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Reaching New Heights? A Sea Cucumber Mystery.

This is an open case; one that has me bemused and amused.

While diving near the Great Bear Rainforest in Jackson Narrows, my buddy Tavish Campbell came upon a Giant Sea Cucumber in this very unusual position (Apostichopus californicus, aka California Sea Cucumber).

It was stretched straight up and down, head end up.

Giant Red Sea Cucumber reaching for new heights? Dive buddy - Tavish Campbell. ©Jackie Hildering

Giant Sea Cucumber reaching for new heights? Dive buddy – Tavish Campbell. ©Jackie Hildering

As you likely know, this species is most often horizontal; “face” down cruising up to around 4 meters a day along the ocean bottom, mopping up nutritious particles with mucus-covered bushy white tentacles. When there is good stuff stuck on the tentacles, these retract into the mouth (with sandy casts coming out the other end).

A Giant Red Sea Cucumber in its usual position, horizontal so that it can feed by mopping up particles. This one has a nudibranch crossing over it (Flabellina trephine). ©Jackie Hildering

A Giant Sea Cucumber in its usual position, horizontal so that it can feed by mopping up particles. This one has a nudibranch crossing over it (Flabellina trophina). ©Jackie Hildering

So why would this individual assume such a remarkably vertical position? Could it be feeding related? It was extending and retracting its mouth tentacles repeatedly but clearly this was not effective in gathering any snacks.

Giant Red Sea Cucumber with buddy Tavish Campbell. ©Jackie Hildering

Giant Sea Cucumber with buddy Tavish Campbell. Mouth tentacles extended. Note all the tube feed revealing its relatedness to sea stars and sea urchins (phylum Echinodermata). ©Jackie Hildering

My best hypothesis is that this was mating related. Giant Sea Cucumbers have separate sexes and rise up in a python-like position to release their sex cells (see figure below from A Snail’s Odyssey). This pose reduces the number of sex cells that settle to the ocean bottom, unfertilized.

Giant Sea Cucumbers spawning in phython-like pose. Source: A Snail’s Odyssey.

Additional strategies to enhance the chances of fertilization are to twist back and forth and/or intertwine with a partner while releasing gametes. (This species will also catapult back and forth when trying to escape predation by Sunflower Stars).

Striving to ensure your DNA gets passed on does not happen randomly however. As with all broadcast spawners, there is a cue so that the release of sex cells is coordinated. (See my other blog “Sea of Love – Broadcast Spawning“). Giant Sea Cucumbers are known to mate in the shallows from April to August repeatedly “dribble spawning”.

Our high-reaching Giant Sea Cucumber friend was indeed in the shallows and it was significantly warmer there. Was the temperature a cue that it was time to mate? Was s/he trying to sense the presence of a partner or others of his/her kind already broadcasting?

Was s/he reaching to new heights to allow even better distribution of sex cells than the python pose?

Was this individual even old enough to mate as they do not sexually mature till age 4? It’s size certainly suggested it was older since maximum size for the species is reported to be 50 cm.

Had we had more air we could have waited and likely concluded what was up with this behaviour.

As is so often the case however I surfaced with even more questions and a greater sense of wonder about the life below. And yes, this time it may be that I was laughing so hard I was sputtering sea water as well.

Unsolved mystery! ©Jackie Hildering

More on the species’ spawning: “The gametes stream from a single gonopore within the ring of tentacles (but see Fig. 2), and fertilisation takes place in the open water. The eggs are relatively large and yolky in sea cucumbers, and develop to a feeding larval stage known as an auricularia. After a 3-5wk period floating in the plankton, the larvae metamorphose and settle to the sea bottom.” Source: A Snail’s Odyssey.

Two Giant Sea Cucumbers in spawning position, April 2021 ©Jackie Hildering. The orange animals are Orange Sea Cucumbers and they were spawning too and what a spectacular spectacle that is. See my blog at this link.

