Halloween Urchins

What happens when you try to dress a sea urchin up for Halloween? Apparently, the urchin tries on the outfit but ends up wearing something else. But we had reason to hope our costumes would work.


Urchins primarily eat algae and kelp, often grabbing bits of food out of the water. Then they use their tube feet and spines to convey food from whatever part of the body first contacts it, to their mouth. Animal Caretakers enjoy offering them long strands of kelp just to watch this process.

It’s also common for green sea urchins to have non-food items all over their top and sides. They will hold onto those items for days or longer. It’s hard not to think that they must somehow benefit from doing this. Our green urchins are all carrying something, usually small shells or bits of coral. This behavior has been extensively studied. Possible explanations offered by scientists are refreshingly similar to the reasons anyone else might think of:

♣ To protect themselves from predators
♣ To protect themselves from wave action
♣ To take the brunt of collisions with flotsam and jetsam
♣ To protect themselves from harmful UV radiation
♣ In case there’s something edible on the item, they can eat it later
♣ Holding debris is an inadvertent result of being able to hold useful things like food and substrate

Recently in the Halloween holiday spirit, we offered our sea urchins something small and lightweight to hang onto. In the hopes of illustrating this behavior we offered a Star Wars Imperial Stormtrooper helmet. For a couple of days it worked, but so far the urchins show a strong preference for the shells and bits of debris that would be more natural in their habitat.

We want our animals’ enrichment to fill their needs as well as provide learning opportunities for our guests. The Stormtrooper helmet was fun and offered a good way to open conversations about this behavior, but so far the urchins are having none of it. And they get to decide.


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The Quarantine Scene

Last week, we told the story of a mysterious sea star that may have literally fallen out of the sky and into our lives. With continuing bad news about Sea Star Wasting Disorder, Animal Care staff had recently implemented a quarantine protocol for new animals going into our tide pool touch tank. Our recent visitor was a good test for our new procedure.


The original home of our animals, Puget Sound, is cold – from 8 degrees (44˚F) in winter, to 14 degrees (57˚F) in late summer. Naturally, our touch tank animals need cold water to stay healthy. The price of chillers, a machine that cools and recirculates tank water, is expensive. But we realized we could use a small refrigerator and modify it with a thermostat to bring the temperature within the required range for the health of our tide pool animals.

Once we fitted our fridge with containers for the types of animals we would be housing, we created a manifold of air bubblers to keep the animals’ water well oxygenated. Each day we do a 50% water change, using synthetic sea salt mix. By changing out the water, we dilute and over time flush out any pollutants the animals have in their bodies. The frequent, large water changes also mean the tanks never accumulate toxins such as ammonia, and if we remove the water with care, we clean up most of the waste and uneaten food at the same time.

Our quarantine process has worked very well as a temporary life support system, but as a method for preventing Sea Star Wasting Disorder it has one obvious flaw: If any animal other than a sea star is a carrier, it will not show any symptoms. Therefore, there is no obvious way to determine if an animal is safe to be around our stars.

Somewhat arbitrarily, we hold wild-collected animals for 30 days regardless of species, and those transferred from other facilities for a variable amount of time. Anemones are mostly water. Ten days of 50% water change should lead to them trading out most of their native water for new, ‘clean’ synthetic water mix. Other echinoderms, such as urchins, are not thought to be carriers but are quarantined longer than anemones simply because of their closer relationship to the sea stars.

And what about new sea stars? Our intention had been not to introduce any. But when one was brought to us, we determined that 30 days should be enough time to see if symptoms developed. Sadly, we didn’t need even ten days. We do not know if our little star succumbed to wasting disorder, or to the trauma of being removed from the water and attacked by gulls. Our quarantine care could not help it. The star showed lack of motor control, loss of body substance, and eventually its limbs began to deteriorate. At that point, Animal Care gave it a swift and humane end of life.

