Starfish

Although they aren’t technically fish, sea stars are animals that are still present in nearly every coastal habitat and can be found as low as the abyssal layer. You can identify a starfish by its bumpy skin and flat center surrounded by long limbs that give the appearance of a star.

These slow-moving but sensitive fish come in a wide array of colors; although you should never pick one up, trying to find starfish along the beach is a wonderful seaside activity.

Incredible Starfish Facts!

• Delicate structure: Starfish are animals that are made up of a fragile network of thin muscles and tiny ligaments. This is why they move so slowly — and also why they shouldn’t be handled.
• Extended senses: Starfish do not have a central nervous system; instead, their entire body is made up of a collection of sensory nerves. Starfish observe the world through small eyes located at the ends of their “arms.”
• Natural regeneration: Starfish possess the ability to regrow a limb that is lost. This process is slow, and it only occurs if the starfish survives the pain of the initial break. Some species of starfish can break off their own limbs to escape from predators.
• Vascular system: Starfish don’t actually have blood in their bodies. Instead, they pump seawater through their vascular structure in order to carry nutrients and oxygen.

Evolution and Origins

Starfish, also known as Asterozoans, are a diverse and ecologically successful group of spiny-skinned echinoderms that happened to first appear in fossil records close to 500 million years ago. They appeared in the Ordovician period. In fact, starfish are the most primitive members of the Asterozoan family. Additionally, the five arms of starfish are leftovers from these ancient ancestors.

Today, starfish are found all over the world in different tropical coral reefs, coastal waters, and the world’s oceans. Not only that, but starfish most likely evolved from ancient animals called crinoids.

Although ancient fossils reveal that starfish have been around for a very long time, due to pollution and other man-made reasons, starfish risk a decline in population numbers.

Classification and Scientific Name

The aquatic animal that is commonly known as a starfish is also frequently called a sea star. All of these animals fall into the class Asteroidea; in the scientific community, they are frequently known as asteroids. The zoological name Asteroidea translates to “star-shaped — “aster” means “star,” and “eidos” refers to “shape.”

Asteroidea is one of the largest classes in the Echinodermata family. Other echinoderms include sea urchins, sea cucumbers, and sand dollars. Most echinoderms have the same five-pointed structure as common sea stars, but plenty of these animals — including some of the different types of starfish — are capable of having far more complicated structures.

Species

There are over 2,100 distinct species of starfish, and more are frequently discovered during oceanic research. The many types of these animals are as varied as the different places where they are found.

With so many bright colors and creative forms, it’s no surprise that so many sea stars have colloquial and zoological names that express their unique types of beauty.

Some of the most notable types include:

• Common starfish: Asterias rubens is a simple, five-pointed animal with a peachy orange color. Also known as sugar starfish, you can find these aquatic animals all along the Atlantic coast.
• Sunflower starfish: Pycnopodia helianthoides is found in the Pacific Ocean. These sea stars can have up to 24 limbs and come in all different types of colors.
• Royal starfish: Astropecten articulatus live in the West Atlantic. Like sugar starfish, they have five points; however, they are distinguished by their bold purple and orange colors.
• Necklace starfish: Fromia monilis is a West Pacific starfish named for the plates on its body, which look a lot like the beads on a necklace. In some areas, they’re known as tiled starfish.
• Chocolate chip sea stars: Protoreaster nodosus is found in the Pacific Ocean near Indonesia. These animals can be recognized by their black spikes, which look like chocolate chips.

Appearance

Starfish are flat aquatic animals that move slowly and stick to the ocean floor. Most of them have a central disk surrounded by five or more arms. The mouth is usually located in the middle of the disk, and the ends of its arms feature light-sensitive eyespots. The skin is covered in small spines, and the bottom of its limbs is usually lined with hundreds of small tubular feet that are used for gradual movement.

Starfish are animals that come in an amazing array of colors and variations. From bold purple stripes to pointed black horns, there’s no limit to the different types you might find. There are small species that are only an inch or two across, and there are large starfish that can get as big as a foot. Every region is different; you may need to take a walk along the beach to see your local sea stars.

Distribution, Population, and Habitat

These animals are found along every coast in the world. Because they use seawater as part of their vascular system, they cannot live in any type of freshwater. You can find them in coral reefs, muddy bays, underwater kelp forests, and pretty much every other kind of aquatic environment.

Although starfish are found all over the world, some species — such as the sunflower sea star (Pycnopodia helianthoides) and the live-bearing sea star — are listed as critically endangered by the IUCN, while others are not considered threatened. Human presence has destroyed many of the coral reefs that house the world’s different starfish species. These animals are incredibly important to their local ecosystems, and the recent decline of their species has threatened the biodiversity of many different regions.

Diet: Predators and Prey

These animals are carnivores that consume nearly all types of small ocean life. Depending on where they live, they may eat mussels, oysters, clams, sea snails, fish, and even other starfish.

These animals are also seen as prey by many different types of ocean-faring life. Mammals like seals and otters may choose to eat them as a snack; other threats include birds, crabs, and large carnivorous fish.

Reproduction and Lifespan

These animals are solitary creatures, but they come together in large groups for mating purposes on a semi-annual basis. They typically mate by pairing off with an opposite-gender partner. Both sea stars will release a spawn cloud into the water; once the eggs are fertilized, they will drift to the ocean floor.

These animals do not appear to care for their young after the eggs are laid. The embryos hatch before they are fully developed; as the young grow, they will slowly gain limbs and assume their adult form. These animals can live up to 10 years, with some rare species possibly reaching 35 years, and will continue to develop and regrow their limbs as they age

Fishing and Cooking

These animals are not eaten as a staple food anywhere in the world. Some exotic restaurants sell fried starfish; however, between the fact that they are naturally toxic and the various state- and federal-level regulations on the sale of this sea animal, these restaurants are seldom profitable enough to continue providing them as a product.