Cnidarian Characteristics
- Diploblastic; endoderm & ectoderm separated by mesoglea
- Radial symmetry
- Presence of cnidae/nematocysts in cnidocytes (stinging cells) (see photo at right)
- Alternation of polyploid (polyp) and medusoid generations
- Gastrovascular cavity with single mouth/anus
- Tissue grade organization
- Additional Classes not represented in lab:
- Cubozoa: box jellies and sea wasps.
- Staurozoa: stalked jellyfish.
- Myxozoa: spore-producing parasites
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Discharged Nematocyst of Hydra sp.
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Class Hydrozoa — Hydroids
Characteristics
- Alternation of generations: polypoid generation usually dominant
- Medusae usually small, transparent
- A few (fire corals) produce coral-like calcareous skeleton
- Polyps usually colonial, with interconnected coelenterons
- No cells in mesoglea
- Nematocysts only in epidermis (not gastrodermis)
- Marine and fresh waters
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Hydra sp., stained longitudinal section, 100x (Order Hydroida)
See also labeled photo.
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Hydra sp., stained whole mounts showing sexual and asexual reproduction, 10x
See also labeled photo.
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Pennaria sp. hydroid colony, stained whole mount (Order Hydroida)
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Obelia sp. colony, stained whole mount, 40x (Order Hydroida)
See also labeled photo.
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Obelia sp. medusa, stained whole mount, 100x (Order Hydroida)
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Green Hydra, Chlorohydra viridissima (Order Hydroida)
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Eudendrium sp. hydroid colony (Order Hydroida)
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Clytia sp. hydroid colony (Order Hydroida); preserved specimen
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Umbrella Jellyfish, Eutonina indicans medusa (Order Hydroida)
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Angled Hydromedusa, Gonionemus sp. (Order Hydroida)
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Bell Jelly, Polyorchis penicillatus (Order Hydroida)
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Blade Fire Coral, Millepora complanata, Belize (Order Milleporina)
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Portuguese Man-O-War, Physalia physalis, in tidepool, Kenya (Order Siphonophora)
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By-The-Wind-Sailor, Velella velella, beached, CA (Order Chondrophora)
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Class Anthozoa — Anemones & Corals
Characteristics
- Lack medusoid stage
- Polyps solitary or colonial
- Coelenteron (gastrovascular cavity) subdivided by longitudinal folds of tissue
- Tentacles in multiples of 6 or 8
- Marine only
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Sea anemone dissection (Metridium sp.)
Check answers on labeled photo.
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Giant Green Anemone, Anthopleura xanthogrammica, CA (Subclass Hexacorallia, Order Actiniaria)
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White-spotted Rose Anemone, Urticina lofotensis (Subclass Hexacorallia, Order Actiniaria)
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Mushroom Anemones, Discosoma sp. (Subclass Hexacorallia, Order Corallimorpharia)
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Boulder coral, Montastrea annularis (foreground) and Brain corals, Diploria sp., Belize (Subclass Hexacorallia, Order Scleractinia)
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Yellow pencil coral, Madracis agaricites, Belize (Subclass Hexacorallia, Order Scleractinia)
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Elkhorn coral, Acropora palmata, reef, Belize (Subclass Hexacorallia, Order Scleractinia)
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Moon Coral, Favites sp. (Subclass Hexacorallia, Order Scleractinia)
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Stony Coral, possibly Stylophora sp. (Subclass Hexacorallia, Order Scleractinia)
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Tube Anemone, Pachycerianthis sp., (Subclass Hexacorallia, Order Ceriantharia)
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Leather Coral, Sarcophyton trochelisphoram, a soft coral (Subclass Octocorallia, Order Alcyonacea)
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Kenya Tree Coral, Capnella sp., a soft coral (Subclass Octocorallia, Order Alcyonacea)
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Sea Fan, Gorgonia sp., Belize (Subclass Octocorallia, Order Gorgonacea)
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Orange Gorgonian, Adelogorgia phyllosclera? (Subclass Octocorallia, Order Gorgonacea)
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Organ Pipe Coral, Tubipora musica, skeleton (Subclass Octocorallia, Order Stolonifera)
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Fleshy Sea Pens, Ptilosarcus sp. (Subclass Octocorallia, Order Pennatulacea)
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Class Scyphozoa — Jellyfish
Characteristics
- Medusoid stage predominates; polyps inconspicuous
- Thick gelatin-like mesoglea
- Often pigmented
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Upside Down Jellyfish, Cassiopea andromeda (Order Rhizostomae). This species relies on endosymbiotic algae.
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Northern Sea Nettle, Chrysaora melanaster (Order Semaeostomae)
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Pacific Sea Nettle, Chrysaora fuscescens (Order Semaeostomae)
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Spotted Jellyfish, Mastigias papua (Order Rhizostomae)
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Moon Jelly, Aurelia labiata, adult medusa (Order Semaeostomae)
See also labeled photo.
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Moon Jelly, Aurelia labiata, polyps
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Moon Jelly, Aurelia sp., life cycle stages; stained whole mounts
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