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RADIATA-animals with radial symmetry
PHYLUM CNIDARIA• Cnidarians
are animals with stinging tentacles
BODY STRUCTURE• Radial symmetry• No organ systems• Nerve net (primitive nervous system)
–Whole body responds no matter what was stimulated
• Outer membrane, inner membrane and jelly middle called mesoglea–Oxygen diffuses right into its body, CO2
diffuses out
BODY STRUCTURE• Have sensory organs
–Statocysts…balance organ
–Box jellies have 4 pairs of eyes
See Fig 7.3 pg 126Hydra
BODY STRUCTURE• Primitive muscle cells- weak swimmers• Incomplete digestive tract- one
opening for waste and food• Lack all other systems and no body
cavity• Do have hormones to communicate
between cells
REPRODUCTION
• Some Cnidarians have an alternation of generations, vary as to dominant stage
•Medusa is the sexual body plan
•Polyp is the asexual body plan
•Larvae is called planula
See Fig 7.2 pg 125
FEEDING
• Cnidoblasts / nematocysts – stinging cells– Used in defense and to paralyze prey– After being triggered these cells cannot be re-
used so they must be regenerated
• Planktonic version are carnivorous, sessile version are filter feeders
• Food is digested in the cavity
Cnidaria Taxonomy
• Class Hydrozoa - Siphonophores
• Class Anthozoa – Coral
• Class Cubozoa - Box Jellies
• Class Scyphazoa - Jellyfish
Class Hydrazoa
Portugeuse Man O War, Hydra
Dominant phase is polyp
Found as colonial animals or individuals
Individuals of a colony cannot exist on their own
Class Hydrazoa
• Different polyps have different roles– Feeding polyps– Reproductive polyps– Special tentacle polyps– Float polyps
Class Anthazoa• Sea Anemones
– Live as a polyp attached to the substrate
• Coral– Colonial polyps with a limestone exoskeleton– Polyps share a stomach– Feed on plankton and have symbiotic algae that
live in their tissue and give them nutrition– Build reefs using Ca in the water and CO2 from
their algae
See Fig. 7.19 pg 135An Anthozoan/Sea Anemone
See Figs 7.24, 7.26 pg 138-39A Zoantharian Coral
Class Scyphazoa
• Spend most of their life as umbrella shaped medusa
• Size range from cms to meters across• Typical NJ jellies- moon, purple and lion’s
mane jellyfish• Population explosions of 100s or 1000s of
these animals is currently a concern• Major predators include tuna, swordfish,
moonfish, triggerfish and certain kinds of sea turtles
Aurelia
Moon jellyfish, AureliaFig 7.16, 17 pg 134
Pelagia
Cyanea
Class Cubazoa
• More square shaped than regular jellies
• Powerful stings that cankill a human
• Good swimmers
Ecology
• Important predators
• Corals are most diverse places in the ocean
• Important food source for some animals
• Huge blooms are occurring recently because of warming ocean temperatures (??) or because of overfishing (???)
Treatment of Stings • minimize the number of nematocysts
discharging into the skin
• remove the tentacles that adhere to the skin by using sand, clothing, towels, seaweed
• meat tenderizer, sugar, vinegar, plant juices and sodium bicarbonate have all been used with varying degrees of success.
• Do not use : Methylated spirits, picric acid and human urine
http://en.wikipedia.org/wiki/Image:Haeckel_Ctenophorae.jpg
Phylum Ctenophora
• Common name….comb jellies
• Unique Characteristics
– Comb plates (not tentacles)
– Medusa stage only
– Luminescence common
– Position of paired tentacles changes
symmetry to biradial
Ecology
• Form a large percent of the plankton
• Can regenerate depending on damage
• Feed on plankton including: larvae, worms, jellyfish, other comb jellies, and sometimes small fish.
• Same predators as jelly group
Image ID: nur01002, National Undersearch Research Program (NURP) Collection Credit: OAR/National Undersea Research Program (NURP)
Difference From Cnidaria
– No alternation of generations (medusa only)
– No nematocysts have sticky cells instead
– Biradial symmetry, two tentacles
– Combs not tentacles
– Complete digestive system
• Similarities
–Nerve net
–Lack of organ systems
–Similar role in marine oceans
Comparison Ctenophora to Cnidaria
Taxonomy Phylum Ctenophora
Ctenophore
See Fig 7.28 pg 140Ctenophoran Comb Jelly
Fig 7.28 pg 140CtenophoreComb Jelly
Fig. 7.28
See Fig 7.28 pg 140Ctenophoran Comb Jelly
See Fig 7.28 pg 141Ctenophoran Comb Jelly
Table 9.3