Posts Tagged ‘Coral’

Fluorescence and bioluminescence

When I arrived in Lembeh this time it was just after Christmas. However, I was up for another Christmas treat. Simon here from NAD had ordered a bunch of cool stuff from Nightsea, strobe filters, filters for the lens and a cool pair of yellow spectacles, which waited for me here.  I have now tried this system during my stay and will in this blog give a short overview over what I learned from shooting it. But first of all I want to give a brief explanation over what fluorescence is, and why we can find it in nature. BTW, the complete system is available for rent here in NAD if you wish to try it out.

Fluorescent hard coral

Fluorescent hard coral

First of all, fluorescence is often confused with bio-luminescence. Bio-luminescence is found in more and more animals, and in a number of mushrooms as well. Well-known examples are those of plankton giving of light when disturbed, deep-water organisms with light organs, mushrooms glowing in the forests, fire flies and for northern areas glowworms. Bio-luminescence is the emitting of light involving a chemical reaction. Very generally, the light emitting substance is a protein called luciferin, which emits light through a chemical reaction catalyzed and oxidized by an enzyme, called luciferase. Thus, a chemical provides the energy fueling bio-luminescence, using oxygen in the process.

Bioluminescing mushrooms

Bio-luminescing mushrooms

Fluorescence, in contrast, is the emission of light where energy from one (or on rare occasions two) photon excites an electron into a higher energy orbital. After a short time, the electron will return to its former level, emitting the excess energy as light of another wavelength. No oxygen will be used in this process, as the light emittance is fuelled by the energy in the photon. Many different subjects in nature fluoresce. Despite that, we can seldom see the fluorescence, as the emitted light level is low, or in wavelengths we cannot detect. One notable exception is the red or orange anemones that we sometimes can se in much deeper water than red and orange colors from sunlight penetrate water. Despite being fairly poorly understood on a biological level, fluorescence is used in many applications, from mineralogy, oil detection, microbiology and forensic work.

Fluorescent hard coral

Fluorescent hard coral

So why do things bio-luminesce or fluoresce? Bio-luminescence in marine systems is used for at least three widely different purposes. Most of the deep-sea bio-luminescence seems to be used in order to attract prey.  Second, a number of fish living in the zone deep enough for a little light to get through, use bio-luminescence to counter shade the ventral side of them, so shading against the faint surface light can not be used by predators to find prey. Third, and maybe most speculative, it is thought that small crustaceans that bio-luminesce do so to deter small predators. Why would small predators be afraid of light? Well, if a small more or less translucent predator eats a bio-luminescing crustacean, the small predator will light up and attract the next step upwards in the food chain, increasing small predators risk risk of being killed them selves.

Fluorescent lizardfish

Fluorescent lizard fish

What is the point of fluorescence in marine systems? For a number of shallow water cnidarians, mainly the ones using zooxanthellae for their energy input, fluorescence has been suggested to be a way to control excess levels of sun exposure, limiting the damaging effects of uv-light.

Fluorescent hard coral arm

Fluorescent hard coral

Both proteins in the coral itself as well as chlorophyll in the zooxanthellae associated with the coral may fluoresce. The available evidence, however, does not really support this theory.

Fluorescent hermitcrab

Fluorescent hermit crab

A number of other animals fluoresce. Some crustaceans, such as the anemone hermit crab fluoresce. Also some bristle-worms, fish and cephalopods fluoresce. There seems to be no reason for these animals to fluoresce, so much fluorescence simply seems to be a side effect of other processes in living creatures. Whatever the cause of fluorescence it really is quite magical to see the different sources of fluorescence light up leaving the rest of the surroundings pitch black when diving. Try it out, it is an experience I am sure you will not forget!

Fluorescent anemone

Fluorescent anemone

What did I then learn from shooting this system? A to me very surprising fact is that people are not wildly enthusiastic over the results! That might of course be my results that are lacking. Furthermore, the best results, bleak as that may be, are when there are more than one fluorescent color in the picture. Third, and maybe most important is that it is a lot of fun to try it! I look very much forward to try it on coral reef sites such as in the Red sea as well as on land in rain forests. In a month or so I might get back to you with results from that.

A crab up your butt!

All divers interested in critters sooner or later will get interested in crustaceans. Some of the crustaceans are considered “must see” items, such as harlequin shrimp, tiger shrimp, several of the extremely small shrimp recently found here in Lembeh, emperor shrimp and a host of other shrimp. The keyword here is shrimp.  Crabs on the other hand seldom elicit the same interest from divers. However, many crabs have at least as interesting life styles as shrimp, and many are also colorful and attractive, such as the amazing xeno crabs.

