1. Visual communication 3/3/11
Lecture #11
Visual communication
3/3/11

2. Most diverse invertebrates are insects
Live in many different habitats
Under ground
Cave
Aquatic
Forest
Field
Live in different light conditions
Diurnal to nocturnal

3. Insect visual pigments
Opsin protein bound to the chromophore
Insects have two chromophores
A cis retinal vitamin A1 carotene
A3 11-cis 3-hydroxyretinal xanthophylls
In combination with same opsin, each chromophore makes a visual pigment which absorb at slightly different wavelengths

4. Compound eye = many ommatidia
We’ll talk about the optics starting next week. For now lets focus on the visual pigments.
Visual pigments are in rhabdoms

5. Photoreceptors Ciliary Microvillar Rod Cone Octopus Insect
There show the similarities and differences between vertebrate and invertebrate photoreceptors. Both increase the amount of cell membrane which is full of visual pigment.
Bradbury and Vehrencamp “Animal Communication” figure 9.2
Rod Cone Octopus Insect

6. Rhabdoms Each visual cell has a microvillar part
The microvilli of all the visual cells project into the center to make the rhabdom
The microvilli are like bristles on a toothbrush

7. Rhabdoms The microvilli contain the visual pigment
Absorption of light excites the visual cells

8. Bee ommatidium
UV B G
This shows the bee visual pigments and how the rhabdoms are arranged so that all wavelengths will be detected and so compared at once.

9. Spaethe and Briscoe 2005
Fig 4 showing UV gene expression which varies in different ommatidium being either 0 (double head arro) 1 (single arrow) or two rhabdoms

10. Bees have compound eyes and ocelli
Ocelli gather light and are thought not to produce images. Lens sits right on top of receptor cells see, Cornwell He quotes others that say the image distance is 5 times behind the retina not at the retina.
Ocelli are used for navigation and also contain UV opsins

11. Drosophila eyes WT
cinnabar
sepia
white
800 ommatidia per eye

12. Drosophila ommatidium
There are 8 rhabdomeres that make up rhabdom
6 are around center
2 in center - one on top of the other
Cells are numbered
R1-6
R7, R8

13. Drosophila visual pigments
Pigments are numbered Rh1-Rh6

14. Visual pigment arrangements
Light
The six outer rhabdomeres (R1-R6) surround the two inner ones.
Inner ones are one on top of other, R7 and R8
The same visual pigment is in R1-R6
Rh1 - green
R1-R6 used for motion detection
L means cells project to lamina
M cells project to medula where color is likely processed

15. Drosophila visual pigment Rh1 is in most of rhabdomeres (R1-6)

16. Two combinations for R7/R8 cells
From Wernet…Desplan 2003 “Homothorax switches function of Drosophila photoreceptors from color to polarized light sensors

17. Visual pigment combinations in R7/R8
There are two combinations of pigments. You can have 1) Rh3 in R7 and Rh5 in R8 This is the pale combination
Or 2) Rh4 in R7 and Rh6 in R8. This is the yellow combination
Note: Rh2 is in the ocelli

18. Rh2 is expressed only in ocelli
Rh2 is in the ocelli

19. Rh2 is expressed in ocelli

20. R7/R8 cells are used for color vision
Wernet R1-R6 cover entire retina. Project to lamina (L, part of optic lobe). R7 and R8 project to medula
30% %

21. What spectral ranges are being compared?
Pale: UV vs blue
Yellow: UV vs green/yellow - see next slide for immuno of this combo

22. Individual ommatidia - stained for opsin
Rh1 / R1-R6
Rh4 / R7
Rh6 / R8
Rh4 is UV pigment; Rh6 is green/yellow sensitive pigment

