Cnidarians l Phylum Cnidaria l Includes jellyfish anemones

Cnidarians l Phylum Cnidaria l Includes jellyfish, anemones, corals, & sea pens l Next level of complexity after sponges l Tissues are specialized to perform specific functions. l Also called coelenterates This term is not used often anymore!

Invertebrates Phylum Cnidaria

Coelenterates Even though not used often anymore… Refers to 2 Phylums combined: Phylum Cnidaria & Phylum Ctenophora - Ctenophora: - Cnidaria: • Have a hollow body cavity, & very simple tissue organization Comb Jellies Jellyfish, Sea anemones, Corals, & Sea pens

Cnidarians l Have NO bones l Have NO heart l Have NO brain l Have NO “real” eyes l Have NO respiratory system

Cnidarians: Body Plan l Display radial symmetry, which is a regular arrangement of similar body parts around a central axis. l l Look the same from all sides Have no head, front, or back

Cnidarians: Body Plan Have an oral surface where the mouth is & an aboral surface on the opposite side.

Occur as 2 basic forms: Polyp: A sac-like attached stage (sessile) Medusa: Bell-like stage Polyp Medusa Some experience both forms during their life time, and others spend their entire lives as one of the two forms.

Cnidarians: Anatomy l Have a centrally located mouth surrounded by tentacles which are slender, finger like extensions. l Use tentacles to catch & handle food

Cnidarians: Anatomy l The mouth opens into a gut (enteron) where food is digested. - The gut has only one opening, the mouth.

Cnidarians: Anatomy l The mesoglea is extremely thick, has a jelly like consistency & makes up the largest portion of the animal This is how jellyfish got their name.

Tentacles l They capture small prey by discharging their cnidocytes (stinging cells), which are unique structures found on the tentacles.

How Cnidarians Sting l At the narrow outer edge of the cnidocyte is a short trigger hair called a cnidocil (“trigger”). Upon contact with prey, the contents of the nematocyst are explosively discharged, firing a dart-like thread containing neurotoxins.

How Cnidarians Sting l These stinging cells contain poison arrows connected to threads called nematocyts. * Cnidarians can still sting when they are dead!!

Tentacles l The tentacle then brings the victim to the mouth to be digested. l The food passes through the body cells, and the waste must go back out of the mouth.

Jellyfish Eating

Jellyfish Feeding Video Clip

Cnidarians: Anatomy l 2 Layers of cells form the body wall - Ectoderm: external layer - Endoderm: internal layer that lines the gut

Feeding Zooplankton: Drifting microscopic animals

Feeding Phytoplankton: Drifting microscopic plants.

Feeding l After paralyzing its prey, a cnidarian pulls the prey through its mouth and into its gastrovacular cavity. l Gastrovascular Cavity: A digestive chamber with one opening. l Food enters & waste leaves the body through that opening.

Response to Environment l l Cnidarians gather information from their environment using specialized sensory cells. Both polyps & medusas have a nerve net. Nerve Net: A loosely organized network of nerve cells that together allow cnidarians to detect stimuli such as the touch of a foreign object.

Response to the Environment l l Cnidarians have statocysts which are groups of sensory cells that help determine the direction of gravity. Ocelli are eyespots made of cells that detect light.

Movement Hydrostatic Skeleton: consists of a layer of circular muscles & a layer of longitudinal muscles that together with the water in the gastrovascular cavity, enable the cnidarian to move. • Medusas move by jet propulsion. • Muscle contractions cause the bell-shaped body to close like a folding umbrella. • This action pushes water out of the bell, moving the medusa forward.

Cnidaria Reproduction l Some reproduce asexually by budding (in polyps) l Some reproduce sexually by releasing gametes. l Some sexual forms are monoecious and others are dioecious l Eggs and sperm are released into the stomach and then through the mouth into the sea.

Cnidaria Reproduction l In some cases, to reproduce, a male releases his sperm into the surrounding water (spawn). l The sperm then swims into the mouth of the female jellyfish, allowing the fertilization of the ova.

