L13 Echinoderms Flashcards
Which evolutionary lineages are the echinoderms in?
Deuterostomes
What are deuterostomes?
Blastopore becomes the anus, radial and indeterminate cleavage
What are the general characteristics shared by the deuterostomes?
Display pentamerous, radial symmetry
Body can be divided into five parts - not related to other radially symmetrical groups
Triploblastic
Coelomate
Bilateral symmetry exhibited in the larvae
What is the evidence that they reverted back to being radially symmetrical?
Bilateral larvae
how genes expressed in same order as bilateral larvae
What is the internal skeleton made of?
Ossicles - crystal structure separated by tissues, made of co3, can increase in size without moulting
What are tube feet and how are they moved?
Podia, unique in the echinoderms, used for locomotion, feeding and respiration.
Movement is generated by the water vascular system.
What is the water vascular system?
System of canals that uses sea water, circular central canal, and radial down each arm. Used to control ampulla, which control the podia. Valves open and close, controlling the amount of water in the podia
What are the different classes in the echinodermata?
Asteroidea, Echinoidea, Ophiuroidea, Crinoidea, Holothuroidea
What are the Asteroidea and what are the general characteristics?
Starfish
Exclusively marine
Nervous system is a nerve net, all arms connected by radial nerve ring
Arms used to grab and take in prey
Food passed to mouth along ambulacral groove
What are the Ophiuroidea and what are the general characteristics?
Brittle stars No ambulacral groove Podia used in suspension feeding Move by thrashing arms Bursal slits for respiration Can change colour with chromatophores in skin Ossicles more prominent - very flexible
What are the Echinoidea and what are the general characteristics?
Sea urchins
Spines, which are used for movement and defence
Ossicles fueses into a test
Aristotles lantern - modified ossicles forming teeth like structures
Oral and aboral surface
May be asymmetrical - almost bilateral
e.g. sea potato
What are the Holothuroidea and what are the general characteristics?
Sea Cucumbers
Bilateral symmetry can be seen
Deposit or suspension feeders
Reduced/absent ossicle
Large podia on dorsal side for locomotion
Can produce holothurin toxin
Can change rigidity as connective tissue is mutable
Can release internal organs out of body and regenerate
Respiratory trees branch from anus
What are the Crinoidea and what are the general characteristics?
Sea lollies and feather stars Most ancient groups, have form of ancestral types Found in deep sea Attached or swimming Suspension feeders Ossicles present in calyx
