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Adam P Summers - One of the best experts on this subject based on the ideXlab platform.
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correction for huber et al hard prey soft jaws and the ontogeny of feeding mechanics in the Spotted Ratfish hydrolagus colliei
Journal of the Royal Society Interface, 2008Co-Authors: Daniel R. Huber, Mason N. Dean, Adam P SummersAbstract:Correction for ‘Hard prey, soft jaws and the ontogeny of feeding mechanics in the Spotted Ratfish Hydrolagus colliei ’ by Daniel R. Huber, Mason N. Dean and Adam P. Summers (J. R. Soc. Interface 5 , 941–952. (doi: 10.1098/rsif.2007.1325)). On page 948, figure 7( b ) was printed incorrectly. The correct version of figure 7 is printed below.
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hard prey soft jaws and the ontogeny of feeding mechanics in the Spotted Ratfish hydrolagus colliei
Journal of the Royal Society Interface, 2008Co-Authors: Daniel R. Huber, Mason N. Dean, Adam P SummersAbstract:The Spotted Ratfish Hydrolagus colliei is a holocephalan fish that consumes hard prey (durophagy) but lacks many morphological characters associated with durophagy in other cartilaginous fishes. We investigated its feeding biomechanics and biting performance to determine whether it can generate bite forces comparable with other durophagous elasmobranchs, how biting performance changes over ontogeny (21–44 cm SL) and whether biomechanical modelling can accurately predict feeding performance in holocephalans. Hydrolagus colliei can generate absolute and mass-specific bite forces comparable with other durophagous elasmobranchs (anteriorZ104 N, posteriorZ191 N) and has the highest jaw leverage of any cartilaginous fish studied. Modelling indicated that cranial geometry stabilizes the jaw joint by equitably distributing forces throughout the feeding mechanism and that positive allometry of bite force is due to hyperallometric mechanical advantage. However, bite forces measured through tetanic stimulation of the adductor musculature increased isometrically. The jaw adductors of H. colliei fatigued more rapidly than those of the piscivorous spiny dogfish Squalus acanthias as well. The feeding mechanism of H. colliei is a volume-constrained system in which negative allometry of cranial dimensions leaves relatively less room for musculature. Jaw adductor force, however, is maintained through ontogenetic changes in muscle architecture.
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uniform strain in broad muscles active and passive effects of the twisted tendon of the Spotted Ratfish hydrolagus colliei
The Journal of Experimental Biology, 2007Co-Authors: Mason N. Dean, Emanuel Azizi, Adam P SummersAbstract:SUMMARY A muscle9s force output depends on the range of lengths over which its fibers operate. Regional variation in fiber shortening during muscle contraction may translate into suboptimal force production if a subset of muscle fibers operates outside the plateau of the length–tension curve. Muscles with broad insertions and substantial shortening are particularly prone to heterogeneous strain patterns since fibers from different regions of the muscle vary in their moment arms, with fibers further from the joint exhibiting greater strains. In the present study, we describe a musculotendon morphology that serves to counteract the variation in moment arm and fiber strains that are inherent in broad muscles. The tendon of the anterior jaw adductor of the Spotted Ratfish Hydrolagus colliei is twisted such that the distal face of the muscle inserts more proximally than the proximal face. Using quantitative geometric models based on this natural morphology, we show that this inversion of insertion points serves to equalize strains across the muscle such that at any gape angle all fibers in the muscle are operating at similar positions on their length–tension curves. Manipulations of this geometric model show that the natural morphology is `ideal9 compared to other hypothetical morphologies for limiting fiber strain heterogeneity. The uniform strain patterns predicted for this morphology could increase active force production during jaw closing and also decrease passive resistance to jaw opening. This divergence from `typical9 tendon morphology in the jaw adductors of H. colliei may be particularly important given the demands for high force production in durophagy.
Daniel R. Huber - One of the best experts on this subject based on the ideXlab platform.
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correction for huber et al hard prey soft jaws and the ontogeny of feeding mechanics in the Spotted Ratfish hydrolagus colliei
Journal of the Royal Society Interface, 2008Co-Authors: Daniel R. Huber, Mason N. Dean, Adam P SummersAbstract:Correction for ‘Hard prey, soft jaws and the ontogeny of feeding mechanics in the Spotted Ratfish Hydrolagus colliei ’ by Daniel R. Huber, Mason N. Dean and Adam P. Summers (J. R. Soc. Interface 5 , 941–952. (doi: 10.1098/rsif.2007.1325)). On page 948, figure 7( b ) was printed incorrectly. The correct version of figure 7 is printed below.
