chapter 22 echinoderms phylum...
TRANSCRIPT
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