Bi 212: Lecture 6Bi 212: Lecture 6

Phylum Echinodermata

Phylum Echinodermata:Phylum Echinodermata:Spiny-skinnedSpiny-skinned

Evolutionary relationshipsEvolutionary relationships

and HOX genes

Deuterostomes!

Echinodermata: 4 key featuresEchinodermata: 4 key features Calcareous internal skeleton

Parts: Plates, spines and pedicellariae

Why considered “internal”? Symmetry

Bilateral symmetry (larvae) Pentamerous radial symmetry

(adults) Water vascular system

Derived from coelom Layout (next slide shows…) Key function: tube foot control Other functions

Mutable connective tissue What does this mean?

Body plan: Other aspectsBody plan: Other aspects Perivisceral coelom

Houses organs Gas exchange Hydrostatic skeleton

Digestive system Can be highly branched Complete in some

Nervous system No brain Branches parallel water

vascular system Sensory (sea stars)

Eye spots Receptors associated with

tube feet No circulatory system No excretory system

Class Asteroidea: Class Asteroidea: sea starssea stars

Feeding Stomach eversion Enzymes

Respiration Tube foot ? ? Dermal papulae

? Protection

Mechanisms?

Class Echinoidea:Class Echinoidea:Sea urchins and othersSea urchins and others

Feeding Aristotle’s lantern Main type of food?

Respiration Tube foot ? ? Peristomial gills ?

Protection Mechanisms?

Class Holothuroidea: Sea Class Holothuroidea: Sea cucumberscucumbers

Symmetry? Feeding

Deposit feeders (what does this mean?)

Respiration Respiratory tree?

Water entry into tree?

Body surface ? Tube feet ? ?

Protection Cuvarian tubules Evisceration…

Class Ophiuroidea:Class Ophiuroidea:Brittle stars, basket starsBrittle stars, basket stars

Class CrinoideaClass CrinoideaSea liliesSea lilies