Flamboyant Cuttlefish

It’s been a long time since I put a critter in the spotlights, so it’s time for one of my personal favourites: the Flamboyant Cuttlefish! I am definitely not the only one to like this amazing little animal, for most divers it is high in the top 10 of critters to see. With good reason as well, Flamboyant Cuttlefish are one of the most beautiful and intriguing inhabitants of sandy dive sites.

flamboyant-cuttlefish2

Flamboyant Cuttlefish (Metasepia pfefferi) striking a pose

The small cephalopod many divers call “Flamboyant Cuttlefish” are in fact two species: the Flamboyant Cuttlefish (Metasepia pfefferi) and the Paintpot Cuttlefish (Metasepia tullbergi). The first one lives in Malaysia, Indonesia, Papua New Guinea and the north of Australia. The Paintpot Cuttlefish is found further north, from the Gulf of Thailand all the way up to southern Japan. Both species are classic muck dive critters, they only occur on muddy or sandy bottoms, so you will have to move away from coral reef to encounter them.

flamboyant-cuttlefish3So why does this animal deserve the effort of searching sandy plains for days on end, in the hope catching a glimpse of it? To start with (the name is a bit of a give-away) they are very flamboyant critters. We are talking yellows, pinks, blacks and whites, all at once! If that wasn’t enough, they often change their colours into “traveling waves”, even more so than normal cuttlefish or octopuses. From my experience, smaller Flamboyant Cuttlefishes have the brightest colours and make the most extravagant displays. When I write small, I do mean really small: adults do not grow much bigger than 8cm. They ideally sized Flamboyant Cuttlefish for the best colour-show  would be around 3-5 cm!

If finding an animal that size seems difficult, you might also want to consider the following. When they are not disturbed, hunting, or mating, Flamboyant Cuttlefish are anything but flamboyant. In their “standard” state, they blend in perfectly with their background, so they will be a mottled grey, brown, or black. For this reason some divers or photographers are tempted to disturb the animal to better see its colours. It is obvious that this is a bad idea, as it will stress out the cuttlefish. Be patient  instead, observe it for a while and you might even be rewarded by seeing it hunt small shrimp, lay eggs, or even mate!

Another thing that is special about them is that they do not swim, but walk across the bottom. To do so they use two of their arms and an adaptation of their mantle. They can swim, but only do so when they’re startled and over short distances. I could easily spend an entire dive watching these guys wander across the seafloor, little blobs of colour on a quest to eat as many shrimp as possible. It might be because of the awkward way they walk, but I always imagine them to be mildly grumpy animals. A bit like an old man with stiff joints who can’t walk that well, grumbling to himself about how the terrible weather…

flamboyant-cuttlefish4

A juvenile Flamboyant cuttlefish (M. pfefferi) walking across the rubble

An interesting mystery surrounding these animals is whether or not they are toxic. Their colours would suggest some form of aposematic colouration, in the same way nudibranchs advertise their toxicity with bright colours. Some authors have even suggested flamboyant cuttlefish might mimic nudibranchs such as the Ocellate Phyllidia (Phyllidia ocellata). I have however, not read a single bit of conclusive evidence of this. It seems to be one of these “facts” people have assumed, written about and then it just got copied. To date there seem to be no papers out their describing whether or not Flamboyant Cuttlefish really are toxic, and which toxin they would produce. If anyone would have come across that information, I would be very grateful if you could share it with me and the rest of the world.

As is often the case with small critters, we don’t know very much about them. But that doesn’t have to stop us enjoying looking at them. Which is why I couldn’t resist adding a video of one of these guys. The title is a bit too sensational, but the footage is great, enjoy!

 

 

Black sand: Origins

The species I study are found in a very specific habitat. Unlike many (dare I say most) marine biologists who work in the tropics, I hardly spend any time at all on coral reefs, mangroves or seagrass beds. I estimate that since starting my PhD, roughly 80% of my dives were done over sand. No coral, no rocks, hardly any distinctive feature at all, just wide expanses of sand. Mind you, not just any kind of sand, the critters I look for seem to be found most often on black sand.

blacksandbeach

A black sand beach in Lembeh Strait, Indonesia

For those who have never had the pleasure of diving over black sand or those used to diving in places like Egypt, Maldives or the Great Barrier Reef, the idea of a black sand beach or dive site might seem strange or hard to imagine. When reading the words “tropical beach”, most of us imagine powdery white sand, turquoise water, and a bunch of palm trees added for good measure. But I am happiest starting my dive from a beach as black as my (soul) wetsuit and dive boots. The first time you see a true black sand beach is mesmerising and even a bit alienating, it somehow doesn’t seem right. The water looks grey instead of blue, darker, and less inviting than those beautiful blue lagoons from travel brochures. Until you put your head under water and start looking around…

But why are some beaches black? What is the difference between the powdery white sand of Maldives and the pitch black sands of Lembeh or Hawaii? After the ICRS conference in Honolulu last week I decided to go have a closer look at the origins of my preferred study systems: active volcanoes! There are few places on this world better suited to do this than on Hawaii’s big island. Accompanied by Jamie, a marine scientist specialising in underwater soundscapes, I set off to find out how close to a volcano one needs to get before the hairs on your legs get scorched off 😉

Lava_jungle.jpg

Lava flow making its way through the forest

Turns out the answer is: not very close at all. In what was the highlight of our trip we flew in an open-doors helicopter over a lake of magma and a lava stream running down a mountain. Even hovering 50m above the lava you can feel the incredible heat emanating from the stream! The Kilauea volcano is one of the most active volcanoes in the world, and has been erupting since 1983. The result is an amazing landscape of solidified lava, covering vast expanses of the island.  During our 3 day stay in the Volcano National Park, we visited lava tubes, hiked over solidified lava lakes, were awestruck by the raw spectacle of watching a volcanic crater at night, and got sunburned ambling across a frozen lava wasteland that was a village until only few year ago. While we were in Hawaii, there were no lava streams entering the ocean, but there were plenty of places where it recently did.

Lava_ocean

Fresh lava flow in the ocean

Liquid lava flowing in the ocean is one of the two ways black sand beaches can be formed. The lava is so hot that when it runs into the cold water, it causes explosions that shatter tiny fragments of volcanic sand/glass around. This process can happen so fast that a black sand beach can be formed overnight! The size of these fragments can be from small boulders to actual fine sand, dependent on the temperature of the lava and the water. The dark colour of the sand is caused by the mixture of minerals inside the lava, the minerals giving the darker colours are mostly iron oxides such as magnetite.

The other way black sand beaches are formed, is through erosion of black volcanic rocks by rivers, which then carry the black grains of sand down to the ocean. Depending on which other types of rock the rivers flow over other minerals will be added to the mix, resulting in sand colours that can range from pitch black to dark brown or even beige or green. For any geology-inclined readers, this site has got all the details you could possibly want to know about black sand.

blacksand

Black sand + dive boots

So to summarise: black sand ecosystems are formed by some of the most epic geological processes in the world, magma from the centre of the earth erupting and shaping the world as we know it. The powdery white sand beaches of Maldives on the other hand, are mostly formed by the build-up of whole lot of parrotfish poop***. An interesting process for sure, but give me an epic black sand beach over a pile of fish poop any day 😉

 

***Technically speaking parrotfish poop, eroded corals, shells and bits of other stuff, but I’m taking some freedom here 😉