Sunflower sea star

Episode 118 – Sunflower Sea Star: Limb from Limb

“And today we’re talking about an arms race that moves about three feet per minute, but more on that later…”

We all love starfish, cute, slow-moving, harmless little creatures whose desiccated husks make for great souvenirs from your trip to Key Largo. But not all starfish can be as whimsical as Patrick Star, some are far more strange and nefarious. The ironically named sunflower sea star is one such animal. Crawling across the seafloor at a disturbing speed, this enormous echinoderm has dozens of tentacled arms, eats whatever it can find, and even rips off its own arms. Why? Well, let’s just say things are going viral here in Life, Death, and Taxonomy.

Description

  • The sunflower sea star is a large starfish with a distinct sun or sunflower shape, due to its abundance of arms.
  • It comes in orange, yellow, red, brown, and purple.
  • They’re described to have a soft velvet texture.
  • Like other sea stars, they have a skeleton that’s similar to a mesh that protects their squishy organs.

Measure Up

Welcome to the beloved Measure Up segment. The official listener’s favorite part of the show! The part of the show when we present the animal’s size and dimension in relatable terms through a quiz that’s fun for the whole family. It’s also the part of the show that’s introduced by you when you send in audio of yourself saying, singing, or chittering the words measure up into ldtaxonomy at gmail dot com. We have a new measure up intro this week from Alexi.

Armspan

  • 1 m (3.3 ft)
  • How many Sunflower Starfish go into the height of the tallest sunflower?
  • Hint: The flower was grown in Hans-Peter Schiffer in Karst, Germany. Han-Peter has held the same record twice before. 
  • Answer: 9 starfish. The sunflower was 9.17 m (30’1”)

Number of Arms

  • 16 to 24 limbs
  • How does the number of arms a sunflower starfish has compare to the number of spiral arms that the milky way has?
  • Hint: After years of debate, a 2013 study confirmed the number of spiral arms there are in the milky way.
  • Answer: 6 milky ways. The milky way has four spiral arms. 

General Info

  • Sunflower sea stars live in the American northwestern pacific ocean, particularly in Puget Sound and Alaskan waters. 
  • However, it’s harder to find them these days because of a phenomenon called sea star wasting disease.
    • The disease affects echinoderms, causing mass deaths in local populations.
    • In some places, the disease is associated with rising water temperatures, leading some to suspect climate change as the cause.
    • But a 2016 study found that the number of deaths seemed to increase with cooling water temperatures around Oregon.
    • The study concluded by calling for more robust studies to help better predict these outbreaks.
  • They enjoy areas that are rich with seaweed, in intertidal and subtidal areas.
  • The sea stars move at about three feet per minute using their 15,000 tube feet.
  • They love to eat sea urchins, but they’ll also snack on other slow prey like snails, clams, sea cucumbers, sea stars, and dead or dying squid.
  • They reproduce by broadcast spawning, which is not a radio dating show. 
    • It’s a method of reproduction where a female will release eggs into the water for males to fertilize. 
    • Their larvae are planktonic and feed on the surface for several weeks before settling to the seafloor to transform into juveniles.

Major Fact: Ripped Limb from Limb

  • Jesus says in Matthew 5:30: “If your right hand causes you to sin, cut it off and throw it away”.
    • While he was obviously instructing us to flee from temptation and remove idols from our lives, the sunflower sea star took the passage a little too literally.
  • These sea stars, and about 40 other species of sea stars, are systematically pulling their own arms off until they die. 
    • Most starfish can pull off their own arms or release an arm that has been grabbed in order to fool or escape predators such as the king crab. 
    • But these stars aren’t doing this for any advantage, they just seem to be falling apart for no reason.
  • Turns out, we’re not the only ones going through a pandemic.
    • No one is 100% sure, but researchers think that this is the result of Sea Star Wasting Disease, or the Sea Star-Associated Densovirus. This is kind of like leprosy for starfish.
    • The first symptom is that the star will stop eating and wander around aimlessly.
    • Then white spots start to appear and grow on the star’s body leading to tissue damage to the tissue.
    • Starfish and sea urchins use a water vascular system to do pretty much everything. They move water throughout their bodies to move their arms, extend or retract their tubed feet, move food through the digestive system, and even to breathe. This system fails during the disease and the star can no longer grip onto things.
    • Eventually, the body structure breaks and the start starts leaving arms behind. So while it looks like they’re pulling their arms off (like they might to escape predation), their arms are actually just falling off as the star drifts along. 
    • Pretty soon after that, the starfish dies. This can all happen in the course of a few days.
  • Starfish have been hit with plagues like these back in the ’70s, but this most recent one started in 2013 and has lasted ever since. There is a video of thousands of sunflower sea stars littering the seafloor off the coast of Canada in the Atlantic.
  • No one is sure exactly why this is happening. Of course, most people jump to global warming as the disease seems more prevalent in warmer areas. There is also a parasite that attacks starfish and thrives in warmer water. But the initial outbreak took place in colder waters, so researchers can’t pin that as the reason.
  • A zoo in Washington lost more than 250 of its starfish to the epidemic and eventually managed to stop it with antibiotics.

Ending: So stay inside, stay active, and keep your limbs close at hand like a healthy sunflower sea star here in LDT.

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