Fish communication Flashcards
What are the different ways in fish comunicate?
Vision, olfaction, sound, electrosensation, mechanoreception
All the focusing is done by what in fish?
Why?
Lens
Because the cornea and water have the same refractive index
What is the refractive index?
How much light gets bent.
Where does actual image forming take place?
Retina
What are the different layers or cell types in the retina?
At the back is the pigment epithelium, then photoreceptors (rods and cones), then nuclear layer (inner and outer) then ganglion cells whose axons form the optic nerve.
Cones are for what type of vision?
Rods?
Cones - photopic, bright light and colour - lots of photons
Rods - scotopic vision - dark, low light
Describe the retinomotor adaptation.
Rods are sensitive to light and can get photobleached so, this comes into play.
In the presence of lots of light, the pigment epithelium will migrate down and the rods will migrate up/stretch (stay attached, essentially elongate) to prevent photobleaching and protect the rods from bright light.
When the light is dim, the opposite occurs, pigment layer migrates back up, and rods go back in the path of photons.
What is spherical abberation?
Beams of light at the edges of a sphere will get focused at a different spot then those travelling through the middle of the sphere.
What is chromatic abberration?
same as spherical abberation but with colour.
Colours have different wavelengths and get distorted differently in a perfect sphere - blue bends more than red.
How are both types of abberations corrected in fish?
The fish lens will have different protein layers with different refractive indices which will correct for both chromatic and spherical abberations.
How does a fish focus light?
Change the focus on the retina by moving the lens back and forth.
This is done by a muscle and the suspensory ligament.
The muscle will flex or relax to change focus. The ligament will return it to place after muscular relaxation.
Why does light go through all the cell layers before detection?
If it was too close, couldn’t get retinomotor adaptation - functions to protect rods.
What is resolution?
What is sensitivity?
What are both based on?
Resolution means you can tell individual items apart.
Sensitivity means you have a greater ability to sense photons.
Both depend on the photoreceptor-ganglion ratio.
Describe the Pr-Gc ratio as it pertains to good resolution.
Good resolution, can tell items apart, not particularly good in dim light.
Closer to a one to one ratio or PR to GC (PR > GC still)
Describe the Pr-Gc ratio as it pertains to sensitivity.
All the photoreceptor information gets summed into few ganglion cells, so high PR:GC ratio.
Higher summation ratio of photoreceptors to ganglia, need less light.
What fish would have a lower PR:GC ratio?
Fish that need good resolution, lots of bright light available.
What fish would have a higher PR:GC ratio?
Fish that live in turbid environments, more active at night, deeper sea fish.
Higher sensitivity.
What are colours due to?
Pigments, achromatic elements and structural colours.
What gets reflected is what?
The colour
Where are pigments localized to?
Pigment cells called chromatophores.
Pigments in chromatophores will affect ______ colour.
Apparent
What are achromatic colours?
Absorb light rather than reflect them.
Different type of pigment that can be synthesized: guanine crystals which reflect all colours and melanin - show black.
What are structural colours?
Light that bounces off of fish scales, bones or skin and arent true pigments.
Green, blue, violet
Rapid or seasonal colour change will be the product of what?
Achromatic and pigments
Which has the longer wavelength, red or blue?
Red
UV light is what wavelength?
below 400nm (blue)
What is the purpose of having UV cones in fish?
To see small zooplankton.
How do we know what cones fish have?
MSP - microscpectrometry
Opsin genes
What is MSP?
Take fish eye, place on slide and shine different lights on the cones to determine the absorbance peaks.
What are opsin genes?
Opsin is a pigment in different cones which absorb light differently.
For this method, grind up eyeball and see which opsins are expressed.
Why do available wavelengths of light matter?
Since this will determine what the fish looks like in a given habitat.
Fish that live deep will often be red since red doesnt penetrate deep in the water, only blue.
Will thus be camouflaged.
Apparent colour is affected by available _________.
wavelengths
Mechanoreception is detection of a _________ stimulus.
It is accomplished, in fish, by two systems. These are?
Mechanical
Ear and lateral line
What does the ear detect, more or less. What does the lateral line detect, more or less?
Ear detects sound waves that move the water.
Lateral line detects water movements, prey movements, not necessarily sound.
What is the sound receptor in the ear?
Hair cell
Why is the otolith necessary for hearing?
Fish are the same density as water, hair cell needs to bend to release NT for signal transduction.
So, there is no relative movement of the hair cell and the fish.
This is why the otolith is necessary.
The otolith sits on top of the hair cells and is more dense than the water.
When sound waves push against the fish and the otolith, there will be relative movement, causing the hair cell to bend, leading to mechanotransduction of the sound stimulus.
Causes ion channels to open and release NT.
What is the duality of underwater sound?
Pressure wave
Particle motion
What is a pressure wave?
Pressure moving back and forth, high and low pressure being transmitted in the water.
What is particle motion?
As sound moves through water, shakes water particles which can directly cause bending of hair cells.
Close to the source, a fish will detect _______ ______, far from the source a fish will detect _______ ________.
particle motion
pressure wave
What are the two parts of sound that matter for any kind of detection?
Frequency - pitch - i.e. what is sounds like - repetition rate
Intensity - loudness
Threshold deals with ________, bandwidth deals with.
Intensity
frequency
What is threshold?
How quiet something can be and still be heard. Related to intensity.
What is bandwidth?
The range of frequencies that can be heard.
If hearing is important, evolution will lead to increases in ______ and _________.
bandwidth and threshold
All fish can hear to at least below _____.
600 Hz
Frequency on the __-axis, sensitivity on the __-axis.
Sensitivity is given in ____.
x
y
decibels
For the frequency vs. sensitivity graph, what are the key points of this?
Fish that hear a wider bandwitdh also are more sensitive.
Why can shad hear ultrasound?
Listening for dolphins, their main predators.
What are the different hearing specializations?
Weberian ossicles
Auditory bullae
Swimbladder extensions
Branchial bubbles
What are weberian ossicles?
Give an example species with this.
Modified vertebrae that connect the swimbladder to the ear.
Direct connection
predominant in shallow water.
Minnows
What do shad have to allow them to hear ultrasound?
auditory bullae
Bubbles that are directly connected to the ear by a ligament.
When the bladder shakes, makes bullae shake back and forth, which pulls the ear.
What do swimbladder extensions do for hearing?
Give an example species.
when the swim bladder is closer to the ear, more likely to transfer pressure waves from sound.
Indirect connection.
Drum
How do branchial bubbles help with hearing?
For fish that can hold air bubbles in the branchial chamber, as long as the bubble is there, will vibrate increasing hearing.
How can fish hear pressure?
Pressure is converted to particle motion by things like the swim bladder.
When pressure hits it, shakes, converting that to particle motion at the hair cell level.
Allows fish to hear further from the sound source.
