295
“Actinotrichia are composed not by a bundle of discretely separated collagen
fi brils, but rather of hyperpolymerized collagen molecules. Given the size of the
actinotrichia, such a degree of polymerization would require careful post- translational
processing during collagen biosynthesis and collaboration with other molecules to
reach such a large size. One good candidate for this task is Lysyl hydroxylase 1 (lh1
or plod1), which has been described in cells surrounding the actinotrichia during fi n
development. Lysyl hydroxylases are essential for collagen biosynthesis, catalyzing
the addition of hydroxyl groups to lysine residues. These hydroxylysine residues
serve as attachment sites for carbohydrate chains and participate in the formation of
intermolecular cross-links. In the teleostean actinotrichia, the presence of, at the very
least, a collagen fraction in them was confi rmed additionally by electron microscopy
studies that showed the typical banding pattern of collagen in actinotrichia longitudinal sections. Though recent immunohistochemical studies have suggested actinotrichia are composed of Collagen type II, which would interact with other collagens,
such as Collagen IX,” (Durán et al. 2011 ; see also Gross and Dumsha 1958 ; Huang
et al. 2009 ; Montes et al. 1982 ; Ramachandran 1962 ; Sastry and Ramachandran
1965 ; Schneider and Granato 2007 ).
Recently, the non-collagen fraction of actinotrichia has been termed as actinodins ,
which are correspondingly encoded by actinodin genes (And). These genes only
present in fi sh lineages and, signifi cantly, they seem to be implicated in fi n/limb
evolution (Zhang et al. 2010 ).
Recently van den Boogaart et al. ( 2012 ) demonstrated that actinotrichia contribute
to increase the mass of water accelerated backward during swimming. The amount,
dimensions, orientation and growth of actinotrichia were measured at various
locations along the fi nfold in several developmental stages of common carp
( Cyprinus carpio ) and zebrafi sh ( Danio rerio ). Actinotrichia morphology correlated
with expected lateral forces exerted on the water during swimming. The authors
proposed the analytical model that predicts the extent of camber from the oblique
arrangement of the actinotrichia and curvature of the body. Camber of the fi nfold
during swimming was measured from high-speed video recordings and used to
evaluate the model predictions. Based on structural requirements for swimming and
strain limits for collagen, the model also predicts optimal orientations of actinotrichia
(van den Boogaart et al. 2012 ).
7.3 Chemistry of Fish Fin: Elastoidin
Protein of the shark fi n origin with properties of both collagen and elastin was
termed elastoidin by Krukenberg ( 1885 ). He identifi ed signifi cant amount of sulfur
within elastoidin fi bers, which did not yield gelatin when boiled with water. Unlike
elastin, the elastoidin fi bers were resistant to enzymatic treatment with pancreatic
trypsin (Kemp 1977 ). In some shark species, elastoidin fi bers may be several millimeters wide and up to 30 cm long (Damodaran et al. 1956 ). They show longitudinal
striations, however, are shiny and transparent, and may be brownish or yellowish, in
7.3 Chemistry of Fish Fin: Elastoidin
“Actinotrichia are composed not by a bundle of discretely separated collagen
fi brils, but rather of hyperpolymerized collagen molecules. Given the size of the
actinotrichia, such a degree of polymerization would require careful post- translational
processing during collagen biosynthesis and collaboration with other molecules to
reach such a large size. One good candidate for this task is Lysyl hydroxylase 1 (lh1
or plod1), which has been described in cells surrounding the actinotrichia during fi n
development. Lysyl hydroxylases are essential for collagen biosynthesis, catalyzing
the addition of hydroxyl groups to lysine residues. These hydroxylysine residues
serve as attachment sites for carbohydrate chains and participate in the formation of
intermolecular cross-links. In the teleostean actinotrichia, the presence of, at the very
least, a collagen fraction in them was confi rmed additionally by electron microscopy
studies that showed the typical banding pattern of collagen in actinotrichia longitudinal sections. Though recent immunohistochemical studies have suggested actinotrichia are composed of Collagen type II, which would interact with other collagens,
such as Collagen IX,” (Durán et al. 2011 ; see also Gross and Dumsha 1958 ; Huang
et al. 2009 ; Montes et al. 1982 ; Ramachandran 1962 ; Sastry and Ramachandran
1965 ; Schneider and Granato 2007 ).
Recently, the non-collagen fraction of actinotrichia has been termed as actinodins ,
which are correspondingly encoded by actinodin genes (And). These genes only
present in fi sh lineages and, signifi cantly, they seem to be implicated in fi n/limb
evolution (Zhang et al. 2010 ).
Recently van den Boogaart et al. ( 2012 ) demonstrated that actinotrichia contribute
to increase the mass of water accelerated backward during swimming. The amount,
dimensions, orientation and growth of actinotrichia were measured at various
locations along the fi nfold in several developmental stages of common carp
( Cyprinus carpio ) and zebrafi sh ( Danio rerio ). Actinotrichia morphology correlated
with expected lateral forces exerted on the water during swimming. The authors
proposed the analytical model that predicts the extent of camber from the oblique
arrangement of the actinotrichia and curvature of the body. Camber of the fi nfold
during swimming was measured from high-speed video recordings and used to
evaluate the model predictions. Based on structural requirements for swimming and
strain limits for collagen, the model also predicts optimal orientations of actinotrichia
(van den Boogaart et al. 2012 ).
7.3 Chemistry of Fish Fin: Elastoidin
Protein of the shark fi n origin with properties of both collagen and elastin was
termed elastoidin by Krukenberg ( 1885 ). He identifi ed signifi cant amount of sulfur
within elastoidin fi bers, which did not yield gelatin when boiled with water. Unlike
elastin, the elastoidin fi bers were resistant to enzymatic treatment with pancreatic
trypsin (Kemp 1977 ). In some shark species, elastoidin fi bers may be several millimeters wide and up to 30 cm long (Damodaran et al. 1956 ). They show longitudinal
striations, however, are shiny and transparent, and may be brownish or yellowish, in
7.3 Chemistry of Fish Fin: Elastoidin