Xeno crab

Xeno crab

As those of you that have read my earlier posts might already understand, one of the aspects I find the most interesting when diving is the close symbiotic relationship between many marine animals, where one animal provides another animal with living quarters. Most crabs are free living and do not show symbiotic relationships to other animals. In contrast, here in Lembeh some really fascinating examples of symbiosis between crabs and other animals can be studied.

First of all, unknown to me until my last visit, there is a crab that quite violently excavates a hole into a soft coral and then lives there. It doesn´t seem to matter much what kind of a soft coral it is. This crab is extraordinarily hard to find, as it most of the time is totally buried into the coral. It comes in a couple of color varieties, which seems to some extent be related to which host they inhabit. This of course indicates that the crab sometimes will be outside its hole and walking around on the coral, using the color to blend in, but despite looking a lot for the crab I have never found it outside its lair.

Soft coral burrowing crab

Soft coral burrowing crab

The second crab on my list does a similar, but less violent, excavation into the rope sponges littering the sea floor in dive sites such as TK. This crab does not disappear into the sponge but at least during daytime it clings to the sponge, fitting into the excavation it has dug so tightly that ii is nearly indistinguishable from the sponge.

Sponge excavating crab

Sponge excavating crab

Third on my list, and a crab that I always look for but very rarely find, is the Xenia crab (not to be confused with the Xeno crab). This crab lives its life in between the polyps of some of the species of the pulsating Xenias soft corals.

Xenia soft coral crab

Xenia soft coral crab

Fourth are the swimming crabs living their whole life on a sea cucumber. These crabs are very flat, and have hooks on their legs. They use these hooks to attach their legs to the skin of the sea cucumber, and with the help of their claws they are able to pull the skin of the sea cucumber partly over them selves, thus being very hard to find for a predator. When they get tired of life on the outside of the sea cucumber, they actually hide themselves inside the ass of the host. Next time you see a sea cucumber, take a look up its butt. There just might be a crab looking out on you from the inside!

Sea cucumber crab

Sea cucumber crab

Fifth, and probably the most beautiful of the symbiotic crabs, are the soft coral crabs, or candy crabs as they are known as. These tiny crabs have small hooks on their exoskeleton where pieces of their host Dendronephtyid soft coral will be attached. The crab will also color match itself to the coral, so finding those crabs are best left to an experienced guide.

Soft coral crab on soft coral in Lembeh

Soft coral crab on soft coral

Finally, and maybe in many ways the weirdest and most special of the crabs here in Lembeh, are the Xeno crabs. These crabs live their whole life on a single wire coral, where they attach polyps from the wire coral to their exoskeleton, thus decreasing the risk that any fish will pick them of the wire coral.

Xeno crab on wire coral in Lembeh

Xeno crab on wire coral

Interestingly enough, very little is known about the details of any of the symbiotic relationships I have described here. Without doubt there is a career for a PhD-student interested in cool crab life styles waiting to be done. It is quite evident that some of the crabs incur a cost for their hosts, but it could also be that the hosts in some way has a benefit from its lodger. The quantification of costs and benefits for those relationships is probably quite hard to do, but wouldn’t it be the dream job of all!

The Asshole Fish and his friends.

Purple Coral Crab, room-mate of Mr Assholefish

The Purple Coral Crab, (Trapezia serenei).

The last few days I have been spending several hours diving in the same place freezing my ass off looking for this stupid fish, that I have named the asshole fish.  The asshole fish lives in Seriatopora Corals from 1m to 10m depth and I hate him.
He gets his name because he has some kind of attention deficit disorder and he cant sit still.  Everytime you get him in focus he moves to a slightly different position where he ends up with a piece of the beautiful coral getting in the way of an important detail, so then you have to wait for him to come back to that spot again – or try repositioning the camera to get him in his new location.  Or as inevitably happens you decide not to reposition and wait.  And wait.  Keep waiting. Notice that he’s in a great position so its worth moving.  You move to the other side of the coral.  He promptly moves back to where you were.  Asshole fish.

You go back to your original place and decide to wait for him to move around his mini territory, hopefully returning to his sitting place that is sharply in focus whilst you’re just waiting

Mr Assholefish and Mrs Assholefisch.  Laughing from the other side of the coral.
The Redhead Coral Goby cannot sit still and is very annoying to photograph.

for him to pop in, you make a deal with him in your head ‘just come here little fishy, i’ll get the shot i want and i’ll leave you alone, we’ll all be happy then,  pleaaaaaasssssseeeee‘  Of course he jumps back into the prime position you want him in, but just for long enough to seemingly laugh… then go off again chasing his mate.   Yes there are two asshole fish in one piece of coral.  It’s taken you 30mins to realise this.

So now you have Mr Assholefish and Mrs Assholefisch (she’s German) sitting in the other side of the piece of coral, laughing at you.  You hold your nerve and wait. maybe pee a little to alleviate the boredom.

