Invertebrates - Echinodermata (Sea stars, sand dollars)

echinodermata

sea stars and sand dollars

what species are echinodermata?

exclusively marine

larve body plan

bilateral

adult body plan

radial or pentaradial (arms of 5 or more)

hox genes

control the change from bilateral to radial symmetry

tissue types

triploblastic and eucoelomate

protosome or deuterosome

deuterosome

ossicles

bones that are an endoskeleton, covered by epidermis

each arm/section…

has digestive glands, gonads, and tube geet

tube feet

help with moving, feeding, sensing environment, and sticking to substrate

water vascular system

— central canal with radial canals in each arm

— radial canal collected to tube ffit

— tube fit extend or retract depending on amount of water present in the radial canal

nervous system

- simple

— central nerve ring and radial ring in each arm

- no brain but sensory organs

respiratory system

Gas exchange occurs through water vascular system

circulatory system

hemal system

hemal system

— vessels parallel to water vascular system

— circulates nutrients

— removes metabolic waste products

digestive system

mouth on ventral side, anus on dorsal side

reproduction

- dioecious

— external fertilization, produce bilateral larvae

— can reproduce asexually by fragmentation

class asteroidea

- five thick arms extending from central body

— sea stars

class ophiuroidea

- five long, thin arms extending from central body

— brittle stars

class echinoidea

— no arms, hemispherical shape with tube ffit

— sand dollars

class crinoidea

— sea feathers and sea lillies

class holothuroidea

exhibit "functional" bilateral symmetry as adults

— sea cucumber