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