Phylum Cnidaria

Cnidarians

diploblasts, radial symmetry, stops developing at gastrula stage

Epidermis

ectoderm

Mesoglea

made of polysaccharides (long carbs), collagen, water

Gastroderm

endoderm

Epithelio cells

epidermis/gastroderm, outer touches water, inner has longitudinal muscles (contractile fibers)

Nutritive cells

line gastrovascular cavity, channels that bring food to cells, inner has circular muscles (contractile fibers)

Interstitial cells

can turn into other cell types

Cnidocytes

stinging cells, triggered by touch and chemicals (fish mucus)

Nerve cells

nerve net between epidermis/gastrodermis

Class Hydrozoa

popyp-dom, colonies of different polyp types

Gastrozooids

digest and distribute food

Gonozooids

reproductive, make and disperse medusae

Dactilozooids

stinging tentacles

Bract

shingles of tissue, heavily armed with cnidocytes to cover/protect

Pneumatophores

gas-filled floats

Nectophores

pump seawater to propel colony

Planula

produced by medusae, solid cell ball w/ cilia that becomes polyp

Arborescent colony

tree-like, grows up and outward

Encrusting colony

flat mat of polyps, gastro/gonozooids stick out

Order Leptomedusae

obelia, hydractina

Obelia

connected by stolons, chitanous exterior, arborescent

Stolons

stem-like tubes

Hydractinia “snail fur”

live on hermit crab shells, gono/gastro/dactilo/spines, medusae trapped inside

Order Anthomedusae

hydra

Hydra

FW, no medusa stage, bumps in stolon where sperm/eggs released