Phylum Cnidaria
Dec 30, 2015
Phylum Cnidaria
General Characteristics About 9000 species _____________________ Simple nervous system
__________________ Diploblastic organization
EndodermEctoderm
General Characteristics Cont’d-• Either tubular or bell shaped• _______________________• Only animal with
cnidocytes• Cnidocytes-specialized
stinging cells (on tentacle)• _______________________• All marine (aquatic)
____________________________
• Cnidarians’ bodies are organized around the gastrovascular cavity, where digestion takes place• GV has a single opening
that serves as both mouth and anus
2 Layers of Cells
–Diploblastic: •__________________________
–Gastrodermis: lines GV cavity–Epidermis: lines the outside of
the body (the skin)
• In between the two layers is the _________- a jelly-like substance.
Cnidarian Body Wall
Stinging Cells• Have Cnidocytes–________________–Contain nematocysts: barbed
thread-like structures inside the cnidocyte that shoots out and can puncture and poison or entangle prey
Cnidocyte
Feeding
• _______________________________
• Inner gastrodermis secretes digestive juices into gastrovascular cavity which digests food and circulates nutrients
Feeding Cont.
Nervous and Movement
•_________________ & sensory receptors
•Muscles help in directional movement & capturing prey
Life Cycles
• Cnidarians have two body forms that are representative of the sexual and asexual life cycles that they undergo.
–_______–Medusa
Polyp
–_______–_______–Usually attaches to a substrate
at the aboral end–Oral end is surrounded by
feeding tentacles
Medusa
_________________________Sexual (dioecious)Shaped like an upside-down bowlTentacles surround the mouth
that is housed underneath the bell
• When cnidarians display both forms at some point in their lives, they are said to display an __________________________
_________________________ Both sexual and asexual Sexual
Gametes released into waterFertilization takes place to
create free-swimming planula Asexual
By budding
Generalized Cnidarian Life Cycle
__________________________
• Scyphozoa: Jellyfish
• Anthozoa: Sea anemones & Corals
• Hydrozoa: Hydra
• Cubozoa: Box Jellies
Class Hydrozoa
• Ex. Hydras
• __________________• Includes hydras, fire corals, and
Portuguese Man of War• Display alternation of generations–Polyp –Medusa
Class Scyphozoa
• True Jellyfish• ___________________________–Small polyp stage during life
cycle
_____________________
• Similar to Scyphozoans, except that their medusa is cuboidal• Includes the box jellyfish–1 of the 10 most venomous
animals on the planet–Kills 12 people per year
Class Anthozoa
• Polyps that are flower-like• ___________________• Includes sea anemones, corals,
sea whips, and sea fans