Echinoderms

Echinodermata meaning

Spiny skin

Echinoderms Body cavity, Symmetry, Skeleton, Digestive system, Circulatory system, Nervous system, Reproductive system, Gonads

Coelomate

Radially symmetrical

5 rayed (Pentaradial)

CACO3 skeleton (Calcareous)

Water vascular system (Gas exchange, feeding motion)

Complete Digestive system

Open/Reduced system (No heart

-Central ring and vessels

Reproduction

Sexual External

Ciliated, Free swimming larvae

Habitat

Sea coasts/Sea shores

Complexity

They are complex but radial

Classes of Echinoderms

Asteroidea (Starfish)-Space

Echinoidea (Sea urchins/sand dollars)-Echi (Ichy)

Holothuroidea (Sea cucumbers)

Ophiuroidea (Brittle stars)

Sea stars morphology (Symmetry, digestive system, habitat, light detecting)

1. Sea stars possess 5 or more arms radiating from a central disk

2. The mouth is on the oral surface (underside)

3. They are found worldwide in various shapes and color

4. Most have a simple light-sensitive eyespot at the end of each ray (arm).

Sea star stomachs

TWO STOMACH, Each with different function

1. Cardiac Stomach - Can be pushed outside of mouth to engulf and digest food and is brought INSIDE so Pyloric Stomach

2. Pyloric Stomach - Further digests food and moves it to the intestine and the anus - Allows Larger food to be consumed

Vascular system

Consists of a central ring and a series of canals that end in TUBE FEET. These tube feet are used for movement, feeding, and bringing in water for gas exchange.

Sea urchins characteristics (Size, shape, spines, digestive system)

Spines are 1-3cm and have a GLOBOID shape with NO RAYS OR ARMS up to 20cm

• Ball and socket joints allow them to move

• If you touch spine, then the spines will coverage there

• Have a MOUTH with 5 CaCO₃ teeth

• ARISTOTLES LANTERN

Aristotle Lantern

The mouth structure of sea urchins, composed of 5 calcium carbonate teeth and a fleshy tongue.

Spines (Echinoderms)

Spines are observed on many echinoderms, can be soft or hard and sharp, and deter predators.

Pedicellariae

Pincer-like structures that protrude from the body surface between the spines, keeping the body surface clear of encrusting organisms.

Defense Systems (Echinoderms)

Echinoderms utilize spines and pedicellariae as defense mechanisms. They also CAMOFLAGUE with their natural color into their environment.

Ecological roles (Echinoderms)

• Starfish prevent agal mats from growing on coral reefs

• After death-limestone formations +

• Part of the food chain and produce food for other creatures

• Ecosystem management and feed on dead/ decaying organisms

• Sea Cucumber provide habitats for parasites and when they burrow, they increase levels of oxygen and ecological tiering

• Sea Urchins release nutrients in rocks and they graze to reduce rate of colonization (Like worms)

• Sand dollars; burrow, they increase levels of oxygen and ecological tiering