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hard prey soft jaws and the ontogeny of feeding mechanics in the Spotted Ratfish hydrolagus colliei
Journal of the Royal Society Interface, 2008Co-Authors: Daniel R. Huber, Mason N. Dean, Adam P SummersAbstract:The Spotted Ratfish Hydrolagus colliei is a holocephalan fish that consumes hard prey (durophagy) but lacks many morphological characters associated with durophagy in other cartilaginous fishes. We investigated its feeding biomechanics and biting performance to determine whether it can generate bite forces comparable with other durophagous elasmobranchs, how biting performance changes over ontogeny (21–44 cm SL) and whether biomechanical modelling can accurately predict feeding performance in holocephalans. Hydrolagus colliei can generate absolute and mass-specific bite forces comparable with other durophagous elasmobranchs (anteriorZ104 N, posteriorZ191 N) and has the highest jaw leverage of any cartilaginous fish studied. Modelling indicated that cranial geometry stabilizes the jaw joint by equitably distributing forces throughout the feeding mechanism and that positive allometry of bite force is due to hyperallometric mechanical advantage. However, bite forces measured through tetanic stimulation of the adductor musculature increased isometrically. The jaw adductors of H. colliei fatigued more rapidly than those of the piscivorous spiny dogfish Squalus acanthias as well. The feeding mechanism of H. colliei is a volume-constrained system in which negative allometry of cranial dimensions leaves relatively less room for musculature. Jaw adductor force, however, is maintained through ontogenetic changes in muscle architecture.
Mason N. Dean - One of the best experts on this subject based on the ideXlab platform.
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correction for huber et al hard prey soft jaws and the ontogeny of feeding mechanics in the Spotted Ratfish hydrolagus colliei
Journal of the Royal Society Interface, 2008Co-Authors: Daniel R. Huber, Mason N. Dean, Adam P SummersAbstract:Correction for ‘Hard prey, soft jaws and the ontogeny of feeding mechanics in the Spotted Ratfish Hydrolagus colliei ’ by Daniel R. Huber, Mason N. Dean and Adam P. Summers (J. R. Soc. Interface 5 , 941–952. (doi: 10.1098/rsif.2007.1325)). On page 948, figure 7( b ) was printed incorrectly. The correct version of figure 7 is printed below.
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hard prey soft jaws and the ontogeny of feeding mechanics in the Spotted Ratfish hydrolagus colliei
Journal of the Royal Society Interface, 2008Co-Authors: Daniel R. Huber, Mason N. Dean, Adam P SummersAbstract:The Spotted Ratfish Hydrolagus colliei is a holocephalan fish that consumes hard prey (durophagy) but lacks many morphological characters associated with durophagy in other cartilaginous fishes. We investigated its feeding biomechanics and biting performance to determine whether it can generate bite forces comparable with other durophagous elasmobranchs, how biting performance changes over ontogeny (21–44 cm SL) and whether biomechanical modelling can accurately predict feeding performance in holocephalans. Hydrolagus colliei can generate absolute and mass-specific bite forces comparable with other durophagous elasmobranchs (anteriorZ104 N, posteriorZ191 N) and has the highest jaw leverage of any cartilaginous fish studied. Modelling indicated that cranial geometry stabilizes the jaw joint by equitably distributing forces throughout the feeding mechanism and that positive allometry of bite force is due to hyperallometric mechanical advantage. However, bite forces measured through tetanic stimulation of the adductor musculature increased isometrically. The jaw adductors of H. colliei fatigued more rapidly than those of the piscivorous spiny dogfish Squalus acanthias as well. The feeding mechanism of H. colliei is a volume-constrained system in which negative allometry of cranial dimensions leaves relatively less room for musculature. Jaw adductor force, however, is maintained through ontogenetic changes in muscle architecture.
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uniform strain in broad muscles active and passive effects of the twisted tendon of the Spotted Ratfish hydrolagus colliei
The Journal of Experimental Biology, 2007Co-Authors: Mason N. Dean, Emanuel Azizi, Adam P SummersAbstract:SUMMARY A muscle9s force output depends on the range of lengths over which its fibers operate. Regional variation in fiber shortening during muscle contraction may translate into suboptimal force production if a subset of muscle fibers operates outside the plateau of the length–tension curve. Muscles with broad insertions and substantial shortening are particularly prone to heterogeneous strain patterns since fibers from different regions of the muscle vary in their moment arms, with fibers further from the joint exhibiting greater strains. In the present study, we describe a musculotendon morphology that serves to counteract the variation in moment arm and fiber strains that are inherent in broad muscles. The tendon of the anterior jaw adductor of the Spotted Ratfish Hydrolagus colliei is twisted such that the distal face of the muscle inserts more proximally than the proximal face. Using quantitative geometric models based on this natural morphology, we show that this inversion of insertion points serves to equalize strains across the muscle such that at any gape angle all fibers in the muscle are operating at similar positions on their length–tension curves. Manipulations of this geometric model show that the natural morphology is `ideal9 compared to other hypothetical morphologies for limiting fiber strain heterogeneity. The uniform strain patterns predicted for this morphology could increase active force production during jaw closing and also decrease passive resistance to jaw opening. This divergence from `typical9 tendon morphology in the jaw adductors of H. colliei may be particularly important given the demands for high force production in durophagy.
