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Jacob Geleijns - One of the best experts on this subject based on the ideXlab platform.

Nicholas C Wegner - One of the best experts on this subject based on the ideXlab platform.

  • gill morphometrics of the thresher sharks genus Alopias correlation of gill dimensions with aerobic demand and environmental oxygen
    Journal of Morphology, 2015
    Co-Authors: Thomas P Wootton, Chugey A Sepulveda, Nicholas C Wegner
    Abstract:

    Gill morphometrics of the three thresher shark species (genus Alopias) were determined to examine how metabolism and habitat correlate with respiratory specialization for increased gas exchange. Thresher sharks have large gill surface areas, short water-blood barrier distances, and thin lamellae. Their large gill areas are derived from long total filament lengths and large lamellae, a morphometric configuration documented for other active elasmobranchs (i.e., lamnid sharks, Lamnidae) that augments respiratory surface area while limiting increases in branchial resistance to ventilatory flow. The bigeye thresher, Alopias superciliosus, which can experience prolonged exposure to hypoxia during diel vertical migrations, has the largest gill surface area documented for any elasmobranch species studied to date. The pelagic thresher shark, A. pelagicus, a warm-water epi-pelagic species, has a gill surface area comparable to that of the common thresher shark, A. vulpinus, despite the latter's expected higher aerobic requirements associated with regional endothermy. In addition, A. vulpinus has a significantly longer water-blood barrier distance than A. pelagicus and A. superciliosus, which likely reflects its cold, well-oxygenated habitat relative to the two other Alopias species. In fast-swimming fishes (such as A. vulpinus and A. pelagicus) cranial streamlining may impose morphological constraints on gill size. However, such constraints may be relaxed in hypoxia-dwelling species (such as A. superciliosus) that are likely less dependent on streamlining and can therefore accommodate larger branchial chambers and gills.

  • The red muscle morphology of the thresher sharks (family Alopiidae).
    Journal of Experimental Biology, 2005
    Co-Authors: C. A. Sepulveda, Nicholas C Wegner, Diego Bernal, Jeffrey B. Graham
    Abstract:

    SUMMARY A more medial and anterior position of the red aerobic myotomal muscle (RM) and the presence of a vascular counter-current heat exchange system provide the functional elements that facilitate regional RM endothermy in tunas, lamnid sharks and the common thresher shark ( Alopias vulpinus ). The convergent RM morphology among all species capable of RM endothermy suggests that RM position is a strong predictor of fish endothermic capacity. The present study investigated the comparative RM morphology of the other two thresher shark species (bigeye thresher, Alopias superciliosus , and the pelagic thresher, Alopias pelagicus ), for which there is no information regarding their capacity for RM endothermy, and compared these data with published works on A. vulpinus . The digitization of transverse sections along the body of A. superciliosus and A. pelagicus enabled quantification of the relative amount of RM and the position and placement of the RM along the body. The RM in both A. superciliosus and A. pelagicus is positioned subcutaneously, along the lateral edges of the myotomes, and is distributed relatively evenly over the trunk of the body. The position of maximum RM area is at 50% fork length ( FL ) for A. superciliosus and at 75% FL for A. pelagicus . The amount of RM (mean ± s.e.m.) is 2.31±0.11% and 3.01±0.10% in A. superciliosus and A. pelagicus , respectively. When compared with A. vulpinus , all three alopiid sharks have a similar amount of RM. However, A. superciliosus and A. pelagicus differ from A. vulpinus in that they do not possess the medial and anterior RM arrangement that would likely facilitate metabolic heat conservation (RM endothermy).

Martin Brazeau - One of the best experts on this subject based on the ideXlab platform.

Elizabeth A Dinsdale - One of the best experts on this subject based on the ideXlab platform.

  • Mitochondrial recovery from shotgun metagenome sequencing enabling phylogenetic analysis of the common thresher shark (Alopias vulpinus)
    Meta Gene, 2018
    Co-Authors: Michael P. Doane, Sean M. Harrington, Kyle Levi, Alejandro A. Vega, Dnyanada Pande, Dovi Kacev, Elizabeth A Dinsdale
    Abstract:

    Abstract The common thresher shark (Alopias vulpinus) is an important fisheries species in the northeastern Pacific Ocean along California, USA and Mexico; yet genetic understanding of this species is incomplete. Using IonTorrent PGM generated metagenomic libraries constructed from the skin surface, we recovered the complete mitogenome of the common thresher shark. The length of the mitogenome was 16,712 basepairs and consisted of 22 tRNA, two rRNA, 13 protein coding sequences, a replication origin and a control region, similar to other Alopias spp. The median coverage across the mitogenome was 21 ×, ranging from 1 to 48 × coverage. The mean GC content of the mitogenome was 37.83%. Using the 13 protein coding genes of the mitogenome, we show phylogenetic placement of the common thresher shark with the pelagic thresher (Alopias pelagicus; a posterior probability of 1). In addition, the inclusion of this mitogenome increased certainty for the placement of the Lamniformes family with the Carcharhiniformes family (a posterior probability of 1), rather than with the Orectolobeformes family, as has been previously reported. The availability of the common thresher shark mitogenome will aid phylogenetic inference and population based studies of this important fisheries species.

