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Invertebrates Phylum Phylum Cnidaria Cnidaria Slide 2 Cnidarians Phylum Cnidaria Phylum Cnidaria Includes jellyfish, anemones, corals, & sea pens Includes jellyfish, anemones, corals, & sea pens Next level of complexity after sponges Next level of complexity after sponges Tissues are specialized to perform specific Tissues are specialized to perform specific functions. functions. Also called coelenterates Also called coelenterates This term is not used This term is not used often anymore! often anymore! Slide 3 Coelenterates Even though not used often anymore Refers to 2 Phylums combined: Phylum Cnidaria & Phylum Ctenophora - Ctenophora : Comb Jellies - Cnidaria : Jellyfish, Sea anemones, Corals, & Sea pens Have a hollow body cavity, & very Have a hollow body cavity, & very simple tissue organization simple tissue organization Slide 4 Cnidarians Have NO bones Have NO bones Have NO heart Have NO heart Have NO brain Have NO brain Have NO real eyes Have NO real eyes Have NO respiratory system Have NO respiratory system Slide 5 Cnidarians: Body Plan Display radial symmetry, which is a Display radial symmetry, which is a regular arrangement of similar body parts around a central axis. regular arrangement of similar body parts around a central axis. Look the same from all sides Look the same from all sides Have no head, front, or back Have no head, front, or back Slide 6 Cnidarians: Body Plan Have an oral surface where the mouth is & an aboral surface on the opposite side. Slide 7 Occur as 2 basic forms: Polyp: A sac-like attached stage (sessile) Medusa: Bell-like stage Medusa: Bell-like stage Some experience both forms during their life time, and others spend their entire lives as one of the two forms. Polyp Medusa Slide 8 Cnidarians: Anatomy Have a centrally located mouth surrounded by Have a centrally located mouth surrounded by tentacles which are slender, finger like tentacles which are slender, finger like extensions. extensions. Use tentacles to catch & handle food Use tentacles to catch & handle food Slide 9 Cnidarians: Anatomy The mouth opens into a gut (enteron) where food is digested. The mouth opens into a gut (enteron) where food is digested. - The gut has only one opening, the mouth. Slide 10 Cnidarians: Anatomy The mesoglea is extremely thick, has a The mesoglea is extremely thick, has a jelly like consistency & makes up the jelly like consistency & makes up the largest portion of the animal largest portion of the animal This is how jellyfish got their name. Slide 11 Tentacles They capture small prey by discharging their cnidocytes (stinging cells), which are unique structures found on the tentacles. They capture small prey by discharging their cnidocytes (stinging cells), which are unique structures found on the tentacles. Slide 12 How Cnidarians Sting 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. neurotoxins Slide 13 How Cnidarians Sting These stinging cells contain poison arrows connected to threads called nematocyts. These stinging cells contain poison arrows connected to threads called nematocyts. * Cnidarians can still sting when they are dead!! Slide 14 Tentacles The tentacle then brings the victim to the mouth to be digested. The tentacle then brings the victim to the mouth to be digested. The food passes through the body cells, and the waste must go back out of the mouth. The food passes through the body cells, and the waste must go back out of the mouth. Slide 15 Jellyfish Eating Slide 16 Jellyfish Feeding Video Clip Slide 17 Cnidarians: Anatomy 2 Layers of cells form the body wall 2 Layers of cells form the body wall - Ectoderm : external layer - Endoderm : internal layer that lines the gut Slide 18 Feeding Zooplankton : Drifting microscopic animals Slide 19 Feeding Phytoplankton : Drifting microscopic plants. Slide 20 Feeding After paralyzing its prey, a cnidarian pulls the prey through its mouth and into its gastrovacular cavity. After paralyzing its prey, a cnidarian pulls the prey through its mouth and into its gastrovacular cavity. Gastrovascular Cavity : A digestive chamber with one opening. Gastrovascular Cavity : A digestive chamber with one opening. Food enters & waste leaves the body through Food enters & waste leaves the body through that opening. that opening. Slide 21 Response to Environment Cnidarians gather information from their environment using specialized sensory cells. Cnidarians gather information from their environment using specialized sensory cells. Both polyps & medusas have a nerve net. 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. Slide 22 Response to the Environment Cnidarians have statocysts which are groups of sensory cells that help determine the direction of gravity. 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. Ocelli are eyespots made of cells that detect light. Slide 23 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. Medusas move by jet propulsion. Muscle contractions cause the bell-shaped body to close like a folding umbrella. 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. This action pushes water out of the bell, moving the medusa forward. Slide 24 Cnidaria Reproduction Some reproduce asexually by budding (in polyps) Some reproduce asexually by budding (in polyps) Some reproduce sexually by releasing gametes. Some reproduce sexually by releasing gametes. Some sexual forms are monoecious and others are dioecious Some sexual forms are monoecious and others are dioecious Eggs and sperm are released into the stomach and then through the mouth into the sea. Eggs and sperm are released into the stomach and then through the mouth into the sea. Slide 25 Cnidaria Reproduction In some cases, to reproduce, a male releases his sperm into the surrounding water (spawn). In some cases, to reproduce, a male releases his sperm into the surrounding water (spawn). The sperm then swims into the mouth of the female jellyfish, allowing the fertilization of the ova. The sperm then swims into the mouth of the female jellyfish, allowing the fertilization of the ova. Slide 26 Cnidarian Reproduction In other cases, sexual reproduction takes place with external fertilization in water: 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. Slide 27 Jellyfish Review Video Clip Slide 28 Class Hydrozoa Types of Cnidarians Slide 29 Types of Cnidarians: Hydrozoans Class Hydrozoa Hydra - They can be found in most unpolluted fresh- water 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. Slide 30 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. Slide 31 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 Slide 32 Types of Cnidarians: Hydrozoans Class Hydrozoa Portuguese man-of-war Consist of feather or bushy colonies of polyps. - Some polyps are specialized floats, which may be gas-filled may be gas-filled - Other polyps form the long tentacles used to capture prey. capture prey. Slide 33 Types of Cnidarians: Hydrozoans Portuguese Man-of-War Portuguese Man-of-War Slide 34 Class Scyphozoa Types of Cnidaria Slide 35 Types of Cnidarians: Scyphozoans Class Scyphozoan Class Scyphozoan Includes jellyfish Includes jellyfish Have a rounded body, or bell. Have a rounded body, or bell. Swim w/ rhythmic contractions of the bell, but swimming ability is limited & are carried by ocean currents. Swim w/ rhythmic contractions of the bell, but swimming ability is limited & are carried by ocean currents. Slide 36 Class Scyphozoans 95% of body is made of water 95% of body is made of water Here before dinosaurs and sharks Here before dinosaurs and sharks Inhabit all oceans of the world Inhabit all oceans of the world Slide 37 Moon Jellyfish also called Common Jellyfish Slide 38 Moon Jellyfish Life Cycle - 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 Planula is the larval stage, small, & covered in cilia Planula is the larval stage, small, & covered in cilia 4. The planula settles on a hard surface & develops into a polyp to become sessile Planula Slide 39 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 Slide 40 Jellyfish Reproduction Slide 41 Class Scyphozoans: Importance * Jellies are considered a delicacy by many