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