Zoology unit 14

What type of animal are starfish?

Echinoderms

What is the first developmental stage of enterolocoelous deuterostomates?

Fertilization of egg and sperm

Single fertilized egg is a

Zygote

What begins after the fertilization of a starfish egg?

A period of rapid cleavage by mitosis

Mitosis produces a greater number of

Progressively smaller cells

What structure is produced by the cleavage of a fertilized starfish egg and is hollowed out in the center?

Blastula

New tissue layer produced by

Budding on the ectoderm

Ectoderm, mesoderm, endoderm

Become skin, muscles/connective tissues, and the digestive tract

What process transforms the blastula into a gastrula with two distinct layers?

Invagination

What are the two distinct tissue layers produced during gastrulation?

Ectoderm and endoderm

What is produced when the digestive tract of a starfish is completed?

Bipinnaria

What is the next stage after bipinnaria in starfish development? When the digestive tract migrates (the mouth and anus migrate to the left and right side)

Brachiolaria

What marks the oral side of a starfish?

The mouth

What marks the aboral side of a starfish?

The anus

What allows a young starfish to attach during its temporarily sessile stage?

Adhesive pads

What is created after a short period of sessile existence in starfish development?

A young sea star

Echinoderms examples

Brittle Star, sea cucumber, sea star, sand dollar, sea urchin, crinoids

What is a defining characteristic of deuterostomes?

The second opening in the blastula becomes the mouth during early embryonic development. (Then the digestive system reverses again)

What does the blastopore become in deuterostomes?

The blastopore becomes the anus.

What type of coelomates do deuterostomes develop into?

Deuterostomes develop into enterocoelous coelomates.

enterolocelous ceolomate

anus develops first

endoskeleton of echinoderms

Composed of calcarous plates (ossicles) held in place by collaged ligaments and movaable under the control of muscles (skeleton?)

What type of symmetry do larvae in echinoderms exhibit?

Bilateral symmetry

What type of symmetry do adult echinoderms exhibit?

Pentaradial symmetry (5 axes)

What happens to the symmetry of echinoderms during metamorphosis?

They change from bilateral symmetry to pentaradial symmetry.

What are some degenerate features of adult echinoderms?

No head end or brain, few specialized organs.

What is the status of the blood vascular system in echinoderms?

It is absent or reduced.

What type of epidermis covers phylum Echinodermata?

Pigmented epidermis

What are the spines in phylum Echinodermata derived from?

Ossicles

Ossicles have

Plates composed of calcium salts beneath the epidermis (collected by cords of collagen-hold form w/out musc. Movement) Cords of muscle that allow free movement

Ossicles are able to move by

Cords of muscle that allow free movement

What are pedicellaria in Echinodermata?

Tiny pinchers that aid in food capture and keep the surface clean

What are papulae in Echinodermata?

Extensions of the coelom through the skin that allow diffusion of gases and wastes

What are ossicles in Echinodermata?

Plates composed of calcium salts located beneath the epidermis

What connects the ossicles in Echinodermata?

Cords of collagen that can change state between flexible and rigid

What allows free movement in Echinodermata?

Cords of muscle

What surrounds the oral side of Echinodermata?

Nerve ring

What do the nerves in Echinodermata do?

Radiate into the arms

Where are tactile receptors found in Echinodermata?

Embedded in the epidermis and on sensory tentacles

What type of eye do Echinodermata have?

Single eye (ocelli) at the tip of each arm

Where is the mouth located in the digestive system of phylum Echinodermata?

On the oral (lower) surface

What type of parts does the mouth of Echinodermata have?

Chewing parts or a beak

What is unique about the cardiac stomach in Echinodermata?

It can be everted to allow external digestion! (Closest to outside)

What connects the cardiac stomach to the ceca in Echinodermata?

The pyloric stomach

What do the ceca in Echinodermata do?

They carry nutrients into each arm

Circulation is

Rudimentary and unrelated to circ. Of body fluids

Circulatory fluid

Surrounds stoughmach and extends into arms

Circulation may assist

In distributing nutrients (to ceca)

What is the primary function of the water vascular system?

Provides locomotion.

How does water enter the water vascular system?

Through the madreporite.

What is the pathway of water in the water vascular system after entering through the madreporite?

