Cool Papers! Part 1: An appetite for glass

By Danielle Ludeman

As scientists, we all have to keep up to date on the happenings in our field.  Although reading papers is not usually my favorite part of doing research, I love that moment when I stumble across a really cool paper and immediately want to run and share my find with someone.  Whether you react that way or not, cool papers help to remind us of why we do what we do, and motivate us to keep plugging away at our own research, because we just might get a cool paper out of it too.  So to share some of the cool papers in marine science that are out there, I am going to post them to this blog.  And what better way to start off the cool papers section than to post about a paper from the Bamfield Marine Science Station’s very own Jackson Chu (and former member of the Leys lab) and his recent paper on predators of glass sponge reefs published in Invertebrate Biology.  Now I may be a little biased in thinking this paper is really cool because it’s about sponges.  And I was part of the 2009 research cruise when the first nudibranchs on the glass sponges were found.  But seriously – glass-eating nudibranchs?! Super cool.

Alright let’s back up a second here – glass sponge reefs?  Yup, glass sponges (Class Hexactinellida) in the deep, deep waters off of British Columbia form huge reefs, much the same way that corals form reefs in tropical waters!  These vast and majestic glass sponge reefs span hundreds of kilometers along the coast – one of them even lies just at the doorstep to Vancouver, at the base of the Fraser River.  Yet even though they live just below our feet, their deep-water habitat of about 100-200m deep meant that we only discovered them about 25 years ago, and we still have much to learn about this important ecosystem!

Glass sponge reef in the Strait of Georgia, viewed from ROPOS. Photo credit: A Kahn

Glass sponges are made out of just that – glass.  They form a silica-based skeleton that comprises >90% of their body weight, leaving less than 10% to organic living tissue. Because of this, very few animals are expected to feed on them.  But in 2009 and 2011, while surveying the reefs aboard a research vessel equipped with the remotely operated vehicle ROPOS, Chu and Leys noticed two species of large dorid nudibranchs, Peltodoris lentiginosa and Archidoris odhneri, sitting on top of some of the glass sponges on two of the three reefs visited.  Now because nudibranchs are notorious sponge-eaters, they had a hunch that these cute little guys may actually be voracious predators in disguise.

Glass sponge-eating dorid nudibranchs found during the 2009 cruise of the Strait of Georgia glass sponge reefs. Photo credit: D Ludeman

So how do you know the nudibranchs are actually eating the sponges? By looking inside their stomachs!  By doing so, Jackson found that their stomach and fecal contents were full of spicules unique to both of the main reef-forming species of glass sponges, making these two species of dorid nudibranchs the first known predators of BC’s glass sponge reefs.  And the small amount of organic tissue compared to glass in the sponges must mean the nudibranchs have to eat A LOT of glass to sustain their large size! Nom nom nom.

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2 thoughts on “Cool Papers! Part 1: An appetite for glass

  1. Best blog post ever! The best part of science is when somebody else describes your work as cool!

    Dani, there’s a mini prequel to your story that I never get to tell during proper conferences:

    Way back in 2007-2008, back when you were volunteered in the lab and helped me look through all those images for the mapping paper, one image among the thousands had a funny white blob on the top right corner with pink patches on it (R1112_DSC_061503_112338_08504.JPG). Nobody in the lab at the time could guess what it was – it was kind of like I had a UFO sighting during my project in 2007.

    Then, during a cable survey off the coast of Washington, a few small glass sponges (Aphrocallistes vastus & Heterochone calyx) were found – like cactus (or tumbleweeds?) in a seafloor desert of mud. Lo and behold, a familiar looking white blob with pink patches was sitting there right next to those sponges. Luckily an invertebrate expert was on board and gave me an ID on the funny blob, “Peltodoris lentiginosa”, and he said, “They only eat demosponges”. I thought, NO WAY? Those varmints are next to some glass sponges, Doc…I have this blurry, photo of a white blob with pink blotches sitting on glass sponges from 2007…

    So along came our 2009 cruise, I made “WANTED DEAD OR ALIVE” posters with that blurry photo from 2007 and told everybody to keep their eyes out for “white blobs with pink blotches, sitting on even bigger creamy white blobs”. And Sally with her eagle eyes was able to find some for us at Galiano reef.

    Four cruises, >2,000 photos, and 5 years later, you see the end product, the paper, of that funny tangent to the glass sponge reef story of my Master’s.

    Moral of the story – there’s a lot of cool biology to be discovered in your own backyard still, you just gotta keep looking.

    • Awesome! Thanks so much for this prequel Jackson! I love hearing the ‘behind the scenes’ of research. I definitely remember the excitement on the cruise when the nudibranchs were spotted. It was even more exciting than seeing the six-gill shark (although that was pretty cool as well)! It’s great motivation knowing that cool science might be right before our eyes 🙂

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