Zoology Chapter 16: Echinoderms

Phylum Echinodermata

Name literally means spiny skin, members have a calcareous endoskeleton, no head, complete digestive system, pentaradial symmetry in adults and bilateral larvae

Ossicles

Calcium carbonate plates that form the endoskeleton in Echinoderms

Water-filled Vascular System

water-filled canals used for locomotion, attachment, and/or feeding

Ring Canal

part of the water-filled vascular system that surround the mouth

Radial Canals

branch from the ring canal (arms); part of the water-filled vascular system

Lateral Canals

branch off the radial canals; part of the water-vascular system

Tube Feet

at the end of the lateral canals (often with suction cups)

Madreporite

sieve-like opening into the water-vascular system; "sifts" and "strains" the water as it inters the system; the "mother pore"

Hemal System

consists of strands of tissue that circulate fluid and may aid in transporting molecules; sea star "blood"

Nervous System of Echinoderms

includes a nerve net and nerve ring; sensory receptors (light, chemical, and mechanical) on body surface and tube feet

Excretory System of Echinoderms

gases, nutrients, and metabolic wastes diffuse across tube feet and other structures (mostly ammonia)

Pedicellaria

pincer-like, claw shaped structure on the outside of the body wall used for cleaning and protection

Echinodermata Reproduction

mostly sexual reproduction, dioecious, external fertilization; free-swimming, bilateral larvae

Asexual Reproduction in Echinoderms

the ability to regenerate lost arms (common) or even an entire different organism if a portion of the central disc is present (only in certain species)

Class Asteroidea

Sea Stars; brightly colored, 5 arms generate from central disc, predators (on snails, crustaceans, bivalves) or scavengers (detritus); everts stomach into bivalves to weaken adductor muscles

Class Ophiuroidea

Brittle stars and basket stars; largest echinoderm class; move in a snake-like motion

Class Echinoidea

Sand Dollars and Sea Urchins; have an endoskeleton fused into a test; no arms but show pentaradial symmetry; feed on algae, invertebrates, and detritus

Test

the endoskeleton of sea urchins fused together

Aristotle's Lantern

the chewing mouth part of a sea urchin

Class Holothuroidea

Sea Cucumbers; "earthworms of the sea"; soft muscular body, elongated shape; lie on the bottom of the ocean floor; consume organic matter; tentacles around mouth; respiratory trees pump water through the body

Class Crinoidea

Sea Lilies and Feather Stars; most primitive echinoderm class; Filter Feeders: Sea Lilies are stalked and sessile, Feather Stars swim and creep

Stone Canal

Connects the madroporite to the ring canal

ampulla

Muscular structure used to expand and contract the tube feet

pedicellaria

Small pincer like spines used for cleaning

Dermal Branchiea

Spines used for gas exchange

pyloric cecum

Large digestive organs found in the arms of asteroidia

dioecious

Organisms with individual males and females

monecious

Organism with both male and female reproductive organs in one body.

Ophiuroidea (photo)

Asteroidea (Photo)

Crinoidea (photo)

Holothuroidea (photo)

Echinoidea (Photo)

Autotomy

Defense mechanism where organism can detach and leave parts of their body to the predator and escape

Sea Cucumber

Oral

Side of echinoderm with the mouth

Aboral

Side of echinoderm that does not contain the mouth

regeneration

Ability to regrow lost body parts, a characteristic of echinoderms

Central Disk

Portion of body from with the arms extend, often contains the madreporite

Number of stomach in sea stars

Two - cardiac and pyloric, cardiac stomach can extend out of body, pyloric cannot