1. Phylum -Coelenterata
Tamboli Alija Z. Dept of Zoology, S.M.Joshi Collge , Hadapsar. S.Y.B.Sc.

2. Class Hydrozoa Body plan Colony Growth Life History
Polyps are small and may occur
as solitary or colonial

4. Colonies grow in one of 3 main patterns
Hydrorhizal
Monopodial
Sympodial
Colony Growth Forms

5. Obelia hydroid has prominent medusa and polyp

6. Gonionemus Hydractinea Planula larva Obelia Hydra
Hydrozoan have evolved a variety of life cycles that include reduction of polyp in Gonionemus, loss of medusa in Hydractinea, and direct development in Hydra
Gonionemus
Hydractinea
Planula
larva
Obelia
Hydra

7. Immortal Jellyfish Turritopsis nutricula,
the immortal jellyfish, is a hydrozoan whose medusa form can revert to the polyp stage after becoming sexually mature.
Involves Stem cells
and
Trans-differentiation
of cells
Transdifferentiation one differentiated cell type transforms into another
Theoretically, this process can go on indefinitely, effectively rendering the jellyfish biologically immortal,[3][5] although, in nature, most Turritopsis are likely to succumb to predation or disease in the medusa stage, without reverting to the polyp form

8. Polymorphism within colonies of Hydrozoa consists of 4 different polyps: feeding, reproductive, stinging, and defensive (spine)
bio.fsu.edu/.../images/Female-Hydractinia.jpg

9. Siphonophores: Composed of clonally produced multicellular zooids
Highest division of labor & most precise organization
ll the zooids in a given siphonophore colony are descended from a single fertilized egg. The egg develops into the protozooid, a polyp that gives rise through budding to all the other zooids of the colony.
All the zooids in a given siphonophore colony are descended from a single fertilized egg. The egg develops into the protozooid, a polyp that gives rise through budding to all the other zooids of the colony, including the float!.

10. Characteristics of the Anthozoa (Sessile, inactive lifestyle)
ClassAnthozoa
Diversity
Body plan
Cloning
Symmetry
Life History

11. Hexacorallia
Actinaria (anemones)
Scleractinea (corals)
Octocorallia
Alcyonacea
(soft corals)
Gorgonacae
(sea fans etc.)

12. Anthozoan Polyp
What morphological characteristics associated with a larger polyp size?

13. Clonal reproduction in anemones
Internal or external budding
Pedal laceration
Fission
Tentacular brooding

14. Anthopleura elegantissima
The Aggregating Anemone
Clonal wars
Competition for space,
Self-nonself recognition
Research shows individuals have specialized roles
Ayre, David, and R. K. Grosberg, 2005 Animal Behavior 70:
Francis, L, 1976 Biological Bullentin 150:

15. Acrorhagi (non-feeding tentacles)
Inflates, contacts , nematocyst fire and stick; scarring
Most acrorhagi wins
If attacked, a warrior often retaliates
If significant injury, retreat by pedal locomotion
Multiple attackers at once can cause extensive injury and death

16. Diversity of Class Anthozoa
SubClass Hexacoralia
Order Scleractinea
Stony Corals

17. Class Anthozoa:
SubClass Octocorallia
soft corals
Soft Corals
Stoloniferan corals

18. Class Anthozoa:
SubClass Octocoralia
Soft corals

19. Class Anthozoa:
SubClass Octocoralia
Sea Pens
Sea Pansies
Sea Fans

20. Two Scenarios for the evolution
Of the Cnidarian Classes
18s r-DNA, mt DNA, & new morphological studies support idea that the Anthozoa is the basal group

21. Generalized life cycle of Cnidarians
In what way are life cycles altered in the 4 classes?
Ancestral Anthozoa: polyp adult only; sexual and asexual
Hydrozoa: medusa stage evolved; becomes sexual adult
Scyphozoa: medusa stage dominant; polyp small, asexual
Cubozoa: loss of polyp stage