PHYLUM CNIDARIA

Presented by:

Gabitan, John PauloTero, Nariza L.Valencia, Juliet D.Zapanta, Schola Marie

• Radially symmetrical cnidarian body is organized as a hollow sac with the mouth and surrounding tentacles located at one end.

• Based on molecular data, some systematists have proposed that cnidarians share a common ancestor with the clade of bilateral animals.

• Cnidarians have two body shapes: polyp and medusa.

• Polyp form, represented by hydra, typically has dorsal mouth surrounded by tentacles.

• Medusa form, the mouth is located in the lower concave or oral surface; the convex upper surface is the aboral surface.

• Cnidarians get their name from specialized cells called cnidocytes that contain stinging organelles.

• It is found mainly in epidermis especially on tentacles.

• Cnidocytes contain stinging “thread capsule” called nematocysts

• Cnidarians use their tentacles to capture prey and they push it into the mouth and it leads to gastrovascular cavity, where digestion takes place.

• Mouth is the only opening into gastrovascular cavity that serves for both ingestion of food and expulsion of undigested material. Gas exhange and excretion occur by diffusion.

• Cnidarians are diploblastic meaning thay have 2 definite tissue layers.

• Ectoderm which give rise to outer (covering of body) and endoderm gives rise to inner gastrodermis, which lines the gastrovascular cavity and functions in digestion.

• These thin layers are separated by a thick, jellylike mesoglea, which is mainly acellular.

• Cnidarians have nerve cells that form nerve nets connecting sensory cells in the body wall to contractile cells and gland cells.

• Hydrostatic skeleton supports the body and allows movement.

GROUPS

HYDROZOANS

SCYPHOZOANS

CUBOZOANS

ANTHOZOANS

HYDROZOANS

HYDRA

• Mainly marine but some are freshwater species

• Alternation of polyp and medusa stages in most species (polyp form only in Hydra)

• Some form colonies

SCYPHOZOANS

• “True” jellyfish• Mainly marine• Typically inhabit

coastal water, free swimming medusa most prominent form• Polyp stage is often

reduced

JELLYFISH

CUBOZOA

BOX JELLYFISH

• Inhabit tropical and subtropical waters

• Have polyp stage but medusa form most prominent

• Square shape when viewed from above

• Actively hunt prey• Complex eyes that

form blurred images

ANTHOZOA

SEA ANEMONES

• Marine• Solitary or colonial

polyps• No medusa stage

in most• Gatrovascular

cavity divided by partitions into chamber, increasing area for digestion

REPRESENTATION ORGANIZATION

ECONOMIC IMPORTANCE

• Coral reefs (Anthozoans) serves as a habitat of fishes and this may also serve as a tourist attraction to humans.

• They also provide a home for algae which creates oxygen that we breathe. The coral reefs are also important because the polyps, algae, and animals in that habitat are a major food source for other animals.