrids
#4
G J Johnson, R C Buckworth, H Lee, J A T Morgan, J R Ovenden, C R McMahon
Multivariate and machine-learning methods were used to develop field identification techniques for two species of cryptic blacktip shark. From 112 specimens, precaudal vertebrae (PCV) counts and molecular analysis identified 95 Australian blacktip sharks Carcharhinus tilstoni and 17 common blacktip sharks Carcharhinus limbatus. Molecular analysis also revealed 27 of the 112 were C. tilstoni × C. limbatus hybrids, of which 23 had C. tilstoni PCV counts and four had C. limbatus PCV counts. In the absence of further information about hybrid phenotypes, hybrids were assigned as either C...
October 24, 2016: Journal of Fish Biology
https://www.readbyqxmd.com/read/27723102/dicephalous-v-diprosopus-sharks-record-of-a-two-headed-embryo-of-galeus-atlanticus-and-review-of-the-literature
#5
V Sans-Coma, C Rodríguez, M A López-Unzu, M Lorenzale, B Fernández, L Vida, A C Durán
As far as is known, this paper gives the first description of a two-headed shark embryo belonging to an oviparous species, Galeus atlanticus (Carcharhiniformes: Scyliorhinidae). The specimen was detected among 797 embryos intended for cardiovascular studies, which represents a defect incidence of 0·13%. Each head had a mouth, two eyes, a brain, a notochord and five gill openings on each side. The two heads fused behind the gills. On the single body, there were four anticipated dorsal fins, two anterior, right and left and two posterior, right and left...
October 9, 2016: Journal of Fish Biology
https://www.readbyqxmd.com/read/27684706/shark-conservation-an-educational-approach-based-on-children-s-knowledge-and-perceptions-toward-sharks
#6
Kwok Ho Tsoi, Sau Ying Chan, Yeung Chung Lee, Brian Ho Yeung Ip, Chi Chiu Cheang
Shark conservation has become a focus of current international conservation efforts. However, the misunderstanding of sharks and their negative public portrayal may hinder their conservation. More importantly, the consumption of shark fin, which is very common in Chinese cultures, poses a significant threat to sharks. Hong Kong has long been the world's largest shark fin trading center. Shark conservation would become more sustainable if public understanding of this predatory fish and an appreciation of its ecological significance could be promoted...
2016: PloS One
https://www.readbyqxmd.com/read/27537913/cyanobacterial-neurotoxin-bmaa-and-mercury-in-sharks
#7
Neil Hammerschlag, David A Davis, Kiyo Mondo, Matthew S Seely, Susan J Murch, William Broc Glover, Timothy Divoll, David C Evers, Deborah C Mash
Sharks have greater risk for bioaccumulation of marine toxins and mercury (Hg), because they are long-lived predators. Shark fins and cartilage also contain β-N-methylamino-l-alanine (BMAA), a ubiquitous cyanobacterial toxin linked to neurodegenerative diseases. Today, a significant number of shark species have found their way onto the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Many species of large sharks are threatened with extinction due in part to the growing high demand for shark fin soup and, to a lesser extent, for shark meat and cartilage products...
2016: Toxins
https://www.readbyqxmd.com/read/27457414/great-hammerhead-sharks-swim-on-their-side-to-reduce-transport-costs
#8
Nicholas L Payne, Gil Iosilevskii, Adam Barnett, Chris Fischer, Rachel T Graham, Adrian C Gleiss, Yuuki Y Watanabe
Animals exhibit various physiological and behavioural strategies for minimizing travel costs. Fins of aquatic animals play key roles in efficient travel and, for sharks, the functions of dorsal and pectoral fins are considered well divided: the former assists propulsion and generates lateral hydrodynamic forces during turns and the latter generates vertical forces that offset sharks' negative buoyancy. Here we show that great hammerhead sharks drastically reconfigure the function of these structures, using an exaggerated dorsal fin to generate lift by swimming rolled on their side...
2016: Nature Communications
https://www.readbyqxmd.com/read/27339437/waves-traces-and-shark-fins
#9
Steven McVea, Kate Skehin, Mark Terris
No abstract text is available yet for this article.
