|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
First published online July 20, 2006
Journal of Experimental Biology 209, 2920-2928 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02325
Material properties and biochemical composition of mineralized vertebral cartilage in seven elasmobranch species (Chondrichthyes)
1 Department of Ecology and Evolutionary Biology, 321 Steinhaus Hall,
University of California, Irvine, CA 92697-2525, USA
2 Shriners Hospital for Children, 12502 Pine Drive, Tampa, FL 33612-9499,
USA
* Author for correspondence (e-mail: porterm{at}uci.edu)
Accepted 13 May 2006
 |
Summary |
|---|
 TOP Summary IntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Key words: mineralized cartilage, stiffness, ultimate strength, collagen, proteoglycan
|
Introduction |
|---|
|
TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
). This quote is
emblematic of the perception that the skeleton of cartilaginous fishes is
mechanically inferior to that of bony fishes. A strong argument against this
common wisdom is that cartilaginous fishes perform at functional extremes. For
example, whale sharks are the biggest fish in the sea
(Gudger, 1941). They have
skeletons many times larger than those of the largest bony fish. Also, shark
skeletons endure tens to hundreds of millions of loading cycles in their
transoceanic migrations (Bonfil et al.,
2005; Boustany et al.,
2002; Carey and Scharold,
1990). Furthermore, we suppose that in some sharks, the skeleton
must resist the high loads that occur during burst swimming.
The vertebral column of a shark is subjected to a variety of loading
regimes depending on swimming speed and mode. During anguilliform swimming,
the left and right sides of individual vertebrae are alternately loaded in
tension and compression and the rate and frequency of loading vary with
swimming speed (Lindsey, 1978;
Sfakiotakis et al., 1999).
However, faster subcarangiform and thunniform swimmers exhibit less local
lateral displacement (Gemballa et al.,
2006). The rising intramuscular pressure imposes a different load
by compressing the entire vertebral column in the cranial to caudal direction
(Martinez et al., 2002;
Vogel, 1988;
Wainwright et al., 1978).
Vertebral deformation under these loads must be very low to efficiently
transfer these muscularly applied loads.
There is a well known relationship between loading regime and the
properties of biological materials
(Wainwright et al., 1976). For
example, a weight bearing horse femur is more than three times as stiff as a
mature red deer antler, though the latter is far tougher than the former
(Currey, 1999). Although
swimming is a `low impact' mode of locomotion, it has been shown to increase
bone density in humans (Falk et al.,
2003). The loads imposed by long duration, fast swimming suggest
that vertebrae of faster swimming sharks might be stiffer and stronger than
slower swimmers.
The amount and arrangement of mineral are important determinants of
material properties. Currey, examining a variety of bones, found that
increasing bone mineral content by just 10% can nearly double the material
stiffness (Currey, 1999). For
example, bony fish vertebrae exposed to higher loads have more mineral and the
mineral is arranged so that second moment of area is higher than in normal
vertebrae (Kranenbarg et al.,
2005a; Kranenbarg et al.,
2005b). The mineral content and arrangement of elasmobranch
vertebrae vary among species, and it has been suggested that additional
calcification may develop in a response similar to bone modeling
(Ridewood, 1921;
Urist, 1962).
Differences in vertebral mineralization in elasmobranchs should have
implications for the spine's ability to resist deformation from the loads
imposed by swimming. Vertebral centra consist of a double cone of mineral with
elaborations varying by taxa (Ridewood,
1921) (Fig. 1). For
example, shortfin mako (Isurus oxyrinchus) vertebrae have flattened
plates of mineral around the perimeter of the double cone, whereas the silky
shark (Carcharhinus falciformis) has a continuous crust of thick
mineral (Fig. 1). Cartilage
mineralization in elasmobranch vertebral centra is `areolar'; calcium
phosphate hydroxyapatite is found in web-like patterns of varying density
throughout the centra (Moss,
1977). By contrast, the rest of the skeleton is `tesselated'
consisting of tiny blocks of mineralized tesserae, sometimes occurring in
multiple layers, on the surface of a hyaline cartilage skeletal element
(Dean and Summers, 2006).
|
Elasmobranch vertebral cartilages have both an unmineralized and
mineralized phase. The unmineralized phase is a gel consisting of water and
proteoglycan in a matrix of collagen fibers; the second and third components
are important contributors to material properties in mammals. Collagen is an
important contributor to strength in cartilage
(Currey, 2002). Elasmobranch
cartilage contains one third type I collagen and the remaining portion is type
II (Rama and Chandrakasan,
1984). Proteoglycans are the major noncollagenous organic
component in elasmobranch cartilage
(Michelacci and Horton, 1989).
