19 cubozoa medusa form is dominant polyp is very tiny

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Unformatted text preview: tes (top) and Ovaries (bottom) appear as rounded projections Ø།  Sperm are released and fertilize attached ovary Ø།  Development to cysts form, breaks loose à༎ can survive the winter •  Spring Ø།  Warmer water prompts hatching •  Colonial Obelia have a more typical life cycle of hydrozoa Fig 13.7 Scyphozoa – “true jellyfish” •  •  many of the largest jellyfish float in open sea •  One order sessile, attached to seaweeds Life cycle of Aurelia Fig 13.19 Cubozoa •  Medusa form is dominant •  Polyp is very tiny / unknown •  Umbrella is square •  1+ tentacles at each corner •  Strong swimmers •  Feed on fish in nearshore areas •  The sea wasp (Chironex fleckeri) •  Potentially fatal sting •  Death within a matter of minutes Fig 13.21 Anthozoa – “flower animals” •  Polyps dominate the life cycle –  No medusa •  For replication à༎ planula larvae •  Gastrovascular cavity divided by septa / mesenteries –  Hold the gonads, when produced •  3 subclasses à༎ Hexacorallia –  6-fold symmetry –  Sea anemones –  Stony corals –  Zoanthids Fig 13.21 Anthozoa – “flower animals” Sea Anemones (you will see one in the lab) •  Larger and colourful •  Attach with pedal disc –  can glide along a surface •  Ciliated oral disc & pharynx –  creates water current (O2, waste) –  hydrostatic skeleton •  Symbiotic zooxanthellae –  photosynthetic algae –  provide nutrients for anthozoa –  algae has a safe place to live Fig 13.21 Anthozoa ✔ Divided gut ✔ Tentacles ✗ Ciliated mouth ✗ Pedal Disc Hexacorallian (Stony) Coral •  Similar to anemones •  Produce calcereous exoskeleton –  Produced by epidermis at base of animal –  Create ridges, sclerosepta, that allow retraction –  In colonies, sheet of tissue covers the colony, connecting gastrovascular cavities of all polyps Fig 13.28 Anthozoa Hexacorallian (Stony) Coral •  Similar to anemones •  Produ...
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