Deuterostomes

Phylum echinodermata

• ancient group of marine animals, with about 6000 living species

• characterized by deuterostome development and an endoskeleton

What fundamental body shift does the echinoderm larva undergo during development?

larvae have bilateral symmetry and and adults have pentaradial symmetry

The echinoderm body plan was thought to have evolved from _______

a bilateral ancestor

What defines the oral surface?

the mouths

Echinoderm Endoskeleton

• found internal to a delicate epidermis which contains thousands of neurosensory cells

• nerve ring (nervous system)

• no brain

What is the endoskeleton composed of?

ossicles

Ossicles

composed of either moveable or fixed hard calcium carbonate plates 

In some animals tissue density can be changed, what is an example?

sea cucumbers can go from squishy to hard

What allows the extension of tube feet?

perforated by pores

Where is collagenous tissue located?

in the endo skeleton

What is the function of mutable collagenous tissue?

• provides ability to autotomize body parts

• regeneration (in starfish and brittle stars)

• Evisceration (in sea cucumbers)

Autotomize

cutting off body parts internally to escape predators/parasites

Evisceration

expel digestive system/respiratory tract in case of discomfort and can regenerate later

What does the hydraulic system do?

Aids in movement and feeding

What is the hydraulic system composed of?

a central ring canal from which 5 radial canals extend into each of the body’s 5 parts

Madreporite

opening for water entry into stone canal

Ampulla

muscular sac for tube feet control

What helps the organism move?

the contraction of ampulla muscles in different areas

True or False: Retractor muscles need to contract at the same time

False

What happens after the ampulla contracts?

water is forced into tube foot and the tube foot extends

What is another name for longitudinal muscles?

retractor muscles

Contraction of Longitudinal muscles

• unilateral contraction bends tube foot

• if all contract while ampulla is relaxed , water is forced back into ampulla

How does respiration occur?

through body wall and tube feet; no respiratory system

What type of circulatory system is present in echinoderms

open circulatory system

How is waste disposed of if there is no excretory system?

nitrogenous waste disposed of by diffusion through tube feet

Echinoderms have a _____ digestive system with _____ _____

complete, extracellular digestion

Reproduction

• gonochoric

• external fertilization

• free-swimming bilateral larvae

• some can reproduce asexually by splitting

free-swimming bilateral larvae

• develop in plankton

• metamorphose into sedentary adults

There are more than ____ extinct classes

20

How many extant classes are there?

5

What do all 5 extant classes have in common?

all have pentaradial symmetry

What are the 5 extant classes?

Asteroidea, Crinoidea, Echinoidea, Holothuroidea, and Ophiuroidea

Animals in Asteroidea

sea stars and sea daisies

Animals in Crinoidea

sea lilies and feather stars

Animals in Echinoidea

sea urchins and sand dollars

Animals in holothuroidea

sea cucumbers

Animals in ophiuroidea

brittle stars

Characteristics of Asteroidea

• predators in intertidal zone

• 5 arms (or multiples of 5)

Characteristics of Echinoidea

• feed mostly on algae

• no arms

• 5 rows of tube feet

• protective moveable spines

Characteristics of ophiuroidea

• detritovore

• 5 arms

• tube feed lack ampullae (used for feeding not locomotion)

• no anus (no complete gut)