Sources / more information:

A Snail’s Odyssey; Learn About Sea Cucumbers
Giant Sea Cucumber Walla Walla Edu
The Marine Detective: Sea of Love – Broadcast Spawning

The Case of Stones in Sea Lions’ Stomachs

Did you know that stones are commonly found in the stomachs of Steller sea lions?

These stomach stones or “gastroliths” are as big as 12 cm!

Share your theories about why you think this might be after viewing the video below. It provides you with information to help with this Marine Detective case.

Happy sleuthing to you!

Note that yes, gastroliths have been found in the stomachs of other seal and sea lions species including the California Sea Lion, Zalophus californianus (Source: Drehmer and Oliverira).

Click here for SeaDoc footage of Steller Sea Lions playing with California Sea Cucumbers.

Research into gastroliths in Steller Sea Lions

C. R. Shuert and J. E. Mellish “Size, mass, and occurrence of gastroliths in juvenile Steller sea lions (Eumetopias jubatus),” Journal of Mammalogy 97(2), 639-643, (11 January 2016).

Includes:

Abstract: “In summary, our opportunistic assessment of gastroliths in temporarily captive Steller sea lions showed that a large proportion of juvenile animals (e.g., one-third or more) may haveone or more stones at any given time. The regurgitation of gastroliths correlated best with leaner, but not poorer body conditions, and during the summer months, possibly indicating a weak association as a digestion aid. We found little evidence to suggest that they assist in buoyancy and satiation; it is even more unclear as to what drives an individual to regurgitate them. With a lack of strong conclusions relating to a particular use, we can only conclude that they appear to serve a function in sea lions and are not ingested accidentally. A combined assessment of regurgitated and in vivo gastrolith measurements may shed more light on the subject and allow for direct evaluation and conclusions as to their functionality in sea lions.”

“Gastroliths, deﬁned as stones or concretions in the digestive tract, occur in many extant vertebrate taxa and throughout the fossil record of marine tetrapods (Wings 2007). Most information is anecdotal, with limited data on occurrence and size(e.g., Labansen et al. 2007). Adjusting buoyancy, alleviating hunger, and aiding in digestion are the most popular theories for the presence of gastroliths in marine mammals (Taylor 1993). Gastroliths have been described in all 3 families of pinnipeds including otariids (e.g., South American sea lions Otaria byronia—Drehmer and Oliveira 2003), phocids (e.g., harp seals Phoca groenlandica—Nordøy 1995), and odobenids (Gjertz and Wigg 1992)”

A note about the Marine Mammal Regulations in Canada

Amended Regulations (since July 2018) include that it is illegal to target marine mammals for the purposes of swimming with them (unless permitted by a research license). See the Marine Mammal Regulations at www.SeeABlowGoSlow.org.

Further sources

Drehmer, C J, and L R. Oliveira. “Occurrence of Gastroliths in South American Sea Lions (Otaria byronia) from Southern Brazil.” Latin American Journal of Aquatic Mammals. 2.2 (2003).

Scheffer, V.B. and Neff, J.A. (1948) Food of California sea lions. Journal of Mammalogy 29(1): 67-68

Taylor, Michael A. “Stomach Stones for Feeding or Buoyancy?: The Occurrence and Function of Gastroliths in Marine Tetrapods.” Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. (1993)

Wings, Oliver. “A Review of Gastrolith Function with Implications for Fossil Vertebrates and a Revised Classification.” Acta Palaeontologica Polonica. 52 (2007): 1-16. Print.

Attack of the Sea Slugs!

[Update March 2018 – There has been a reclassification of this species of nudibranch whereby Hermissenda crassicornis is also being referenced as the “Thick-Horned Nudibranch. Please see my blog at this link for that information.]

This is an Opalescent Nudibranch (Hermissenda crassicornis).

Opalescent nudibranch. The white batch is a colony of animals known as kelp-encrusting bryozoan. © 2014 Jackie Hildering; www.themarinedetective.ca

Here is one climbing giant kelp with hooded nudibranchs in the background.