Cnidarian Reproduction l In other cases, sexual reproduction takes place with external fertilization in water: External Fertilization: Takes place outside the body. The male & female releases eggs and sperm at the same time.

Jellyfish Review Video Clip

Types of Cnidarians Class Hydrozoan

Types of Cnidarians: Hydrozoans Class Hydrozoans Hydra - They can be found in most unpolluted freshwater ponds, lakes, and streams - They are usually a few millimeters long and are best studied with a microscope - Hydra has a tubular body secured by a simple adhesive foot called the basal disc.

Types of Cnidarians: Hydrozoans Class Hydrozoans Hydra - At the free end of the body is a mouth opening surrounded by one to twelve thin, mobile tentacles. - Hydras are generally sedentary or sessile, but can move, especially when hunting.

Types of Cnidarians: Hydrozoans Hydra - They move by bending over and attaching themselves to the substrate with the mouth and tentacles & then release the basal disc. - The body then bends over and makes a new place of attachment with the foot. - They “inch-worm” or “somersault” to move

Types of Cnidarians: Hydrozoans Class Hydrozoans Portuguese man-of-war Consist of feather or bushy colonies of polyps. - Some polyps are specialized floats, which may be gas-filled - Other polyps form the long tentacles used to capture prey.

Types of Cnidarians: Hydrozoans Portuguese Man-of-War

Types of Cnidarians Class Scyphozoans

Types of Cnidarians: Scyphozoans Class Scyphozoan l Includes jellyfish l Have a rounded body, or bell. l l Swim w/ rhythmic contractions of the bell, but swimming ability is limited & are carried by ocean currents.

Class Scyphozoans l 95% of body is made of water l Here before dinosaurs and sharks l Inhabit all oceans of the world

Moon Jellyfish also called Common Jellyfish

Moon Jellyfish Life Cycle - Planula Each jellyfish is either male or female 1. Males release sperm into surrounding water 2. Eggs get suck in pits on the oral arms, and are fertilized by sperm 3. The egg develops into a planula l Planula is the larval stage, small, & covered in cilia 4. The planula settles on a hard surface & develops into a polyp to become sessile

Moon Jellyfish Life Cycle 5. The polyp begins reproducing asexually by budding, and now called a scyphistoma 6. Budding produces miniature medusae called ephyrae 7. After ephyrae are released, they gradually grow into adult forms

Jellyfish Reproduction

Class Scyphozoans: Importance * Jellies are considered a delicacy by many people. * Low in fat & calories * Rich in nutrients. * Others claim they taste like rubber bands.

Class Scyphozoans: Importance * Food source for fish, sea turtles, and other organisms

Looks like a Jellyfish to sea, but isn’t! Clear plastics (such as bags and balloons) are often mistaken for jellyfish by animals such as the endangered leatherback sea turtle. When they eat plastic, these animals will often starve to death as the plastic clogs their intestines and they can no longer digest food.

Save the Sea Turtles! Recycle Plastic Bags & Make sure they do not find their way into the ocean!

Class Cubozoans l Some are among the most dangerous marine animals. * Sea wasp, also known as the box jellyfish, of Australia & Southeast Asia - Extreme pain immediately when touched by tentacles Within minutes, heart failure may occur

Types of Cnidarians: Anthozoans l Class Anthozoan l Includes sea anemones & corals l Solitary or colonial polyps l Lack medusa stage l Have more advanced gut – contains several thin partitions called septa that provide extra surface area for digestion of larger prey.

Types of Cnidarians Class Anthozoan

Coral Spawning

Types of Anthozoans l Sea Anemones: Large muscular polyps.

Sea Anemone Importance: Provides Homes Clownfish are protected from the anemones’ stinging cells by their mucus. They catch food and feed the anemone. Eggs are laid near or under the anemone and tended and protected by the male clownfish.