Gregor M. Cailliet - One of the best experts on this subject based on the ideXlab platform.
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evidence of stability in a chondrichthyan population case study of the Spotted Ratfish hydrolagus colliei chondrichthyes chimaeridae
Journal of Fish Biology, 2012Co-Authors: Lewis A K Barnett, David A. Ebert, Gregor M. CaillietAbstract:Results presented here provide evidence of an exception to the generalization that all chondrichthyan populations are especially vulnerable to exploitation to the extent that they remain at low abundance for a protracted or indefinite duration even after exploitation rates are reduced. Delta log-normal generalized linear models (GLM) and cluster analysis of fishery-independent catch-per-unit-effort (CPUE) data from 1977 to 2006 indicated the presence of at least two distinct stocks of Spotted Ratfish Hydrolagus colliei off the U.S. West Coast. CPUE of the continental slope and northern continental shelf and upper slope populations did not vary between 1977 and 1995 and increased from 1995 to 2006. On the basis of the timing of these changes, it is likely that both fishing and climate influenced these trends. Sex and size-specific differences in bathymetric distribution, along with the identification of nursery sites, indicate that fishery by-catch could have a significant effect on population growth. These aggregative behaviours, combined with low fecundity, indicate that H. colliei may be vulnerable to irreversible population depletion by fisheries mortality. Temporal abundance trends indicated, however, that their population size has increased significantly within the last decade, a demonstration of population stability. A literature review indicated that there is also evidence for population stability in other chondrichthyans. The paradigm that all chondrichthyan populations fail to rebuild in response to exploitation, therefore, may not be as broadly applicable as previously thought. Thus, it is not necessarily sufficient to make generalizations regarding the vulnerability of chondrichthyans across higher taxonomic scales.
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Maturity, fecundity, and reproductive cycle of the Spotted Ratfish, Hydrolagus colliei
Marine Biology, 2009Co-Authors: Lewis A K Barnett, David A. Ebert, Ryan L. Earley, Gregor M. CaillietAbstract:Size at maturity, fecundity, and reproductive periodicity were estimated for the Spotted Ratfish, Hydrolagus colliei (Lay and Bennett, 1839), off the coast of California, Oregon, and Washington. Maximum body size and size at median maturity were greater for females than males. Skeletal muscle concentrations of the steroid hormones testosterone (T) and estradiol (E_2) predicted similar, but slightly smaller sizes at maturity than the morphological criterion. Stage of maturity for males was estimated identically using internal organs or external secondary sexual characters, thus allowing non-lethal maturity assessments. Size at median maturity was greater north of Point Conception for females, and north of Cape Mendocino for males. Peak parturition occurred from May to October, with increased concentrations of E_2 in skeletal muscle of females correlating with ovarian recrudescence during November to February. No significant seasonal trends in female T were apparent, but mean female 11-ketotestosterone (11KT) was 300% greater in April than any other month during the parturition season. There was a marginal evidence for increased number and size of ova with maternal size. Extrapolation of the hypothesized 6 to 8-month egg-laying season to observed mean parturition rates of captive specimens yielded an estimated annual fecundity of 19.5–28.9 egg cases. Differences in fecundity among higher taxonomic classifications of chondrichthyans were detected with chimaeriform fishes more fecund than lamniform, myliobatiform, squaliform, and rhinobatiform fishes, and less fecund than rajiform fishes.
D A Lovejoy - One of the best experts on this subject based on the ideXlab platform.
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identification of gonadotropin releasing hormone and associated binding substances in the blood serum of a holocephalan hydrolagus colliei
Peptides, 1993Co-Authors: D A Lovejoy, Judy A King, Nancy M Sherwood, Richard E PeterAbstract:Abstract The identity of the gonadotropin-releasing hormone (GnRH) form and the presence of GnRH-binding substances in the blood serum of the holocephalan, Spotted Ratfish ( Hydrolagus colliei ), were investigated. The GnRH-like peptides in the serum were identified on the basis of relative hydrophobicity using reverse-phase HPLC. [His 5 ,Trp 7 ,Tyr 8 ]GnRH (chicken GnRH-II) was the only GnRH form detected in the serum. It has been previously shown to be the only GnRH form in the brain of this species. The presence of GnRH-binding substances was inferred by anomalous HPLC elution of GnRH, ultrafiltration behavior, and by the direct binding of iodinated GnRH analogues by blood serum components. The mean GnRH concentration in the extracted blood serum was 125 ± 11 pg ml −1 ( n = 5 ) in males and 64 ± 48 pg ml −1 ( n = 4 ) and 155 ± 26 ( n = 4 ) in two separate groups of females. Measurement of GnRH in the blood serum is complicated by the presence of GnRH-binding substances, which may cause the coprecipitation of GnRH during extraction with organic solvents. The high concentration of GnRH and the presence of GnRH-binding substances suggest that systemic blood is the route by which GnRH reaches the gonadotropes and/or that GnRH may have a hormonal role in H. colliei .
