Test 6 - Complex Animals - Echinoderms

What does Echino mean

Spiny

What does dermata mean

Skin

Body cavity status and symmetry

Coelomate, pentaradial

What is a common part found in their body structure (ray)

Five rayed, pentaradial

What type of skeleton

Calcareous

What vascular system does it have and what does it do.

Water vascular system, used for gas exchange, feeding, and locomotion

What digestive system

Complete

Describe their circulatory system

Open/reduced circulatory system, without a heart, with a central ring and vessels

Nervous system description

Simple radial nervous system, no brain

Reproductive system description

Gonads which take up significant space

Describe the reproduction

Sexual, dioecious, most external fertilization

Describe larva

Ciliated, free swimming

Where live

Abundant on most sea coasts especially on rocky shores

Four classes

Asteroidea, Echinoidea, Holothuroidea, Ophiuroidea

Examples of Asteroidea

Starfish

Examples of echinoidea

Sea urchins, sand dollars

Examples of holothuroidea

Sea cucumbers

Examples of Ophiuroidea

Brittle star

Sea stars possesses five or more

Arms which radiate from a central disk

Where are sea star mouth located

On oral surface underneath

Sea stars are found… in a variety of…

All over the world, variety of shapes and colours

Where are eye spots on sea star

Simple light sensitive eye spots at the end of each ray/arm

Describe the two stomachs of sea stars and their functions.

1. Cardiac stomach: pushed out of mouth to engulf and digest food. Once digested, food passed to pyloric stomach

2. Pyloric stomach: further digests food and passes it on to intestines, anus (located on aboral surface (top))

Allows sea stars to eat larger food

Describe the internal structure of sea stars

Central ring and a series of canals that eventually end in tube feet

Sea star tube feet help

Movement, feeding, bringing in water for gas exchange

How long are sea urchin spines

Mostly 1-3 cm, but can be found up to 20 cm long

Shape of sea urchins

Globoid shape, no rays or arms

What does the sea urchin have to move, and how

Ball and socket joints on the spines which allow them to move, if you touch the spines there the surrounding spines will converge there

Describe sea urchin mouth cavity

5 CaCO3 teeth, fleshy tongue called Aristotle’s lantern

What are the three defense systems of echinoderms

1. Spines (hard/sharp or soft)

2. Pedicellariae: pince like structures that protrude from the body surface between spines. Keeps body surface clear of encrusting organisms

3. Camouflage with natural colour

What are some ecological roles of echinoderms.

• Starfish and brittle stars prevent growth of algal mats on coral reefs

• Ossified skeletons of echinoderms are major contributors to many limestone formations

• Part of the food chain, larvae produce food for other creatures

• Death of echinoderms is often followed by an increase in seaweed growth and destruction of reefs

• Sea urchin grazing reduce the rate of colonization of bare rock

• Burrowing of sand dollars and sea cucumbers depletes the sea floor of nutrients and encourages deeper penetration which increase levels of oxygen and ecological tiering

• Sea urchins bore into rocks releasing nutrients

• Sea cucumbers provide habitats for parasites

• Echinoderms feed on dead and decaying organisms (detritus)