Opalescent nudibranch © 2014 Jackie Hildering; www.themarinedetective.ca

I know! Aren’t they astonishingly beautiful? Opalescent Nudibranchs are one of the most powerful ambassadors for shattering the misconception that warm waters are home to more colourful life. They truly help in raising awareness about the incredibly exotic and vibrant life hidden just below the surface in the dark, rich, cold waters of the NE Pacific.

But they help with something else too.

I recently received a video clip of Opalescent Nudibranchs from Tavish Campbell, taken while with Pacific Wild documenting the life that would be at risk if tanker traffic came to Caamano Sound. Tavish, who is a fellow-diver and appreciator of all things marine, asked, “Hey Marine Detective, what’s going on here?!” What I saw led me to realize how this species is also a very powerful engager for addressing another default notion we humans seem to have.

We tend to bestow judgemental labels on animals depending on our interpretation of their beauty. We are inclined to think beautiful animals are “nice”, “cute” and “benign”, and foreign looking animals are “mean”, “ugly” and/or “bad”.

While I appreciate that some organisms may be more aesthetically pleasing than others, there is no “ugly” in Nature and there certainly isn’t “bad”. Organisms look and live as they do because it works. Their appearance and behaviours are the result of expanses of time longer than we humans, as newcomers, can truly appreciate. Organisms’ adaptation allow them to survive and fulfil their niche in Nature’s puzzle so that there is the greatest chance of balance. [Insert “God” instead of “Nature” if this is your preference.]

Therefore, for example, there are no “bad” kinds of orca but rather orca populations whose job in Nature is to eat other marine mammals. There are dolphins that sometimes kill other marine mammals without this being for the purposes of food (no matter how much this conflicts with the “Flipper-like” identities we have imposed on them). Sea otters do things that definitely are NOT cute and . . . it also means that beautiful sea slugs will also do what they need to in order to survive.

I take such comfort in not needing to judge Nature. It just is. In contrast, human behaviours too often do NOT enhance the potential of balance in Nature or even the chances of our own survival.

So here’s the jaw-dropping video. Ready . . .?

Opalescent Nudibranchs in all their beauty, are extremely voracious predators and, as is evident in the video, will also attack their own kind. Reportedly, fights most often result when the animals come into contact head-to-head. The animal closest to the head or end of the other has the advantage of getting in the first bite and thereby the greater likelihood of killing their opponent and eating them.

But, they are hermaphrodites, they need one another to mate! As hermaphrodites, there is not even male-to-male competition for females! So why, when your chances of finding a mate as a sea slug are already pretty limited, would you kill another of your kind instead of mating with them?

I hypothesize that it would have to do with the balance between needing to eat and needing to mate and/or that there is some sort of genetic competition going on. That’s all I got. Insert rap awe and wonder here. I may not know why they do what they do but I do know, there has to be an advantage to their survival.

What I also know for sure is that this gives a whole new meaning to “slugging it out”!

Opalescent nudibranch egg mass. http://jackiehildering.smugmug.com/Underwater/Sea-slugs/

Opalescent Nudibranch egg mass. Every species of nudibranch has distinct egg masses i.e. they are species specific. 2014 Jackie Hildering; http://www.themarinedetective.ca

Views from the Mast

How high can you get in seeing dolphins and humpbacks?

Captain Tavish Campbell knows.

The 1.5 minute clip below reveals his unique perspective from atop the 100′ mast of the beautiful schooner Maple Leaf.

From on high, he shares with us the view of hundreds of Pacific white-sided dolphins and a bubble-netting humpback whale.

I have the joy of sometimes serving as naturalist for Maple Leaf Adventures with Tavish. He allowed me to put together this clip for the David Suzuki Foundation’s Ocean Stories Campaign, both of us hoping that the breathtaking beauty might inspire people to undertake more positive action to protect the great biodiversity of the North Pacific.

What’s your Ocean Story? You can help inspire connection and positive change by sharing your story with DSF up to midnight on October 31st.