Sensory Reception Flashcards
Chemoreception
Taste and olfaction
Taste Receptors
Mouth, head, gills, barbels, fins
NOT ON TONGUE
Olfaction
Nares on front of the head, paired pouch, incurrent and excurrent openings
Not connected to the mouth
High sensitivity to pheremones, food, etc – used for homing in salmon
Mechanoreception
inner ear (motion and sound detection)
Semicircular canals
Motion balance (fluid filled) – 3 canals
Ciliary attachment between otolith and canal wall
movement causes fluid to distort cilia
Otolith
Inner ear bone (aragonite)
Used to detect sound
Sagitta is the major bone used for sound reception and is highly variable between species
density similar to seawater
Rapid growth hatchery fish effects on otoliths
Wild fish have aragonite sp gr = 2.9
Hatchery fish replace aragonite with vaterite sp gr = 2.66
Asteriscus
This can be highly variable in Ostariophyseans
Otolith aging
They allow for the most precise aging of fish
Can see years spent in fresh and saltwater
Fish sound sensitivity
They are most sensitive to low frequency sounds
They use swim bladder to amplify high frequency sounds
Gas molecules in the air bladder vibrate and this amplifies the sounds
The closer the swim bladder is to the ear the better
Gadiform Swim Bladder Hearing
They have shifter the SB more anterior to detect cetaceans
Clupeiforms/Mormyrids Swim Bladder Hearing
The SB has shifted to enter the inner ear
Ostariophyseans Swim bladder hearing
The Weberian apparatus connects the SB to the skull
Sharks/Rays Hearing
They have no otoliths because they cannot produce bone
They have low sensitivity to sounds especially high frequency sounds
Sharks often use air/water interface as a “bladder” to amplify sound from below to detect it
Skates/rays use the sand grains they burry under to amplify sound waves and detect sound
Anthropogenic Noise Effect on Predation
They found on reef ecosystems that increasing noise pollution caused predation to increase
The prey cannot hear as well with all the noise
Lateral Line
Fluid-filled canals on trunk and head with canal neuromasts
Neruomasts
They are transducers that convert mechanical stimulus to electrical
They all connect to 10th cranial nerve
There are 2 types: They can be canal neuromasts or superficial neruomasts
Later line fluid
Bony fish use low-viscosity mucous that is filled with potassium
Sharks simply use sea water
What is the purpose of a split lateral line?
Kind of like having two ears
Allows for increase perception of 3D space
Lateral Lines of Cave Fishes
Many will have tons of canals all over the head
This allows for detection of walls and space even in pitch darkness
How do neuromasts function?
Bundles of cells that have cilia extensions ranging from large and stiff to small
Stiff kinocilium and many stereocilia
All these cilia are connected in a row by tip links
The tip links end on a spring gate which is slightly open at rest
Has a very low level of ion flow
Fluid movement moves the cilia which pulls on the tip link pulling the gate open or closed
This changes the amount of ion flow occurring in the cell
The fish then can sense this change in depolarization and sense its environment
Sensitivity of the lateral line
Researchers found that fish were able to detect vortices from copepods minutes after they were there
Vortices caused by fish swimming can be detected up to 30 minutes after
Electroreception
Pit organs: modified neuromasts for detection of the electric field
Canals with highly conductive fluid inside, but non-conductive walls
Electrosensitivity
Voltage differential detection to 0.1 microvolts per cm
Inactive fish prey emits 500 microvolts per cm on the substrate
Fish prey 10cm at depth emits 0.2 microvolts per cm
Porbeagle shark has a sensitivity to 1 nanovolt (0.001 microvolt per cm)
Electroreception Earths Magnetic field
Ability to detect earth’s field when swimming (0.4 microvolts per cm)
Ocean currents generate electrical currents of 0.5 microvolts per cm)
Nociception
Identical genes, and nerves that are seen in mammals and birds
Fish feel pain.
Vision
Pineal Eye: Light-sensitive cells on the dorsal region of the brain
Ultrasensitive to low light levels (moonlight and starlight)
Sharks, tuna, zebrafish
Eye: lens with the highest refractive index in vertebrates, light coming parallel behind the body is detected
Most have pupil size, but sharks have an adjustable iris
Rod and Cone sensitivity
Scotopic sensitivity: rods (Rhopodsin (Marine) and Porphyropsin (FW))
Photopic sensitivity: cones (Iodopsins)
Tapetum
Guanine crystals used to reflect light from the back of the eye again to be more sensitive to low light levels
Shallow water fish transfer pigments and cover tapetum during day
Marine Light Attenuation
At 1m depth when light detected vertically this is polychromatic full spectrum light, but when horizontally detected it is monochromatic (reduced spectrum)
At 25m depth light is detected as monochromatic (reduced spectrum) when it is vertical and horizontal
Peak Rod sensitivity for marine fishes
The peak rod sensitivity will match the dominant wavelength of back welling light
Peculiarity of deep-sea fish rods
They can often 2 types of rods (this is rare in animal kingdom)
The two different rods have different peak sensitivities, allowing them to interpret color
Dominant Wavelength in different aquatic ecosystems
475 nm in the open ocean
530 in coastal ocean and clear lakes
600 in bogs, swamps, creeks, lakes
What match rods to back welling light?
primarily objects are observed against back welling light
Increase sensitivity to reflectance of an object, increase contrast between object and bacground
Cone pigment sensitivity
Most fish cone pigments do not match back welling light, they are offset
Could increase the contrast of object if the object is brighter than background
Perceive the background as black, make fish more obvious
Why do tuna have matched colour opsin and mahi mahi have offset
Tuna hunt fish from below, prey is always darker than background
Mahi mahi hunt fish from horizontal
