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
• It 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.

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

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

17. 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

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

19. • 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

21. 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).