23. Light polarization
Orientation of oscillation of photon’s electric field

24. Can analyze polarization with polarizers

25. Polarization
Single polarizer lets through light polarized in one direction

26. Polarization
Add a second polarizer at 90 degrees to 1st

27. Black and white What does it mean when something is white?
What does it mean when something is black?

28. Light sources Sun, flashlight - not polarized
Laser - partially polarized

29. Reflection can cause polarization
S = senkrecht = perpendicular
P = in plane of incidence
We will call these perpendicular and parallel
Light can be polarized in the plane (p-polarized) or
perpendiculat to the plane (s-polarized)

30. Reflection can cause polarization
S = senkrecht = perpendicular
P = in plane of incidence
We will call these perpendicular and parallel
s-polarization (R ) is reflected more than p-polarization (R||)

31. Reflected light n
nair=1 i
This applies to normal incidence

32. Transmitted light is refracted (Snell’s law)
nair=1 i

33. Two polarization planes reflect differently
S = senkrecht = perpendicular
P = in plane of incidence
We will call these perpendicular and parallel
s-polarization (R ) is reflected more than p-polarization (R||)

34. Fresnel equations to calculate reflectance of either polarization
Note - any incident polarization can be expressed as a sum of different amounts of parallel and perp polarization i
What happens to light that is not reflected?

35. Reflectance - light polarized perpendicular to plane is reflected more
This calculation was done for air / glass interface.
Depends on angle of incidence

36. Brewster’s angle is incident angle at which reflected light becomes totally polarized
This calculation was done for air / glass interface.

37. Reflectance - both polarizations approach same reflectance at normal incidence (=0)

38. Simple equation works for unpolarized light at <45°
Unpolarized light is average of both polarizations.

39. At large angles, reflectance goes to 1 for both polarizations

40. Light reflecting from surface is polarized
Light is coming towards us and bounces off water. The light polarized in this plane is not reflected very much. Light polarized perpendicular to this plane (going left right in the picture) is reflected most. If the polarizer passes horizontal light (as on left) light goes through. If blocks horizontal and passes vertical polarized light (of which there isn’t any) there is no reflection and can see into water.

41. Polarization off surfaces
Reflectance from gray matt surface is pretty much independent of polarization - matt surface scatters light more than reflects.
Reflectance from water is mostly in the horizontal direction. That light is blocked if polarizer is ||
polarizer
Fig 2.8

42. Light from the sun is unpolarized
Each photon has polarization - but group of them have random polarizations

43. Sun light gets polarized
Bradbury and Vehrencamp Animal Communication Chapter 7

44. Polarized light patterns in sky

45. Polarized light patterns in sky

46. Polarized light field in sky

47. Animals can use these sky patterns
Insects (bees) and fish
Uses
Navigation and local orientation
Time of day
Migration

48. Drosophila - Three kinds of ommatidiaUV
Wernet et al 2002
Pale
Yellow

49. Dorsal rim area (DRA) is sensitive to polarized light - rh3 pigment
Note how the microvilli (the toothbrush bristles) are all aligned in the same direction. This makes all of these cells sensitive to the same polarization of light.
Red line separated DRA cells (above) which have large center cell and non-DRA (below) which have smaller central cell. Can see one or two DRA cells at top.
Wernet et al 2002
Note rh3 in both

50. Bristles of rhabdomere can further orient visual pigment in membrane
The lines are meant to be the 11-cis retinal molecules. They absorb light best when light is polarized along their axis.

51. Bristles of rhabdomere can further orient visual pigment in membrane

52. Cells in dorsal rim area will preferentially detect polarized light
Wernet 2002

53. Polarized light patterns in sky
Bee’s orientation will determine DRA receptor absorption

54. Polarized light patterns in sky

55. Polarized light field in sky

56. Polarization detection
The polarization field in the sky. The small yellow circle is the sun. The lines show the direction of the light polarization with longer lines showing more polarization.
The ommatidia in the dorsal rim area which are specialized to have two perpendicular kinds of rhabdoms to detect alternate polarizations.
Polarization response of the neuron wired to the dorsal rim area ommatidia.
Labhart 2002, field crickets