They add compressive strength to mammalian cartilage by increasing the
swelling pressure through their hydrophilic interactions with water
(Koob, 1989;
Koob and Vogel, 1987).
Furthermore, the presence of proteoglycans has been shown to inhibit
calcification in elasmobranch cartilage
(Gelsleichter et al., 1995;
Takagi et al., 1984).
The present study provides the first description of the material properties and biochemical components of mineralized elasmobranch cartilage from a diversity of species that exhibit a wide variety of swimming speeds and lifestyles. The goals of this study were: (1) Measure the material stiffness (Young's modulus), ultimate strength and yield strain of vertebral centra in compression; (2) quantify the water, collagen, proteoglycan (PG) and mineral content of the mineralized cartilage; and (3) determine if the biochemical composition of the cartilage significantly contributes to it's material properties. We hypothesized, firstly, that the fastest swimming elasmobranchs will have the greatest compressive strength and material stiffness. Second, elasmobranch cartilage will have similar water, collagen and PG contents to mammalian cartilage. Finally, the biochemical components of elasmobranch cartilage will have significant positive relationships with material properties.
|
|
Materials and methods |
|---|
|
TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
|
The requiem sharks (Carcharhiniformes) are fast swimming, maneuverable
sharks found both in and off shore
(Compagno, 2003). The two
members of the Carcharhinidae we sampled are a near shore (Ca.
plumbeus) and a pelagic species (Ca. falciformis). Hammerheads
(Sphyrnidae) are very flexible, fast swimming sharks, and are found near shore
and well off shore to depths of 200 m
(Kajiura et al., 2003).
The shortfin mako (I. oxyrinchus Lamniformes: Lamnidae) is a
regionally endothermic, high-speed predator of marlin, tuna and other pelagic
bony fishes (Block and Carey,
1985; Wolf et al.,
1988). It is believed to be the fastest swimming shark
(Carey and Teal, 1969). Makos
inhabit the pelagic zone of the world's oceans to 150 m.
Gulper sharks (Squaliformes: Centrophoridae: Centrophorus sp.) are
relatively sluggish, bottom dwelling sharks capable of short bursts of
high-speed swimming (Compagno,
1984). They are found in bathydemersal marine habitats below 200 m
in depth.
Finally, the Pacific electric ray (Torpediniformes: Torpedinidae) is a slower swimming, demersal, marine species off the Californian coast. It is capable of delivering a dangerous electric shock, and it is remarkable among rays and skates for using its caudal fin for axial undulation.
Material properties
We removed vertebrae from the region of the first dorsal fin from fresh and
freshly frozen vertebral columns. There is evidence that freezing tissues
before testing has no effect on the material properties of the specimen
(Panjabi et al., 1985). We
excised neural and hemal arches from the centra leaving an unadorned disk of
mineralized cartilage (Fig. 1).
Centra volume was obtained by water displacement to 0.1 ml. Centra were massed
to 0.01 mg and each centrum was digitally photographed with a scale bar and
the cross-sectional area (the anterior/caudal surface) was calculated using
ImageJ software (NIH).
Centra were kept in elasmobranch Ringers solution
(Forster et al., 1972) for no
more than 2 h before being subjected to material testing. Using an MTS Mini
Bionix with a 50 kg load cell we performed a quasi-static compressive test to
failure at a strain rate of 2 mm s-1 on at least nineteen (and as
many as 33) vertebrae from each species
(Table 1). Cartilage stiffness
is greater at higher strain rates and we were interested in testing the limits
of elasmobranch mineralized cartilage (Li
et al., 2003). The resulting load-displacement curves were
analyzed with Matlab v 12 (Mathworks Inc.). Stress-strain curves were
generated and ultimate strength, material stiffness (Young's modulus) and
yield strain were obtained for each vertebra. Ultimate strength is the maximum
stress that can be applied to a material before it fails, and material
stiffness is the ratio of stress to strain in the elastic region of the
stress-strain curve. Yield strain (
) is the percentage length change of
the material at which irrevocable shape change occurs
(Vogel, 2003). We calculated
stress using the cross-sectional area of the vertebra, this intentionally
ignores the structural heterogeneity of the vertebrae. We do not have
sufficient information on the properties of the mineralized and unmineralized
phases nor on their distribution to avoid this simplification. Data from each
vertebra were analyzed three times to ensure accurate estimation of material
properties.
