PHYLUM: CNIDARIA

Classes of Cnidaria Class Hydrozoa (e.g., Hydra, Obelia) Class Scyphozoa (e.g., Aurelia) Class Cubozoa (e.g., cube jellies) Class Anthozoa (anemones and corals) Subclass Hexacorallia (sea anemones, hard corals) Subclass Octocarallia (sof corals)

General Characteristics Entirely aquatic; mostly marine, but with a few freshwater species; may be solitary or colonial Metazoan, with true tissues. Diploblastic – two germ layers outer cell layer known as ectoderm (epidermis), inner cell layer known as endoderm (=gastrodermis), with a non-cellular mesoglea between.

General Characteristics The internal body space (gastrovascular cavity) lined with gastrodermis has a mouth, but no anus (incomplete digestive tract) Possess cnidocytes with special cell organelles - nematocysts, used for defense and offense

General Characteristics cont. Phylum exhibits polymorphism Metagenesis- alternation of generation Polyp (often sessile) and the medusa (free swimming). The polyp stage reproduce asexually, while the medusa stage usually reproduces sexually Reproduction is asexual by budding and/or sexual, producing a ciliated planula larva

Figure 13.02 Two general body forms

Class Hydrozoa solitary or colonial alternation of asexual polyps and sexual medusae

Figure 13.09

Life Cycle of Hydra SEXUAL REPRODUCTION ASEXUAL REPRODUCTION

Hydra with Bud Ovary Bud

Hydra with Gonads Testes

Gastrovascular cavity Hydra c.s. Epidermis Mesoglea Gastrodermis

Figure 13.09 Obelia Life Cycle

Obelia - Medusa Gonad Tentacle Gastrovascular cavity

Obelia – Hydroid colony Gastrozoids = Hydranth Gonozoids = Gonangium

Obelia – Hydroid Colony Gonozooid Hydrozooid

Gonionemus Gonad

Physalia – Portuguese Man-O-War - a colony, not an individual It is not a jellyfish!!

Class Scyphozoa True Jellyfishes polyp stage reduced or absent bell-shaped medusae margin of bell with eight notches which are provided with sense organs all marine

Aurelia - Medusa

Aurelia - Planula larva

Aurelia - Scyphistoma

Aurelia - Strobila

Aurelia - Ephyra

Class – Anthozoa Sea Anemones and Corals all species occur as polyps only, no medusae; gastrovascular cavity partitioned by at least eight septa with nematocysts Solitary or colonial all marine.

Some Hydrozoans

Figure 13.07

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Figure 13.15a

Figure 13.15b

Some Scyphozoans

Jellyfishes

Figure 13.16

Figure 13.17

Some Anthozoans

Sea Anemones

Figure 13.25

Figure 13.29

Corals

Figure 13.32

Figure 13.33a

Figure 13.33b

Figure 13.28

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Figure 13.26b

Figure 13.26c

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Phylum Ctenophora The Combjellies

General Characteristics Biradial symmetry Eight rows of comb plates Tentacles possess colloblasts Triploblastic (three cell or germ layers) Mesoglea (loose mesenchyme) is jelly-like material strews with fibers and amebocytes and contains true muscle cells Aboral sense organ (statocyst) Digestive system: mouth, pharynx, stomach, branched canals and anal pore Monoecious, with both eggs and sperm produced from endodermal lining of digestive canals beneath comb plates

Figure 13.36

Figure 13.36a

Figure 13.38

Figure 13.38a

Figure 13.38b

Figure 13.35

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