The diving photographer community has numerous “bucket list” type of organisms. The what is often just as important as how you take the photograph, if not more. Photographs from diving have that added element of shared understanding with the viewer (“It may be a blue blob, but we both know it’s a rare blue blob”). In Hong Kong, we no longer– or probably never– have a lot of those wow factor creatures marine ecosystems. Our bucket list items are probably the most common at dive sites elsewhere.
On top of that, water quality can fluctuate from a milky blue, clear green, muddy olive, to the rare crystal turquoise waters during the winter. But, having been pushed to find subjects during my dives this past year and more, one thing keeps the interest going no matter the conditions– nudibranchs.
Nudibranchs, nudies–or as divers in HK colloquially call them in Chinese– “sea bunnies”, peak during the colder months. They thrive in rocky reef areas, especially at islands with steep granite rock faces underwater, or sometimes in mucky bottoms. I once saw a meme shared by ecologists of a nudibranch and its David Bowie outfit counterpart. For invertebrates that are essentially cannibalistic sea slugs, these sea bunnies come in the most incredible forms and colors.
Sometimes nudibranchs are so colorful or opulently decorated that distinguishing their “heads” can be difficult. They generally follow a body shape that’s a little elongated, with a mouth and two “bunny ears” at the anterior and then gills like a sprouted flower on the tail-end of their back. The bunny ears are actually their smell/taste organ and you can tell them apart from the more ridged appearance (usually).
Although I’ve spent nearly a year regularly diving in Hong Kong, I haven’t had the time to read up on nudibranchs. In the quickest Wikipedia research I could do, some nudies like the disco medusa above have tentacle-like protrusions called cerata, which are venomous for defense. I have yet to touch one, thank god, but they add to the flair, don’t they?
Some nudibranchs are definitely not as conspicuous. I call this big boy below the mucky cocoa dust. I’ve seen them quite a few times now, and they’ve all been on the large side…
This species of nudibranchs (“black sesame boy”) are one of my favorites, mostly for their posing. They’ve been popping up everywhere on the encrusting algae and these bubble shaped macroalgae in shallow coral areas. Just last week, I saw some that were around half a millimeter long. Those had me squealing.
Some sea bunnies are quite uncommon, but most of them pop-up around the tail end of winter time to get busy. This cerata-covered flamboyant nudie is one of those more uncommon species. I’ve only seen this sea bunny once, and it was at a mucky wreck.
With most of these nudies, you’ll notice they’ve attracted little dots of muck on them too. The algae they love to hang around on are great at grabbing on to all the particles in the water. Sometimes, I do wish I could clean them up with a cotton bud.
As cute and incredibly beautiful as they are with their colorations, the general rule in nature is that incredibly bright and colorful patterns serve as a visual warning to potential predators that they are poisonous (or pretending to be).
Most of the ones above are quite small, from millimeters to about 2 cm. However, I’ve just recently learned from a dive at Kung Chau that nudibranchs can grow to huge proportions as well.
No matter how many times I’ve dove in the same spots, thinking I’ll see the same things, nudies keep on coming up with great surprises. If you’re obsessed (I don’t blame you), these sea bunnies I’ve collected over a year in photographs are nothing compared to some actually Insane ones in Indonesia and Philippines. I hope these blobs of color have sparked some joy! Go Google nudibranchs or scroll through that David Bowie-nudie parallel blog for even more ☺