An important caveat regarding our measure of stress is that we assumed the vertebrae were a homogeneous material; the entire cross section of the vertebrae bore the compressive force. This is plainly not the case as there are distinct inhomogeneities in mineral distribution among species (Fig. 1). However, the interaction between the mineralized and unmineralized portions of the vertebrae is probably quite complex and not amenable to simple modeling as a layered composite. In our results it is very probable that the stress in the mineralized parts of the vertebrae is higher than our reported values whereas in the unmineralized regions we have overestimated this parameter. This work is intended to set the stage for further examination of the role of the mineralization of the vertebrae in responding to load.
Compositional analysis
After material testing, centra were lyophilized for 24 h and massed again
to obtain dry mass (organic material + mineral content). Water content was
calculated by subtracting dry mass from wet mass and dividing by wet mass. A
sub-sample of 10 lyophilized vertebrae from each species was placed in a
450°C furnace for 24 h to remove the organic portion of the dry mass.
After 24 h the vertebrae were removed from the furnace and the ash-free dry
mass was recorded. Mineral content was calculated by dividing the ash-free dry
mass by the dry mass.
Collagen content was determined using a hydroxyproline assay
(Bergman and Loxley, 1963).
Dried vertebrae were homogenized in a Thomas Scientific tissue mill with 0.20
mm mesh size. Once homogenized, approximately 50 mg (to the nearest mg) of
each sample was acid hydrolyzed in 1500 µl of 6 mol l-1
hydrochloric acid at 100°C for 18 h. Samples were dried under vacuum to
remove the HCl and were resuspended in 1500 µl distilled water. Samples (10
µl) were diluted 1:100 with distilled water and 200 µl of isopropanol
were added to each sample. Then 100 µl of 7% choloramine-T were added
before incubation for 4 min at room temperature. After adding 1.25 ml of
Ehrlich's reagent and incubating at 60°C for 25 min, 300 µl were plated
and the absorbance at 558 nm was measured with a Bio-Tek µQuantTM
spectrophotometer. Samples were measured against a standard 400 p.p.m.
hydroxyproline solution of (trans-4-hydroxy-L-proline; Arcos
Organics, NJ, USA) which was diluted to generate a standard curve. Collagen
concentration was calculated assuming 10% hydroxyproline
(Miller, 1971). Each centra
had three to five replicate samples for the hydroxyproline assay which were
averaged for analysis.
A second 50 mg sub-sample of each vertebra was used to determine the PG
content (Farndale et al.,
1986). Samples were digested with papain extract and buffer at
60°C for 12 h, then heated to 100°C to denature the enzyme. Samples
were centrifuged at approximately 13 800 g for 10 min and the
resulting pellet was washed three times with 99% ethanol. The pellet was then
resuspended in 400 µl 0.05·mol l-1 sodium acetate, pH 7.4
and 5 µl of the resuspended sample was diluted 1:25 with distilled water.
1000 µl of dimethylmethylene blue (DMMB) indicator solution was added to
the sample and the absorbance was measured immediately with a Bio-Tek
µQuantTM spectrophotometer at 525 nm. Samples were measured against a
standard of 0.2 mg ml-1 chondroitin sulfate-6 (Seikagaku
Coroporation, Tokyo, Japan), which was diluted to generate a standard
curve.
Statistical analysis
The scarcity of fresh material of some species (i.e. Centrophorus
ssp.) made a two-stage analysis of variance necessary. Our first model
assessed variation between species with each vertebra taken as an independent
sample. A second analysis performed on the subset of species with multiple
individuals (Torpedo, Isurus and Ca. falciformis) tested
whether there was significant variation among individuals of a species. This
second analysis was a nested ANOVA with [vertebral centra] nested within
[individual animal] to show that variation in material stiffness and ultimate
strength were due to variation between vertebral centra rather than different
animals (Sokal and Rohlf,
2001; Zar, 1999).
There remains the possibility that we were not able to measure a systematic
difference in material properties along the vertebral column. We have
insufficient material for such a comparison and doubt it would show
significance given the small number of vertebrae sampled relative to the
number of precaudal vertebrae in these species.
