It’s Nudibranch Time!

I know what some people are thinking: this is just another wannabe influencer jumping on the opalescent nudibranch bandwagon. All ‘those kids’ are clamouring for more nudibranch content, so he’s just taking the creatively bankrupt decision to get some easy clicks. There are so many opalescent nudibranch memes and videos going around that anyone can get some easy views at the cost of any self respect.

My response to those uncharitable people: It has nothing to do with the popular trends; I’m just on the wavelength of the younger generation and share many interests, such as Tiktok, Fortnite, and of course all the nudibranches. That’s just who I am.

Obviously, Nudibranches don’t need any explanation for anyone who is remotely up-to-date. But I try to keep this blog accessible to a wide audience, no matter how uncool they may be. For all those old people who aren’t as [note to self: what word do those little $&!%s use for ‘hip’ now? find out and put that word here] as me, I guess I’d better explain the new hot craze sweeping the world. Take notes, and maybe you’ll get some street cred from the younger generation, GRANDPA!

It’s a slug.

But you’re not picturing it right. it’s a cool slug.

No. An underwater slug.

I’m really not describing it correctly, am I? I guess you have to be ‘with it’ to really understand. Or just look at a picture… which I probably should have done at the beginning. Here’s a nudibranch.

An oplaescent nudibranch, to be exact; there’s a lot of different nudibranches worldwide, but the opalescent nudibranch is only found on the pacific coast between northern Mexico and Alaska. It’s very colourful. Is it dangerous? Well, it’s a small slug. It is carnivorous, but only for immobile underwater animals. My research suggests that is a small minority of my audience, at best. And again, it is a small slug. So… probably not.

Poisonous, though? LOOK AT IT! There are only two reasons an animal would be that colourful:

1: It’s a sex thing

2: It’s warning you not to eat it.

it’s not number one. Nudibranches aren’t really into ‘sex things’ or ‘attracting mates of the opposite sex’; they’re hermaphrodites. That leaves option two. Either they’re poisonous, or want you to think they’re poisonous, and I’m not going to eat one to find out. The internet, however, says they’re not pretending; they can absorb toxins from some of the animals they eat without issue, and store those toxins to make themselves poisonous. So maybe they’re edible, if you put them on the right diet first? These ones probably don’t diet, though.

At the time I took my photos, I was on a trip to Haida Gwaii(aka the Queen Charlotte Islands) off the British Columbia Coast. Y’know. Here.

They were living just under the surface of the water, climbing on a floating lodge…

situated about… here? Maybe?

I don’t know exactly where it was; I didn’t drive there. Something to do with no ‘roads’ in the area. I think that’s about the right area, however. I had booked onto a tour to see the southern parts of the islands, and the lodge was one of the overnight stays. It was fun to enjoy a nice relaxing cruise. By ‘cruise’, I mean four days on a 12-person zodiac, getting rained on. I don’t really know what a ‘cruise’ means, is what I’m saying. It son’t one of those cool things to know about. A cruise is something for old people.

Anyways, Haida Gwaii isn’t the ideal destination for warm, sandy beaches and lounging on the coast. Sure, there are a few sandy beaches, and lot more beaches with small pebbles, large pebbles, and rocks, but a lot of the coast is just rocky. That isn’t as good for lounging, but on the other hand, it gives sea-life a firm foundation to grow on. And there’s a lot of life off the coast; some of it breathtaking…

.. and some of it really, really, disturbing.

Which brings me to the opalescent nudibranch. The nudibranches probably were all around, living below the shoreline, but they’re small. The ones I saw were about 2-3 cm; Probably there are bigger ones, but I’d have to explore the cold pacific water to find them; water populated with…

… yeah.

On the bright side, I didn’t have to actually look for them; the nudibranches couldn’t have been any easier to photograph. They were just a few inches below the waterline on the lodge, and I could take photos just by pointing my camera straight down at them. That would reduce distortion from the water as much as possible; I did bring waterproof cameras on this trip, but I didn’t (and still don’t) have any waterproof full spectrum cameras. Also, my waterproof cameras were very quickly ceasing to be either waterproof or cameras.

Of course I’d try to take photos outside the visible range. Look at them! They’re [insert current word for ‘cool’ here]!

General rule: If the colours are weird, that makes me want to investigate them further. Of course, there was one more issue that affected my photographs.

