285
swimming, the pectoral fi ns are generally actuated synchronously with one another
in forward swimming. Speed can be increased gradually by increasing fi n beat
amplitude and/or frequency. Labriform swimmers change to body-caudal fi n
swimming near their peak speed,” (Hale et al. 2006 ). The bluegill sunfi sh ( Lepomi
machrochirus ) use their pectoral fi n as a fl apping propulsor for both manoeuvring
and steady swimming. “This fi n is a highly deformable and controllable surface,
which can be made to fl ap, feather, and row, as well as to take on a variety of complex
three-dimensional shapes,” (Gottlieb et al. 2010 ).
The transmission of muscle force and motion to individual fi n rays determine the
thrust production as well as the common biomechanics of fi n motion in fi sh.
Following observations have been reported in this aspect:
– “Force transmission to the fi n is determined by the contractile mechanics of the
muscles and the structure of the fi n skeleton;
– the osteological differences in fi n shape, fi n ray morphology, bony processes at
the bases of the fi n rays, and the fi n radials have functional implications;
– fi n shape has clear consequences for fi n thrust mechanics, related to a trade-off
between the effi ciency of fast swimming and maneuverability in slowly swimming species;
– a rowing stroke is capable of producing stronger thrust transients for maneuvers
when it is performed with a more rounded, distally broadened, paddle-shaped
fi n. In contrast, a more slender, tapering, wing-like fi n is more effi cient for swimming at higher sustained speeds using a dorsoventral fl apping stroke;
– aspect ratio shows a strong correlation with swimming performance, with higher
aspect ratio fi ns enabling higher critical swimming speeds than paddle-shaped fi ns;
– the labriform swimmers with elongated, wing-like fi ns and a steeper (more
dorsoventral) stroke plane can achieve and maintain higher swimming speeds
than can labriform swimmers; who have lower-aspect-ratio paddle-like fi ns and
shallower stroke planes,” (Thorsen and Westneat 2005 ; see also Walker and
Westneat 1997 , 2000 , 2002 ).
Furthermore, it was reported that “the variation in bony processes at the bases of
the fi n rays is striking and has clear functional implications for fl apping and rowing
fi ns. Flappers have processes that are pronounced toward the leading edge and taper
off toward the trailing edge. Rowers have pronounced processes along all rays, with
special connections for the ABS and ABP that allow for control over a central pivot.
Mechanical (force) advantage of fi n rays can be expected to vary on a continuum
between rowers and fl appers; rowers should have a higher mechanical advantage,
while higher performance swimmers should have a lower mechanical advantage with
a concomitant increase in fi n velocity advantage,” (Thorsen and Westneat 2005 ).
Recently, a biorobotic pectoral fi n was developed in the Lab of George Lauder.
This model construct was used in investigations concerning the fl exural rigidities
and the fi n’s propulsive forces (see for details Tangorra et al. 2010 ; Gottlieb et al.
2010 ). Thus, briefl y, “the design of the biorobotic fi n was based on a detailed analysis
of the pectoral fin of the bluegill sunfish ( L. macrochirus ). The biorobotic fin
was made to execute the kinematics used by the biological fi n during steady
swimming, and to have structural properties that modeled those of the biological
7.1 Fish Fins and Rays: Diversity, Structure and Function
swimming, the pectoral fi ns are generally actuated synchronously with one another
in forward swimming. Speed can be increased gradually by increasing fi n beat
amplitude and/or frequency. Labriform swimmers change to body-caudal fi n
swimming near their peak speed,” (Hale et al. 2006 ). The bluegill sunfi sh ( Lepomi
machrochirus ) use their pectoral fi n as a fl apping propulsor for both manoeuvring
and steady swimming. “This fi n is a highly deformable and controllable surface,
which can be made to fl ap, feather, and row, as well as to take on a variety of complex
three-dimensional shapes,” (Gottlieb et al. 2010 ).
The transmission of muscle force and motion to individual fi n rays determine the
thrust production as well as the common biomechanics of fi n motion in fi sh.
Following observations have been reported in this aspect:
– “Force transmission to the fi n is determined by the contractile mechanics of the
muscles and the structure of the fi n skeleton;
– the osteological differences in fi n shape, fi n ray morphology, bony processes at
the bases of the fi n rays, and the fi n radials have functional implications;
– fi n shape has clear consequences for fi n thrust mechanics, related to a trade-off
between the effi ciency of fast swimming and maneuverability in slowly swimming species;
– a rowing stroke is capable of producing stronger thrust transients for maneuvers
when it is performed with a more rounded, distally broadened, paddle-shaped
fi n. In contrast, a more slender, tapering, wing-like fi n is more effi cient for swimming at higher sustained speeds using a dorsoventral fl apping stroke;
– aspect ratio shows a strong correlation with swimming performance, with higher
aspect ratio fi ns enabling higher critical swimming speeds than paddle-shaped fi ns;
– the labriform swimmers with elongated, wing-like fi ns and a steeper (more
dorsoventral) stroke plane can achieve and maintain higher swimming speeds
than can labriform swimmers; who have lower-aspect-ratio paddle-like fi ns and
shallower stroke planes,” (Thorsen and Westneat 2005 ; see also Walker and
Westneat 1997 , 2000 , 2002 ).
Furthermore, it was reported that “the variation in bony processes at the bases of
the fi n rays is striking and has clear functional implications for fl apping and rowing
fi ns. Flappers have processes that are pronounced toward the leading edge and taper
off toward the trailing edge. Rowers have pronounced processes along all rays, with
special connections for the ABS and ABP that allow for control over a central pivot.
Mechanical (force) advantage of fi n rays can be expected to vary on a continuum
between rowers and fl appers; rowers should have a higher mechanical advantage,
while higher performance swimmers should have a lower mechanical advantage with
a concomitant increase in fi n velocity advantage,” (Thorsen and Westneat 2005 ).
Recently, a biorobotic pectoral fi n was developed in the Lab of George Lauder.
This model construct was used in investigations concerning the fl exural rigidities
and the fi n’s propulsive forces (see for details Tangorra et al. 2010 ; Gottlieb et al.
2010 ). Thus, briefl y, “the design of the biorobotic fi n was based on a detailed analysis
of the pectoral fin of the bluegill sunfish ( L. macrochirus ). The biorobotic fin
was made to execute the kinematics used by the biological fi n during steady
swimming, and to have structural properties that modeled those of the biological
7.1 Fish Fins and Rays: Diversity, Structure and Function