##Morphology and Reproductive structures

For Degree and PG Students

1. VOLVOX OO

3. Colonial, spherical or broadly elliptical

Macroscopic —pin head — 0.5- 1.5 mm

500 — 50000 chlamydomor like cells

Haploid gametophyte

Arrangement is definite

Coenobium (specific arrangement and definite number
Embeded in a mass of mucila

Each cell surrounded by mucilage sheath

Each cell of coenobium performs its own function of nutrition,
respiration & excretion

Cells are inter connected by plasmodesmata

5. Single layer along the periphe

Centre hollow- mucilage/gelatinous (V

Chlamydomon:

d, posterior rounded

terior point

Anterior thick ce

wall ] apair of contractile vacuoles

Anterior two fl lla = in length - from ba

al granules

Nucleus at the cent

oid

up shap:

etior eye spot central pyri

loroplast-posterior- an

Chlo a, b. Carotenes, nthophylls

Starch

6. ASEXUAL

During favourable condition
Posterior end of colony

2- 20 cells - gonidia

Generative Cell

Vegetative Gell

Lack eye spot, flegella, more
pyrinoids

2,4- 8- curved plate(plakea
stage)/octant stage

Central hollow and pore anterior
(Phialopore)

Anterior end towards hollow
space- cruciate plakea stage

7. Sphere cell turn completely
inside out through phialopore

Develop eye spot and flegella

Volvex colony

Duaghter colony inside the
gonidial wall

Release through repture

8. SEXUAL

RODUCTION

Oogamous
End of the season
Homothallic (V. globator)
Heterothallic (V. aureus)
Monoecious — protandrous
Y. aureus- Protogynous
Male- antheredium
Female — oogonium

Haploid gametophyte

9. | ANTHERIDIUM/ ANDROGONIDIA |

Posterior part of the colony
From vegetative cell
Loss flegella — antheridial cell
Protoplast divides Mitotically
16 - 128 /512
Secrete cell wall, flegella — sperms
Curved plate
Liberate clusters

Yellow in colour

10. / GYNOGONIDIA

Posterior
Develops to vogonial cell
Loses flegella, eye spot
Protoplast gets rounded- egg /
ovum
Haploid
Peripheral chloroplast
Yellow

11. Somatic cell

mature egg ” Oospore

12. Chemotactic stimulations

Only one fuse

ZYGOTI

Secrere thick wall- oospore
Oospore

Haematochrome- ted
May po to dormant stage
Oospore

o Fe wall
2%7 Oovonium i

Volvox - Fertilization and oospore formation

13. V. minor, V. aureus —new colony as

asexual
V.Rousseletii- 4 haploid- 1 survive —
form zoo spore / meiospore

/s

rmer— new coenobium

Pacthenogenesis reported from
V.aureus

14. Daughter colony

ASEXUAL
CYCLE

Juvenile colony Antheridia Oogonia
{n) in) (n)

SEXUAL |
CYCLE

Antherozold Egg
In)

Fig. 8. Volvox. Graphic life cycle