Join me in the cold, dark, life-sustaining NE Pacific Ocean to discover the great beauty, mystery and fragility hidden there.

Attack of the Sea Slugs!

This is an opalescent nudibranch.

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

Opalescent nudibranch – species up to 8 cm long. The white patch on the right is a colony of animals known as “kelp-encrusting bryozoan”. © 2014 Jackie Hildering; http://www.themarinedetective.ca

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

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

   © 2014 Jackie Hildering; http://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

6 Responses to “Attack of the Sea Slugs!”

  1. Paul Sim

    I think I missed the link for the jaw dropping video …is it just me. I know I can be awefully thick some days.

    [Also from Paul]
    Submitted on 2014/02/10 at 3:10 pm
    A friend has pictures recently of one eating a different type of nudi (I think it might have been a F. verrucosa or whatever they’re called now). We sent his pictures to Donna Gibbs and she in turn sent them to Dave Behrens who said they he thought it might be more common behavior than most divers think. I dunno, I had never seen this in my 1200+ dives so maybe I am blind or always in the wrong place at the wrong time. It is pretty cool though.

    Reply
    • The Marine Detective

      Hello Paul, great to have additional confirmation from these high authorities and sure, seeing now how intense and quick the attacks are, our chances as divers of seeing the behaviour are quite limited. HOWEVER, I also contend that it is far more likely to happen in non-wild settings e.g. in aquariums, in laboratories, or when animals are put in close proximity when being collected. I think that most early day aquarium collectors have stories of big “oops” moments when they put glaucid aeolids together and then find a bag or jar full of bits and pieces. When researching for this blog I found this one account of an opalescent taking out a 3-lined aeolid (includes video) when they were put in close proximity. http://www.seaslugforum.net/message/20455
      There has also been research done on the predation and cannibalising when the animals are in a laboratory settings. I don’t think any of us can know how often in happens in the wild.

      Reply
  2. Good Jacqui

    Excellent footage and great blog Jackie, I recognize the truth in what you say about the ‘cute’ animals getting better press.

    Reply

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