Phylum Cnidaria And Ctenophora

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Cnidaria means_________

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"nettle-like" which refers to nettle plants that can sting.

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Phylum Cnidaria General Characteristics

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1. Radial Symmetry and Oral/Aboral Ends

2. one opening for food and wastes (incomplete digestive tract); gastrovascular cavity

3. Tisse level of organization (nerve net)

4. Contain nematocysts( stinging organelles in cnidocytes or nematocytes)

5. Most are marine

6. polymorphic (can be polyp:sessile or Medusa:mobile)

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Cnidocyte/Nematocyte

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"stinging cell"; Organelle with cnidocyst/nematocyst inside; Cnidocytes are connected via a nerve net; contain a cnidocil which is a modified cilium and a trigger

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Cnidocyst Discharge

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Capsule surrounding Cnidocyst has high calcium concentration, and therefore high osmotic potential; when the cnidocil is triggered, Ca channels open and calcium diffuses into cnidocyte cytoplasm and the cnidocyte now has a high osmotic pressure, water rushed in and hydrostatic pressure increases, thus releasing the cnidocyst.

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Class Hydrozoa

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contain mesoglea and velum in medusa (mobile) stage

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Hydra

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in class hydrozoa; contain gastrovascular cavity, gastrodermis, epidermis, and mesoglea; its tentacles are made up of wart-like structures which are clusters of cnidocytes; Hypostome is the cone shaped structure that supports the mouth and surrounding tentacles; Testes are multiple bulges near mouth, ovary is a large bulge mid-body; Asexual budding occurs and bud eventually constricts at base and detaches from adult.

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Cnidocyte Anatomy

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Cnidocil(trigger); operculum (trap-door); Barb/spines (drill); Filament (penetrates skin of animal and injects toxins)

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Class Hydrozoa (Obelia)

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hydranths (feeding polyps); gonangia (reproductive polyps) contain medusa buds which are released through the gonopore;

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Hydrozoan Obelia Life Cycle

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Budding of medusa in gonangia; hydromedusa (medusa of hydrozoans) are released; gametes from hydromedusa(dioecious) combine gametes to form a zygote which develops into planula larva; planula larva settle on the bottom and become a colony; they then grow into a colonial hydrozoan (contains hydranths and gonangia)

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Hydromedusa

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Tentacles capture food and move it to the mouth, contain adhesive pads and Contain tentacular bulbs which make and store cnidoblasts; Manubrium bears the mouth and four short oral lobes which grip food, gastrovascular cavity is in the center of the manubrium; 4 radial canals, which are lined with gonads;Ring canal is the tube around the bell margin; velum is the shelf-like membrane thats found only in medusa of hydrozoa.

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Physalia (Portuguese Man-of-War)

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Class Hydrozoa; Pneumatophore is the gas-filled float; Dactylzooid (fishing polyp, long and coiled and filled with cnidocytes); gastrozooids( polyps that digest prey caught by dactylzooids, blunt end which can either attach to stunned prey and release digestive enzymes or where smaller, stunned prey are inserted by the dactylzooid followed by release of digestive enzymes); Gonozooids (reproductive polyp, bushy in appearance)

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Class Scyphozoa

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Larger jellyfish(up to 2m in diameter); dioecious; lacks a velum and has more mesoglea relative to medusa in hydrozoa); adult medusa feeds on zooplankton that get caught in the bell, and zooplankton are moved via cilia to the oral arms, mouth, and finally the gastric pouches which contain gastric filaments which can sting and release digestive enzymes; digested material is moved through the organism through ring and radial canals

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Class Scyphozoa adult medusa anatomy

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Tentacles; Rophalium (indentation along bell margin, contain statocyst (orientation sensor) and ocellis (light sensor)); Oral arms (4 fleshy structures hanging from mouth); mouth (opening at the base of oral arms); radial canals; Ring canal; Gastric pouches (4, contain gonads and gastric filaments on inner edge with cnidocytes); Gonads are horshoe shape, and line gastric pouch

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Class Scyphozoa life cycle

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dioecious; internal fertilization; planula larva develops into scyphistoma( feeding stage); develops into strobila (stacks of ephyrae) (asexual repro. stage); ephyrae swims off and matures

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Class Anthozoa

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lack a medusa life stage; coral and sea anemone; Anemone contain a mouth, oral disc, and tentacles; A septal perforation (hole) allows digested material to move between sections of the gastrovascular cavity; Complete septa divide gastrovascular cavity; incomplete septa increase SA of gastrovascular cavity

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Class Cubozoa

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Sea wasps; some small, translucent, dangerous; bell square with tentacles at each corner

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Phylum Ctenophora

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biradial (paired tentacles); nematocysts absent (except for some species that eat cnidarians); no polymorphism; anal opening; many are bioluminescent (color produced depends on chemical absorbed); combes (fused cilia) move it through the water

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Ctenophora means__________

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"comb bearing"

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Corals

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1. Hard corals: polyps in calcium carbonate skeletal cup

2. Soft corals: endoskeleton with spicules

3. Hermatypic Corals (hard corals that form reefs), many contain zooxanthellae; support diverse ecosystem