Natural History of Sharks, Skates, and Rays

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Natural History of Sharks, Skates, and
Rays Sensory Biology MARE 380 Dr. Turner
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Sensory Biology
Legendary 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
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Sensory Performance
Often characterized in two ways Sensitivity
minimum stimulus detected by the system Acuity
the ability of the system to discriminate
stimulus characteristics - location, type, etc.
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Sensory Performance
Vision Hearing Mechanosenses Electrosenses Olf
action other Chemosenses
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Vision
Eyes 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
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Vision
Nearly 360 visual field Blind areas in front of
snout behind head Binocular overlap small
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Vision
Some species (carcharhinids sphrynids) have a
3rd eyelid (nictitating membrane) Extends from
lower nasal corner to protect eye from abrasion
during feeding or contact
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Vision
Some sharks w/out membrane can roll eye into
orbit to protect (e.g. white, whale shark)
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Vision
Unlike Teleosts have dynamic iris increase
size of pupil in dim decrease in bright
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Vision
Unlike Teleosts have dynamic iris increase
size of pupil in dim decrease in bright
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Vision
Unlike Teleosts have dynamic iris increase
size of pupil in dim decrease in bright
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Vision
Unlike Teleosts have dynamic iris increase
size of pupil in dim decrease in bright
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Vision
Possess yellowish pigments in eye similar to some
teleosts diurnal terrestrial animals Also
tapetum lucidum reflective back retina Color
vision hypothesizednot known
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Vision
a) tapetum lucidum reflective plates behind
retina (b) intensifies light that strikes
it When light increases a black melanin makes
them opaque (c)
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Hearing
Do 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 sound
Upper portion balance 3 semicircular canals
(a,b,c) utricle (d)
Lower portion hearing saccule (sacculus) (e)
which receives sounds along endolymphatic duct (f)
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Hearing
Can localize on sound which shows directional
hearing to 10
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Mechanosenses
Detection 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
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Mechanosenses
Mechanosensory Neuromast group of sensory hair
cells surrounded by support cells and covered by
gelatinous cupula Functional unit of all lateral
line end organs
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Mechanosenses
Distributed on skin surface in grooves on raised
papillae (skates, ray, some sharks) or b/w
modified placoid scales (sharks)
A pore B mucus-lined inner canal C sensory
cilia D sensory nerves
b
c
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Mechanosenses
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Mechanosenses
Although 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)
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Electrosenses
All elasmobranchs possess an elaborate ampullary
electroreceptor system that is exquisitely
sensitive to low-frequency electric stimuli
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Electrosenses
Consists of subdermal groups of electroreceptive
units Ampullae of Lorenzini Originally thought
to be mechanoreceptors
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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
What?
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Is This Them?
Is this them? Are these they? Who talks like
that?!? - Henchman 21 24
Consists of (ampulla) a subdermal canal about
1mm wide that projects to the surface
A pore B canal C ampullae D nerves
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Olfaction Chemosense
Originally thought to be most important
mechanisms for finding food Lateral olfactory
epithelium (sacs)
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Olfaction Chemosense
Each nares is blind slit divided in 2 by
fold Water forced into specific olfactory cells
as moves through nostril flow-thru
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Make Sense?
a - Acoustic-lateralis system
d Ampullae of Lorenzini
b - smell
c - sight