Starfish
Anything and Everything
You ever wanted to know
Table of Contents
Introduction……………………………………………..…………1
Anatomy……………………………………………………………….2
Classification……………………………………….…….……….4
Habitat……………………………………..…………………………5
Prey………………………………………………….…………………..8
Predators……….………………………………………………….10
Locomotion…………………………………….………………….11
Regeneration……………………………………….……………12
Glossary……………………………………………….……………14
About the Author……………………………………..……15
Introduction
Here at the Ecotarium Touch Tank live two
different species of starfish: the Forbes’ Sea
Star and the Northern Sea Star (or in Latin:
Asterias forbesi and Asterias vulgaris). These
two species are found in the New England area
and live in similar environments.
Although
sometimes called starfish, they are technically
sea stars because sea stars are invertebrates.
Anatomy
This is an
Asterias
Although some sea stars
forbesi.
can have up to 10 arms,
Asterias starfish always
have 5 arms which grow
The underside of sea
stars is comprised of
hundreds of tiny tube
feet with a mouth
in the center.
from a central disk, forming the classic star shape.
Mouth
Tube Feet
The stomach, located in-
The tube feet are used
side the mouth, has the
by starfish to move
ability to come outside of
around and to help
the mouth and digest food
them capture
outside of the body.
prey.
2
A madreporite is located on
Starfish do not have
the central disk and is used
a head like humans
to control the movement of
do, but they do have
the starfish about the ocean.
a mouth on their underside.
Asterias forbesi
Madreporite
are usually a tan,
Central Disk
Adult starfish have radial
symmetry meaning that their
structure is the same in a cir-
brown, red, or pink and
in some rare cases, an
Arm
olive green with
orange tones.
cular pattern. Starfish larva,
or baby starfish, are bilaterally symmetric when they
hatch, meaning they are the
same on the left side of their
body as on their right.
Asterias vulgaris
are usually an orangish-brown but can
also be reddish-brown and in some
are cases, reddish-violet. The starfish
shown here is an Asterias vulgaris.
3
Classification
Kingdom: Animalia
Phylum: Echinodermata
Order: Forcipulatida
Suborder: Asteriadina
Family: Asteriidae
Genus: Asterias
Species: vulgaris
Latin Name: Asterias vulgaris or A. vulgaris
Common Name: Northern Sea Star
All animals are organized using a series of names, starting with the
most general and ending with a name only specific to that individual
creature. Kingdom is the name which refers to the largest group of
animals which this organism is related. Each title from there narrows down the range of creatures down to the species which the
most specific way to describe an animal. Scientists use the Latin
4
Kingdom: Animalia
Phylum: Echinodermata
Order: Forcipulatida
Suborder: Asteriadina
Family: Asteriidae
Genus: Asterias
Species: forbesi
Latin Name: Asterias forbesi or A. forbesi
Common Name: Forbes’ Sea Star
Animalia is the kingdom which includes approximately 10 million
species throughout the world which are multi-cellular and rely upon
other organisms for food. Echinodermata is a phylum comprised of
about 7000 non-extinct organisms dwelling solely in salt-water environments and literally means “spiny skinned.” Forcipulatida is an
order comprised of starfish with a similar bone structure. Asteriadina and Asteriidae are more specific classifications for the
types of starfish, and Asterias forbesi and Asterias vulgaris are
two genus and species of starfish, differing only in minor ways.
Habitat
Mussel Bed
Both species like to live on rocks or boulders near a
source of food. Sometimes they even live in mussel or
clam beds because that is one of their food sources. The
Northern Sea Star is sometimes found in kelp (a type of
seaweed) beds too.
Sea Stars
Canada
United States of
America
6
Nova
Scotia
Gulf of
Maine
East Coast
Gulf of Mexico
Starfish live in the ocean because they can only survive in salt water.
And although the 1,800 species of starfish are found all over the
world, both the Forbes’ Sea Star and the Northern Sea Star live in
7
Prey
Sea stars prey upon and eat
other miniature marine animals which live on the ocean
floor, usually invertebrate
marine animals, crustaceans,
and mollusks. Some of their
most common prey consists
of mussels, clams, scallops,
or snails. Starfish also scavenge and eat any dead animals they find in their habitat.
8
A starfish will use the suction cups on its tube feet to
grasp onto their prey and pry the shells apart. Once it
is open (even if just by a tiny bit) the starfish will insert
its stomach into the shell and digest the tissue. After
digestion, the starfish will pull its stomach back inside
its body.
Starfish stomach outside
of its body
9
Predators
Because starfish have spiny skin, they are not very tasty to many undersea animals. Predators do not obtain a lot of nutrition from sea
star skin so they tend to prey upon other animals. One animal that will
eat starfish is seagulls.
Starfish have one of the best forms of
defense against predators: being able
to regenerate limbs and sometimes
whole bodies. Because starfish can regenerate, their population isn’t drastically affected by predator attacks, and
in fact, this adaptation makes it very
10
Locomotion
Starfish have a water vascular system which is the way starfish move about the ocean floor. Water enters through the madreporite and is channeled to each of the arms. The starfish expands
and contracts its muscles to push water in and out of its tube feet
and move around. Although the tube feet have suction cups, they
are not used for walking. A starfish would take about a minute to
walk from the bottom to the top of this page (a speed of about 1
foot/minute).
Madreporite
Tube feet (on bottom)
11
Regeneration
During evolution starfish have developed a unique way to survive predator attacks: they regenerate their arms. Regeneration is the ability to re-grow an arm if it is detached from the body. For Asterias
forbesi and Asterias vulgaris as long as the central disk is there, it
will grow a new arm. This adaptation is most useful for when a sea
star is attacked by a predator and loses an arm during the fight;
they just grow a new one in the days following the attack.
12
Missing arm
Sea stars can also detach their own arms if it
is damaged or being restrained by a predator.
Sometimes two arms grow where there used to
only be one, so the sea star will have an extra
limb. A broken sea star may even form two new
organisms.
13
Glossary
Bilateral Symmetry: one side having the same appearance as the
14
About the
Natalie is a student at the Massachusetts Academy
of Mathematics and Science at WPI located in
Worcester, MA who will be graduating from high
school in 2009. A native of Jefferson, MA, Natalie
enjoys arts and crafts as well as playing with her 6
other siblings. Someday hopes to graduate from college and possibly work for the FBI.
15
Illustration
Credits
Cover Page:
http://www.hickerphoto.com/data/media/164/starfish_0509.jpg
Table of Contents: page i:
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Introduction: page1:
http://lovescupcakes.files.wordpress.com/2008/01/bubbles.jpg
Anatomy: page2:
http://www.touchthesea.org/forbeslv2.jpg
Anatomy: page3:
http://www.clarku.edu/departments/biology/biol201/2004/jcurtis/Sea%20star%20
Project/Title%20Page_files/starfish%20title%20page%20pic.gif
Habitat: page6:
http://www.mms.gov/omm/pacific/kids/Tidepool_Math/Common_Species/mussel%20
bed%20with%20sea%20stars%20on%20the%20island.jpg
Habitat: page7:
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Classification: page4:
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Classification: page5:
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Prey: page8:
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prey: page9:
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Predators: page10:
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page11:
http://img209.imageshack.us/img209/7543/northernstarep9.jpg
Regeneration: page12:
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Regeneration: page13:
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