Data were analyzed in SPSS v12.0 (SPSS Inc. 2003. SPSS 12.0 FPR Windows Student Version; SPSS Inc., Chicago, IL, USA) using ANOVA (P<0.05). Comparisons among species were made using a Games Howell post hoc test in the SPSS 12.0 data pack, which tests comparisons and does not assume equal variances. The relationship between material properties and biochemical constituents was tested using linear regression analyses in SPSSv.12.0 (SPSS Inc. 2003). In the box and whisker plots of material and compositional data where the box represents the ±95% confidence intervals, the mean for each species is represented by the bold horizontal line, and the whiskers are the ranges obtained for each species.
|
Results |
|---|
|
TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
|
Yield strains were significantly different among groups (F6,147=27.576; P<0.001) (Fig. 3C and Table 1). Yield strain in T. californica vertebral centra was significantly greater than the shark species examined here (P<0.007). Ce. sp. A had the lowest yield strain of all the sharks and was nearly four times lower than T. californica (P<0.044). Strain was the only material property that showed a significant [individual animal] effect.
Regardless of species the vertebrae failed in a similar manner: the anterior and posterior mineralized cones developed two types of cracks: circumferential cracks that divided the centrum into annuli, and radial cracks running from the center of the cone to the outer edge. The cones that form the central `spindle' collapsed outwards, flattening and becoming more oblique. The I. oxyrinchus vertebrae showed an additional fracture modality in the plates of calcification between the cones (Fig. 1). Each plate failed in Euler buckling, generally at the midpoint of the plate when viewed laterally. These multiple failures led to a distinctive chevron pattern in the formerly parallel plates.
Compositional analysis
There were significant differences in water content between species
(F6,153=70.485; P<0.001)
(Fig. 4A and
Table 1). T.
californica had less water in the vertebral cartilage than all shark
species (P<0.001). Ce. granulosus had greater water
content than Ce. sp. A.
|
We found significant differences in PG content between species (F6,82=10.5310; P<0.001) (Fig. 4C and Table 1). Ce. granulosus vertebrae are lower in PG content than the other species (P=0.019). The I. oxyrinchus and carcharhinids (except Ca. falciformis) had more PG than the squalids (Ce. granulosus and Ce. sp. A) and T. californica (P=0.027). I. oxyrinchus had more than twice the PG content of the Ce. granulosus.
Collagen content in the vertebral centra varied between species by nearly 10% (F6,85=4.054; P=0.001) (Fig. 4D and Table 1). The carcharhinid sharks (S. zygaena, Ca. falciformis and Ca. plumbeus) had significantly greater collagen concentrations (24.5-26.8%) than T. californica (17.4%) (P=0.009).
Correlating biochemical components and material properties
Biochemical constituents were significant predictors of material properties
of elasmobranch vertebrae. Water, mineral and collagen content all
significantly increased the ultimate strength of this cartilage (adjusted
R2=0.451, 0.342 and 0.175 respectively;
P<0.001) (Fig. 5).
PG content, although differing among species had little predictive power.
Water, mineral and collagen content were all significant predictors of
increasing material stiffness (adjusted R2=0.446, 0.243
and 0.218, respectively; P<0.001), however, PG content was not
(Fig. 6).
|
|
|
Discussion |
|---|
|
TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Material properties
Stiff skeletons will transfer energy more efficiently at all swimming
speeds, so high speed fish should have the stiffest skeletons
(McHenry et al., 1995).
Animals with stiff bodies are best able to resist skeletal deformation from
the forces of tendon pulling on them during swimming. Our data supported this
hypothesis: the carcharhinids (396-563 MPa) were stiffer than the squalids
(322-425 MPa), which were in turn stiffer than T. californica (25.5
MPa) (Fig. 3B and
Table 1). However, contrary to
our hypothesis, I. oxyrinchus vertebral centra fall in the middle
range of material stiffness values.
The material stiffness of elasmobranch cartilage falls into the range of
mammalian bone which varies from 4 MPa in trabecular bone to 34 100 MPa found
in a fin whale ear bone (Currey,
1999) (Fig. 3B).
The stiffness of trabecular bone, the primary component of mammalian
vertebrae, ranges from 4 to 350 MPa in humans and 35 to 7000 MPa in non-human
models (horse and bovine) (Hodgskinson and
Currey, 1992). More specifically, trabecular bone from human and
ewe lumbar vertebrae range from approximately 600 to 3000 MPa
(Mitton et al., 1998;
Rho et al., 1994). The
variation in elasmobranch vertebral material stiffness is less than a quarter
of that found in trabecular bone of mammalian vertebrae.