June 23, 2016: Archives of Disease in Childhood. Education and Practice Edition
https://www.readbyqxmd.com/read/27291051/rethinking-trade-driven-extinction-risk-in-marine-and-terrestrial-megafauna
#10
Loren McClenachan, Andrew B Cooper, Nicholas K Dulvy
Large animals hunted for the high value of their parts (e.g., elephant ivory and shark fins) are at risk of extinction due to both intensive international trade pressure and intrinsic biological sensitivity. However, the relative role of trade, particularly in non-perishable products, and biological factors in driving extinction risk is not well understood [1-4]. Here we identify a taxonomically diverse group of >100 marine and terrestrial megafauna targeted for international luxury markets; estimate their value across three points of sale; test relationships among extinction risk, high value, and body size; and quantify the effects of two mitigating factors: poaching fines and geographic range size...
June 20, 2016: Current Biology: CB
https://www.readbyqxmd.com/read/27220775/seasonal-migration-of-the-starry-smooth-hound-shark-mustelus-asterias-as-revealed-from-tag-recapture-data-of-an-angler-led-tagging-programme
#11
N W P Brevé, H V Winter, H M J Van Overzee, E D Farrell, P A Walker
The primary aim of this long-term angler-led tagging programme was to gain information about seasonal changes in distribution of the starry smooth-hound shark Mustelus asterias, along the Dutch coast for management and conservation purposes. Between 2011 and 2014, M. asterias comprised 92·6% (n = 2418) of the total elasmobranch catch (n = 2612) by the licenced group of taggers within the Dutch Delta of which 2244 M. asterias were fin-tagged with plastic rototags. Sex and total length (LT ) composition inside the eastern tidal basin (Oosterschelde) were significantly different, i...
August 2016: Journal of Fish Biology
https://www.readbyqxmd.com/read/27220618/corticotropin-releasing-hormone-family-evolution-five-ancestral-genes-remain-in-some-lineages
#12
João C R Cardoso, Christina A Bergqvist, Rute C Félix, Dan Larhammar
The evolution of the peptide family consisting of corticotropin-releasing hormone (CRH) and the three urocortins (UCN1-3) has been puzzling due to uneven evolutionary rates. Distinct gene duplication scenarios have been proposed in relation to the two basal rounds of vertebrate genome doubling (2R) and the teleost fish-specific genome doubling (3R). By analyses of sequences and chromosomal regions, including many neighboring gene families, we show here that the vertebrate progenitor had two peptide genes that served as the founders of separate subfamilies...
July 2016: Journal of Molecular Endocrinology
https://www.readbyqxmd.com/read/27095494/a-shared-role-for-sonic-hedgehog-signalling-in-patterning-chondrichthyan-gill-arch-appendages-and-tetrapod-limbs
#13
J Andrew Gillis, Brian K Hall
Chondrichthyans (sharks, skates, rays and holocephalans) possess paired appendages that project laterally from their gill arches, known as branchial rays. This led Carl Gegenbaur to propose that paired fins (and hence tetrapod limbs) originally evolved via transformation of gill arches. Tetrapod limbs are patterned by asonic hedgehog(Shh)-expressing signalling centre known as the zone of polarising activity, which establishes the anteroposterior axis of the limb bud and maintains proliferative expansion of limb endoskeletal progenitors...
April 15, 2016: Development
https://www.readbyqxmd.com/read/27077022/hydrodynamic-study-of-freely-swimming-shark-fish-propulsion-for-marine-vehicles-using-2d-particle-image-velocimetry
#14
Mannam Naga Praveen Babu, J M Mallikarjuna, P Krishnankutty
Two-dimensional velocity fields around a freely swimming freshwater black shark fish in longitudinal (XZ) plane and transverse (YZ) plane are measured using digital particle image velocimetry (DPIV). By transferring momentum to the fluid, fishes generate thrust. Thrust is generated not only by its caudal fin, but also using pectoral and anal fins, the contribution of which depends on the fish's morphology and swimming movements. These fins also act as roll and pitch stabilizers for the swimming fish. In this paper, studies are performed on the flow induced by fins of freely swimming undulatory carangiform swimming fish (freshwater black shark, L = 26 cm) by an experimental hydrodynamic approach based on quantitative flow visualization technique...
