Kingdom Kingdom AnimaliaAnimalia

Phylum CnidariaPhylum Cnidaria

CharacteristicsRadial symmetryDiploblastic organization, 2 official tissue layers

Gelatinous MesogleaGastrovascular cavityNerve netCnidocytes called nematocysts

Coilednematocyst

Reproduction/Life Cycle

Most alternate generations between polyp and medusa form

Polyp – asexual, sessile, produce more polyps (colonial) or medusae (pl.) by budding…

Medusae – dioecious & free swimming; fertilized larva (Planula) settles & forms a polyp

CnidariansCnidarians

Feeding

Use nematocysts to stun or kill prey

Tentacles bring food to mouth

Digested in gastrovascular cavity

Support and Locomotion

Hydrostatic Skeleton (supported by water)

Polyps – somersault, inchworm, walk on their tentacles…

Medusae – swim, use water currents

Classification Class Hydrozoa

Most variable class Class Scyphozoa

True jellyfish Class Cubozoa

Cube jellyfishes Class Anthozoa

Largest class

Class Hydrozoa Mostly marine, but only class with

freshwater members! Most display alternation of

generations, but polyps are dominant form

Cnidocytes – only in epidermis Gametes released outside, from

epidermis Medusae have a ‘velum’ (shelf-

like lip), used for jet propulsion

Hydra

Freshwater

Polyps only, no medusae

Gonozooid(reproductive

zooid)

Gastrozooid(feeding zooid)

Obelia

Portugese Man-o-War, Physalia

Colony of polyps…

Cannot swim (floats)

Cnidocytes are lethal to small vertebrates and dangerous to humans

Class Scyphozoa “True Jellyfish” – medusa dominant body form

Cnidocytes in the epi + gastrodermis

Gametes released into gastroderm, then out of mouth

Medusae lack a velum

Moon Jellies, Aurelia

Stinging Nettle, Mastigias

Lions Mane, Cyanea

Record bell was 7 feet across, 120 ft. tentacles!

Class CubozoaMedusae are cuboidal

Polyps are reduced or absent

Tentacles hang from corners

Ex. Sea Wasp (type of Box Jellyfish)

Class AnthozoaPolyps only, no medusae

Gastrovascular cavity is divided into sections, with mesentaries

Sexual and asexual reproduction

Sea anenomes, corals, sea fans

Sea Anemones

Corals

Sea Fans