We further supposed that the vertebrae of swiftly swimming sharks must be
strong to withstand the forces exerted on them. Two factors contribute to this
increase in force on the vertebral column. First, as an animal swims faster,
the forces exerted directly by the muscles increase in amplitude and frequency
(Coughlin and Rome, 1996).
Second, the internal pressure of a shark increases with swimming speed,
compressing the axial skeleton (Martinez
et al., 2002; Wainwright et
al., 1978). Indeed, we found that ultimate strength of the
vertebrae did follow a pattern similar to our findings for stiffness: the
carcharhinids (23.7-24.3 MPa) had the strongest centra followed by the
squalids (14.7-20.8 MPa), and T. californica (4.5 MPa)
(Fig. 3 and
Table 1). The makos (I.
oxyrinchus), the fastest swimming sharks, again did not support our
hypothesis. It is important to note that vertebral cartilage does appear to
fail in nature, so compressive strength is a biologically relevant property
(Fig. 7).
|
)
(Fig. 3A). Cezayirlioglu et al.
(Cezayirlioglu et al., 1985)
reported ultimate compressive strength values of the human tibia and femur
(206 and 213 MPa, respectively) that were ten times higher than average
elasmobranch vertebral cartilage (17 MPa). A better comparison is with
trabecular bone in human lumbar vertebrae (3.2 MPa) and sheep vertebrae (23.4
MPa) (Mitton et al., 1998;
Rho et al., 1994) - and our
data for shark vertebrae overlap this range.
Data from the fastest shark, the shortfin mako (I. oxyrinchus) a
regionally endothermic, piscivorous fish, did not support our hypotheses.
Perhaps, the root of this incongruity is in the recently described novel force
transmission mechanism makos use to propel themselves through the water
(Donely et al., 2004;
Donely and Shadwick, 2003).
Like tunas, and in contrast to other sharks, makos have extremely long
myoseptal tendons that carry much of the muscular load directly to the tail
(Gemballa et al., 2006;
Shadwick and Gemballa, 2006).
This arrangement allows the body to remain rigid during swimming with only the
tail oscillating.
Biochemical composition
Collagen volume fraction is a good predictor of stiffness in cartilage
tissue culture from rabbits, and as collagen content increases so does the
tensile stiffness of condylar cartilage from human femurs
(Kempson et al., 1973;
Simha et al., 1999). We also
found collagen to be a predictor of both material stiffness and ultimate
strength -a 25% increase in collagen content corresponds to a 53.8% increase
in material stiffness and a 38.7% increase in strength (Figs
5 and
6).
The surprisingly large PG component in mineralized elasmobranch vertebrae
(Fig. 4C) can be accounted for
if it is restricted to the non-mineralized portion of the vertebrae. This is
likely because PGs are partially or completely removed during the cartilage
calcification process and the presence of PGs seems to inhibit calcification
(Gelsleichter et al., 1995;
Takagi et al., 1984). In
contrast to mammalian cartilage and tendon, which has a similar PG component
(15-25% dry mass), we found the material properties of elasmobranch vertebrae
are not predicted by PG content (Koob,
1989; Koob and Vogel,
1987; Venn and Maroudas,
1977) (Figs 7 and
8). This suggests that the mineralized portion of the vertebrae dominates the
material properties of the vertebrae in compression. Although the mineral is
probably important under most testing conditions, we propose that dynamic
testing rather than the quasi-static results presented here would reveal a
link between PG content and material properties.
The presence of a large mineral fraction is the most striking difference
between elasmobranch and mammalian cartilages. Shark vertebral cartilage is
more like mammalian bone, the mineral content of which can range from 54% in
trabecular bone to 94% in compact bone; whereas mammalian cartilage is
essentially void of mineral (Currey,
2002) (Fig. 4B).
Mineral content is a great predictor of stiffness and strength in mammalian
bone (Currey, 1999;
McCalden et al., 1997). For
instance, a 20% loss in mineral content corresponded to a 35% decrease in
strength, and a 60% mineral loss reduced strength by 75%
(Shah et al., 1995).
Similarly, in elasmobranch vertebrae, a 20% decrease in mineral content
corresponded to a decrease of 55.6% in strength and decreased material
stiffness by 59.0%. Again, these results suggest that the mineralized
structures dominate the compressive properties of elasmobranch vertebrae.