We are sorry to lose the star, but grateful to volunteer David Ashlin and Animal Caretaker Katie Malmberg for recognizing that this animal was not a resident of our touch tank. And a big “Thank you” to Christopher Russell for developing our quarantine process that lets us prevents problems before they entered our tide pool system.


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Gifts from the MaST Center

Guests who were around at Pacific Science Center’s Salt Water Tide Pool at noon Friday got the wonderful experience of meeting a bevy of new creatures.

Staff and volunteers from Highline Community College’s MaST (Marine Science and Technology) Center led by Kaddee Lawrence, with expert information from Rus Higley, hand delivered a group of exciting Puget Sound organisms. These new residents are for us to share with anyone who wants to learn more about the diversity of our regional shoreline.

In addition to bringing an infusion of bright color, the animals are an assorted mix of species. Best of all, they are a mix of non-aggressive animals that will not try to eat each other.

Many of the sea stars in our collection are Pisaster species, among the most predacious of all creatures in the intertidal zone. Yet, we love how durable they are, and how happily they eat readily available shellfish. With the new sea star species, we hope to have animals that are easily cared for and unlikely to eat other members of the exhibit. If these sea stars do well, the folks at MaST have offered to help us replace our current Pisaster population with these less hungry brethren. We will then plan a second round of new animals to include chitons, limpets and other animals that easily get eaten. Already our exhibit is more diverse by the addition of:

2 - Red sea urchins (Strongylocentrotus franciscanus)
1 - Purple sea urchin (Strongylocentrotus purpuratus)
1 - California sea cucumber (Parastichopus californicus)
1 - Kelp crab (Pugettia productus)
2 - Vermillion sea star (Mediaster aequalis)
2 - Blood stars (Henricia leviuscula)
1 - Mottled star (Evasterias troscheli)
1 - Sun star (Solaster dawsoni)
25 - Plumose anemone (tiny)(Metridium sp)
2 - Swimming anemone (Stomphia coccinea)

We can’t say “thank you” enough to the scientists at MaST. However, if you find yourself down in Des Moines, at Redondo Beach on a Saturday morning, stop by and thank them for us! The program hosts a weekly open aquarium, where the public meets their animals and their wonderful staff and volunteers. This is a great way to extend your knowledge of marine life.


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Urchins AND Snakes!!

This morning, Life Sciences' Sarah Moore and Brianna Todd appeared on KING 5 TV's "New Day Northwest." In addition to green sea urchins, the live television audience got to visit with Esteban, our boa constrictor. Here's the clip!


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Sea Urchins in the Spotlight!

Monday morning (January 31) Life Sciences Manager Sarah Moore and Lead Animal Caretaker Brianna Todd will feature our newest tide pool residents, green sea urchins, on "New Day Northwest." The KING 5 local news show begins at 11AM. Tune in!




Pacific Science Center's segment will discuss these and other delicate animals and how they fit into our fragile ecosystem. Our green sea urchins are a gift from Highline Community College's aquarium at Redondo beach.

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Tide Pool Census 2009

Pacific Science Center’s Puget Sound Saltwater Tide Pool is home to animals collected under a Scientific Collection permit, issued by the Washington State Department of Fish and Wildlife (WSDFW). Without a permit, it is illegal to gather animals from beaches. With a permit, it is still Pacific Science Center’s responsibility to take animals correctly, gathering only what will be used and leaving the environment as intact as possible.



Each year we submit a list of all the animals we have collected in the last 12 months. In addition to being a requirement, this is a tool for us to assess how well different species do in the exhibit.

Below is a list of the animals collected in 2009 and the census of animals present at year’s end. This is a shorter version of the list we give the WSDFW, which gives details to genus or species level.

In some cases, there are more animals listed than we collected in 2009. The extras are animals collected in previous years – a sign that they are doing well in husbandry for that group.


Other animals are collected in substantial numbers and yet none are present at year’s end. In the case of shellfish, this is planned. Clams, barnacles and mussels are collected as food items for the sea stars. In other cases, such as “small assorted animals” we may still have the animals but cannot find them. Isopods, tiny anemones and small shrimp routinely work their way into our filter beds, where they live free from predators, and well nourished by the remnants of food left by other animals.



