locomotion in rajiformes

3). The complex actuation of the wings has been mimicked successfully through a variety of means including tensegrity structures, electroactive polymers, and fluid muscles. Rajiform locomotion is a unique swimming style found in the batoid fishes (skates and rays) in which thrust is generated by undulatory waves passing down the enlarged pectoral fins. [8], Rajiform swimmers move by undulating the distal parts of their pectoral fins with multiple waveforms present on the fin at a time. There are animals that move on land, in the air, in trees, and in the water. Fish interact with the fluid environment using a variety of surfaces – paired fins, median fins and the body itself (Harris, 1936; Standen and Lauder, 2005; Standen and Lauder, 2007; Tytell et al., 2008; Webb, 2006). Rajiformes is one of the four orders in the superorder Batoidea, flattened cartilaginous fishes related to sharks. As no significant differences in amplitude were found between swimming speeds, data were pooled (N=24). This movement from one place to another is called locomotion, and there are lots of different types. Locomotion helps us to move from place to other. More recent work has recognized the diversity of locomotion within the group, distinguishing two modes: (1) mobuliform oscillation, underwater flapping flight dominated by dorsoventral excursion, and (2) rajiform undulation, via a propulsive wave of bending that passes from anterior to posterior along the pectoral fin (Webb, 1994). To best portray the propulsive wave of the right pectoral fin, non-orthogonal perspectives are shown, and anterior is to the right. Unlike other fishes, which typically interact with the fluid environment via multiple fins, undulating rays modulate a single control surface, the pectoral disc, to perform pelagic locomotion, maneuvering and other behaviors. 5A). (A) Amplitude, as mid-disc value (deep blue/red) and maximum amplitude (light blue/red); (B) frequency; (C) mid-disc wavespeed; (D) body angle, the incline of the dorsal midline relative to the horizontal. Locomotion by rays and skates has been set apart since early classifications of swimming modes, with the eponymous ‘rajiform mode’ originally encompassing locomotion by any elasmobranch with expanded pectoral fins, from manta rays (Myliobatidae: Mobulinae) to stingrays (Dasyatidae) (Breder, 1926). ... fins, which reach as far forward as the sides of the head, with a generally flattened body. Both of these are brought about by the jointefforts of the skeletal and muscular systems. Studies of mobuliform locomotion have found surprising maneuverability and efficiency in manta rays and other, typically large, ‘underwater fliers’ (Heine, 1992; Parson et al., 2011); the charismatic manta is the basis of several bio-inspired robots (e.g. The distinction is more than kinematic: oscillators are typically pelagic, and have high-aspect-ratio fins, whereas undulators are primarily benthic, with a low-aspect-ratio pectoral disc (Rosenberger, 2001). [14] We compare these variables between speeds to quantify the kinematic changes that increase thrust and allow stingrays to swim faster. 10A,B). Only a relatively small region of the pectoral fin (~25%) undulates with significant amplitude (>0.5 cm). The cartilaginous fishes are distinguished fro… As no significant differences in amplitude were found between swimming speeds, data were pooled (N=24). A backward movement of the compound radial in the horizontal plane characterizes the propulsive phase. approximately 2 cm posterior to the mid-disc; neither mid-disc nor maximum amplitude changes significantly with speed (ANOVA, P=0.74 and 0.88, respectively; Fig. In addition to anteroposterior bending associated with the propulsive wave, notable mediolateral curvature of pectoral fin radials occurs during swimming by P. orbignyi (Figs 9, 10). From muscle fiber analysis it appears that punting may be a primary mode of transportation at low speeds (about 1/3 Body lengths per second) in some skates and rajiform locomotion may be used when for specific situations. Amplitude was calculated for each point as half of the total dorsoventral excursion. [1][2], Mobuliform swimming is common in pelagic Myliobatiformes species such as manta rays and is characterized by a flapping motion of the pectoral fins. Mean values of the principal component described by frequency and mid-disc wavespeed differed significantly between swimming speeds (ANOVA, P<0.01; Fig. Our data contradict this idea: potential excursion should correspond to angular displacement, increasing with fin span, yet maximum amplitude occurs posterior to the maximum disc width (0.7 versus 0.5 DL). It is very similar in appearance to flight in birds. - Skates are shaped from a rounded to diamond shape. A new preprint by Goto et al. Though the wavespeed ‘trough’ does not differ from surrounding values by a statistically significant margin, it does suggest the radial path taken by the propulsive wave, which moves around the perimeter of the disc rather than parallel to the midline. In stingrays, retaining a concave-down fin shape is also likely to have hydrodynamic significance, as it will affect flow passing beneath and beside the fin. Strouhal number was determined by fL/U, with disc length used as the characteristic length L. Wave number, defined as the number of waves present on the fin at one time, was calculated relative to both disc length and disc perimeter. Undulatory swimmers propel themselves by passing a wave of bending along a flexible fin or body surface; modulations of the wave produce changes in swimming speed or instigate maneuvers. The major changes in waveform that determine velocity (frequency and wavespeed) may be accompanied by minor changes in secondary parameters such as amplitude and wavelength. Animal locomotion. We determined values for maximum positive (concave up) and negative (concave down) curvature. They are able to execute asynchronous movements with their crura to make turns which negates the need to bank during turns, which may provide stealth benefits in addition to the reduced water movement. Using three cameras (250 frames s−1), we gathered three-dimensional excursion data from 31 points on the pectoral fin during swimming at 1.5 and 2.5 disc lengths s−1, describing the propulsive wave and contrasting waveforms between swimming speeds. 