06 chap 13 cnidaria and ctenophora
TRANSCRIPT
Phylum Ctenophora
Comb Jellies
sk. Parazoa
Protostomeembryology
Deuterostomeembryology
ph. Cnidariaph. Porifera
sk. Eumetazoa
asymmetrical, cellular level
Bilateral,triploblastic
Radial,diploblastic
symmetrical, tissue level
choanoflagellate-like ancestor
k. Animalia
Ctenophore biology
• 100-150 species• 8 rows of comblike plates for
locomotion• Lack stinging cells (except 1 sp.)
– Cnidocytes from prey• Colloblasts- glue cells used for
feeding and adhesion
Ctenophore Diversity
Beroa
Cestum
Coeloplana, rarecreeping
Ctenophore Taxa
• Class Tentaculata– Tentacle bearing
• Class Nuda– Tentacles absent
Phylum Cnidaria
Radially symmetrical Eumetazoathat sting
Major Characteristics
• Two tissue layers– epidermis and gastrodermis, connected
by non-cellular mesoglea• Radial symmetry• Cnidocytes - stinging cells• Incomplete gut - “gastrovascular cavity”• Polyp, medusa, and planula body forms
CnidocyteLike Hickman Fig. 13-3
cnidocil ortrigger
nucleus
20 types of nematocysts!
2m/s
40,000x accel. gravity
A fearsome tiny weapon !
A combination of osmoticand hydrostatic pressureopens the opeculum forces outthe thread
Two Types of BodiesFig. 13.2
polyp(attached, mouth-up)
medusa(free-drifting, mouth-down)
Cnidarian Cell Types– Cnidocytes
• Stinging cells (penetrants, volvents, glutinants)– epithelio-muscular
• covering and muscular contraction, epidermal, shorten body or tentacles
– nutritive-muscular• Circulate water and food
– Gland• Secrete adhesive and create gas bubble
– sensory / nerve• Coordinate movement
– interstitial• Stem cells found at base of epitheliomuscular cells
Hydra Cell Typesfood in gastro-vascular cavity
gland cell
cnidocytes
epithelio-muscular cell
nutritive-muscular cell
mesoglea
interstitial cell
Cnidarian Life Cycles• Sexual medusa
– has gonads, produces gametes by meiosis• Drifting planula
– non-feeding, short-lived, settles in new location
• Asexual polyp– reproduces by budding
Obelia Life Cyclecompare Fig 13.9
planula larva
medusa
polyp
asexual buddingforms a colony
sexual fertilization
Aurelia Life CycleHickman Fig. 13.18
syphistoma strobila
Classification of the Cnidaria
• phylum Cnidaria– class Hydrozoa– class Scyphozoa– class Anthozoa
Class Hydrozoa
• Polyp usually dominant• Medusa is usually small and short-lived
– freshwater Hydra has no medusa OR planula
– medusas of one order (including Man-’o-War) remain attached to colony
• Some polyp colonies resemble hard corals– fire corals
Hydrozoan Polyp Colony
More Hydrozoans
A hydrozoan medusa
freshwater Hydra with ovary
float (modified polyp)gamete-producing medusoidsfeeding hydroidsstinging tentacles
HydrozoanMan-’o-War
Colonycompare Hickman
Fig. 13.14
Class Scyphozoa
• solitary medusa stage is dominant– some are nearly 10m long
• polyp small and short-lived– buds off juvenile medusas, not more
polyps• “true” jellyfish
ScyphozoaFig 13.19
Class Cubozoa• Formerly a subdivision of Scyphozoa
Class Anthozoa• medusa absent• Polyp dominant, often small but produces
large colonies in amazing forms– polyp produces gametes– sometimes compared to a sessile medusa– planula disperses
• hard and soft corals, sea anemones, sea fans, sea pansies, sea whips
AnthozoaFig. 13.21
Sea pen
Sea fan, whip coral
Sea anemone
The End.