phylum echinodermata introduction. about 6000 species, all marine echinodermata
TRANSCRIPT
Phylum EchinodermataIntroduction
• About 6000 species, all marine
Echinodermata
• secondary pentamerous radial symmetryinternal skeleton
• water vascular system
Echinodermata Major characteristics
Water Vascular System
• Madreporite
• stone canal
• ring canal
• radial canal
• lateral canals
• Ampulae
• tube feet
CLASSIFICATION OF ECHINODERMATA
• Class Asteroidea
• Class Ophiuroidea
• Class Echinoidea
• Class Holothuroidea
• Class Crinoidea
Class AsteroideaTrue Starfishes
Class Asteroidea True Starfishes• arms not sharply
delineated from central disc
• tube feet with suckers; used for– Locomotion– obtaining food
• madreporite and anus aborally located
• some have pedicellariae - jawlike appendages of epidermis
• Feeding– Mouth– cardiac stomach-
can be extruded– pyloric stomach– pyloric caecae– Anus
– feed primarily on sessile organisms
Class Asteroidea True Starfishes
• Circulation– poorly developed with fluid filled chambers;
– no heart; coelom ciliated for fluid movement
• Excretion– no special organs
– general diffusion across body surfaces like tube feet
• Respiration– no special organs
– across body membranes
• Nervous System– associated with epidermis
– circular oral nerve ring with branches into arms
Class Asteroidea Systems
• Epidermis- outer surface; includes – mucous cells– epithelium– Pedicellariae- jawlike appendages of the epidermis
• can open and close• used to clean body of debris or put debris on body
• Dermis- includes – nerve cells– connective tissue
• Skeleton- below dermis– made of ossicles– lattice like connections– Calcium carbonate– with spines and tubercles
• Muscle layer- below dermis• Peritoneum that lines coelom
Asteroidea Body wall
• are dioecious; external fertilization
• usually 10 gonads; 2 in each arm
• have fissiparity- division of central disc into two animals
Asteroidea Reproduction
• free living larvae
• bipinnaria- first larval form develops into
• brachiolaria - shows development of arms
Asteroidea Reproduction
Class OphiuroideaBrittle Starfishes
• 5 arms usually
• central disc well marked off, no branches of gut in arms
Class OphiuroideaBrittle Starfishes and Basket Stars
• no anus, no ambulacral groove
• madreporite on oral surface
• no suckers on tube feet, no ampullae (have a valve to control pressure)
• no pedicellariae• able to move quickly
and snake like hence their class name
Class OphiuroideaBrittle Starfishes and Basket Stars
Class Echinoideasea urchins, sea bisquits, sand dollars
• no arms• skeleton is
fused into a solid test
• tube feet have suckers
• covered with moveable spines and pedicellariae
Class Echinoidea
Class Echinoideaspecialized mouth structures - Aristotle's Lantern
Class Holothuroidea Sea cucumbers
• body elongated in oral-aboral axis
• skeletal system reduced or absent
• no spines or pedicellariae
• mouth and anus at opposite ends of body
Class Holothuroidea Sea cucumbers
• no external madreporite
• tube feet with suckers• respiration through
anal respiratory tree• dioecious; single gonad• suspension or detritus
feeders • commensal
relationship with pearl fish
Class Holothuroidea Sea cucumbers
Class Crinoidea Sea Lillies
• most are extinct• most primative• all sessile, with
stalk that attaches to substrate
• have branched arms for filter feeding
• no suckers on tube feet
• no madreporite• no pedicellariae
Class Crinoidea Sea Lillies