Six-rayed sea stars make great moms! Unlike most sea stars, mama six-rayed sea stars are VERY involved in their kids' lives, caressing and protecting their babies for months. When they're big enough, the youngsters venture out on their own to ruthlessly hunt down their tiny prey.

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DEEP LOOK is an ultra-HD (4K) short video series created by KQED in San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Explore big scientific mysteries by going incredibly small.

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The California shoreline is home to the tiny six-rayed sea star. About the size of a bottle cap, these diminutive starfish have an unusually attentive style of raising their young.

“Most sea stars use a broadcast spawning method,” says Berenice Baca-Ceballos, a graduate student at San Francisco State University. Broadcast spawners release huge numbers of eggs and sperm directly into the water. The lucky ones meet and develop into larvae that grow up all on their own. Most never reach adulthood.

But mama six-rayed stars of the genus Leptasterias are different. “The mother sea star will sit on her eggs for about two to three months until her eggs develop, hatch, and grow into little juvenile sea stars,” says Baca-Ceballos. “She’s like a mother chicken. The female sea star sits on her eggs until the little baby sea stars, that look like delicate living snowflakes, are ready to adventure out.“

This style of holding on to their young as they develop is called brooding. While six-rayed sea stars have many fewer offspring than most sea stars, they spend more time taking care of their young.

“By protecting her young, the six-rayed star increases the chances that her babies will survive,” Baca- Ceballos says.

--- How do starfish move?
Starfish move using hydraulic pressure. They have a system of canals, called the water vascular system, which run through their bodies. The canals connect to a large number of tiny flexible tube feet that end in adhesive pads. A starfish contracts muscles to adjust the hydraulic pressure in the tube feet, allowing it to crawl along surfaces.


--- How do starfish eat?
Starfish are mostly carnivores. Many types of starfish eat shellfish like mussels, clams and snails. A starfish will use its numerous tube feet to slowly pry open its prey’s shell. Once it has opened the shell enough, the starfish will extend its stomach out through its mouth to digest its prey alive. Some types of starfish also eat small fish, plankton and detritus.

--- Do starfish have eyes?
Starfish usually have a simple eyespot at the tip of each arm. Also called ocelli, these eyespots can only sense light and dark.

---+ For more information:

The Cohen Lab at San Francisco State University studies six-rayed sea stars of the genus Leptasterias.

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Ever Seen a Starfish Gallop? | Deep LooK
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Sea Urchins Pull Themselves Inside Out to Be Reborn | Deep Look
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A Sand Dollar’s Breakfast Is Totally Metal | Deep Look
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