Phylum Cnidaria 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 stomach (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

Cnidoblast

Nematocyst

Nervous System • Nerve cells interconnect to form a nerve net

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 Chironexdeadly 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

Box Jellyfish Sting

Chironex- Sea Wasp

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

Tube Sea Anemone

Sea Anemone

Soft 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 in them • The polyps take up calcium in the sea water and zooxanthellae, which live inside the polyp, take up CO 2, which make limestone

Zooxanthellae

Hard Coral

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 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.

Atafu Atoll: South Pacific

Symbiosis and Cnidarians • Symbiosis: literally means to live together 1. Mutualism: both organisms benefit from living together 2. Commensalism: one organism benefits, the other is unaffected 3. Parasitism: one organism benefits, one is harmed.

Clownfish and Anemones

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? _______

Coral and Zooxanthellae

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

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

Life Cycle

Deep Sea Comb Jelly

On a sheet of paper do the following 1) Title the paper: Porifera, Cnidaria, and Ctenophora Lab 2) Number your paper from 1 -22 3) Leave space on #11, #14 and #16 for drawings (about 5 lines) 4) Use your Porifera Notes and Cnidaria Notes to answer the questions (answers only, don’t worry about writing the questions)