CHAPTER 22

Echinoderms

Phylum Echinodermata

Characteristics

All members have a _____________________ skeleton

Spiny endoskeleton consists of ____________________

Unique _______________-_____________________ system

Possess _______________________ and dermal ______________________

______________________ symmetry in adults

Phylum Echinodermata: Diversity

Asteroids or _______________________

Mostly ________________________

Ophiuroids or ________________________

Move by bending their __________________________ muscular arms

May be scavengers, browsers, or commensal

Holothurians or ______________________

Mostly ________________________ or deposit feeders

Echinoids or _________________________

Found on hard bottoms while sand dollars prefer sand substrate

Feed on _______________________

Class Asteroidea

Diversity

Common along __________________________ and may aggregate on rocks

Some live on muddy or sandy bottoms, or among _____________________ reefs

Approximately 1500 living species

Range from a centimeter across to about a ________________ across and may be brightly colored

Form and Function

External Features

Have a _______________________ disc with tapering arms extending outward

Body is flattened and flexible, with a pigmented and ciliated _______________________

Mouth is on the _________________________ or ________________ surface

______________________________ runs from the mouth to the tip of each arm

Usually there are _________ arms but there may be more

Ambulacral groove bordered by rows of ___________________ feet

_________________________ nerve located in center of each ambulacral groove

Under the nerve is an extension of the coelom and the _________________ canal of the water-

vascular system

_______________________ or other dermal tissue covers these structures

_______________________ surface is spiny

At base of spines are groups of ____________________-like pedicellariae

Keep the body surface free of ____________________

___________________ (dermal branchiae or skin gills) are soft projections

Function in _________________________

On the aboral side is a circular __________________________

Sieve leading to the water-vascular system.

Endoskeleton

Under the epidermis is the mesodermal _________________________

Small calcareous plates or _____________________

Bound together by an unusual form of mutable (change) collagen termed

___________________ collagen

Ossicles penetrated by meshwork of spaces filled with fibers and dermal cells, the

________________________

Muscles in the body wall move rays and partially close ambulacral grooves

Coelom, Excretion, and Respiration

Spacious body coelom filled with ____________________ is one coelomic compartment

Fluid contains amebocytes (_______________________)

_____________________ peritoneal lining of coelom circulates fluid around the cavity and into

papulae

Respiratory ______________ and _________________ diffuse across the papulae and tube feet

Some wastes are picked up by __________________________, which migrate to exterior

Water-Vascular System

This system is unique to echinoderms

Consists of system of ______________, _____________ feet, and ________________ ossicles

Functions in ___________________, food-gathering, ___________________, and

____________________

Opens to outside at ______________________ on aboral side

Madreporite leads to _________________ canal, which joins the ________________ canal that

encircles the mouth

____________________ canals diverge from ring canal and extend into each ray

____________________ vesicles may also be attached

Function in fluid storage and regulation of internal ____________________ of water

vascular system

Inner end of each tube foot called an _____________________

Lies within the coelom

Outer end of each tube foot bears a ____________________

Water-vascular system operates __________________________

_____________________ in lateral canals prevent backflow

Muscles in ampulla contract forcing fluid into and __________________________ the tube feet.

Small _________________ canals, each with a one-way valve, connect radial canal to tube feet

Contraction of ___________________________ muscles in tube foot retracts it, forcing fluid

back into the ampulla

Small muscles in end of the tube foot raise the middle section, creating ___________________

Sea star can move while being firmly adhered to the substrate

Move in one direction but not in unison

Cutting a ______________________ nerve ends coordination in one arm

Cutting a ______________________ nerve ring stops all movement

Feeding and Digestive System

Mouth leads through a short esophagus to large central _______________________

Lower __________________ part of stomach can be everted through the mouth during feeding

