Chaetognaths, Echinoderms, and Hemichordates Flashcards

Flashcards about Chaetognaths, Echinoderms, and Hemichordates

What are Chaetognaths?

Small group of about 100 genera with straight bodies that resemble torpedoes or darts, generally pelagic marine predators commonly called arrow worms.

What are the three sections of a Chaetognatha's body?

Head, trunk, and postanal tail.

What does the head of a Chaetognatha contain?

A large vestibule with teeth flanked by curved chitinous spines used for seizing prey.

Are Chaetognatha hermaphroditic?

Hermaphroditic with either cross- or self-fertilization.

What are Xenoturbellida?

Yellowish, wormlike ciliated body form that reaches 3 cm in length and feeds on bivalves and bivalve eggs.

What are the shared characteristics of the clade Ambulacraria, which contains Echinodermata and Hemichordata?

Share a three-part (tripartite) coelom, similar larval forms, and an axial complex made of highly specialized metanephridia.

What are two characteristics that all members of the phylum Echinodermata have?

External spines or protuberances and a calcareous endoskeleton consisting of plates or scattered ossicles.

What unique features do echinoderms possess?

Water-vascular system, pedicellariae, dermal branchiae, and pentaradial symmetry in adults.

What are the five classes of Echinodermata?

asteroids (sea stars), ophiuroids (brittle stars), holothurians (sea cucumbers), echinoids (sea urchins), and crinoids (sea lilies and feather stars)

What type of connective tissue do mesodermal endoskeletons bind together with?

mutable collagen called catch collagen that can be changed from liquid to solid by nerve control

What functions does the water-vascular system serve in echinoderms?

Locomotion, food-gathering, respiration, and excretion.

Where does the water-vascular system open to the outside?

The madreporite on the aboral side.

What are the two parts of an asteroid's stomach?

Lower cardiac and upper pyloric where short intestine leads aborally from stomach to intestinal ceca and then to anus.

What are the three distinct units of the sea star nervous system?

The oral system of a nerve ring and radial nerves in each arm that coordinate the tube feet, the deeper hyponeural system forming a ring around anus and radial nerves, and the epidermal nerve plexus that coordinates responses of dermal branchiae.

From what body part can some species of sea stars regenerate a completely new sea star body?

Detached arm.

What are small, disc-shaped animals discovered in deep water off New Zealand called?

Sea Daisies.

What are some ways that brittle stars differ from sea stars?

That they lack pedicellariae or papulae, ambulacral groove is closed and coated with arm ossicles, tube feet lack suckers and aid in feeding but have limited use in locomotion, and the madreporite is on the oral surface.

How do ophiuroids feed?

Browsing or suspension feeding on small particles, with some being carnivorous.

What are the characteristics of brittle star test.

Compact body enclosed in an endoskeletal test; they lack arms but their tests show five-part symmetry with five ambulacral areas.

What is the difference between regular and irregular urchins?

Regular urchins have a hemispherical shape with radial symmetry, while irregular urchins (sand dollars and heart urchins) are bilateral with short spines.

What complex set of chewing structures is inside the echinoid test?

Aristotle's lantern.

Which class of echinoderms contains members that are both structurally strange and physiologically odd?

Holothuroids

What are the physical characteristics of holothuroids (sea cucumbers)?

Greatly elongated in the oral-aboral axis with ossicles are reduced (soft body).

What features do sessile forms of calyx have that other forms don't?

They have cirri.

What are the characteristics of hemichordates?

Vermiform bottom dwellers, living in shallow waters with cosmopolitan distribution, are fragile and secretive, and are mostly sedentary or sessile.

What is the name for acorn worms, which are sluggish, wormlike creatures that live in burrows in the mud and sand?

Enteropneusts.

What are the three distinct regions of an enteropneust's body?

Tongue-like proboscis, short collar, and long trunk.