Fascinating Facts on Sea Urchins and Starfish

Sea Urchins

• Sea Urchins come in a full range of colors from sand colored to bright pinks and dark purples.
• Sea Urchins have over 200 species. They are interesting creatures that are bilateral. They have five sections that are equally the same size.
• Sea urchins have spiny shells for protection and five sets of “legs” that are really tubes that they
• use to propel themselves across the ocean floor.
• Some of the species have poisonous soft spines. They live in warm water oceans.
• They can grow from 3 cm round to 10 cm round. They can live up to 200 years.
• They can live up to 200 years (the red sea urchin is the longest living creature on the planet) most species live for about 30 years. They spend their days moving around the ocean floor feeding. They can live in warm waters at depths as low as 20 feet all the way to depths of 5000 feet. They do not do well in captivity because the breeding conditions can not be completed duplicated without the ocean currents so while a sea urchin may live in captivity it will not reproduce well
• Their mouth is at the bottom half of their body.
• They have a mouth and an anus. They have a simple digestive system. Basically they can easily eliminate what they take in.They scoot around on their “legs” eating whatever they come across on the ocean floor. The sea urchin has quite a few natural predators. The sea otter is it biggest natural predator in the ocean. They will eat as many sea urchins as they can find. Man is the next biggest predator, although some people would say that man is the biggest predator. Sea urchin is a delicacy in some cultures. Their rows (eggs) are also a delicacy so they are hunted by divers in the warm ocean waters.
• Sea Urchins are harmless animals that pose no threat except for one sea urchin that is poisonous to fish.
• The flower urchin is the only poisonous species and it has an unusual symbiotic (equally rewarding) with the clown fish. The spines on the flower urchin contain a paralytic that will paralyze predators. The clown fish builds an immunity to this paralytic so that it can feed off the flower urchin. The clown fish does a funny dance where it gently brushes up against the spines of the flower urchin to expose itself to just a bit of the poison at a time. After a few hours of its dance it can easily approach the flower urchin and feed off the parasites that live in and around the spines. This helps the flower urchin by removing the parasites that can cause disease and cause the spines to fall out leaving it defenseless. So the relationship works out for everybody involved.
• Sea Urchins breed by releasing their egg into the ocean. The egg is fertilized and quickly, within about 12 hours becomes an embryo
• A surprising number of sea urchin survive this process. Once the embryo floats to the ocean floor it takes a few months for it to become an actual sea urchin. It goes through many different stages from larvae to sea urchin. It eventually builds its spiny shell and becomes a full-fledged sea urchin. The female sea urchin can release up to 1000 eggs at a time, a small percentage of these eggs go on to become sea urchins because there are a lot of sea animals that dine on them before they are ever fertilized.A surprising number of sea urchin survive this process. Once the embryo floats to the ocean floor it takes a few months for it to become an actual sea urchin. It goes through many different stages from larvae to sea urchin. It eventually builds its spiny shell and becomes a full-fledged sea urchin. The female sea urchin can release up to 1000 eggs at a time, a small percentage of these eggs go on to become sea urchins because there are a lot of sea animals that dine on them before they are ever fertilized.

Starfish

• They usually have five arms
• On each of a sea star’s five arms, the bottom side of the limb presents a peculiar yet extraordinary feature. Each arm contains up to 15,000 tiny little ‘tube feet,’ which are able to orchestrate movements that ‘walk’ the sea star along…often quite efficiently. With more than 2,000 species of sea stars in our ocean today, there are individuals that present with 10, 20 or even 50 arms.
• They can regenerate
• The ability to regrow body parts might sound like a bit of a fictional superpower, but for sea stars, it’s all just a part of their reality. Don’t let the fact that their arms are all coordinated around a center point fool you; the majority of sea star’s vital organs are actually housed in their arms. While some species require the core of their body to be in one piece in order for limb regeneration to occur, others have been known to grow an entirely new body from just one detached arm! This mechanism allows sea stars to prove themselves awfully resilient, living for up to 35 years in the wild.
• The first part of digestion occurs outside of the sea star’s body
• The anatomy of a sea star’s digestive system is quite alarming, and has an incredibly unique two-part stomach system. Here’s what happens during the digestive process: first, a sea star moves its entire body on top of its prey, so that its mouth is centered on the organism of choice. It will then use its sac-like cardiac stomach to ooze digestive enzymes onto their prey. Once the flesh of the prey is broken down enough, the second stomach portion (known as the pyloric stomach) engulfs the prey to complete digestion internally.
• They can be cannibals
• While your first instinct may be to consider sea stars as harmlessly docile grazers, most are actually insatiable carnivores. While they normally feed on organisms like coral, sponges, shellfish and algae, some will eat whatever they can manage to get their stomachs onto, and that includes—you guessed it—other sea stars, even of the same species. The chocolate chip sea star (Protoreaster nodosus) is just one sea star that has been documented to behave in this manner, but it’s said to be more of a chance mishap than a purposeful act of attacking the same species.

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