2016: Robotics and Biomimetics
https://www.readbyqxmd.com/read/27055057/identifying-the-demon-whale-biter-patterns-of-scarring-on-large-whales-attributed-to-a-cookie-cutter-shark-isistius-sp
#15
Peter B Best, Theoni Photopoulou
The presence of crater-like wounds on cetaceans and other large marine vertebrates and invertebrates has been attributed to various organisms. We review the evidence for the identity of the biting agent responsible for crater wounds on large whales, using data collected from sei (Balaenoptera borealis), fin (B. physalus), inshore and offshore Bryde's (B. brydeii sp) and sperm whales (Physeter macrocephalus) examined at the Donkergat whaling station, Saldanha Bay, South Africa between March and October 1963...
2016: PloS One
https://www.readbyqxmd.com/read/27010301/first-isolation-of-tenacibaculum-maritimum-in-a-captive-sand-tiger-shark-carcharias-taurus
#16
Daniela Florio, Stefano Gridelli, Maria Letizia Fioravanti, Renato Giulio Zanoni
This report describes a case of the first isolation of Tenacibaculum maritimum from a captive-bred adult female sand tiger shark (Carcharias taurus) housed at the Cattolica Aquarium (Italy). The animal showed, between the second dorsal fin and the precaudal pit, skin lesions characterized by the presence of abundant whitish necrotic tissue. Through routine bacteriological examination, a bacterium was isolated from a skin lesion and subsequently identified as T. maritimum by phenotypic characters and species-specific polymerase chain reaction...
March 2016: Journal of Zoo and Wildlife Medicine: Official Publication of the American Association of Zoo Veterinarians
https://www.readbyqxmd.com/read/26930611/use-of-photo-identification-and-mark-recapture-methodology-to-assess-basking-shark-cetorhinus-maximus-populations
#17
Mauvis A Gore, Peter H Frey, Rupert F Ormond, Holly Allan, Gabriella Gilkes
Following centuries of exploitation, basking sharks (Cetorhinus maximus) are considered by IUCN as Endangered in the Northeast Atlantic, where they have now been substantially protected for over two decades. However, the present size of this population remains unknown. We investigated the use of photo-identification of individuals' dorsal fins, combined with mark-recapture methodology, to investigate the size of populations of basking shark within the west coast of Scotland. From a total of 921 encounters photographed between 2004 and 2011, 710 sharks were found to be individually identifiable based on dorsal fin damage and natural features...
2016: PloS One
https://www.readbyqxmd.com/read/26894334/moving-stereotactic-fiducial-system-to-obtain-a-respiratory-signal-proof-of-principle
#18
Roberto Caballero Pinelo, Rodolfo Alfonso, Yelina González Pérez, Albin Ariel García, Arnaldo Rubio
The purpose of this study was to obtain a respiratory signal with the use of an add-on device to a specific stereotactic body frame and evaluate precision and accuracy of the method, with the use of a dynamic phantom. The authors designed and constructed a simple add-on device which, attached to a stereotactic body frame, provides information of the patient's respiratory signal in every CT axial image acquired. To assess the approach, 12 CT studies were acquired, on a phantom that simulates respiratory motion, which was placed inside the frame with the add-on device...
2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/26869274/ontogeny-of-head-and-caudal-fin-shape-of-an-apex-marine-predator-the-tiger-shark-galeocerdo-cuvier
#19
Amy L Fu, Neil Hammerschlag, George V Lauder, Cheryl D Wilga, Chi-Yun Kuo, Duncan J Irschick
How morphology changes with size can have profound effects on the life history and ecology of an animal. For apex predators that can impact higher level ecosystem processes, such changes may have consequences for other species. Tiger sharks (Galeocerdo cuvier) are an apex predator in tropical seas, and, as adults, are highly migratory. However, little is known about ontogenetic changes in their body form, especially in relation to two aspects of shape that influence locomotion (caudal fin) and feeding (head shape)...
May 2016: Journal of Morphology
https://www.readbyqxmd.com/read/26869186/re-evaluation-of-batoid-pectoral-morphology-reveals-novel-patterns-of-diversity-among-major-lineages
#20
Christopher M Martinez, F James Rohlf, Michael G Frisk
Batoids (Chondrichthyes: Batoidea) are a diverse group of cartilaginous fishes which comprise a monophyletic sister lineage to all neoselachians or modern sharks. All species in this group possess anteroposteriorly expanded-pectoral fins, giving them a unique disc-like body form. Reliance on pectoral fins for propulsion ranges from minimal (sawfish) to almost complete dependence (skates and rays). A recent study on the diversity of planform pectoral fin shape in batoids compared overall patterns of morphological variation within the group...
April 2016: Journal of Morphology
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