Upper stomach is smaller and connected by ducts to a pair of ____________________ ceca in

each arm

__________________ is difficult to see

Consume a wide range of food

Sea urchins

Molluscs

Sea stars pull _____________________ apart and evert stomach through crack

Small particles carried up ambulacral grooves to mouth

Hemal System

System of tissue strands enclosing unlined _______________________

Hemal system may play a role in distributing ______________________

Nervous System

The ________________ system of a nerve ring and radial nerves coordinate the tube feet

_____________________ system aboral to oral system forms ring around anus and extends into

roof of each ray

_____________________ nerve plexus coordinates responses of dermal branchiae to tactile

stimulation

___________________ organs are scattered over the surface and an ___________________ is at

tip of each arm

React to touch, temperature, chemicals, and light intensity

Mainly active at ____________________

Reproductive System, Regeneration, and Autonomy

Sexes __________________ in most

Pair of _____________________ in each interradial space

Fertilization is ______________________

Eggs and sperm are shed into the water in early summer

__________________________ lost parts

Cast off injured arms and regenerate new ones

An arm can regenerate a new sea star if at least one-________________ of central disc is

present

Free-swimming larva, ______________________, has cilia arranged in bands

Ciliated tracts become larval ________________

Larva grows three adhesive arms and a sucker at the anterior

Now called a ___________________________

Brachiolaria attaches to substrate and undergoes metamorphosis into a _________________

juvenile

Arms and tube feet appear, animal detaches from stalk and becomes a young sea star

Class Ophiuroidea

Form and Function

Largest in number of species

Over 2000 species

Arms of ________________________ stars are slender and distinct from the central disc

Lack _______________________ or ______________________

Ambulacral groove is _____________________ and coated with ossicles

Madreporite is on the ___________________ surface

Tube feet lack _________________ and ____________________

Each jointed arm has a column of articulated ossicles called ________________________

Arms are moved in _________________ for locomotion

Five movable plates act as ___________________ and surround mouth

No ___________________

Skin is leathery and surface cilia are mostly lacking

Class Echinoidea

Diversity

Approximately 950 species of living echinoids

Sea urchins lack _____________________ but their tests show five-part symmetry

Up-folding brings the ambulacral areas up to the area of the __________________

Most sea urchins have a hemispherical shape with ________________ symmetry and long spines

Sand dollars and heart urchins (___________________ echinoids) have become bilateral with

short spines

Echinoids occur from intertidal regions to deep ocean

Form and Function

Echinoid test has movable, stiff _____________________

Tube feet extend along the 5 ambulacral rows

Spines articulate on “______________-and-_____________” joints moved by small muscles at

the bases

Some species have pedicellariae with ______________________ glands that secrete a toxin that

_______________________ small prey

5 converging teeth

Anus, genital pores, and madreporite are ______________________-

Inside the test is Aristotle’s lantern

Complex set of _____________________ structures

Ciliated siphon connects esophagus to _________________________

Food can be concentrated in the intestine

Sea urchins are largely omnivorous

But primary diet consists mainly of _________________

Sand dollars filter particles through spines

Class Holothuroidea

Diversity

Approximately 1150 species of holothuroids

As common name suggests, these animals resemble _______________________

Greatly _______________________ in the oral-aboral axis

Ossicles are greatly reduced and body is soft/__________________________

Some species crawl on the ocean bottom, others are found under rocks or burrow

Form and Function

Most have tube feet only on the ambulacra that faces the substratum (the ______________).

There may be three ambulacra

All tube feet, except oral tentacles, are absent in burrowing forms

________________ tentacles are 10–30 tube feet surrounding the mouth

Digestive system opens into a ____________________

_________________________ tree also empties into cloaca

_________________________ lies free in the coelom

Respiratory tree also serves for ___________________________

_____________________ exchange also occurs through the skin and tube feet

Sea cucumbers use ventral tube feet and muscular body waves to move

Some trap particles on the mucus of tentacles

Others graze sea bottom with tentacles

Cast out part of _______________________________ when irritated

Must regenerate these tissues

One small fish, Carapus, uses the ____________________ and respiratory tree of a sea

cucumber for shelter