Echinodermata Characteristics Quiz

Characteristics of Echinodermata

• Echinoderms are classified as deuterostomes, exhibiting unique developmental patterns.
• Adults feature radial symmetry, with a five-part body plan.
• Internal skeletons are composed of calcareous ossicles.
• A water vascular system facilitates movement through tube feet.
• Notable for regeneration abilities, all members are exclusively marine.

Ossicles

• Ossicles are calcareous plates forming the internal skeleton of echinoderms, providing structural support.

Phylum Members

• Common members of Echinodermata include sea stars, sea urchins, sand dollars, and sea cucumbers.

Etymology

• The term "Echinoderm" derives from Greek, with "echino" meaning spiny and "derm" meaning skin.

Classification of Echinoderms

• The five classes of echinoderms are distinguished by the arrangement of their ossicles.

Dermal Gills

• Dermal gills are small projections that assist in respiration and excretion through diffusion.

Pedicellariae

• Tiny pincers called pedicellariae maintain the body surface cleanliness by removing debris.

Madreporite

• The madreporite is an opening that filters water into the echinoderms' water vascular system.

Ambulacral Structures

• An ambulacral groove is a channel on the oral side where tube feet extend.
• The ambulacral ridge lies at the top of the groove, harboring the radial canals.

Class Specifics

• Class Asteroidea includes sea stars, characterized by small, blunt spines.
• In oral view, sea stars display tube feet, arms, spines, mouth, and ambulacral groove.
• Aboral view shows arms, anus, spines, central disk, and madreporite.

Larval Symmetry

• The bipinnaria larval stage of sea stars exhibits bilateral symmetry.

Other Classes

• Class Ophiuroidea consists of brittle stars.
• Class Crinoidea includes sea lilies and feather stars.
• Class Echinoidea comprises sea urchins and sand dollars.
• The test in echinoids is a solid structure formed by fused ossicles.

Noteworthy Structures

• Aristotle's lantern refers to sea urchins' oral apparatus for grazing; it consists of five ossified plates.
• The sea urchin's test exhibits pentaradial symmetry characteristic of adult echinoderms.

Class Holothuroidea

• Sea cucumbers belong to this class and have unique adaptations.

Evisceration

• Evisceration is a defense mechanism in sea cucumbers involving the forceful expulsion of internal organs.

Water Vascular System

• This system comprises canals filled with a watery fluid, enabling tentacle and tube foot movement.