296
contrast to the white ordinary connective tissue surrounding them. They are spindleshaped, tapering to fi ne points at either end. Cross sections show peripheral grooves
and layers of concentric lamellae (Kemp 1977 ). Some authors (Damodaran et al.
1956 ; Sastry and Ramachandran 1965 ; Kimura and Kubota 1966 ; Chandross 1982 )
suggested that elastoidin may be responsible for the abnormal size of ceratotrichia
fi brils. It was found in elasmobranch and teleost fi sh species (Garrault 1936 ) as well
as in Latimeria (Geraudie and Meunier 1980 ). According to Tsuchiya and Nomura
( 1953 ), scientist with the name Kuo-Hao Lin in 1926 analysed the yellow fi sh
fi ber in the tissue of the shark fi n, and called it “substance A”. The author found its
nitrogen distribution and its amino acid content. These authors also proposed to
change the defi nition “elastoidin” into “ selachin ”.
Initial studies into the amino acid composition (Damodaran et al. 1956 ; Kimura
and Kubota 1969 ), physico-chemical properties (Kimura and Kubota 1966 ), the
ultrastructure (McGavin and Pyper 1964 ; Woodhead-Galloway and Knight 1977 ;
Chandross and Bear 1979 ), as well as X-ray diffraction patterns (Ratho and Misra
1970 ; Hukins et al. 1976 ) of elastoidin have been performed. Some studies
(Ramachandran 1962 ; Sastry and Ramachandran 1965 ) showed that elastoidin was
“a mix of collagenous and non-collagenous proteins, but neither the particular collagen types nor the identity of the non-collagenous proteins could be determined,”
(Durán et al. 2011 ). Although the hydroxyproline content of elastoidin fi bers is
similar to that of collagen from teleost fi sh (Damodaran et al. 1956 ), they differed
from other collagens in containing of relatively high amount of tyrosine (7.15 %) as
well as cysteine (0.35 %). Gross and Dumsha ( 1958 ) reported that elastoidin fi brils
contained 0.77 % carbohydrate.
Studies on molecular packing in elastoidin spicules of the spurhound Squalus
acanthias has been carried out by Woodhead-Galloway et al. ( 1978 ). Here, the
results obtained:
“Low-angle X-ray diffraction showed that, despite the well-defi ned regular
axially projected structure, there is no long-range lateral order in the packing of
molecules in native (undried) or dried elastoidin spicules from the fi n rays of this
fi sh. The equatorial intensity distribution of the X-ray diffraction pattern from native
elastoidin indicates a molecular diameter of 1.1 nm and a packing fraction for
the structure projected on to a plane perpendicular to the spicule (fi bril) axis of 0.31
(the value for tendon is much higher, around 0.6). Density measurements support this
interpretation. When the spicule dries, the packing fraction increases to 0.43, but
there is still no long-range order in the structure. It was observed that the X-ray
diffraction patterns provide no convincing evidence for any microfi brils or subfi brils
in elastoidin. Gel electrophoresis shows that the three chains in the elastoidin
molecule are identical. The low packing fraction for collagen molecules in elastoidin
explains the difference in appearance between electron micrographs of negatively
stained elastoidin and tendon collagen. In elastoidin, but not in tendon collagen, an
appreciable proportion of the stain is able to penetrate between the collagen
molecules,” (Woodhead-Galloway et al. 1978 ).
7 Fish Fins and Rays as Inspiration for Materials Engineering and Robotics
contrast to the white ordinary connective tissue surrounding them. They are spindleshaped, tapering to fi ne points at either end. Cross sections show peripheral grooves
and layers of concentric lamellae (Kemp 1977 ). Some authors (Damodaran et al.
1956 ; Sastry and Ramachandran 1965 ; Kimura and Kubota 1966 ; Chandross 1982 )
suggested that elastoidin may be responsible for the abnormal size of ceratotrichia
fi brils. It was found in elasmobranch and teleost fi sh species (Garrault 1936 ) as well
as in Latimeria (Geraudie and Meunier 1980 ). According to Tsuchiya and Nomura
( 1953 ), scientist with the name Kuo-Hao Lin in 1926 analysed the yellow fi sh
fi ber in the tissue of the shark fi n, and called it “substance A”. The author found its
nitrogen distribution and its amino acid content. These authors also proposed to
change the defi nition “elastoidin” into “ selachin ”.
Initial studies into the amino acid composition (Damodaran et al. 1956 ; Kimura
and Kubota 1969 ), physico-chemical properties (Kimura and Kubota 1966 ), the
ultrastructure (McGavin and Pyper 1964 ; Woodhead-Galloway and Knight 1977 ;
Chandross and Bear 1979 ), as well as X-ray diffraction patterns (Ratho and Misra
1970 ; Hukins et al. 1976 ) of elastoidin have been performed. Some studies
(Ramachandran 1962 ; Sastry and Ramachandran 1965 ) showed that elastoidin was
“a mix of collagenous and non-collagenous proteins, but neither the particular collagen types nor the identity of the non-collagenous proteins could be determined,”
(Durán et al. 2011 ). Although the hydroxyproline content of elastoidin fi bers is
similar to that of collagen from teleost fi sh (Damodaran et al. 1956 ), they differed
from other collagens in containing of relatively high amount of tyrosine (7.15 %) as
well as cysteine (0.35 %). Gross and Dumsha ( 1958 ) reported that elastoidin fi brils
contained 0.77 % carbohydrate.
Studies on molecular packing in elastoidin spicules of the spurhound Squalus
acanthias has been carried out by Woodhead-Galloway et al. ( 1978 ). Here, the
results obtained:
“Low-angle X-ray diffraction showed that, despite the well-defi ned regular
axially projected structure, there is no long-range lateral order in the packing of
molecules in native (undried) or dried elastoidin spicules from the fi n rays of this
fi sh. The equatorial intensity distribution of the X-ray diffraction pattern from native
elastoidin indicates a molecular diameter of 1.1 nm and a packing fraction for
the structure projected on to a plane perpendicular to the spicule (fi bril) axis of 0.31
(the value for tendon is much higher, around 0.6). Density measurements support this
interpretation. When the spicule dries, the packing fraction increases to 0.43, but
there is still no long-range order in the structure. It was observed that the X-ray
diffraction patterns provide no convincing evidence for any microfi brils or subfi brils
in elastoidin. Gel electrophoresis shows that the three chains in the elastoidin
molecule are identical. The low packing fraction for collagen molecules in elastoidin
explains the difference in appearance between electron micrographs of negatively
stained elastoidin and tendon collagen. In elastoidin, but not in tendon collagen, an
appreciable proportion of the stain is able to penetrate between the collagen
molecules,” (Woodhead-Galloway et al. 1978 ).
7 Fish Fins and Rays as Inspiration for Materials Engineering and Robotics