Types of Anthozoans/Corals l Stony Corals: - Calcium carbonate skeletons that form coral reefs - More common in tropics

What do Corals Need to Survive? 1. Good Water Quality: • • Low turbidity (cloudiness or haziness of water) Temperature: at least 68° F 2. Sunlight: • • Algae that lives inside corals must have sunlight This is why corals do not live in deep water 3. Zooplankton: • Corals eat zooplankton 4. Water Movement: • • Access to food Flushes sediments off the coral so they can access sunlight

Coral Reef Video Clip

Types of Anthozoans/Corals l Gargonians: - Sea fans - Secrete a branching skeleton made of proteins.

Corals

Zooxanthellae Video Clip

Mutualism in Anthozoans/Corals l Mutualism: A relationship between two species that benefits both members. The association is necessary to both species. l Corals & Zooxanthellae are mutualistic l Zooxanthellae: an algae -- Live in the tissues of coral polyps -- All reef building corals have them -- Helps corals synthesize (make) calcium carbonate

Why Coral Reefs are Important 1. Protect from soil erosion: Waves from the ocean crash onto the shore and over time erode the shoreline. * Coral reefs that border land act as a buffer for the harsh waves. * The reefs cause the waves to slow down or stop them completely. * This prevents erosion of the shoreline and potential property damage.

Why Coral Reefs are Important 2. Breeding Grounds & Shelter: Some species that do not even live in the reef may travel to that reef just to breed. * Coral reefs are very important for replenishing fish populations that people consume.

Why Coral Reefs are Important 3. Tourism & Fisheries: They are important for fisheries & tourism businesses. Restaurants, hotels, SCUBA rentals, boat rentals, tour guides, air travel, cruise lines, and many more industries profit from healthy coral reefs.

Coral Atolls are coral islands. l The center of the atoll is a shallow lagoon. l Formed when a volcanic island’s middle sank into the ocean, and left a ring of land l The island bit of the atoll is a narrow ring of land around the lagoon, with coral reefs all around the outside of the island.

Ecology l Crown of Thrones Starfish: Well known for its voracious appetite for live hard-corals. l One explanation for local population explosions of these destructive starfish is the collection of this starfish's natural enemy, the Triton Trumpet l Many scuba clubs organize "starfish hunts" in which these starfish are rounded up in an effort to save reefs from destruction.

Ecology: Coral Bleaching l The whitening of coral colonies is due to the loss of symbiotic zooxanthellae from the tissues of polyps. l Pollution, temperatures, & disease are being blamed for corals loosing their zooxanthelle.

Stings from Cnidarians Symptoms * Includes corals, jellies, & sea anemones * Painful raised lesions in lines * Muscle spasms may develop * Raised lesions may fill with puss * May cause nausea, vomiting, dizziness, headaches, irregular heart rate

Stings from Cnidarians Treatment * Remove any tentacles (ex: stick) – Lift off skin, don’t scrape off -- Don’t use fingers, tentacles can still sting * Rinse with sea water to wash away nematocysts left on skin * Rinse with vinegar – neutralizes nematocysts -- If there is no vinegar, then urine will work

Stings from Cnidarians Treatment Continued * Can apply Hydrocortisone is redness persists * Seek medical attention if muscle spasms develop -- Doctor will give you calcium gluconate in IV

Death by Cnidarians • Stings are usually mild • Some stings are fatal * Box jellyfish -- Mortality rate of about 20% in 1 st 3 minutes of a sting There isn’t an international data base for mortalities by jellyfish stings – exact numbers of deaths are unknown.

Phylum Ctenophora Look like Cnidarians, but are classified in a different phylum

Phylum Ctenophora Includes comb jellies

Phylum Ctenophora l Have 8 rows of cilia bands, called comb rows, for locomotion l As they swim, the comb rows diffract light to produce a shimmering, rainbow effect.

Phylum Ctenophora l Have colloblasts on tentacles used to capture prey – are adhesive cells that stick to prey l Lack nematocysts l Eat zooplankton only

The End