Phylum Echinodermata lab notes

BIOL 3270
Zoology


DEUTEROSTOME PHYLA
CHARACTERISTICS
1) the blastopore forms the anus
2) the mouth forms as a new invagination on the anterior end of the gastrula
3) cleavage is usually radial
4) the mesodermal tissue forms by enterocoely (formed by out-pocketing of the archenteron).



PHYLUM ECHINODERMATA
1) Spiny skin
2) Reduced cephalization


Class Asteroidea (starfish)
CHARACTERISTICS
1) star-shaped with 5 rays projecting from a large central disc
2) Pentaradial symmetry (not symmetrical internally and larvae are bilateral)

Starfish
IDENTIFY
 Central disc
 Oral surface
 Ambulacral groove (where the tube feet are)
 Aboral surface
 Madreporite (‘pebble’ – opening to the water vascular system)
 Tube feet
 Mouth
 Anus

Starfish pedicellariae
IDENTIFY
 Epidermis
 Valve

Starfish tube feet
IDENTIFY
 Ampulla (suction cup)
 Podium
 Lateral canal
 Longitudinal retractor muscle
 Ampullary muscles

, DEVELOPMENT
Starfish early and late cleavage
 radial cleavage (will produce radial symmetry in adult)
 Relative allocation of cytoplasm to animal and vegetal poles
 Different cell stages

Starfish gastrula
 Anus

Starfish bipinnaria larvae
 Locomotor bands of cilia
 Mouth
 Stomach


Starfish (dissection)
EXTERNAL
 Central disc
 Ambulacral groove
 Ambulacral spine
 Mouth
 Podia (tube feet)
 Madreporite
 Anus

INTERNAL
 Stomach - cardiac (evert cardiac stomach); pyloric
 Pyloric cecum
 Ambulacral ridge
 Ampulla
 Gonads
 Water-vascular system: madreporite, stone canal, ring canal, lateral canal, radial canal,
podium

Questions
 How do the oral and aboral surfaces move (fast, slow)?
 Why do they move this way?
 How do they feed, and why is this an adaptation?




Class Ophiuroidea (brittlestar)
CHARACTERISTICS