57. Why should polarization sensitive receptors work in UV
Rayleigh scattering
Air particles << wavelength of light
10 nm << nm
Scattered intensity
Wavelength of light is similar in size to particles: air

58. Why should polarization sensitive receptors work in UV?
Light scattering depends on wavelength

59. Rayleigh scattering 1/4

60. Rayleigh scattering 1/4UV

61. So to a bee, the sky is…

62. So to a bee, the sky is UV

63. Inverts are “usually” trichromatic
Drosophila

64. Many insects are trichromatic - UV, blue and green pigments
Briscoe and Chittka 2001
Many insects are trichromatic - UV, blue and green pigments
Papilio xuthus - swallowtail butterfly Notonecta - backswimmers Sympetrum rubicundulum - dragonfly Shape is just spectral class
Drosophila melanogaster - fruit fly Gryllus - crickets Libellula needhami - dragonfly circle - UV square blue
Panorpa cognata - scorpion fly Locusta migratoria - locusts Hemicordulia - dragonfly Triangle - green; open red
Apis mellifera - honey bee Periplaneta americana - cockroach Odonata - dragonflies
Photuris are species of fire fly
Ascalaphus macaronius - owl fly
1=11-cis retinal
3=11-cis 3-hydroxyretinal

65. All have UV pigments UV blue green red Present not recorded
Papilio xuthus - swallowtail butterfly Notonecta - backswimmers Sympetrum rubicundulum - dragonfly
Drosophila melanogaster - fruit fly Gryllus - crickets Libellula needhami - dragonfly
Panorpa cognata - scorpion fly Locusta migratoria - locusts Hemicordulia - dragonfly
Apis mellifera - honey bee Periplaneta americana - cockroach Odonata - dragonflies
Photuris are species of fire fly
Ascalaphus macaronius - owl fly UV
green
blue
red

66. Few dichromats - not correlated with lifestyle
Present not recorded
Owlfly
diurnal
Cock roach
nocturnal
Papilio xuthus - swallowtail butterfly Notonecta - backswimmers Sympetrum rubicundulum - dragonfly
Drosophila melanogaster - fruit fly Gryllus - crickets Libellula needhami - dragonfly
Panorpa cognata - scorpion fly Locusta migratoria - locusts Hemicordulia - dragonfly
Apis mellifera - honey bee Periplaneta americana - cockroach Odonata - dragonflies
Photuris are species of fire fly
Ascalaphus macaronius - owl fly UV
green
blue
red

67. A few have red or far red pigments
Present not recorded
Papilio xuthus - swallowtail butterfly Notonecta - backswimmers Sympetrum rubicundulum - dragonfly
Drosophila melanogaster - fruit fly Gryllus - crickets Libellula needhami - dragonfly
Panorpa cognata - scorpion fly Locusta migratoria - locusts Hemicordulia - dragonfly
Apis mellifera - honey bee Periplaneta americana - cockroach Odonata - dragonflies
Photuris are species of fire fly
Ascalaphus macaronius - owl fly UV
green
blue
red

68. Butterflies have 8 rhabdomers like Drosophila
6 on outside are green sensitive
Two stacked rhabdomers
These can be
blue/blue
blue / uv
uv/uv
But 9th cell below

69. Variation in long wavelength sensitivity of butterflies
This is due to sequence changes in the long wavelength opsin gene

70. Evolution of red sensitivity in Lepidoptera
A, alpine
C, crepuscular
D, desert
N, nocturnal
TF, trop forest
TL temperate lowlands
GFV generalist flower visitor
SFV specialist flower visitor
GCF general carbohydrate forager
SP specialist predator
We can map onto the phylogeny which species have these long wavelength pigments. These pigments have evolved multiple times. They do not seem to correlate with habitat or foraging styles. Both nocturnal species with red sensitivity (Spodoptera) and diurnal species without (M. stellaturum) both moths.
Lose several time within butterflies.

71. What is relationship of flower color with pollinator?
Bee
Butterfly
Bird
Nocturnal moth

72. Hypotheses