Phototaxios Flashcards
What is Phototaxis?
It’s the orientation on movement in respect that it can be either positive or negative or be away or towards light
How do larval swim?
They swim in a helical fashion
Rotation means that their dorsal side is directed to the axis of the helix it keeps the body in the right orientation
What is the tropism theory?
Larvae compare the sense of light intensity through two eyes - if one eye gets more light it will travel in that direction
What is photo positive?
They will go towards the light
What is photo negative
Travels away from light
What is the platynerisdumerlli? The worm?
It has a simple visual system
It is a polychete worm
Their cilia beats in rhythm to eachother to generate currents to drive animal through water
What are eyespots in the worm?
They have a shaded cell that block lights from reaching the photo receptor in certain direction
The eye spot is a single photoreceptor which are shaded by the pigmented cell
Eye spots work independently
What is broad spectral sensitivity?
Photo receptor have a broad sensitivity - it is useful in the aquatic and natural environment
What is significant about rhabdomeric receptors?
They have folded apocal membranes and conduct light activations through the IP signalling pathway
What other photo receptors are there?
Ciliary type receptors which have foldedcilliaand conduct via the cGMP signalling pathway
Hope do opsins work?
The opsin photoreceptive protein will respond to a particular wavelength
They opsin then trigger an IP3or cGMP pathway intracellularly
What are the role of cilliated cells in platyneris?
12 ciliated cells
They go around the eyespots which sensitive nerves that are situated for the eyespots
How does swimming work in platynereis
Photicstimulatin of the photo receptor -sensory motor nueron
Directly influences cilarly beating by synpasing with cilarly cells
As eye spot is activated the ACh modulates beat frequency on the ipsilateral side
Water flow is reduced and animal turns
What happens when you shine light on one side of the platyneris
Its body wil flex its trunk according to the eye that has been illuminate. The bending motion drives the animal in the direction of light
What happens when you apply ACh antagonists
They are unable to perform phototaxis
What happens to older larvae in platyneris
They develop 4 visual eyes
They have 2-7 ohototreceptors
They still have non-visual eyes
What happens when you use eye ablation to platyneris?
Use a laser to take out the eyes/one eye or both
Stimulation of one side- it will cause a direction change towards the light
Ablation of a non-visual eye = no effect on Phototaxis
A ablation of all 4 visual eyes = effect on Phototaxis
Are fruit larvae photo positive or negative
They are photonegative they want to avoid light- this is to avoid prey
What behaviours do fruit fly larvae exhibit when light is present
They crawl forward and turn to the light and wave their head to scan the environment.they either accept or reject the light regime (move with or against light)
Turns can be accepted if light conditions are suitable
What happens if you put fruit fly larvae on a lit up checkerboard
The fruit fly will sweep its head
The head sweeps increased at dark:light
The head sweeps decrease light:dark
Why do fruit fly larvae sweep their head
To detect luminosity in the environment
What is the fruit fly larvae’s bolwig organ
The bolwig organ has photoreceptors in it to make up part of the flies visual system
Does the bolwigs organ have an opaque cup?
Yes,it contains photoreceptive cells inside the cup
How does the opaque cup work in the bolwigs organ?
When the larvae sweep its head the light will either hit or not hit the photoreceptors
Which will allow the larvae to change direction