In some cases, though, the species is simply not doing well in our environment. Sand dollars, for example, have very specific habitat needs that are not met in our enclosure. This is an animal we are unlikely to collect in the future.


We had a very marked change in survival rates for anemones, urchins, and sea stars when we installed a hand rinse sink in 2003. Previously these animals could not be touched without rapid loss of health. Now they are highly resilient to touching. Contaminants on people’s hands were more harmful than the physical fact of being touched.


Hermit crabs are a special case because guests are allowed to handle them. Sadly, they did not experience the same jump in survival rates when we got the sink, and we are still working on ways to increase their longevity. The biggest risks to our hermit crabs seem to be, in order from highest to lowest: wandering into unsafe areas, fighting with each other, and rough handling by people. One way we have found to keep them healthy is to keep the population relatively low. An enclosure with twelve to 15 hermit crabs will remain stable, but one with twenty or more will experience losses until the number drops below 15.


Keeping these statistics is the best way for Animal Caretakers to track and assess our tidepool husbandry procedures.

-Sarah Moore, Life Sciences Manager

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How to Watch a Sea Urchin

It can be fun to visit Pacific Science Center on a busy day or to watch something thrilling in the Boeing Imax theater.

But there is a whole other experience to be had on a quiet day. There is time to stroll from one exhibit to the next. In the butterfly house, there is time to smell the flowers. At the tide pool there is time to stop and watch the sea urchins. These mostly vegetarian creatures live to amazing ages – some may be as old as 200 years. Isn’t it worth a little time out of our days to check them out?



Like sea stars, urchins are echinoderms, a group of animals with tube feet, a five-sided body plan and a bumpy skeleton, or test, just under their skin. As their name suggests, the sea stars sometimes hog the limelight, but the urchins are well worth a second look.

The first thing you notice about a sea urchin is its long spines. These are hard and rigid, and are used for movement, defense and to snare bits of seaweed, which the urchins eat. But look more closely and you will see little long, flexible strands called tube feet or pedicellarines, moving about between each of the stiff spines. Their tube feet can grab and hold food and can also help the animal cling to surfaces and sense where it is going. If an urchin loses spines or tube feet, it can eventually grow them back, but this takes months and is stressful to the animal. Instead of touching an urchin, hold a finger between its spines and it will move them to softly squeeze your finger.



If you see an urchin against the glass of the tide pool, there is a good chance you can see its mouth, which is on the underside. The mouth is five sided, beak-like, and has the unusual name of Aristotle’s lantern. When an urchin eats, it passes seaweed to the mouth using its tube feet, like a conveyer belt. This is very exciting to watch, if you can accept that it will take a while. If you see an urchin in the process of eating, plan on spending the next half hour watching in fascination.

Urchins do not have a central nervous system. Information from their many spines and tube feet is passed into a net of neurons, which processes information and helps them go toward food and away from danger. Watch an urchin walk. They may walk slowly, but they are a bundle of moving parts as they go, tube feet waving, spines tapping. The urchin probes the area ahead of it with its spines, much as a blind person might use a cane to test the ground. Then the spines and tube feet convey the animal forward. Urchins almost always keep their mouth side against a surface. But they do not have a forward and backward. If they change direction, they do not need to turn and “face” a new way, as we would, but simply start going that way.



Right now, Pacific Science Center’s two urchins are on the move. Normally they have staked out a small territory in the deep end, but in recent weeks they might be found anywhere in the tide pool. Not only that, but they are usually in motion, racing along at nearly an inch per minute! Over time, urchins will excavate small areas in a stone outcropping, which become their homes.

Come take a look, and expect to leave with a better appreciation of a very different life form. Although we encourage you to take your time and watch these animals, the time frame for this process is years, so do not plan on observing it in a single visit. Better yet, check in on the urchins whenever you like. Consider a Pacific Science Center membership plan!

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