Diego Bernal - One of the best experts on this subject based on the ideXlab platform.

  • The vascular morphology and in vivo muscle temperatures of thresher sharks (Alopiidae)
    Journal of morphology, 2011
    Co-Authors: James C. Patterson, Chugey A Sepulveda, Diego Bernal
    Abstract:

    The thresher sharks comprise a single family (Alopiidae) of pelagic sharks most easily recog- nized by the elongate dorsal lobe of their caudal fin. De- spite morphological similarities among the alopiids, the common thresher (Alopias vulpinus) is unique in that its red, aerobic myotomal muscle (RM) is medially posi- tioned (i.e., closer to the vertebrae), its systemic blood is supplied through a lateral circulation which give rise to counter-current heat exchanging retia, and it is capable of regional RM endothermy. Despite this information, it remains unknown if the other two alopiid species (bigeye thresher, Alopias superciliosus and pelagic thresher, Alo- pias pelagicus) also possess some or all of the character- istics related to regional RM endothermy. Thus, this study aimed to 1) document the presence of vascular specializations necessary for heat retention and RM endothermy and 2) measure the in vivo muscle tempera- tures of all three alopiid species. Laboratory dissections of the thresher species showed that only A. vulpinus possesses the lateral branching of the dorsal aorta giv- ing rise to a lateral subcutaneous circulation and retial system, and that RM temperatures are elevated relative to ambient temperature. By contrast, both A. pelagicus and A. superciliosus have a similar systemic blood circulation pathway, in which the dorsal aorta and postcardinal vein form the basis for the central cir- culation and in vivo RM temperature measurements closely matched those of the ambient temperature at which the sharks were captured. Collectively, the vas- cular anatomy and in vivo temperature data suggest that only one species of thresher shark (A. vulpinus) possesses the requisite vascular specializations (i.e., lateral subcutaneous vessels and retia mirabilia )t hat facilitate RM endothermy. J. Morphol. 272:1353-1364,

  • The functional role of the caudal fin in the feeding ecology of the common thresher shark Alopias vulpinus.
    Journal of fish biology, 2010
    Co-Authors: Scott A. Aalbers, Diego Bernal, Chugey A Sepulveda
    Abstract:

    This study tests the hypothesis that the common thresher shark Alopias vulpinus uses its elongate caudal fin to both produce thrust and immobilize prey during feeding. Underwater video recorded in southern California from 2007 to 2009 revealed 34 feeding events, all of which were initiated with the upper lobe of the caudal fin.

  • The red muscle morphology of the thresher sharks (family Alopiidae).
    Journal of Experimental Biology, 2005
    Co-Authors: C. A. Sepulveda, Nicholas C Wegner, Diego Bernal, Jeffrey B. Graham
    Abstract:

    SUMMARY A more medial and anterior position of the red aerobic myotomal muscle (RM) and the presence of a vascular counter-current heat exchange system provide the functional elements that facilitate regional RM endothermy in tunas, lamnid sharks and the common thresher shark ( Alopias vulpinus ). The convergent RM morphology among all species capable of RM endothermy suggests that RM position is a strong predictor of fish endothermic capacity. The present study investigated the comparative RM morphology of the other two thresher shark species (bigeye thresher, Alopias superciliosus , and the pelagic thresher, Alopias pelagicus ), for which there is no information regarding their capacity for RM endothermy, and compared these data with published works on A. vulpinus . The digitization of transverse sections along the body of A. superciliosus and A. pelagicus enabled quantification of the relative amount of RM and the position and placement of the RM along the body. The RM in both A. superciliosus and A. pelagicus is positioned subcutaneously, along the lateral edges of the myotomes, and is distributed relatively evenly over the trunk of the body. The position of maximum RM area is at 50% fork length ( FL ) for A. superciliosus and at 75% FL for A. pelagicus . The amount of RM (mean ± s.e.m.) is 2.31±0.11% and 3.01±0.10% in A. superciliosus and A. pelagicus , respectively. When compared with A. vulpinus , all three alopiid sharks have a similar amount of RM. However, A. superciliosus and A. pelagicus differ from A. vulpinus in that they do not possess the medial and anterior RM arrangement that would likely facilitate metabolic heat conservation (RM endothermy).