Benny Julian
Many fascinating sea creatures live in our oceans. One of these amazing marine organisms is the starfish.
Starfish are found in nearly all marine environments. Some species of starfish include Arctic Cookie Star, Blood
Star, Bat Star, Crested Star, Dwarf Mottled Star, Morning Sun Star, Giant Pink Star, Northern Sun Star, Rainbow
Star, Rose Star, Sunflower Star, and Vermillion Star.
These animals are one of the most noticeable and attractive creatures
in the world. They are free-living organisms that have a unique flat
body. Their bodies are star-shaped and quite flexible.
Starfish are echinoderms. These critters are related to sand dollars and
sea urchins and have a fivefold symmetry. They have arms in multiples
of five. A starfish can also be referred to as a sea star because they are
not actual fish. There are over 2,000 species of starfish living in the
oceans. A sea star’s habitat ranges from cold to tropical environments.
Purple Sea Star
The internal skeleton of starfish is calcareous and held together with connective tissue. Their body is made up
of plates, spines, and tubercles. Many sea stars look very rigid, but their connective tissue permits them to
become malleable when needed. This feature comes in handy when they are trying to escape predators,
attacking prey, or repositioning themselves.
The mouth of a sea star is located in the center of the body. These creatures do not have developed eyes,
rather a simple lens that is located at the end of each limb. Their eyespots or simple lens are sensitive to light.
Starfish have neurosensory cells all over the skin and these cells are very sensitive to chemicals and touch.
The neurosensory cells are located on the suction cups of their tube feet. Sea stars have very fine details on
the skin called pedicellariae. The pedicellariae are highly effective at discouraging predators and keeping the
skin clean from nasty parasites and organisms. Starfish have thin-walled gills that allow them to exchange
gases and excrete liquids.
These animals have internal organs such as a nervous system, digestive tract, reproductive system, and
vascular system. The vascular system allows them to grab their prey tightly and freely move about in the
water. Starfish have suction cups that allow them to cling to rocks, grab prey, or climb pilings. The digestive
tract takes up most of the space inside of these creatures. They have two stomachs with lobed organs inside
of each one. The lobed organ releases a digestive juice that breaks down food. Waste products pass out on
the opposite side of the mouth. The reproductive organs are located on each limb in the armpit region.
Strange, but true!
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Starfish do not possess a brain or central nervous system. They have a
central ring that joins to the radial nerves that goes down each limb and
connects to a cellular network which covers the entire body.
The skin of starfish is calcified and bony to safeguard them from
predators. They cannot live in freshwater, but they thrive in marine
environments. Very few live in brackish water. These creatures have an
amazing ability to regenerate themselves. If an arm of a sea star is cut
off, it will grow back. The majority of their important organs are housed
in the limbs.
Another awesome capability that a starfish can do is consume prey outside of their bodies. Sea stars have tiny
suction-cupped feet and they use them to force open clams and oysters. Their suction-cupped cardiac
stomach comes out of their mouth and engulfs the prey to digest it. Then it goes back into their body. The
animals they consume include clams, oysters, mussels, scallops, corals, fish, sea pens, sea cucumbers,
tubeworms, anemones, snails, barnacles, sponges, and gorgonians.
These invertebrates have been successful at avoiding prey because very few
animals attack them. They also have several chemical defenses that protect
them from predators. Saponins are chemical compounds that are found in
their skin and they taste nasty to animals. Many sea stars are carnivores
and some are omnivores.
Many people think starfish are boring animals. In reality, they are actually
unique and interesting creatures. From their varied colors and their strange
way of eating, sea stars are a fascinating part of the ocean. Up close, they
are much more active and complex than most people would imagine.
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