Vision in Insects (simple eye, compound eye).pptx

Vision is the ability to detect the light patterns from the environment and interpret it into images. It varies from one organism to another.
The basic light processing unit of an optical system is a photoreceptor forming an organ i.e. eye
Arthropods may possess 2 types of eyes based on their structure and complexity.
Simple eyes
Dorsal ocelli
Stemmata
Compound eyes

1. Vision in Insects By Dr. Lopamudra Samantaray Asst. Professor Utkal University​

2. Vision Vision is the ability to detect the light patterns from the environment and interpret it into images. It varies from one organism to another. The basic light processing unit of an optical system is a photoreceptor forming an organ i.e. eye 2

3. Vision Arthropods may possess 2 types of eyes based on their structure and complexity. Simple eyes Dorsal ocelli Stemmata Compound eyes 3

4. Vision Simple eyes: Dorsal ocelli Light sensitive Found on dorsal or frontal surface of the head coexisting with compound eyes Contain only a single large aperture lens consist Lens element (Cornea) Layer of photoreceptor cells Biconvex transparent cuticle covering these photoreceptor cells which transmit nerve impulse to optic nerve and then to brain. 4

5. Vision Simple eyes: Dorsal ocelli Ocelli cannot form an image and unable to recognize objects can sense wide range of wavelengths Show quick response to changes in light sensitivity 5

6. Vision 2. Compound eyes Made up of large no. of photoreceptor units called ommatidia Eye is covered with transparent cuticle forming a cornea, which is divided into many units/ ommatidium Light will enter independently One ommatidium form single image, the combined to whole image at the end 6

7. Ommatidium Cornea Outermost layer covered by transparent cuticle which functions as biconvex lens Hexagonal units called as corneal facet 2. Corneagen cells Secrets fresh cornea 3. Crystalline cone Second lens Focuses light directly Surrounded by 4 cone cells which provide nourishment Dioptrical region ends

8. Ommatidium 4. Rhabdom Receives light Converts photon’s energy into electrical energy 5. Retinal cells Group of 7 cells surrounding the Rhabdome Provide nutrition and protection 6. Basement membrane Extended into an axon Bundle of 7-8 axon connected to the neurons of optic ganglion which is connected to brain through optic nerve 7. Chromatophores Iris and retinal pigment separate one ommatidium to another

9. Mosaic vision 9 Each ommatidium is capable of producing an independent image of a small part of the object and actually not the entire object. These individual images are combined in the brain forming a complete image of the object that is made of small or mosaic dots and i.e. why it’s called MOSAIC VISION

10. Working of compound eye 10 1. Apposition image: Form in bright light Completely separate the ommatidium Prevent light rays passing from one ommatidium to another Perpendicular rays form point of image Oblique rays absorbed by chromatophores-> no image Formed at short distance only

11. Working of compound eye 11 2. Superposition image: Dim light in nocturnal arthropods Ommatidium are not separated Ommatidium responds to light rays which entered through different corneal facets Overlapping image/ blurry

12. Resolution: Degree of fineness with which an eye forms an image Presence of interommatidial angle In apposition eyes, fineness of image will be greater with smaller ommatidial angle Degree of resolution decreased when eye becomes dark adapted Transduction: Conversion of electrical energy involves the visual pigment. Rhodopsin Flicker fusion rate H igh Adaptation: Natural change from darkness to full light involves change in light intensity The amount of light reaching photoreceptor is regulated. Eg. Ant Camponotus The receptor sensitivity changes 12

13. Color vision: Not all insects see colors. Absorb green range of spectrum (490-540nm) Another maximum absorption in blue range. Honey bee can differentiate yellow, blue-green, violet, ultraviolet, purple, but not red. Eg. Rove Bettle 13

14. Polarization sensitivity: Light is polarized when all vibrations are in one plane i.e. plane-polarized Used it for navigation Seen in social Hymenoptera, Apis 14 Magnetic Sensitivity: Respond to changes in magnetic field Certain used this for navigation Orientation w.r.t. wavelength

15. Field view Well developed compound eye have extensive field view Periplaneta has vision through 360 0. 15 Distance perception Able to judge distance with considerable accuracy. E.g. grasshopper and mantid Stereoscopic mechanism; mantids Motion parallax; grasshopper

16. Visual tracking: Animal’s ability to keep a moving target within specific area of the retinal, often when the animal itself is moving. E.g. dragonfly catches it’s prey Form perception: Eye’s ability to detect form of an object on its resolving power e.g. bees 16

17. Dorsal ocelli: Adult insects and larvae of hemimetabolous insects Adapted for concentration of light and perception of changes in intensity Pathway of rapid conduction 17 Stemmata (lateral ocelli): Larval holometabolous insects Stemmata with single rhabdome e.g. neuroptera Multiple rhabdome

18. Dermal light sense: Tenebrio larva still respond to light when all visual receptors are occluded Epidermal cells are sensitive to light Sensitivity of Brain Light affects neural activity directly by acting on the brain Daylength, regulating diapause is registered directly by brain 18

19. Thank you R.F. Champan , The insect: structure and function, 4 th edition, Cambridge University press Animal Diversity (R.L Kotpal ); Rastogi publication (2018)