Download cnidarians

Anjali Chacko, Michelle Fernandez, Rose Zhang
oMarine
oSpecialized Cells
oCnidocytes – stinging organelles
oSolitary or Colonial
o Polyp
o Dorsal mouth with tentacles
o Ex: Hydra
o Medusa
o Mouth on lower oral surface
o Ex: Jellyfish
Fig. 33-5
o Hydrozoa
o EX: Hydras, Hydroids, Portuguese Man-of-War
o Polyp dominant/ alternation
o Some Colonies
o Scyphozoa
o EX: Jellyfish
o Medusa dominant
o Free Swimming
o Anthozoa
o EX: Sea Anemones, Corals
o No medusa
o Sessile
oRadial symmetry
oHollow sac with mouth and surrounding
tentacles at one end
oMouth leads to gastrovascular cavity
(digestive)
oMouth – ingests food, expels waste
oEpidermis
o Protective covering
oGastrodermis
o Lines gut, digestive
oMesoglea
o Gelatinous, acellular
o Separates epidermis + gastrodermis
1. Paralyze prey with Nematocysts
o Nematocysts
o Stinging cells
o In cnidocytes
o Stimulated – release coiled, hollow thread
o Sticky or long and coil around prey or
barbs/spines
2. Prey then pushed into mouth
3. Lastly, gastrovascular cavity for digestion
o Body motion helps circulate contents
 Through diffusion
 No cell far from surface
 Nerve nets
 Nerve cells that connect sensory
cells in body wall to contractile and
gland cells
 Cells contacted and entire body
responds by crunching in
oAsexual
o Budding – good conditions
o Colony – buds remain on parent
oSexual
o Fall or stagnant water
o Become males and females
Female – ovary – single egg
o Male – testis - sperm
o Zygote – may become covered with shell for
o
Fig. 33-8-3