A TaLE of Two Nudibranchs

Sometimes, the best parts of a science story gets edited out during the process of crafting research to meet the 'peer-reviewed' format.  My blog seems to be the perfect place for these anecdotes that don't quite fit inside the box.  For example, I once published a paper on glass sponge-eating nudibranchs that had quite a fun "behind-the-science" story.

The story goes way back to the start of my marine biology training (late 2007). At the time, I was processing and analyzing  digital still photographs as part of a sponge mapping method I was developing for reef ecosystems in coastal British Columbia, Canada.  Part of that work involved counting and identifying all the other animals living on the sponges. 

​On a cold winter's day in Edmonton, I came across this mystery blob in one (out of ~700) of the images.

In 2007, I was literally fresh off the boat when I started analyzing ROV still images and i came across this mystery blotchy potato. Image courtesy of CSSF/ Sally Leys.

I tried asking several of my then lab-mates if they could ID this weird blotchy potato.  No guesses later, I filed this mystery deep-sea potato away and continued counting squat lobsters to a million.

Fast forward to the next field season (July 2008).  That summer, I explored deep-sea habitats off the southwest coast of Vancouver Island on board the Canadian Coast Guard ship JP Tully with the rov ROPOS.

ROPOS is one of the few ROVs that has a custom built digital still camera system that allows scientists to photograph and visually document things of interest (for me, weird deep-sea critters).

The only constant over the past 10 years - me (this photos is from 2008) logging and capturing still images during an ROV cruise while exploring parts unknown. Image courtesy of Ray Morgan.

In the middle of nowhere, we came across the same blotchy purple potato next to a tiny individual cloud sponge (Aphrocallistes vastus) - the same sponge that forms the reefs I was mapping for my graduate work.

My OCD memory won't let go of biological mysteries. The 'thirst for knowledge' is a pre-requisite for research scientists. That and the ability to count to really high numbers (look at all those squat lobsters).

For this encounter, I was sitting next to Phil Lambert (the gentleman with the camera around his neck) who gave me the nudibranch ID of "Anisodoris lentiginosa".  I asked Phil, "Hey, does that potato eat glass sponges?" which he promptly responded, "No, only demosponges". 

I began to disagree and said that I had seen the same purple blotchy blob in one of my images of glass sponge reefs. The imagery alone wasn't convincing enough to confirm this nudibranch was a predator of the reef-forming glass sponges and that I had just stumbled upon what could be the first documented predator of glass sponges outside of Antarctica (fun fact - also a dorid nudibranch). 

Patience is a virtue with deep-sea work, so I filed my thoughts away and kept counting squat lobsters.

Fast forward to next the field season (Oct 2009).  I had 24 hours to apply my ROV mapping method to three reefs in the Strait of Georgia (the priority for this cruise).  Among other things, I also prepared this document and plastered this 'wanted' poster on the ship as a 'just in case' we stumbled upon these nudibranchs.

While I was mapping reefs in beast-mode, I kept my eye out for those pink blotchy potatoes.  ​It wasn't until I was sleep-deprived and passed out that I woke up in the final hours of the last ROV dive to the surprise that my supervisor had also been keeping her eye out for blotchy pink potatoes.  

WANTED - glass-sponge eating nudibranchs. ©Jackson W.F. Chu

We managed to sample 4 individuals with the ROV which I kept in holding tanks for several months  I can still remember the face and reaction of my future PhD-supervisor when she stepped onto the ship during a crew-change. Her face as she stares into a bucket full of seawater and blotchy potatoes = WHAT ARE THOSE THINGS?!? 

Using a combination of gut-contents analysis and fecal contents analysis, I was able to identify the microscopic glass spicules that let me ID the nudibranch diet back to the glass sponges. I reviewed the HD-video from the reef-mapping exercise and found that we had actually flown over n=26 nudibranchs during the surveys. A follow-up cruise later, we came across a second nudibranch, Doris (Archidoris) odhneri, which also had engorged guts full of glass sponge spicules. Dr. Sandra Millen (who described P. lentiginosa) helped me confirm the nudibranch species IDs. The only thing that still puzzles me is how these nudibranchs can survive on a diet of 'fiberglass' (>90% of those glass sponges is inorganic, non-nutritious silica)?  ​

Doris odhneri next to a light snack - the 2nd documented predator of reef-forming glass sponges. ©Jackson W.F. Chu

When the biology of the organisms you're studying is important, you often gravitate towards simple natural history questions like "what eats my study organism?".  When that question highlights a knowledge gap, you realize how much basic science still needs to be done.

​I've accumulated a lot of these science stories over the years. Stay tuned if you liked this type of "Behind-the-Science" blogpost.