Summary
We have examined the material properties and biochemistry of the
mineralized cartilage found in the vertebrae of seven elasmobranch species.
This tissue behaves similarly to mammalian trabecular bone in material
stiffness and ultimate strength. Collagen contents are more similar to
mammalian bone than to mammalian cartilage, and these vertebrae have mineral
fractions equaling that of mammalian bone. That vertebral cartilage has
bone-like stiffness and strength makes it unlikely that decreased functional
demands were a selective force in the abandonment of a bony skeleton by
cartilaginous fishes (Coates et al.,
1998). The material properties of the tessellated elasmobranch
skeleton may hold similar performance surprises and should be a focus of
future experimental study.
|
Acknowledgments |
|---|
|
References |
|---|
|
TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Ashhurst, D. E. (2004). The cartilaginous skeleton of an elasmobranch fish does not heal. Matrix Biol. 23,15 -22.[CrossRef][Medline]
Bergman, I. and Loxley, R. (1963). Two improved and simplified methods for the spectrophotometric determination of hydroxyproline. Anal. Chem. 35,1961 -1965.[CrossRef]
Block, B. A. and Carey, F. G. (1985). Warm brain and eye temperatures in sharks. J. Comp. Physiol. B Biochem. Syst. Environ. Physiol. 156,229 -236.[CrossRef][Medline]
Bonfil, R., Meyer, M., Scholl, M. C., Johnson, R., O'Brien, S.,
Oosthuizen, H., Swanson, S., Kotze, D. and Paterson, M.
(2005). Transoceanic migration, spatial dynamics, and population
linkages of white sharks. Science
310,100
-103.
Boustany, A. M., Davis, S. F., Pyle, P., Anderson, S. D., Le Boeuf, B. J. and Block, B. A. (2002). Expanded niche for white sharks. Nature 415, 35-36.[Medline]
Carey, F. G. and Scharold, J. V. (1990). Movements of blue sharks (Prionace glauca) in depth and course. Mar. Biol. 106,329 -342.[CrossRef]
Carey, F. G. and Teal, J. M. (1969). Mako and Porbeagle: warm-bodied sharks. Comp. Biochem. Physiol. 28,199 -204.[Medline]
Cezayirlioglu, H., Bahniuk, E., Davy, D. T. and Heiple, K. G. (1985). Anisotropic yield behavior of bone under combined axial force and torque. J. Biomech. 18, 61-69.[CrossRef][Medline]
Coates, M. I., Sequeira, S. E. K., Sansom, I. J. and Smith, M. M. (1998). Spines and tissues of ancient sharks. Nature 396,729 -730.[CrossRef]
Compagno, L. J. V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Rome: United Nations Development Programme.
Compagno, L. J. V. (2003). Sharks of the Order Carcharhiniformes. Caldwell, NJ: Blackburn Press.
Coughlin, D. J. and Rome, L. C. (1996). The roles of pink and red muscle in powering steady swimming in scup, Stenotomus chrysops. Am. Zool. 36,666 -677.
Currey, J. D. (1999). The design of mineralised hard tissues for their mechanical functions. J. Exp. Biol. 202,3285 -3294.[Abstract]
Currey, J. D. (2002). Bones. Princeton: Princeton University Press.
Dean, M. N. and Summers, A. P. (2006). Mineralized cartilage in the skeleton of chondrichthyan fishes. Zoology 109,164 -168.
Donely, J. M. and Shadwick, R. E. (2003).
Steady swimming muscle dynamics in the leopard shark Triakis semifasciata.J. Exp. Biol. 206,1117
-1126.
Donely, J. M., Sepulveda, C. A., Konstandinidis, P., Gemballa, S. and Shadwick, R. E. (2004). Convergent evolution in mechanical design of lamnid sharks and tunas. Nature 429, 61-65.[CrossRef][Medline]
Falk, B., Bronshtein, Z., Zigel, L., Constantini, N. W. and
Eliakim, A. (2003). Quantitative ultrasound of the tibia and
radius in prepubertal and early pubertal female athletes. Arch.
Pediatr. Adolesc. Med. 157,139
-143.
