292
Fish fi n rays can be defi ned according to their origin and structural properties
into dermatotrichia , laterotrichia , ceratotrichia , camptotrichia , lepidotrichia , and
actinotrichia . Here, very brief description of these biological materials-containing
structures.
Dermatotrichia. The dermal fi n rays of elasmobranchs and bony fi shes are
known collectively as dermatotrichia (Lagler et al. 1977 ).
Laterotrichium a small unpaired bone rod above the fi rst pelvic ray probably
derived from a dermatotrichia in some lower Teleostei like Esocidae , Cyprinidae ,
Salmonidae , Osmeridae , Cobitidae , Siluridae and Balitoridae .
Ceratotrichia (Goodrich 1904 ) are large dermal fi bers which are located bilaterally in sharks and are homologous with the fi brous rays called actinotrichia, which
are localized at the distal ends of bony rays in teleosts. As cited in paper by Tsuchiya
and Nomura ( 1953 ), the horny fi bre-like Ceratotrichia, embedded in the shark fi n
are the only part of special human diet in China in the form of soup. Ceratotrichia
showed features similar to both collagen and elastin that led Krükenberg to name
“elastoidin” to the main protein within ceratotrichia (Krukenberg 1885 ).
Camptotrichia – has been found as specifi c rays which support the fi n membranes in Crossopterygii and Dipnoi. It was suggested that camptotrichia may be
homologous to the ceratotrichia of Elasmobranchii. As described in Geraudie and
Meunier ( 1982 ):
“ Camptotrichia constitute the only skeleton of the Dipnoan fi ns. Their fi ne structure
is indeed quite different from the two other Osteichthyan dermotrichia , namely the
actinotrichia and the lepidotrichia found simultaneously in the fi n margin of both
Actinopterygians and Crossopterygians fi ns. Although different from lepidotrichial
bone, the fi ne structure of camptotrichia is more reminiscent of it than of the
elastoidin-formed actinotrichia,” (Geraudie and Meunier 1982 ).
In dipnoan species, Protopterus and Neoceratodus , the camptotrichia have “a
dual structure: only the superfi cial region facing the stratifi ed epidermis is mineralized
while the deep one is made of a dense unmineralized network of collagen fi brils
forming a permanent pre-osseous tissue. In the living lungfi sh Neoceratodus , the
camptotrichia is made of cellular bone,” (Geraudie and Meunier 1984 ).
Lepidotrichia are well described in the paper of Johanson et al. ( 2005 ) as “dermal
elements located at the distal margin of osteichthyan fi ns. In sarcopterygians and
actinopterygians, the term has been used to denote the most distal bony hemisegments and also the more proximal, scale-covered segments which overlie endochondral
bones of the fi n. In certain sarcopterygian fi shes, including the Rhizodontida , these
more proximal, basal segments are very long, extending at least half the length of
the fi n. The basal segments have a subcircular cross section, rather than the crescentic
cross section of the distal lepidotrichial hemisegments, which lack a scale cover and
form short, generally regular, elements. In rhizodonts and other sarcopterygians,
e.g. Eusthenopteron , the basal elements are the fi rst to appear during fi n development,
followed by the endochondral bones and then the distal lepidotrichia,” (Johanson
et al. 2005 ).
Two parallel and symmetrical bony demirays that form jointed segments within
the fi n are the main structural elements of lepidotrichia (Fig. 7.7 ). The demirays
7 Fish Fins and Rays as Inspiration for Materials Engineering and Robotics
Fish fi n rays can be defi ned according to their origin and structural properties
into dermatotrichia , laterotrichia , ceratotrichia , camptotrichia , lepidotrichia , and
actinotrichia . Here, very brief description of these biological materials-containing
structures.
Dermatotrichia. The dermal fi n rays of elasmobranchs and bony fi shes are
known collectively as dermatotrichia (Lagler et al. 1977 ).
Laterotrichium a small unpaired bone rod above the fi rst pelvic ray probably
derived from a dermatotrichia in some lower Teleostei like Esocidae , Cyprinidae ,
Salmonidae , Osmeridae , Cobitidae , Siluridae and Balitoridae .
Ceratotrichia (Goodrich 1904 ) are large dermal fi bers which are located bilaterally in sharks and are homologous with the fi brous rays called actinotrichia, which
are localized at the distal ends of bony rays in teleosts. As cited in paper by Tsuchiya
and Nomura ( 1953 ), the horny fi bre-like Ceratotrichia, embedded in the shark fi n
are the only part of special human diet in China in the form of soup. Ceratotrichia
showed features similar to both collagen and elastin that led Krükenberg to name
“elastoidin” to the main protein within ceratotrichia (Krukenberg 1885 ).
Camptotrichia – has been found as specifi c rays which support the fi n membranes in Crossopterygii and Dipnoi. It was suggested that camptotrichia may be
homologous to the ceratotrichia of Elasmobranchii. As described in Geraudie and
Meunier ( 1982 ):
“ Camptotrichia constitute the only skeleton of the Dipnoan fi ns. Their fi ne structure
is indeed quite different from the two other Osteichthyan dermotrichia , namely the
actinotrichia and the lepidotrichia found simultaneously in the fi n margin of both
Actinopterygians and Crossopterygians fi ns. Although different from lepidotrichial
bone, the fi ne structure of camptotrichia is more reminiscent of it than of the
elastoidin-formed actinotrichia,” (Geraudie and Meunier 1982 ).
In dipnoan species, Protopterus and Neoceratodus , the camptotrichia have “a
dual structure: only the superfi cial region facing the stratifi ed epidermis is mineralized
while the deep one is made of a dense unmineralized network of collagen fi brils
forming a permanent pre-osseous tissue. In the living lungfi sh Neoceratodus , the
camptotrichia is made of cellular bone,” (Geraudie and Meunier 1984 ).
Lepidotrichia are well described in the paper of Johanson et al. ( 2005 ) as “dermal
elements located at the distal margin of osteichthyan fi ns. In sarcopterygians and
actinopterygians, the term has been used to denote the most distal bony hemisegments and also the more proximal, scale-covered segments which overlie endochondral
bones of the fi n. In certain sarcopterygian fi shes, including the Rhizodontida , these
more proximal, basal segments are very long, extending at least half the length of
the fi n. The basal segments have a subcircular cross section, rather than the crescentic
cross section of the distal lepidotrichial hemisegments, which lack a scale cover and
form short, generally regular, elements. In rhizodonts and other sarcopterygians,
e.g. Eusthenopteron , the basal elements are the fi rst to appear during fi n development,
followed by the endochondral bones and then the distal lepidotrichia,” (Johanson
et al. 2005 ).
Two parallel and symmetrical bony demirays that form jointed segments within
the fi n are the main structural elements of lepidotrichia (Fig. 7.7 ). The demirays
7 Fish Fins and Rays as Inspiration for Materials Engineering and Robotics