1. Many photoreceptors based on interaction of two molecules:
ECF
ICF
photoreceptor
membrane
opsin

3. trans-retinal
11-cis-retinal

5. 11-cis-retinal binds to opsin to form
rhodopsin

6. light rhodopsin 11-cis metarhodopsin trans opsin alters PNa
trans-retinal
alters PNa

10. trans retinal
rhodopsin

12. Compound Eyes Present in Insects and Horseshoe Crab
Composed of multiple units called “ommatidia”
Image-forming eyes
Visual acuity less than for vertebrate eye

15. Limulus Ommatidium
lens
Light
r.c.
Retinular
cell
Eccentric
axon
e.c.

16. Lateral Inhibition B A
record from A
record from B

17. Insect Compound Eye