06 Chap 13 Cnidaria and Ctenophora
Transcript of 06 Chap 13 Cnidaria and Ctenophora
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.