Echinoderms 2025

Phylum Echinodermata

Marine animals with calcareous endoskeleton, a complete digestive system, radial symmetry in adults and bilateral larvae

Ossicles

Calcium carbonate pieces of the endoskeleton, each piece is made inside a cell and secreted

Water Vascular System

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

Parts of water vascular system

Madreporite (sieve), ring canal, radial canals, tube feet

Tube Feet

at the end of the radial canals, often with suction cups, one animal may have 1000s

Madreporite

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

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 structures on the outside of the body wall used for cleaning and protection

Echinodermata Reproduction

mostly sexual reproduction, external fertilization; free-swimming larvae

Asexual Reproduction in Echinoderms

can 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; typically have 5 arms radiating from central disc, predators or scavengers; everts stomach into bivalves to weaken adductor muscles

Class Ophiuroidea

Brittle stars and basket stars; largest echinoderm class; move arms 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

solid, inflexible endoskeleton of urchins, ossicles fused together

Aristotle's Lantern

the chewing mouth part of a sea urchin, made of ossicles and muscles, the tips of the teeth are very hard, teeth grow continuously

Class Holothuroidea

Sea Cucumbers; 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 madreporite to the ring canal, named because it is reinforced with plates of CaCO3

ampulla

the bulb of the tube feet, muscular structure used to expand and contract the tube feet

Dioecious

Organisms with individual, or separate sexes, males and females

Ophiuroidea (photo)

This animal belongs to the class

Asteroidea (Photo)

This animal belongs to the class

Crinoidea (photo)

This animal belongs to the class

Holothuroidea (photo)

This animal belongs to the class

Echinoidea (Photo)

This animal belongs to the class

Autotomy

Defense mechanism where organism can severe a body part (usually an arm) and leave it behind to escape from a predator

Evisceration

sea cucumbers eject internal organs to trap or deter a predator, involves liquifying and rupturing of connective tissue, all lost parts will eventually reform

Oral

Side of organism where the mouth is found

Aboral

Side of organism without a mouth

Literal meaning of the word echinoderm

spiny skin

regeneration

Ability to regrow lost body parts

Central Disk

Portion of body from which the arms radiate

Cardiac stomach

positioned on the oral side and can be expelled for extracellular digestion

6

Number of Maine fishermen with active sea cucumber licenses

at least 66, but probably more

Number of sea cucumber species that are overexploited worldwide

Orange-footed cuke

Maine's only commercially important sea cucumber species

Catch tissue

Mutable connective tissue whose stiffness can be rapidly & dramatically altered, helps echinoderms stay in position without using much energy

Suction, ionic interactions, and gland that secretes adhesive substance

How tube feet attach to a solid surface

Picture of Aristotle's Lantern

Cilia

Line inside of water-vascular system and cause the water to circulate

85

Number of echinoderm species that are known to be toxic

Calcite crystals

Found on aboral surface of brittle stars, are lenses that focus light on nerves = "eyes"

Picture of bipinnaria, early sea star larva

Digestive system only in the central disc, has a mouth, no anus, have multiple madreporites on the oral surface and slits called bursae, many hide during the day

What's odd, or unique, about brittle stars

Deposit feeders

Ingest sediments and remove organic material on and in the particles, capture small organisms in sediment

bivalves, sponges, gastropods, worms, and other echinoderms

What sea stars like to eat

Animals that belong to the phylum Echinodermata

sea stars, sea urchins, sea cucumbers, sea lilies, and sea feathers

Picture of pluteus, larval urchin

Picture of ossicles in sea star skeleton

Picture of brachiolaria, later sea star larva

Picture of baby sea star, still pretty microscopic