Corals, Anemones, Sea Fans, and Jellyfish Aquatic Stinging Nettles

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Characteristics of Phylum Cnidaria

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Members of Phylum Cnidaria

•

Phylum Cnidaria includes soft and hard corals, sea anemones, hydroids, sea fans, jelly fish, and siphonophores.

•

Characteristics of Phylum Cnidaria

Anatomical characteristics include: – They are

radially symmetrical

around a central point.

– They have a cup (

polyp

) or made of two layers of cells.

– symmetry umbrella-shaped (

medusa

) body

Polyp - Attached Anemones and Corals Medusa - Free-Floating Jellyfish

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•

Characteristics of Phylum Cnidaria

Anatomical characteristics include: – Polyps can be solitary or colonial; medusa are free floating –

Mesoglea

(jelly-like) separates the two tissue layers.

– Tentacles line the rim of the polyp and medusa with a mouth-like opening in the middle.

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•

Characteristics of Phylum Cnidaria

Anatomical characteristics include: – They have a mouth that opens into the gastro vascular cavity (a space in the middle of their body used for digestion/reproduction).

– They are structurally uncomplicated, with simple nerve net, muscle cells, and light receptors.

– All share the ability to defend themselves with

nematocysts

.

• These stinging structures are composed of special cells called

cnidocytes

.

(You’ve seen better in video…) 6 - 6

•

Special Attributes of Coral and Anemones

The largest class in phylum Cnidaria is class Anthozoa, the corals and anemones.

Over 6,000 species.

– Members of this class are

polyps

that attach to the reef or other substrate.

– Most coral and soft coral are colonial, anemones are individual organisms.

Soft Coral Elkhorn Coral Stalked Anemone

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• Hard coral are the most ecologically significant thanks to the massive calcium carbonate reefs they build.

– Coral colonies can grow for centuries and become so large that they shape coastlines and build entire islands.

– Zooxanthellae live in the tissues of most species of hard coral, providing it food and helping eliminate waste through photosynthesis. Supercharged….

Plate Coral

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•

Special Attributes of Coral and Anemones

Zooxanthellae corals: – Live best in well-lit, clear water.

– Actually thrive in low-nutrient, less productive areas.

– Are sensitive to runoffs, fertilizers, etc. (can kill them) – Become colorless when stressed. This is called coral bleaching – a sign of a diseased and dying colony.

Coral Bleaching

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• • Soft coral and sea fans grow into tree-like structures built on protein skeletons. They are not reef builders.

Anemones have a mutualistic relationship with various species of anemonefish.

– The fish receive protection by living in the anemone and the anemone receives food from the fish.

Diver and Sea Fan Soft Coral

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Special Attributes of Jellyfish

• Jellyfish: –

Are members of class Scyphozoa.

– Range in size from smaller than a coin to more than 1 meter (3.28 feet) across with tentacles more than 3 meters (9.8 feet) long.

– Are

large planktonic organisms

drift with the current.

that swim, but also – Are

weak swimmers

that move by contracting and pulsating their rounded body, or bell.

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• Jellyfish: – Feed on almost anything they catch with their tentacles.

– Some species have very short tentacles and very mild stings, making them more of an annoyance than a threat to swimmers. Others have long tentacles and can sting severely.

– – Are eaten by some species of fish & turtles Box jellyfish have a very potent toxin and can kill several adult humans.

Box Jellyfish Box Jellyfish Stings

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• Special Attributes of Fire Corals and Siphonophores Fire coral: – Belong in the

class Hydrozoa

.

– Colonial organism, looking much like hard corals.

– Different from hard corals - forming more complex colonies and having complex lifecycles.

Tentacles with Nematocysts

– Life cycle alternates between polyp and medusa.

– Most species can sting humans stings can be serious, hence their name.

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• – – – – Siphonophores: – – Belong in the

class Hydrozoa

.

Exist as planktonic colonies, yet within the colonies are specialized polyps adapted to feeding, reproduction, movement and other functions.

Can exceed 40 meters (131 feet) in length.

Can have powerful stings.

Are major predators.

Are a bridge between colonial animals and complex organisms.

Diver with Planktonic Siphonophore

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Special Attributes of Fire Corals and Siphonophores • The Portuguese Man-of-War is a siphonophore with a specialized buoyancy chamber to help it remain at the surface and tentacles underwater to catch prey.

Float Tentacles with stinging, feeding, reproductive polyps

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Comb Jellies - Gelatinous Carnivores

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Comb Jellies - Gelatinous Carnivores

• Characteristics of Phylum Ctenophora – Differences with jellyfish: •

Ctenophores lack bag-like cnidarian body shape and stinging cells.

– All are marine, living in many environments.

–

Have “comb rows” of cilia on bodies for movement.

– Most are small - only a few millimeters or centimeters long.

– Nearly colorless.

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Comb Jellies - Gelatinous Carnivores

•

Characteristics of Phylum Ctenophora

– Exhibit rainbow colored light produced by cilia.

– Have organized tissues but lack true organs.

– Has a nerve net and reproduces sexually.

–

Are carnivorous - eating small plankton.

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