Water absorbs a lot of light outside the visible range. It isn’t opaque in the ranges I usually play around with(excepting thermal infrared, but that’s an outlier), but it takes a bit longer shutter speed than you’d expect. The Nudibranch photo above, for instance, was my best photo, but the ripples in the water meant that even with a relatively quick exposure, I’d have to deal with timing to minimize distortion, and with a longer exposure, the ripples would just make the entire photo look ripply. Again, I couldn’t take these pictures underwater, but rather took them above water looking straight down.

Here’s the same photo again.

Lets do my usual thing and break it into the red, green, and blue colour channels.

There are obvious differences between the three. Most notably, the orange tendrils are bright in the red channel, becoming darker as the wavelength shortens. In the blue channel, they appear as black tips to the organism. On the other hand, blue lines running down the body of the nudibranch are almost invisible in the red channel, as the shade matches the rest of the body. Those lines become more prevalent as the channel shifts into green and then blue, and in the latter are bright white. In fact, blue is the most interesting of the three channels. That’s rare with my photos. I don’t know if that’s me being critical of the blue wavelengths, or of my photography. Here’s a gif of the channels, to more easily compare the three.

By the time I set up my full spectrum camera, the stupid &*!%ing nudibranch had disappeared, so I had to take photos of another, less photogenic, nudibranch. Here it is, also trying to hide from me. Thankfully, they’re small slugs, so don’t hide quickly.

I didn’t crop this photo as much as the other one, as some of the other sea life is wirth looking at as well. The roundish thing at top was a miniscule jellyfish.

Anyways, here’s the channels again.

The spectrum trends for the nudibranch are pretty much the same as the ones above. The shells(mussels, I think), are worth mentioning here, though. They look dark in the full colour photo, but as the channels show, they get darker as the wavelength shortens.

Without any filter, my camera takes full spectrum photos; in theory, that’s visible, infrared, and ultraviolet light. In practice, the camera records so little UV light that it is pretty much a visible/IR photo. Here it is.

Fairly similar, but… redder? The nudibranch’s blue lines ‘pop out’ more here; with the white balance, they actually look more cyan. The mussel shells are now brighter, almost a burgundy colour. as my camera only has three channels for colour, it records infrared as ‘red’. Meaning: There’s something going on with the longer wavelengths.

My Zomei 680 nm filter allows the camera to record a bit of red light, and a lot of near-infrared.

The orange patches on the nudibranch still show up… slightly… but are easy to miss. It mostly seems to all be the same shade in the near-infrared range. In fact, it doesn’t really stand out at all; it is in the middle of the photo, but if you weren’t looking for it, you probably wouldn’t notice it.

The shells, on the other hand, are very different now. They’re much lighter than in the visible photos, and more detail of them can be seen. I have a suspicion why, but lets look at the other side of the spectrum first.

My custom short-pass filter lets violet, UV, and a small bit of blue light through. It is the closest UV filter I have to the visible range, so is usually the best for lower-light conditions. Even so, it was kind of blurry with the moving water.

Even with the blur, however, the blue lines are clearly visible again, and the orange tendrils are very dark. More, they’re dark farther down than with the blue channel. The mussels are dark here again, which supports my hypothesis (‘hypothesis’ is another word used by cool people, by the way). I think there must be algae growing on the shells. The variation of shades seems close to that of vegetation at similar spectra; if the algae obtain energy from photosynthesis, they’ll absorb a lot of short-wavelength light, and reflect more long wavelength light. near-infrared light is usually reflected, making plants appear white. If I’m right, the shells aren’t as bright as above-water plants, probably because the algae are only a thin coating on the shell. They aren’t thick enough to obscure the shell underneath. I couldn’t find any strong data to correlate my hypothesis so far, but did find an article from Ireland suggesting that a variety of algae can colonize mussel shells. It also suggests that the shells are safer than bare rock for the colonies, so I’d guess that some similar rules apply on the pacific coasts.

I didn’t take any photos deeper into the infrared or ultraviolet ranges… well, I did, but they were all blurrier, and didn’t seem worth publishing. Still, what I took was enough to show that the opalescent nudibranch looks different in each spectra. they look most different in the blue and ultraviolet spectra, however; I’d guess that that is the range most of their predators can see in, and infrared isn’t a priority for warning predators away.

Anyhow, I’d write more about the nudibranches, but I just realized they’re not cool anymore, so scrap that. The rest of my trip was cool enough to write about, but not for now, because I’m trying to stay relevant.

Next post: an in depth look at Fidget Spinners!

The nudibranch and lodge photos were taken with a modified Canon Rebel T3i camera. The other underwater photos were taken with a godawful Poloroid underwater camera that doesn’t deserve to be mentioned. Yes I’m still bitter! It’s supposed to be waterproof, not water-soluble!

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