A Sea Cucumber that’s an Apple? - Observation of the Week, 8/17/18

Our Observation of the Week is this Violet Sea Apple, seen off of Taiwan by @huang_shu_chen!

You might have noticed that the number observations from Taiwan have been growing quite a bit (see chart below), showing off the incredible biodiversity of the island and its surroundings. Much of this growth has has been spurred by a community of both researchers and citizen scientists, one of whom is Cheng-Tao Lin (@mutolisp), the current top observer in Taiwan and an Assistant Professor in the Department of Biological Resources at National Chiayi University. Prof. Lin has graciously translated the responses from this week’s observer, so I want to thank him and Shu-Chen for collaborating on this.

huang_shu_chen (whom I’ll refer to as Shu-Chen), is a diving volunteer for the National Museum of Marine Science and Technology in Keelung, Taiwan, and says “My partner and I (see below) do routine underwater work about coral reef restoration, patrol and investigation, and assist in recording species to create a marine diversity checklist. In addition to these routine tasks, I will also take photos of these beautiful marine creatures.”

The beautiful Violet Sea Apple you see above was taken by Shu-Chen during her first dive using an underwater camera with a flash, and she tells me

it is also the first time I saw such a fascinating and gorgeous sea cucumber, just the same as its name, “red apple”. It’s a pity that I did not meet its “flowering” state (when it stretches tentacles to catch plankton). If I had a chance to see its flower, I will upload it to iNat again!

As Shu-Chen says, these creatures are sea cucumbers, although we use a different vegetative term to describe them (apple) due to their more round shape than your standard sea cucumber. The “flowering” behavior she describes is how the creature catches plankton, by extending its frilly tentacles into the water. And like many other sea cucumbers, violet sea apples can expel parts of their sticky innards into the water when threatened, allowing a predator to concentrate on its entrails rather than the rest of its body. If that doesn’t work, they also have two tricks up their sleeves: they can release a toxin known as holothurin (a type of saponin) into the water, and they can also ingest water, allowing them to double in size and use currents and gravity to sweep them to a new home.

Shu-Chen (above) has recently joined iNaturalist, and says

my photos of nature were just silently stored in my own computer disks in the past, but since I learned about iNaturalist platform, and that observation data uploaded to iNaturalist would become part of GBIF data, I’m so glad that they could be used and studied by other people around the world...I also use iNaturalist to create species checklist at the place where I care and concern. It is really convenient to have iNaturalist to record nature observations, and it motivates me to collect more data.

- by Tony Iwane. 


- Why not take a gander at some of the great observations being made in Taiwan? Here are the faved ones

- Some Pearlfish will use the anus of a sea cucumber as a home and/or eat their gonads. This is true

- Sea cucumbers demonstrate some astonishing diversity, check out observations of them here!

Posted by tiwane tiwane, August 17, 2018 08:49 PM

Comments

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Wonderful! Thank you so much @huang_shu_chen.

Posted by susanhewitt 5 months ago (Flag)
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Fantastic! Love seeing such interesting observations from Taiwan 🇹🇼

Posted by metsa 5 months ago (Flag)
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"Some Pearlfish will use the anus of a sea cucumber as a home and/or eat their gonads".....Thanks iNat, I guess you learn something new everyday....

Posted by zabbey 5 months ago (Flag)
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Did you know that cucumbers are one of the healthiest low energy dense high potassium plant foods on the planet? And while apples are a major cause of FODMAP related benign GI functional disturbance symptoms due their relatively high (via selection process over centuries) nonabsorbable simple sugars, GI tract disturbance symptoms from cucumbers are very uncommon.
Of course none of this is relevant to the Taiwanese sea apple holothurians.And my own relevance to Homo sapiens is open to doubt.
Finally, I found the info fascinating.
Thanks again, iNat and our newer Taiwanese contributors☺

Posted by davemmdave 5 months ago (Flag)
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As virtually the only person observing from an island not far away, I love the work coming from Taiwan. Beautiful stuff! 谢谢你!

Posted by thelittleman 5 months ago (Flag)
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Wow! That is wonderful! It is nice to know people are really out there keeping an eye on the reefs. I read last year in a magazine of some nature article that only 10% of our vast ocean have been explored. Welcome to inaturalist and please keep up the great work.

Posted by walkingstick2 5 months ago (Flag)

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