Lecture Exam I

• Cambrian radiation / phylogeny = 2 papers

• Systematics intro

• Protista: 10 phyla

• Animalia: Porifera, Cnidaria

• ~20 questions

• Short answer, essay, life cycle sketch

Phylum Cnidaria•3 Classes:

– Anthozoa– Scyphozoa– Hydrozoa

Characteristics:

• Diploblastic metazoan

• Ectoderm and endoderm separated by acellular mesoglea

• Nervous system: simple nerve net, neurons

Development

• Planula larvae

• ciliated, motile, gastrula larva

Radial symmetry

• Modified into biradial, quadradial, etc…

• Saclike, partitioned, or branched w/ one opening • = mouth and anus

Gastrovascular cavity

Alternating life history forms: polyp and medusa

Polyp

• Radial symmetry

• Oral end = hypostome or manubrium in hydrozoans– flat pedal disc in anthozoans

• Tentacles surround mouth

PolypGastrovascular cavity

• Circulation, digestion, distribution of Circulation, digestion, distribution of nutrientsnutrients

• Hydrozoans: coelenteron is single tubeHydrozoans: coelenteron is single tube

• Scyphozoans: four longitudinal mesenteriesScyphozoans: four longitudinal mesenteries

• Anthozoans: compartmentalized by Anthozoans: compartmentalized by mesenteriesmesenteries

Polyp: support• Hydrostatic, water-filled coelenteron Hydrostatic, water-filled coelenteron

• Anthozoans - bits of sediment and shell Anthozoans - bits of sediment and shell fragments in column wall for supportfragments in column wall for support

• Hydrozoans - flexible horny perisac (periderm) of Hydrozoans - flexible horny perisac (periderm) of chitin from epidermischitin from epidermis

Polyp: movement

• Retractor muscles: longitudinal fibers along mesenteries

• Circular muscles: sphincters– in tentacles and oral disc

• Most polyps sedentary or sessile

• Creep slowly w/ pedal disc musculature• http://www.youtube.com/watch?v=-UI531GMRTM

Medusa• All cnidaria except Anthozoa

• Bell-, dish- or umbrella-shaped

• Exumbrella: convex upper (aboral) surface

• Subumbrella: concave lower (oral) surface– Mouth at center

Free-floating,

mouth down

Medusa

•External surface: epidermis• Internal surface: gastrodermis

•Coelenteron central; extends to radial canals– Usually four radial canals, tentacles,

stomach divided by mesenteries into four gastric pouches

• Stinging structures

•

Nematocysts

Nematocysts: multiple types

• Generic nematocyst (all)– Double-walled capsule w/ toxic mixture of phenols +

proteins– Spines or barbs for penetration, anchor in victim

• Spirocyst (Anthozoa)– Spring-like mechanism– Adhesive tubules wrap around and stick to victim

• Ptychocyst (tube anemones)– Create capsule tubule

Feeding and digestion

Tentacles capture prey, carry to mouth, ingest whole

Extracellular digestion in coelenteron– enzyme-producing cells

Reproduction and DevelopmentHydrozoa

• Polyps = asexual budding

Reproduction and DevelopmentHydrozoan

• Free-living hydromedusa

• Dioecious, release sperm or eggs

Reproduction and DevelopmentScyphozoa

•Asexual reproduction: small polyp = scyphistoma

•Medusa from scyphistoma

• Immature medusa = ephyra

•Most species dioecious

Reproduction and DevelopmentAnthozoa

•Exclusively polyps

•Asexual reproduction

•Fission

•Pedal laceration: pedal disc spreads, anemone moves, leaves small fragments– develop into adult

Class Hydrozoa

Hydroids and hydromedusa

Hydrozoa

Portuguese Man-of-war

Physalia

Class AnthozoaAnemones, corals, sea pens

Exclusively marine

Octocorals

• Soft corals– Gastraxonacea– Helioporaceans– Sea pens and sea pansies– Protoalcyonaria– Stoloniferans– Telestaceans

Sea pen

Class AnthozoaAnemones and true corals

• True sea anemones• True corals (stony corals)

Class Anthozoa

• Black or thorny corals• Ceranthids or tube anemones

Class Scyphozoa

• Jellyfish

Box jelly

Chiropsalmus