Jellyfish, Coral, Sea Anemone, and Hydroids Phylum Cnidaria Jellyfish, Coral, Sea Anemone, and Hydroids

Cnidarians Stinging cell animals Also Known As: Coelenterates: “Hollow Gut” Radial Symmetry: similar body parts surrounding a central axis

Body Plan No segments: oral and aboral sides Hydrostatic Skeleton: fill body cavity with water to remain upright. Shrink down as defense Organized at tissue level. (No true organs) Epidermis: outer cells (ectoderm) Gastrodermis: lines gastrovascular cavity (endoderm) Mesoglea: middle layer of gelatinous material; can be thick or thin.

Digestion Food is digested in the sac-like digestive cavity (only one opening) Extracellular and intracellular digestion Extracellular: outside of cells Intracellular: inside of cells Waste is expelled out of the mouth

Unique Features Cnidoblasts: stinging cells Inside each cell is a nematocyst, coiled thread with barb at the end. The nematocyst can be discharged by either physical or chemical stimulus. Physical- cnidocil (modified flagella) acts as a trigger Contain a poisonous neurotoxin, varies by species

Life Cycle Jellyfish have separate sexes Both sexual and asexual reproduction Sexual: external or internal (depending on species), sperm and egg form a zygote which grows into a swimming larva called the planula. In some cases the planula attaches to a hard substrate and develops into a polyp.

Life Cycle cont. The polyp resembles an upside-down jellyfish medusa. Small umbrella like medusas break off from the polyp by budding (asexual)

Classification of Cnidarians Class Hydrozoa- Hydra, Physalia, and Obelia Class Scyphozoa- True Jellyfish Class Cubozoa- box jellyfish Class Anthozoa- Corals and Sea Anemones

Class Hydrozoa Usually colonial, except Hydra Composition of colonies- 3 types 1. Gastrozoid- responsible for feeding 2. Gonozoids- responsible for sexual reproduction 3. Dactyliozoids- responsible for defense; have numerous nematocysts.

Class Scyphozoa All marine; medusa is dominant life cycle Mesoglea is a large part of the body (mostly dead matter) Gastroderm have nematocysts; food may be eaten alive More toxic than hydrozoans Well developed sensory organs and glands - eyespot and chemoreceptors

Class Cubozoa Cube-like jellyfish Have four flattened, blade-like structures called pedalia Complex eyes with lenses and retinas (no brain though) Only 16 species: Irukandji and Chironex- deadly box jellyfish. Can kill a human in minutes.

Irukandji: Carukia barnes One of, if not the deadliest box jellfish. 2.5 cm (1 inch) in diameter

Class Anthozoa No medusa stage in life cycle Polyps produce eggs and sperm that develop into planula larva Solitary: sea anemone Colonial: coral

Corals and Coral Reefs Corals are colonial cnidarians Dominant form is the polyp Coral reef is a massive structure composed of calcium carbonate built by coral polyps and the organisms that live with them The polyps take up calcium in the sea water and zooxanthellae, which live inside the polyp, take up CO2, which make limestone

Coral Reefs Found only in tropical areas Warm and clear water Shallow water- zooxanthellae require sunlight to photosynthesize Zooxanthellae are the primary producers of the coral reef

Coral Reef Formation Fringing Reef: occurs when a seamount pierces the sea surface to form an island and provides a base on which the coral can grow Barrier Reef: occurs if a seamount subsides slowly enough and the coral continues to grow upward at a rate that is not exceeded by the rising water. A lagoon is formed. Atoll- occurs if the seamount disappears below the surface and the coral reef is left as a ring.

Symbiosis and Cnidarians Symbiosis: literally means to live together Mutualism: both organisms benefit from living together Commensalism: one organism benefits, the other is unaffected Parasitism: one organism benefits, one is harmed.

Sea Anemones and Clownfish Usually, fish the size of clownfish are stung and eaten by an anemone Clownfish become immune to the anemones nematocysts because of a mucus coating The mucus inhibits the anemone’s sting The anemone provides protection and scraps of food for the clownfish The clownfish lures prey into the anemone and cleans the anemone What kind of relationship is this?______________

Corals and Zooxanthellae Zooxanthellae are dinoflagellates that are taken up by the coral polyps. Zooxanthellae contain chloroplasts Coral use the glucose made by the zooxanthellae as an energy supplement The zooxanthellae benefit because they are protected and receive nutrients from the coral polyp. What type of relationship is this? _____________

Phylum Ctenophora Comb Jellies Take notes on your own sheet of paper, only write down what is underlined.

Ctenophora Group of 100 species Oval shaped with radial symmetry Resemble cnidarians but are NOT! Swim with 8 rows of ciliary combs (long cilia fused at the base) Cilia refract light which cause a rainbow effect. Body length varies from a few centimeters to 2 m long.

Habitat Exclusively marine Can be found in cold or warm water

Diet Carnivores Consume fish larvae and plankton Can expand stomach to eat organisms twice their size. Capture prey with two long tentacles armed with sticky cells called colloblasts A few species have nematocysts

Reproduction Sexual reproduction Hermaphrodites No polyp form; only medusa