Farndale, R. W., Buttle, D. J. and Barrett, A. J. (1986). Improved quantitation and discrimination of sulphated glycosaminoglycans by use of dimethylmethylene blue. Biochim. Biophys. Acta 883,173 -177.[Medline]
Forster, R. P., Goldstein, L. and Rosen, J. K. (1972). Intrarenal control of urea reabsorption by renal tubules of the marine elasmobranch, Squalus acanthias. Comp. Biochem. Physiol. 42A,3 -12.[Medline]
Gelsleichter, J. J., Musick, J. A. and Van Veld, P. (1995). Proteoglycans from the vertebral cartilage of the clearnose skate, Raja eglanteria: inhibition of hydoxyapatite formation. Fish Physiol. Biochem. 14,247 -251.[CrossRef]
Gemballa, S., Konstantinidis, P., Donley, J. M., Sepulveda, C. and Shadwick, R. E. (2006). Evolution of high-performance swimming in sharks: transformations of the musculotendinous system from subcarangiform to thunniform swimmers. J. Morphol. 267,477 -493.[CrossRef][Medline]
Gudger, E. W. (1941). The food and feeding habits of the whale shark, Rhineodon typus. J. Elisha Mitchell Sci. Soc. 57,57 -72.
Heupel, M. R., Simpfendorfer, C. A. and Bennett, M. B. (1999). Skeletal deformities in elasmobranchs from Australian waters. J. Fish Biol. 54,1111 -1115.[CrossRef]
Hodgskinson, R. and Currey, J. D. (1992). Young's modulus, density and material properties in cancellous bone over a large density range. J. Mat. Sci. Mat. Med. 3, 377-381.[CrossRef]
Kajiura, S. M., Forni, J. B. and Summers, A. P. (2003). Maneuvering in juvenile carcharhinid and sphyrnid sharks: the role of the hammerhead shark cephalofoil. Zoology 106, 19-28.
Kempson, G. E., Muir, H., Pollard, C. and Tuke, M. (1973). The tensile properties of the cartilage of human femoral condyles related to the content of collagen and glycosaminoglycans. Biochim. Biophys. Acta 297,456 -472.[Medline]
Koob, T. J. (1989). Effects of chondroitinase-ABC on proteoglycans and swelling properties of fibrocartilage in bovine flexor tendon. J. Orthop. Res. 7, 219-227.[CrossRef][Medline]
Koob, T. J. and Vogel, K. G. (1987). Site-related variations in glycosaminglycan content and swelling properties of bovine flexor tendon. J. Orthop. Res. 5, 414-424.[CrossRef][Medline]
Kranenbarg, S., van Cleynenbreugel, T., Schipper, H. and van
Leeuwen, J. (2005a). Adaptive bone formation in acellular
vertebrae of sea bass (Dicentrarchus labrax L.). J. Exp.
Biol. 208,3493
-3502.
Kranenbarg, S., Waarsing, J. H., Muller, M., Weinans, H. and van Leeuwen, J. L. (2005b). Lordotic vertebrae in sea bass (Dicentrarchus labrax L.) are adapted to increased loads. J. Biomech. 38,1239 -1246.[CrossRef][Medline]
Li, L. P., Buschman, M. D. and Shirazi-Adl, A. (2003). Strain-rate dependent stiffness of articular cartilage in unconfined compression. J. Biomech. Eng. 125,161 -186.[CrossRef][Medline]
Lindsey, C. C. (1978). Form, Function, and Locomotory Habits in Fish. New York: Academic Press.
Maisey, J. G., Naylor, G. J. P. and Ward, D. J. (2004). Mesozoic elasmobranchs, neoselachian phylogeny and the rise of modern elasmobranch diversity. In Mesozoic Fishes 3: Systematics, Paleoenvironments, and Biodiversity. Vol.3 (ed. G. Arratia and A. Tintori), pp.17 -56. Munich: Verlag.
Martinez, G., Drucker, E. G. and Summers, A. P. (2002). Under pressure to swim fast. Integr. Comp. Biol. 42,1273 -1274.
McCalden, R. W., McGeough, J. A. and Court-Brown, C. M.
(1997). Agerelated changes in compressive strength of cancellous
bone. The relative importance of changes in density and trabecular
architecture. J. Bone Joint Surg.
79,421
-429.
McHenry, M. J., Pell, C. A. and Long, J. H. J. (1995). Mechanical control of swimming speed: stiffness and axial wave form in undulating fish models. J. Exp. Biol. 198,2293 -2305.
