288
characteristic. Moreover, experimental results showed that anal fi ns of this species
may be a “sensitive bio-indicator for screening environmental estrogenic chemicals,”
(Hayashi et al. 2007 ).
Pelvic Fins The paired pelvic (or ventral) fi ns are located forward from the anal
fi n, and provide additional stability during swimming. In some species, pelvic fi ns
are modifi ed into thread-like long fi ns and used as a tactile organ. For example,
pelvic fi ns by catfi sh ( Corydoras ) are used to hold their eggs during spawning. Fish
like fl ying gurnards ( Dactylopteridae ) use these fi ns to walk on substrates (Macesic
and Kajiura 2010 ).
In contrast to the fi ns discussed above, paired pelvic fi n function remains poorly
investigated. The fi rst study about detailed three-dimensional movements of pelvic fi ns
in fi sh was carried out by Standen ( 2008 ). The author also evaluated hypotheses for
how these fi ns might function. Thus, “during slow-speed swimming, [rainbow] trout
[Onchorynchus mykiss] moved their pelvic fi ns in contralateral oscillations. Each individual pelvic fi n moved in two major oscillations that overlapped during the fi n beat
cycle (left and right fi ns act 180° out of phase): (1) oscillations relative to the transverse
plane (initiated fi rst); and (2) oscillations relative to the sagittal plane (initiated 120°
after the transverse plane oscillations). Both the direction and timing of these oscillations suggested that pelvic fi n motion is, at least partially, the result of active muscle
use, and not due to body and water motion alone,” (Standen 2008 ). “Based on kinematic analysis it appears that pelvic fi n oscillation produced a series of forces. During
the stroke phases when the fi n was actively pushing against fl ow, one can assume the
fi n produced hydrodynamic force. Altogether, during slow-speed steady swimming in
trout, pelvic fi ns have a complex, active motion that appears to have both a dynamicpowered and a static-trim force producing function” (Standen 2008 ).
Some fi sh species use pelvic fi ns for so called “ bentic locomotion ”. One of the forms
of bentic locomotion is “ punting ”: “while keeping the rest of the body motionless,
the skate’s pelvic fi ns are planted into the substrate and then retracted caudally,
which thrusts the body forward,” (Macesic and Kajiura 2010 ; see also Koester and
Spirito 2003 ). The benthic locomotion has been observed only within three families
of Elasmobranchii:
– “The epaulette and bamboo sharks ( Hemiscyllidae ), and horn sharks ( Heterodontidae ),
use their fl exible pectoral and pelvic fi ns to walk and station- hold on the
substrate,” (Macesic and Kajiura 2010 ; see also Pridmore 1995 ; Compagno
1999 ; Goto et al. 1999 ; Wilga and Lauder 2001 ).
– “Within the batoids (rays and skates), only members of the family Rajidae, the
skates, are reported to use their specialized bilobed pelvic fi ns, termed crura, to walk
(each fi n alternately) and punt (both fi ns synchronously) on substrates,” (Macesic
and Kajiura 2010 ; see also Lucifora and Vassallo 2002 ; Koester and Spirito 2003 ).
As reported by Macesic and Kajiura ( 2010 ), “only the clearnose skate, Raja eglanteria ,
and the lesser electric ray, Narcine brasiliensis , performed “true punting”, in which only
the pelvic fi ns were engaged. The skate punted signifi cantly faster than the other species.
Examination of the pelvic fi n musculature revealed more specialized muscles in the true
7 Fish Fins and Rays as Inspiration for Materials Engineering and Robotics
characteristic. Moreover, experimental results showed that anal fi ns of this species
may be a “sensitive bio-indicator for screening environmental estrogenic chemicals,”
(Hayashi et al. 2007 ).
Pelvic Fins The paired pelvic (or ventral) fi ns are located forward from the anal
fi n, and provide additional stability during swimming. In some species, pelvic fi ns
are modifi ed into thread-like long fi ns and used as a tactile organ. For example,
pelvic fi ns by catfi sh ( Corydoras ) are used to hold their eggs during spawning. Fish
like fl ying gurnards ( Dactylopteridae ) use these fi ns to walk on substrates (Macesic
and Kajiura 2010 ).
In contrast to the fi ns discussed above, paired pelvic fi n function remains poorly
investigated. The fi rst study about detailed three-dimensional movements of pelvic fi ns
in fi sh was carried out by Standen ( 2008 ). The author also evaluated hypotheses for
how these fi ns might function. Thus, “during slow-speed swimming, [rainbow] trout
[Onchorynchus mykiss] moved their pelvic fi ns in contralateral oscillations. Each individual pelvic fi n moved in two major oscillations that overlapped during the fi n beat
cycle (left and right fi ns act 180° out of phase): (1) oscillations relative to the transverse
plane (initiated fi rst); and (2) oscillations relative to the sagittal plane (initiated 120°
after the transverse plane oscillations). Both the direction and timing of these oscillations suggested that pelvic fi n motion is, at least partially, the result of active muscle
use, and not due to body and water motion alone,” (Standen 2008 ). “Based on kinematic analysis it appears that pelvic fi n oscillation produced a series of forces. During
the stroke phases when the fi n was actively pushing against fl ow, one can assume the
fi n produced hydrodynamic force. Altogether, during slow-speed steady swimming in
trout, pelvic fi ns have a complex, active motion that appears to have both a dynamicpowered and a static-trim force producing function” (Standen 2008 ).
Some fi sh species use pelvic fi ns for so called “ bentic locomotion ”. One of the forms
of bentic locomotion is “ punting ”: “while keeping the rest of the body motionless,
the skate’s pelvic fi ns are planted into the substrate and then retracted caudally,
which thrusts the body forward,” (Macesic and Kajiura 2010 ; see also Koester and
Spirito 2003 ). The benthic locomotion has been observed only within three families
of Elasmobranchii:
– “The epaulette and bamboo sharks ( Hemiscyllidae ), and horn sharks ( Heterodontidae ),
use their fl exible pectoral and pelvic fi ns to walk and station- hold on the
substrate,” (Macesic and Kajiura 2010 ; see also Pridmore 1995 ; Compagno
1999 ; Goto et al. 1999 ; Wilga and Lauder 2001 ).
– “Within the batoids (rays and skates), only members of the family Rajidae, the
skates, are reported to use their specialized bilobed pelvic fi ns, termed crura, to walk
(each fi n alternately) and punt (both fi ns synchronously) on substrates,” (Macesic
and Kajiura 2010 ; see also Lucifora and Vassallo 2002 ; Koester and Spirito 2003 ).
As reported by Macesic and Kajiura ( 2010 ), “only the clearnose skate, Raja eglanteria ,
and the lesser electric ray, Narcine brasiliensis , performed “true punting”, in which only
the pelvic fi ns were engaged. The skate punted signifi cantly faster than the other species.
Examination of the pelvic fi n musculature revealed more specialized muscles in the true
7 Fish Fins and Rays as Inspiration for Materials Engineering and Robotics