Class Hydrozoa Polyps are small and may occur as solitary or colonial A.Body plan B.Colony Growth C.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 Medusae are small and not as structurally Characteristics of Class Hydrozoa complex as the scyphozoan medusae (Polyp and Medusa are prominent in some species) 1 Siphonophores: Composed of clonally produced multicellular zooids Polymorphism within colonies of Hydrozoa Highest division of labor & most precise organization bio.fsu.edu/.../images/Female-Hydractinia.jpg Velella velella (by-the-wind-sailor) Characteristics of the Anthozoa (Sessile, inactive lifestyle) ClassAnthozoa A. Diversity B. Body plan C. Cloning D. Symmetry E. Life History Diversity of Class Anthozoa • Hexacorallia SubClass Hexacoralia Actinaria (anemones) Order Actinarea Scleractinea (corals) • Octocorallia Alcyonacea (soft corals) Gorgonacae (sea fans etc.) 2 Anthozoan Polyp Symmetry in Cnidaria compared to other animals What morphological characteristics associated with a larger polyp size? Nemanostella Anthopleura elegantissima Clonal reproduction in anemones Internal or external budding § The Aggregating Anemone Pedal laceration Fission Tentacular brooding § 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) Division of Labor Inflates, contacts , nematocyst fire and stick; scarring § Most acrorhagi wins § Scout § Warrior § Reproducer § Reserve § Free edge • If attacked, a warrior often retaliates • If significant injury, retreat by pedal locomotion • Multiple attackers at once can cause extensive injury and death 3 Anemone Line Diversity of Class Anthozoa SubClass Hexacoralia § As a result of the clone Order Scleractinea war, an anemone free zone is established. § Two separate colonies can co-exist, separated by only a few Stony Corals centimeters. Class Anthozoa: Class Anthozoa: SubClass Octocorallia SubClass Octocoralia soft corals Soft corals StoloniferanSoft Corals corals Class Anthozoa: Sea Pens Life cycle of Anthozoans Consists of a SubClass Octocoralia Sea Pansies planula that settles to become a juvenile Sea Fans Less complex. Is this the Ancestral Life Cycle? Which came first Polyp or medusa? 4 Two Scenarios for the evolution Generalized life cycle of Cnidarians Of the Cnidarian Classes In what way are life cycles altered in Hydrozoa, Scyphozoa, Anthozoa and Cubozoa? 18s r-DNA, mt DNA, & new morphological studies support idea that the Anthozoa is the basal group 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 5 .