It passes down through the stone canal and then to the ring canals.

What do the radial canals in the water vascular system distribute?

Water to the radial arms.

What are the bulbs in the water vascular system called?

Ampullae.

What is the function of the ampullae in the water vascular system?

To force water into the tube feet under the control of muscles.

What is the coelom filled with in the context of excretion and reproduction?

Fluid and unspecialized cells.

Coelom bathes

Internal organs

How are nitrogenous wastes excreted and gases exchanged in the organism?

Through papulae.

Are the sexes separate or combined in this organism?

The sexes are mostly separate (dioecious) (not dimorphic)

What type of gonads do these organisms have?

Radial gonads - gametes spread externally.

What regulates the secretion of hormones from the gonads?

Secretions of neurosecretory cells.

What is autonomy in the context of this organism?

The ability to cast off an injured body part.

What does regeneration allow in these organisms?

It allows arms to grow back, requiring some part of the central disc to remain.

Class Asteroidea are

sea stars

What is the symmetry type of Class Asteroidea in adults?

Pentaradial symmetry

Where is the oral side located in Class Asteroidea?

Underneath

Where is the aboral side located in Class Asteroidea?

Above

What runs down the center of the radial arms on the oral side of Class Asteroidea?

Ambulacral groove

What happens to the ambulacral groove when the tube feet are extended in Class Asteroidea?

It is open (when tube feet are extended)

What are the sea stars tube feet surrounded by

Spines

How many radial arms do most Class Asteroidea have?

Usually five

What type of larvae does Class Asteroidea develop from?

Bilateral larvae (bipinnaria)

What is the name of the pentaradial adult form of Class Asteroidea?

Brachiolaria

Class Ophiuroidea are

brittle stars

What is the class of organisms that retains pentaradial symmetry?

Ophiuroidea

How are the arms of Ophiuroidea distinguished from the oral disc?

The arms are more sharply set off from the oral disc.

Do Ophiuroidea have pedicellaria or papullae?

No, they do not have pedicellaria or papullae.

What type of skin do Ophiuroidea have?

Leathery skin with spines.

How are the ambulacral grooves in Ophiuroidea characterized?

They are closed and covered with ossicles.

What is unique about the tube feet of Ophiuroidea?

They lack suckers for feeding but have limited use in locomotion.

What are the arms of Ophiuroidea made of?

Jointed ossicles (vertebrae) connected by muscles and covered by more plates.

What surrounds the mouth of Ophiuroidea?

Jaw-like plates.

Do Ophiuroidea have a stomach with an anus?

No, they have a stomach without an anus.

Where are the organs located in Ophiuroidea?

All organs are located in the central disc.

How do the water vascular, nervous, and hemal systems of Ophiuroidea compare to those of seastars?

They are all similar to those of seastars.

What is the typical activity pattern of Ophiuroidea?

They are largely nocturnal.

Where are the photosensitive structures located in Ophiuroidea?

On the aboral side.

What are the feeding habits of Ophiuroidea?

They are sediment and suspension feeders; some are carnivorous.

Class Echinoidea are

sea urchins and sand dollars

What is the defining characteristic of Class Echinoidea?

They lack arms but retain pentaradial symmetry.

In class echinoidea the ambulactal areas

Wrap around almost to the aboral side

How do echinoids move?

They move by tube feet with some assistance from pedicellaria.

What is the composition of the test in echinoids?

The test is composed of pairs of plates sutured together with rows of spines.

What is the function of the spines in echinoids?

The spines have a ball and socket joint with plates for movement.

What is Aristotle's lantern in echinoids?

It consists of 5 teeth that surround the mouth and extend internally for chewing.

What is the structure of the ambulacral grooves in echinoids?

The ambulacral grooves are closed with radial canals beneath.

How do tube feet function in echinoids?

Tube feet extend through the test, which is made of fused plates.

Do some echinoids have toxins?

Yes, some have soft tests but possess pedicellaria that have toxins.

Class Holothuroidea are

sea cucumbers

What is the general shape of organisms in Class Holothuroidea?

Elongated in the oral-aboral axis.

How are the ossicles in Class Holothuroidea characterized?

Reduced and mostly embedded in leathery dermis.