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

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

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

Obelia hydroid has prominent medusa and polyp

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

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

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

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!.

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

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

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

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

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: 97-110. Francis, L, 1976 Biological Bullentin 150: 361-376.

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

Diversity of Class Anthozoa SubClass Hexacoralia Order Scleractinea Stony Corals

Class Anthozoa: SubClass Octocorallia soft corals Soft Corals Stoloniferan corals

Class Anthozoa: SubClass Octocoralia Soft corals

Class Anthozoa: SubClass Octocoralia Sea Pens Sea Pansies Sea Fans

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

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