Natural History of Sharks, Skates, and Rays Sensory Biology MARE 394 Dr. Turner Summer 2008.
Transcript of Natural History of Sharks, Skates, and Rays Sensory Biology MARE 394 Dr. Turner Summer 2008.
Natural History of Sharks, Skates, and Rays
Sensory BiologyMARE 394Dr. Turner
Summer 2008
Sensory BiologyLegendary sensory abilities
Often exaggerated; some deserved
Not just sense of “smell” but an array of senses working in conjunction
Wired to relative large fish brain
Sensory PerformanceOften characterized in two ways:
Sensitivity – minimum stimulus detected by the system
Acuity – the ability of the system to discriminate stimulus characteristics
- location, type, etc.
Sensory PerformanceVision
Hearing
Mechanosenses
Electrosenses
Olfaction & other Chemosenses
VisionEyes located laterally (Selachians), dorsally (batoids & benthic sharks)
Small related to body size (except Bigeye Thresher)
Nearly 360° visual field
Blind areas in front of snout; behind head
Binocular overlap small
VisionNearly 360° visual field
Blind areas in front of snout; behind head
Binocular overlap small
VisionSome species (carcharhinids & sphrynids) have a 3rd eyelid (nictitating membrane)
Extends from lower nasal corner to protect eye from abrasion during feeding or contact
VisionSome sharks w/out membrane can roll eye into orbit to protect (e.g. – white, whale shark)
VisionUnlike Teleosts – have dynamic iris – increase size of pupil in dim; decrease in bright
VisionUnlike Teleosts – have dynamic iris – increase size of pupil in dim; decrease in bright
VisionUnlike Teleosts – have dynamic iris – increase size of pupil in dim; decrease in bright
VisionUnlike Teleosts – have dynamic iris – increase size of pupil in dim; decrease in bright
VisionPossess yellowish pigments in eye similar to some teleosts & diurnal terrestrial animals
Also tapetum lucidum – reflective back retina
Color vision hypothesized…not known
Visiona) tapetum lucidum – reflective plates behind retina (b); intensifies light that strikes itWhen light increases a black melanin makes them opaque (c)
HearingDo not make noise; hearing shaped by ambient
Shark hearing lower than teleosts, especially those with air-bladder connected to ear
Unknown as to whether attracted to soundUpper portion – balance3 semicircular canals (a,b,c)& utricle (d)
Lower portion – hearingsaccule (sacculus) (e) which receives sounds along endolymphatic duct (f)
HearingCan localize on sound which shows directional hearing – to 10°
MechanosensesDetection of water movements (large & small scale) critical
Lateral line system is stimulated by different movement between the body & surrounding water – used to detect dipole sources (prey) and uniform fields (currents)
Used for rheotaxis, predator avoidance, hydrodynamic imaging, prey detection, social communication & mating in bony fishes
MechanosensesMechanosensory Neuromast – group of sensory hair cells surrounded by support cells and covered by gelatinous cupula
Functional unit of all lateral line end organs
MechanosensesDistributed on skin surface in grooves on raised papillae (skates, ray, some sharks) or b/w modified placoid scales (sharks)
bc
A – poreB – mucus-lined inner canalC – sensory ciliaD – sensory nerves
Mechanosenses
MechanosensesAlthough used for rheotaxis, predator avoidance, hydrodynamic imaging, prey detection, social communication & mating in bony fishes
Limited to prey detection & rheotaxis (Movement of an organism in response to a current of water or air)
ElectrosensesAll elasmobranchs possess an elaborate ampullary electroreceptor system that is exquisitely sensitive to low-frequency electric stimuli
ElectrosensesConsists of subdermal groups of electroreceptive units – Ampullae of Lorenzini
Originally thought to be mechanoreceptors
Ampullae of Lorenzini Marine elasmobranchs – many individual ampullae are grouped into discrete, bilateral cephalic clusters from which project the subdermal canals that radiate in many directions and terminate at individual skin pores on the head of sharks and the head and pectoral fins of skates & rays
Is This Them?“Is this them? Are these they? Who talks like that?!?” - Henchman 21 & 24
A – poreB – canalC – ampullaeD – nerves
Consists of (ampulla) & a subdermal canal about 1mm wide that projects to the surface
Olfaction & ChemosenseOriginally thought to be most important mechanisms for finding food
Lateral olfactory epithelium (sacs)
Olfaction & ChemosenseEach nares is blind slit divided in 2 by foldWater forced into specific olfactory cells as moves through nostril – flow-thru
Make Sense?
a - Acoustic-lateralis system
b - smell
c - sight
d – Ampullae of Lorenzini