Phylum Cnidaria (jellyfish, coral and other stingers…)

Phylum Cnidaria Class Scyphozoa Class Hydrozoa Class Anthozoa Jellyfish Class Hydrozoa Hydras Class Anthozoa Sea Anemones, Coral

Phylum Cnidarian There are about 10,000 species of the phylum Cnidaria, almost all of which are marine. (less than 50 are freshwater) They represent the next highest level of organization in animals They possess true tissues Most radially symmetric Soft-bodied Carnivorous animals that have stinging tentacles.

Cnidarians… The name Cnidaria comes from the Greek word "cnidos," which means stinging nettle. Cnidaria have cnidocytes, stinging cells located on along tentacles. Each cnidocyte contains a nematocyst, a poison filled structure that has a coiled dart. Cnidocytes are arranged around their mouths Casually touching many cnidarians will make it clear how they got their name when their nematocysts eject barbed threads tipped with poison.

Discharged Nematocyst

Life Stages of Cnidarian Two different types of life cycles Polyp is usually sessile Medusa is motile

Two Basic Body Forms of Cnidaria

Cnidarians… They are diploblastic, meaning they develop from two embryonic germ layers, endoderm and ectoderm. The layer in the middle is a jellylike layer called a mesoglea

Feeding Carnivores (predators) Process of feeding Tentacles grab prey Lion’s mane eats another jelly Carnivores (predators) Process of feeding Tentacles sting prey with nematocysts Tentacles grab prey Prey pulled into mouth Prey stuffed into gastro-vascular cavity (incomplete digestive tract – no anus) Undigested food back out mouth

http://www.youtube.com/watch?v=o1A5acWEERA&feature=related

Response Cnidarians gather information from their environment using specialized sensory cells Both polyps and medusas have a nerve net, a loosely organized network of nerve cells. Other sensory cells include: : ocelli (for light) and : statocyst (for gravity) Cnidarians have nerve nets that consist of many individual nerve cells.

Movement Sea anemones have a hydrostatic skeleton. A hydrostatic skeleton consists of a layer of circular muscles and a layer of longitudinal muscles that, with the water in the gastrovascular cavity, enable the cnidarian to move. http://www.youtube.com/watch?v=760lUxyle6I

Cnidarians… Reproduction Most cnidarians reproduce both sexually and asexually. Polyps can reproduce asexually by budding. In most cnidarians, sexual reproduction takes place with external fertilization. External fertilization takes place outside the female's and male’s body.

Ecological Role Predators and prey Neurotoxins in medical research Coral – jewelry, building, reefs (surfing!) Coral reefs - habitat for many -great biodiversity - protect coastline Symbiosis with other organisms

The Jellyfish: Class Scyphozoa (the “cup animals”) -Range from tiny to almost 4 meters across -Some species are extremely venomous- The box jellyfish is the most venomous animal in the world and has killed over 5 500 people since the 1950s. http://www.dailymotion.com/video/xxmf9n_steve-irwin-s-ocean-s-deadliest-box-jellyfish-part-4-9-hd_animals

Class Scyphozoa: True Jellyfish Fried egg jelly

Giant Jelly off Coast of Japan

Hydra and their Relatives -Hydras belong to the class Hydrozoa -Most hydrozoans are colonies of polyps performing specialized functions (Portuguese Man O’ War) -Hydra are freshwater hydrozoans that don’t have a medusa stage. They only live as polyps.

Class Hydrozoa Portuguese man o’ war Varadero, Cuba

Class Hydrozoa Portuguese man o’ war Brought up on the beach by wind. National Geographic - http://www.youtube.com/watch?v=RBdCpcapB0s

Brown Hydra with Buds

Anemones and Corals -This is the class Anthozoa (“flower animal”) -Corals and anemones only have the polyp stage -Anemones are solitary polyps www.youtube.com/watch?v=Dm98n3908QM&feature=related -Corals form colonies of polyps that look like tiny anemones. -Colonies grow over thousands of years producing calcium carbonate structures that build huge reefs that are threatened. -Corals form mutualistic relationships with algae. http://www.youtube.com/watch?v=60jof35WuAo

Class Anthozoa Cabbage Coral

Sea Pen

Class Cubozoa The world most venomous animal is the sea wasp (a kind of jellyfish with 60 tentacles, each 15 feet long) that has enough venom to kill 60 adult humans.

http://attenboroughsreef.com/the_perfect_reef.php