Natural History of Sharks, Skates, and Rays
Locomotion
MARE 380Dr. Turner
Body Form & PropulsionBody form:
Distinctive heterocercal tailExternal morphological symmetryVentrolateral winglike pectoral fins
extending laterally from the body
Distinct from actinopterygian (bony) fishes
Body Form & PropulsionTeleost body forms and propulsion mechanisms
Anguilliform
Carangiform
Subcarangiform
Ostraciform
Propulsion Mechanisms
A&B – Rover PredatorC – Lie-in-wait PredatorD – Surface Oriented FishE – Bottom Oriented FishF – Bottom ClingerG – FlatfishH – RattailI – Deep-bodied FishJ – Eel-like Fish
Body Form & PropulsionChondrichthyan body forms and propulsion mechanisms
Body Forms and Fin ShapesGreat degree of variability in paired & unpaired fins of sharks – 4 body forms
Body Type 1: conical head, large deep body, large pectoral fins, narrow caudal peduncle with lateral keels
Body Form 1Conical headLarge deep bodyLarge pectoral finsNarrow caudal peduncle with lateral keelsHigh aspect ratio tail (high heterocercal); externally symmetricalThunniform propulsion
Fast swimming sharks; reduced pelvic, 2nd dorsal, and anal fins
Body Form 1External symmetrical tail aligns mouth with center of mass & thrust to increase feeding efficiency
Body Form 2Flattened ventral headLess deep bodyLarge pectoral finsLower heterocercalLacks keelsSubcarangiform propulsion
Body Form 2Greatest range of swimming speedsModerately sized pelvic, 2nd dorsal, and anal fins – highly maneuverable
Body Form 3Large headBlunt snoutAnterior pelvic finsMore posterior 1st dorsal finLow heterocercal; small to absent hypochordal lobe (lower), large epichordal lobeSubcarangiform propulsion
Body Form 3Slow swimming speeds; epibenthic, benthic, & demersal
Body Form 4Wide variety of body shapesUnited by few characterisiticsLack anal finLarge epichordal lobeAnguilliform propulsion
Typically deep to deep-sea
Body Form 4Typically deep to deep-sea
Body Form 5Body dorso-ventrally flattenedEnlarged pectoral finsReduction in caudal ½ of bodyTypically benthic; some pelagic
Most batoids, angelsharks, mylobatiforms & Rajiforms
Body Form 5Most batoids, angelsharks, mylobatiforms & Rajiforms
Undulatory Oscillatory
Body Form 6Laterally compressedUndulate pectoral fins; not axial bodyTail long and tapering (leptocercal) to heterocercal
Locomotion in SharksOrientation of the body one of most important factors
1° means of force
Induced swimming with body horizontal (x) and no vertical (y) motion produces positive body angles (lift)
Angle of attack decreases as speed increases toward 2 body lengths/s
How Locomotion is Measured
High speed imagery recorded of shark along with reflective particles in wake
Locomotion in Sharksdd
Locomotion in SharksMotion of the tail is a key aspect to locomotion – complex 3d manner
Kinematics indicates the shark caudal provides thrust and lift by moving water posteriorly and ventrally
Locomotion in Sharks2 distinct types of pectoral fins in sharks
Aplesodic – cardilagenous radials are blunt and extend up to 50% into the fin with the distal web supported only by ceratotrichia*
Plesodic – have radials that extend more than 50% into the fin to stiffen it and supplement the support of the ceratotrichia
*unsegmented, filamentous fin rays
Locomotion in SharksAplesodic fins are more maneuverable; may be used for “walking” on substrate
Locomotion in SharksHeterocercal tail angle causes a change in body angle
Locomotion in SharksWhich causes lift in a swimming shark
Degree of lift is dependent upon the type of tail
Locomotion in SharksBody orientation, tail thrust, and maneuvering the pectoral fins all coordinate in force balance during swimming
Locomotion in Skates & RaysBatoids either undulate or oscillate the pectoral fins
Locomotion in Skates & RaysBasal batoids (guitarfishes, sawfishes, & electric rays)– undulate thick tails like sharks
Locomotion in Skates & RaysRays use strict pectoral fin locomotion Undulation – stingrays
Oscillation – cownose & manta
Movie Movie
Locomotion in HolocephalansChimeras have long flexible pectoral fins; both undulatory & oscillatory