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Phylum Cnidaria (ny DEHR ee a) The Highlights of Jellyfish and Hydra life Video below http://marinebio.org/oceans/coral-reefs/ Examples of Cnidarian Jellyfish Hydra Coral Sea Anemone Cnidarians (ny DEHR ee unz) and Characteristics Invertebrates Stinging Cells Have a central body cavity Radial symmetry – more than one line of symmetry & parts arranged in a circle Pretty Radial Symmetry pics: BODY STUCTURE: Polyp: vase-shaped body plan (like a sea anemone, coral or hydra) Medusa: jellyfish) Bowl-shaped body plan (like a Polyp Mouth opens at the top of its body Tentacles surround the mouth Attach themselves to an underwater surface More on Medusa Adapted to a life of swimming Mouths open downward (at the bottom) and is surrounded by tentacles that dangle Which came first: Polyp or Medusa?? Brooks (1886) proposed a theory still widely accepted – however, being studied (DNA evidence, etc.) •Ancestral cnidarian was a medusa Life Cycle Some Cnidarians have both body plans in their life cycle… Sexual Asexual (budding) Obtaining FOOD!!! Same way for polyps and medusa Use their stinging cells to catch prey Some have sharp spines with venom Venom paralyzes them – pull prey into their mouths with tentacles Prey goes into hollow central body cavity to be digested Waste goes out of mouth. Movement Many Cnidarians can move to escape Jellyfish swim Hydra turn slow somersaults Sea Anemones bend from side to side, stretch out, shrink down or move slowly Nerve net – nerve cells arranged like a basketball net – help with this movement Life in a Colony Some species of Cnidarians spend life in a colony – a group of many individual animals Examples: Coral and Portuguese man-ofwar Coral Reefs Found in warm shallow water Built by cnidarians A coral polyp attaches to a solid surface (broken shell, sunken ship, rock or reef ball) Polyp produces a hard, stony skeleton around its soft body Home to more species of fishes and invertebrates than any other environment https://www.youtube.com/watch?v=eIul2ObvKV8 on Earth - video Coral Reefs in Danger More than 1.5 million recreational divers Divers can cause damage by standing on or even touching fragile reefs Collecting coral for jewelry or decoration (now illegal)…should they ban diving all together? Oil spills, tropical storms, changes in sea level and temperature, and illegal fishing can also harm reefs Portuguese Man-of-War Contains as many as 1,000 individuals that function together as one unit Top of medusa is a gas-filled chamber that allows the colony to float Various polyps with different functions drift below by the tentacles Some polyps catch prey and others digest the prey…some are adapted for reproduction https://www.youtube.com/watch?v=sQyByfmKGJs https://www.youtube.com/watch?v=NbpB5F9CcLc