Phylum Cnidaria

Characteristics:

• Diploblastic; tissues and nervous system • Specialized cells= Cnidocytes (“stinging cells”) • 4 main classes (over 9,000 species): • Class Hydrozoa • Class Scyphozoa= true jellyfish • Class Cubozoa • Class Anthozoa= sea anemones and corals

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Body organization (=Diploblastic)

– Outer layer (Ectoderm)= Epidermis – Inner layer (Endoderm)= Gastrodermis – Mesoglea= Jelly-like layer in-between – Hydrostatic skeleton = gastrovascular cavity which fills with water •

Body Forms

– 2 body forms which alternate through life history: *polyp= sessile column attached by aboral end *medusa= free swimming; inverted bowl shape

• Cnidocytes- Cells which produce cnidae used for attachment, defense, and feeding.

*There are about 30 kinds of cnidae.

Nematocyst – One type of cnidae that may discharge a long tube armed with spines that penetrate prey. These spines deliver paralyzing toxins.

http://www.barbaraharmon.com/illus_a rt/anatomy_biology/nematocyst.jpg

http://creationwiki.org/pool/images/5/5f/Nematocyst_discharged.PNG

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Reproduction

– – Most cnidarians are dioecious (separate sexes) Sperm and eggs released into water/ gastrovascular cavity – Fertilized embryo turns into free swimming larvae called planula; planula attaches to substrate; polyp develops; medusa forms later by budding from polyp

Class Hydrozoa

• The only cnidaria class with: – Freshwater species (as well as marine) – Nematocysts and sex cells only in epidermis – Velum (shelf-like lip around ring canal) present on most medusa – Mouth at end of tubelike manubrium • Some species do not have medusa stage; some species only have very small polyp stage

• Example: Hydra (freshwater; no medusa) http://www.donsmaps.com/images2/herculeshydra.jpg

http://www.isi.edu/robots/self_heal_html/hydra.JPG

• Other Examples…

manubrium

http://www.microscopy-uk.org.uk/mag/imgmay01/obelob.jpg

Obelia Portuguese Man-of-War

Class Scyphozoa

• • • • • • • • “True jellyfish” (Medusa is dominant stage) Lack a velum Cnidocytes in epidermis & gastrodermis Sex cells in gastrodermis Gastrodermal cells have cilia Feed from oral lobes, hanging from manubrium Some species have an ocellus/ocelli (pl.) (photoreceptor/eye) All marine

Largest Jellyfish: lion's mane jellyfish

http://i.telegraph.co.uk/telegraph/multimedia/archive/01423/LionsManeJellyfish_1423038c.jpg

http://farm4.static.flickr.com/3192/3081451429_b4b832e974.jpg

http://www.biopix.com/Temp/JCS%20Aurelia%20aurita%2041520.jpg

Most Common Jellyfish: Moon Jellyfish http://latimesblogs.latimes.com/p hotos/uncategorized/2008/09/11/ do_they_have_their_own_moonw alking_.jpg

Class Cubozoa

• Medusa “cuboidal” (cube) shaped • • • (Tentacles hang from corners) Some species have no polyp stage/or unknown Active swimmers and feeders Some of the most deadly jellyfish • (most deaths within 5 minutes) All marine

Most Toxic Jellyfish: Box Jellyfish of Australia AKA “Sea Wasp” http://lifeinthefastlane.com/wp content/uploads/2008/12/box jellyfish-fatal-sting.jpg

http://www.brisbanetimes.com.au/ffxi mage/2007/03/30/470_box,0.jpg

Class Anthozoa: Anemones and Corals

• • • Lack Medusa stage (all polyps) All marine Anthozoan polyps are more complex than hydrozoan polyps!

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Anemones

– Solitary – Attach to bottom by pedal disk – Mesenterial filaments and acontia bear cnidocytes – Muscle fibers gastrodermal (they can “deflate” and collapse if threatened) – Movement by sliding on pedal disk, crawling on side, walking on tentacles (some can swim!) – Food: Invertebrates, fishes – Both sexual and asexual – Both monoecious and dioecious

http://images.paraorkut.com/img/wallpapers/1024x7 68/c/clown_fish_and_a_sea_anemone-2640.jpg

http://www.lauramhaight.com/images/portfolio/PJAP_PinkSeaAnemone.jpg

http://www.seaotter.com/marine/research/sto mphia/coccinea/pics/swimanemone.jpg

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Corals

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Stony Corals

• Colonies form coral reefs • Calcium carbonate exoskeleton • Similar to anemones • Known for symbiosis with algae called zooxanthellae (these algae use photosynthesis to give products to coral; corals metabolism also provides back to algae) • Colors come from zooxanthellae!

• 90m depth limit (NEED light for zooxanthellae) • No zooanthellae = coral bleaching

http://www.marineaquarium.nl/image s/Acropora%20prostrata.gif

http://www.advancedaquarist.com/2007/12/aafeature2_album/figure1.jpg

http://www.stormcenter.com/media/envirocast/archive/060912/060912_07.jpg

Coral Bleaching http://www.globalwarmingart.com/images/ 4/48/Partially_Bleached_Coral.jpg

http://www.gbrmpa.gov.au/__data/assets/image/0006/13749/Bleaching-and-mortality-dia.gif

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Soft Coral

• • Internal skeleton of protein or calcium carbonate Some have feather-like tentacles • Group Includes: sea fans, sea pens, sea whips, etc.

Sea Pen Sea Fan

Phylum Ctenophora

• • • • • • • • • 90 species: Sea Walnuts or Comb Jellies Spherical form (or flattened) Most diploblastic- Some triploblastic!

True muscle cells in mesoglea Anal opening Comb rows (bands of cilia) from oral to anal openings Tentacles have colloblasts (adhesive cells) that capture prey Monoecious/sexual reproduction external Known for bioluminescense

http://images.enature.com/seashore/seashore_l/sc0127_1l.jpg

http://pt-lobos.com/ctenoimg/leucothea_pulchra-com_bdb13.jpg

http://upload.wikimedia.org/wikipedia/commo ns/1/1e/Sea_walnut,_Boston_Aquarium.jpg