Algal eyespot

comparison of different types of eyespots found in algal community .

1. Algal eyespot jasmine mariya a j dept. of botany , cms college kottayam

2. EYESPOT Pigmented area in certain motile algae involved directly or indirectly in photoreception ( Bold & Wynne ) Is also known as stigma Cluster of lipid globules in red red colour of carotenoid Often seen just beneath the chromatophore membrane

3. Function : Receiving light stimuli Eyespot helps chlamydomonas to swim toward the light There are 5 different types of eyespots based on EM studies by Dodge (1969)

4. TYPE A Is a part of chloroplast but has no association with flagella Eg . Chlorophyceae and cryptophyceae

5. The eyespot apparatus of Chlamydomonas reinhardtii in the light microscope (A1, white arrow-head), in the transmission electron microscope (A2) and as a schematic drawing (A3). Structural intact eyespot apparatuses can be isolated by sucrose density gradient centrifugation (B).

6. Eyespot apparatus of Chlamydomonas reinhardtii It is composed of two highly ordered layers of carotenoid rich lipid globules inside the chloroplast Thee globules exhibit a remarkably a constant diameter They are seen subtended between thylakoid membranes The outer most globule layer is attached to specialized areas of the two chloroplast envelop membranes and the adjacent plasma membrane

7. EM image of eyespot of chlamydomonas

8. TYPE B Eyespot is a part of chloroplast, no association with the swollen flagella Eg : chrysophyceae , xanthophyceae , phaeophyceae

9. TYPE C Eyespots are independent clusters of osmophilic granules Eg . euglenophyceae

10. Euglina gracilis Eyespot

11. E. variabilis

12. TYPE D Osmophilic granules of eyespots have membraneous structures Eg.Dinophyceae

13. Eyespot of Glenodinium foliaceum I t is seen to be situated in a ventral position at the anterior end of the sulcus The eyespot is seen as a flattened sac with rounded edges, which contains two rows of large osmiophilic granules Surrounding the eyespot is a triple- membraned envelope The envelope has no pores and has not been found to be connected with the membranes of any other organelles such as chloroplasts or nucleus.

14. TYPE E Largest eyespots made up of lens,retinoid and pigmented cups Eg.warnowiaceae family of dinophyceae

15. OCELLOID An  ocelloid  is a subcellular structure found in the  family  Warnowiaceae Is analogous in structure and function to the eyes of  multicellular   organisms

16. Structure of an ocelloid Ocelloids contain subcomponents analogous to eye structures including the  lens,   cornea,  iris, and   retina It can be divided into two substructures, the translucent, roundish   hyalosome  and the heavily  pigmented melanosome , also known as the retinal body or pigment cup

17. A negative staining transmission electron micrograph of an ocelloid (white box), indicating the hyalosome (H) and retinal body (R)

18. The hyalosome serves as the refractive lens of the ocelloid ; it is surrounded by a layer of mitochondria serving as the cornea and has constrictive rings analogous to the  iris The retinal body has internal structure reminiscent of  thylakoid  membranes in  chloroplasts and contains proteins related to  bacteriorhodopsin , a light-sensitive protein found in some  archaea

19. Comparison between the structures of the ocelloid (1) and the  vertebrate eye (2). Components are indicated as the hyalosome (H), retinal body/retina (R), and  crystallin lens (C ).