As your mind wanders you start to notice the other denziens that share the coral with Mr Assholefish and Mrs Assholefisch. There are the beautiful Coral Crabs (Trapezia sp.) which occasionally pinch Mr Asshole fish when he gets too close.  They also protect the corals from Crown of Thorns Starfish, such is their commensal relationship.  There also seemed to be some kind of snapping shrimp, who also didn’t like Mr Assholefish and Mrs Assholefisch.

As your eyes begin to strain through the viewfinder,  you look up to observe the coral as a whole – you notice 4 or 5 pairs of orange eyes looking at you.  The Assholefish family have babies.  Baby Assholefish are generally bullied by the adult fish if they go anywhere near the safety provided by the centre of the coral, so they are forced to live out on the tips, where it is coincidentally easier to take pictures.  But do not forget they are assholefish and it is in their DNA to be, well, assholefish.

Baby Assholefish!
Juvenile Redhead Coral Gobies choosing to look away at the exact moment you pull the trigger.

These juveniles will dart back and forth and generally infuriate you, this time because they are too small for he 100mm prime, but if you put the dioptre on there then you are too close and you scare them away. Grrrr!

So, if you want to see the assholefish and friends they are on most divesites, but please be careful with the corals – choose a coral head that has been damaged in the past and has a ‘window’ to the inside. Just in case you are staying elsewhere, the Assholefish normally goes by the name: Redhead Coral Goby (Page 325 in the Reef Fish ID book).

World’s cutest Goby

Blackfin Coral Goby

This is – what i believe – the world’s cutest Goby: The Panda Goby (Blackfin Coral Goby / Paragobiodon lacunicolus). This shy little fish grows to maximum 3cm in size and lives exclusively in Pocillopora damicornis hard corals. His sandy coloured body, with dark fins and his orange head in combination with his face expression make him so attractive to most Goby lovers. But the Panda Goby is not only a cutie … it is also very difficult and frustrating to photograph it: It is hiding deep inside the coral branches – which makes it difficult to light. Plus it is constantly changing position. The key is to watch it for a while and figure out, which branches and spots within the coral it preferrs … and then wait for your shot. It might cost you a whole dive though …

Creature Feature: Solar Powered Nudibranch

Solar Powered Phyllodensium

The Solar-Powered Nudibranch (Phyllodensium longicirrum, Solar-Powered Phyllodensium, Long-Cirri Phyllodensium) is one of the celebrities among the Lembeh Nudibranchs – everybody knows it and everybody likes to see one. The Solar-Powered Nudibranch (SPN) grows to 15 cm in size and is the biggest member of the phyllodensium nudibranchs. As other members of this group, the SPN farms Zoocanthellae algae in its Cerata (tentacles) to create energy through photosynthesis. The flat Cerata have a big surface an therefore lots of space for the algae patches that are separated into individual “solar panels” (that are visible as little brown spots).

The SPN feeds on leather corals of the type Sarcophyton trocheliophorium and stores their toxins to taste bad for potential predators. It usually hangs out around a leather coral until it has consumed it.

Best place to see SPN in Lembeh: Most coral dive sites like for exemple Makawide, Batu Sandar but also Muckdives like Aer Bajo or TK sometimes have SPN.

Photo Tip: Use a wider lens (60mm or wider) as the SPN is relatively big in size. For a big SPN sometimes even Wide Angle can be a good option. The Cerata swing to side to side with the surge … so a good technique is to position yourself in front of the head, prefocus on the rhinophores and wait for a moment when they are both visible.

Joni in love with Angel’s Window


Yesterday morning we went to Angel’s Window for the first dive – a popular Coral Dive on the northern side of the Lembeh Strait. It is a Pinnacle with a cave swim-through, nice walls, good coral life and many critters such as Pygmy Seahorses, Boxer Crabs and Nudibranchs. But yesterday this dive was specially beautiful – the current was very mild and the visibility extemely good (for Lembeh). In this picture you can see our Dive Guide Joni enjoying the fantastic diving conditions. I took this shot from the ladder of the boat and it shows, that you can see the entire piccacle from the surface. We hope to have similar conditions today …

Dragon Shrimp

Dragon Shrimp on Black Coral

On yesterday’s morning dives i came across this beautiful shrimp: A Dragon Shrimp (Miropandalus hardingi). It’s a 2cm long shrimp that lives on black corals and has a green-yellow colouration. Even though it looks a little bit like the more common whip coral shrimps dasycaris zansibarica (on spine) and Pontonides ankeri (no spines) this shrimp has 3 big and long spines on its back that give him its dragon like look. I spend a good 15 minutes photographing this little shrimp while not paying attention to the frenetic tank banging sounds in the background – after the dive it turned out, that i missed a blue ringed octopus and a harlequin shrimp that our guide Stenly had found in the meantime 😉