Michelacci, Y. M. and Horton, D. S. P. Q. (1989). Proteoglycans from the cartilage of young hammerhead sharks Sphyrna lewini. Comp. Biochem. Physiol. 92B,651 -658.[CrossRef]
Miller, E. J. (1971). Isolation and
characterization of a collagen from chick cartilage containing three identical
chains. Biochemistry
10,1652
-1659.[CrossRef][Medline]
Mitton, D., Cendre, E., Roux, J. P., Arlot, M. E., Peix, G., Rumelhart, C., Bardot, D. and Meunier, J. P. (1998). Mechanical properties of ewe vertebral cancellous bone compared with histomorphometry and highresolution computed tomography parameters. Bone 22,651 -658.[Medline]
Moss, M. L. (1977). Skeletal tissues in sharks. Am. Zool. 17,335 -342.
Panjabi, M. M., Krag, M., Summers, D. and Videman, T. (1985). Biomechanical time-tolerance of fresh cadaveric human spine specimens. J. Orthop. Res. 3, 292-300.[CrossRef][Medline]
Rama, S. and Chandrakasan, G. (1984). Distribution of different molecular species of collagen in the vertebral centra of shark (Carcharius acutus). Connect. Tissue Res. 12,111 -118.[Medline]
Rho, J. Y., Zerwekh, J. E. and Ashman, R. B. (1994). Examination of several techniques for predicting trabecular elastic modulus and ultimate strength in the human lumbar spine. Clin. Biomech. 1994,67 -72.
Ridewood, W. G. (1921). On the calcification of the vertebral centra in sharks and rays. Philos. Trans. R. Soc. Lond. B Biol. Sci. 210,311 -407.
Sfakiotakis, M., Lane, D. M. and Davies, B. C. (1999). Review of fish swimming modes for aquatic locomotion. IEEE J. Oceanic Eng. 24,237 -252.[CrossRef]
Shadwick, R. E. and Gemballa, S. (2006). Structure, kinematics, and muscle dynamics in undulatory swimming. In Fish Biomechanics. Vol. 23 (ed. R. E. Shadwick and G. V. Lauder), pp. 241-274. San Diego: Academic Press.
Shah, K. M., Goh, J. C. H., Karunanithy, R., Low, S. L., De Das, S. and Bose, K. (1995). Effect of decalcification on bone mineral content and bending strength of feline femur. Calcif. Tissue Int. 56,78 -82.[CrossRef][Medline]
Simha, N. K., Fedewa, M., Leo, P. H., Lewis, J. L. and Oegema, T. (1999). A composites theory predicts the dependence of stiffness of cartilage culture tissues on collagen volume fraction. J. Biomech. 32,503 -509.[CrossRef][Medline]
Sokal, R. R. and Rohlf, F. J. (2001). Biometry: The Principles and Practice of Statistics in Biological Research. New York: W. H. Freeman.
Takagi, M., Parmley, R. T., Denys, F. R., Yagasaki, H. and Toda, Y. (1984). Ultrastructural cytochemistry of proteoglycans associated with calcification of shark cartilage. Anat. Rec. 208,149 -158.[Medline]
Urist, M. R. (1962). Calcium and other ions in
blood and skeleton of Nicaraguan fresh-water shark.
Science 137,984
-986.
Venn, M. and Maroudas, A. (1977). Chemical
composition and swelling of normal and osteoarthritic femoral head cartilage.
I. Cartilage composition. Ann. Rheum. Dis.
36,121
-129.
Vogel, S. (1988). Life's Devices. Princeton: Princeton University Press.
Vogel, S. (2003). Comparative Biomechanics: Life's Physical World. Princeton: Princeton University Press.
Wainwright, S. A., Biggs, W. D., Currey, J. D. and Gosline, J. M. (1976). Mechanical Design in Organisms. Princeton: Princeton University Press.
Wainwright, S. A., Vosburgh, F. and Hebrank, J. H.
(1978). Shark skin: function in locomotion.
Science 202,747
-749.
Wolf, N. G., Swift, P. R. and Carey, F. G. (1988). Swimming muscle helps warm the brain of lamnid sharks. J. Comp. Physiol. B Biochem. Syst. Environ. Physiol. 157,709 -715.
Zar, J. H. (1999). Biostatistical Analysis. New Jersey: Prentice Hall.
This article has been cited by other articles:
|
|
 |
|
  M. E. Porter, T. J. Koob, and A. P. Summers The contribution of mineral to the material properties of vertebral cartilage from the smooth-hound shark Mustelus californicus J. Exp. Biol., October 1, 2007; 210(19): 3319 - 3327. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