9A) underestimate curvature because of the limited resolution available given the number of points digitized on the distal fin, but we observed dramatic distal curvature directly (Fig. First, the central portion of a stingray's body cannot undulate (in dorsoventral or mediolateral directions) due to a stiffened vertebral column and the fusion of the pectoral girdles with axial cartilages (Compagno, 1999); motion of the medial fin is limited by its attachment to the fixed midline. Finbeats were defined as a full cycle of the propulsive wave, from the initiation of a wave at the anterior edge of the fin through completion as the wave passed off the posterior edge. After initial analysis confirmed that the body midline does not undulate, we slightly reduced the number of midline points analyzed, and present results based on 29 digitized points. For the majority of studied fish species, increases in swimming speed are driven by increases in the frequency of propulsive motions [typically tailbeat frequency (Bainbridge, 1958; Drucker and Jensen, 1996)]. Wingtip vortices result from pressure differences between the dorsal and ventral surfaces of an airfoil or hydrofoil; vortices form around the tip of the foil as fluid moves from high to low pressure, circulating around the fin or wing (Vogel, 2003). Elasmobranchs are known to use their bodies as lift-generating surfaces; among oscillatory rays (Myliobatidae), pitching of the body can be used to generate thrust (Heine, 1992), and in leopard and bamboo sharks (Triakis semifasciata and Chiloscyllium punctatum), a positive body angle offsets torques generated by the heterocercal tail (Wilga and Lauder, 2002). These sequences exhibit the second pattern of distal curvature we observe in P. orbignyi, where concave-down curvature is retained throughout the wave cycle (Fig. Other animals explore both the aquatic and aerial realm more extensively. They have flattened bodies and large, wing-like pectoral fins that are attached to the side of their heads and run the length of their body! The distribution of pectoral thin thickness is such that rajiform swimmers benefit passively from hydrodynamic interaction between the substrate and their fins. In the blue-spot stingray, T. lymma, amplitude at the fin margin increases towards the mid-disc, and then decreases as the wave moves further posterior; the authors describe this pattern of amplitude increase and decrease as a form of ‘narrow-necking’ (Rosenberger and Westneat, 1999). I. Order: Rajiformes Family: Rajidae: Body Plan: - Skate are cartilaginous fish that lack any "true bone". Please log in to add an alert for this article. We calculated curvature using standard methods (see Standen and Lauder, 2005; Taft et al., 2008), via the following equation: One might conjecture that amplitude remains constant because stingrays have maximized potential excursion at the lower swimming speed, and cannot further expand the range of motion. A radially propagating wave, however, when measured along a direct anteroposterior axis, would appear to have greater wavespeed when traveling at a greater angle to that axis, i.e. [9] The thickness of the pelvic fins is highest at the anterior part of fin and lowest at the distal parts of the fin and the posterior fin, generally less than a millimeter. Disc length [4], Rays are at a disadvantage compared to other fish when it comes to maneuverability. Using the DLT Dataviewer 2 program in MATLAB version 7.10 (Hedrick, 2008), we digitized 31 points across the right pectoral fin and along the body midline, determining the x, y and z coordinates of each point in every frame via direct linear transformation to give fin surface deformations in 3-D (Fig. Rajiformes - rays, sawfish, skates : There are around 573 species of fish in this order. Supplementary material available online at http://jeb.biologists.org/cgi/content/full/215/18/3231/DC1. Amplitude increase is nearly linear along the mediolateral axis of the fin, except at the distal margin, where the rate of increase becomes steeper (Fig. For comparison with 2-D kinematic data from previous work (e.g. The direction of the ciliary beat is tailward, causing the animal to glide slowly forward. 11B). Yet mediolateral variations in the structure of fin elements do occur in batoid pectoral fins (Schaefer and Summers, 2005). Further, anterior portions of the disc that move freely during other behaviors, such as foraging (Wilga et al., 2012), are held motionless during undulatory locomotion. LocoMotion has successfully brought new job opportunities to Baja, helping to revive the economy in the wake of Hurricane Odile in September of 2014. Note differences in wave timing between swimming speeds. High-speed video stills from some sequences reveal extreme negative curvature of the distal fin, with a smaller radius than could be resolved given the limited number of points digitized in this region (Fig. Our results for wave frequency and mid-disc wavespeed also fall in the range for species studied by Rosenberger (Rosenberger, 2001). 4B). We chose to work with juvenile potamotrygonids because their small size [mean pectoral disc length (DL) 12.8±0.8 cm, mean disc width (DW) 11.27±0.99 cm] allowed the study of undulatory swimming in a small, controlled volume, yielding high-resolution kinematic data. When wave number is calculated relative to disc length (sensu Rosenberger, 2001), our data yield a wave number of 1.10±0.08 for P. orbignyi, representing just over one complete wave on the Rotational movement is the movement of a bone as it rotates around its own longitudinal axis. TWO FORMS OF MOVEMENT By: Jenil U. Moises 2. Frequency, mid-disc wavespeed and body angle all increase significantly with swimming speed (Fig. [11] As such swimming away from the substrate for extended periods is unsustainable. Calculated values (Fig. Skeletal morphology also reflects locomotor mode, with areas of increased fin stiffness and preferential axes of bending created by the arrangement of fin-radial joints and variations in calcification pattern (Schaefer and Summers, 2005). Most importantly, though, the amplitude pattern presented for T. lymma highlights the limitations of 2-D analyses when interpreting 3-D waveforms. Skeletal structure also determines flexibility in the pectoral fins of longhorn sculpin, Myoxocephalus octodecimspinosus, where variations in segmentation and hemitrich cross-section along the length of individual fin rays allow regionalization of fin function by creating local changes in stiffness (Taft, 2011; Taft et al., 2008). 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