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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.

Have sex and die – the octopus way!

When I visited Lembeh in September/October there were flamboyant cuttlefish around in numbers that I have never seen before. On more or less every dive, we saw one or more flamboyants. Blue ring octopus were not as common, but still there was hardly a day when we didn´t see them. This is very much in contrast to the situation now, at least considering adult octopus and cuttlefish. We have seen some, but while still here, they are not nearly close to the densities experienced in September/October. Where did they all go?

A surviving flamboyant cuttlefish, that probably was out of luck mating in September

A surviving flamboyant cuttlefish, that probably was out of luck mating in September

Actually, cephalopods, the group that octopus and cuttlefish belong to are quite short-lived. Not only that, they only reproduce once and then die! This pattern of reproduction, where an individual grows for almost all its life, mates and then die, are called semelparity.

Mating coconut octopus in lembeh

Mating coconut octopus – not something they will do a lot of times!

Other animals continue living after reproduction and produce other litters some time after. Such a strategy, with multiple reproductive events after the onset of maturity, is called iteroparity.

Giant frogfish, an iteroparous species mating several times during its life cycle

Giant frogfish, an iteroparous species mating several times during its life cycle

The answer is that all life histories, that is the allocation of energy over time, consist of trade offs. Food is seldom unlimited, and if it where, time or developmental rate would limit the options available for an animal. The first ting that needs to be realized is that reproduction, having offspring, is expensive. Experiments have time after time verified that reproducing individuals of a lot of different species die earlier than non-reproducing individuals. That is the first trade off, choosing between a long life or offspring. And having no offspring is a fundamental screw up in nature, as your genes get lost for the future, so choosing long life rather than reproduction is not an option for animals looking for success in life.

Hairy shrimp carrying eggs

Hairy shrimp carrying eggs

The second trade off is that costs are related to the effort that is put into reproduction. Everything else equal, the more offspring that is produced, the less survival or future growth rate an individual will experience.

Baby broadclub cuttlefish that never will meet its parents!

Baby broadclub cuttlefish that never will meet its parents!

The third important trade off is that an individual need to keep significant amounts of energy reserves in order to survive over long time in the future. Up to around 90% of the energy budget might have to be allocated to future survival if that is the goal. Thus, an individual can produce a vastly higher amount of offspring in one reproductive event if no energy is saved for future survival. Thus, if an individual irrespective of reproduction faces quite high mortality rates, it could obviously be advantageous to “go all in”, reproduce with all the effort you can, and save nothing for a very uncertain future. And that is exactly what cephalopods do, invest all they got in one single “big bang” litter instead of saving themselves for another day.

Young blue ring octopus

Young blue ring octopus

The cool effect of that here in Lembeh is that there now are quite a number of minute, fully colored flamboyants around. The young flamboyants are really cool, brightly colored and have a lot of attitude.

Newly hatched flamboyant cuttlefish

Newly hatched flamboyant cuttlefish

Sexual selection – a driving force in marine systems?

Prey are well adapted to evade predators, and predators are correspondingly well adapted to catch prey. For most of us it is pretty reasonable to accept that such adaptation happens by natural selection, leading to long-term evolution of animals, making them better to either catch prey or evade predators, whatever end of the food chain you happen to be on. Thus natural selection affects traits such as foraging efficiency or anti-predator behaviours that lead to longer lives, quicker growth rates and, both directly and indirectly, higher reproduction rates. Most of my earlier blogs have more or less built on the assumption of natural selection affecting adaptations of animals.

Bright warning colour on nudibranch. Probably a result of natural selection favouring nudis clearly advertising their poisonous properties.

Bright warning colours on nudibranch. Probably a result of natural selection favouring nudis clearly advertising their poisonous properties.

There is  another kind of selection, sexual selection, that is a little bit harder to understand. Sexual selection is the process where traits that directly affect the likelihood of securing a mate is changed over time, leading to the evolution of traits that sometimes seem to act contrary to natural selection in that sexually selected traits rather decrease life expectancy and growth rates. There are many examples of traits governed by sexual selection on land. Bird song, brightly colored males in many birds and lizards, antlers on deer and males adapted for fighting other males for access to females are examples that we all can relate to. It is thought that sexual selection in terrestrial systems are well as important as natural selection in shaping many aspects of populations and also a major force in driving speciation.

Male macaque with teeth adapted to fight other males over harem rights

Male macaque with teeth adapted to fight other males over harem rights

Are there examples of sexual selection in marine animals? Well, such examples are without doubt not as obvious as on land. The most obvious is dimorphism between sexes, that is that the two sexes differ in size.  Many fishes, such as many species of wrasses and groupers, have males that are much larger than females. Males of such species secure their mating by either fighting with other males for mating rights or showing of to females in order to make the female choose the performer.  This is certainly a sexually selected character. Some crabs seem to have very large males as compared to females, and that could be related to mating coinciding with female molting. Males can detect this molting some days before it actually happens, and try to protect “their” female from other males. Thus large males will be able to fend of smaller males, thus monopolizing pre-molting females.

Large male crab guarding female crab against other males

Large male crab guarding female crab against other males

When females are lager than males, it is very seldom a sexually selected character. In most marine monogamous species with a size difference between the sexes, the female will be the larger. This is not due to the female competing for mates, as the pair is monogamous, but rather that size affects egg production positively much more than size affects sperm production. Thus, in many cases, it makes sense for a monogamous pair to consist of a large female and a small male.

Large female false clown anemone fish with small male

Large female false clown anemone fish with small male

Another possible example of a sexually selected trait could be the extraordinarily long “nose” that some xeno crabs have. I have no idea if this is correct, or even if “nose” length of xeno crabs are related to sex, but is could be.

Xeno crab with an extremely long "nose"

Xeno crab with an extremely long “nose”

Otherwise, I find it surprisingly rare with clear sexually selected traits in marine animals. It could be related to the mating methods many marine animals use, where sex cells are released into the water and is more or less anonymously left by themselves to find a suitable cell to fuse with. This method of mating somewhat precludes mate choice or mate competition, thus making the force of sexual selection very weak compared to that of natural selection.  I will get back to mating methods on reefs and reef-near areas in a later blog.

TK delivers!

Whenever you visit the same dive area several times, some dive sites seem to consistently deliver more than others, and, correspondingly, some less than you would wish. Here in Lembeh my favorites are the Aer Bajo sites and Hairball, where many uneventful starts of dives have been turned around to glorious experiences. The different TK sites on the other hand have for some reason not really caught my interest that much, despite that if I really think hard I actually have seen some really neat animals there. My expectations for yesterday´s morning dives were less than stellar, as the first dive was in Nudi retreat (coral dive, why??) and TK 3. Nudi retreat delivered a couple of cool Xeno crabs as well as a beautiful soft coral crab, which was fine, and perfectly OK. Happy with that. TK on the other hand, in the words of a well known dive resort owner,  just kicked the balls out of any kind of negative feeling about that site.

Paulus, my dive guide for the day, first found a weird flat crab buried into the rope sponges that are so common in TK (pictures coming in a later blog).  Just after that a great Janolus nudibranch posed nicely,

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followed by a number of “commoner” nudis, and a beautifully colored devilfish, showing of its pectoral fins.

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A couple of minutes later in a small patch of rope sponges and debris, two beautiful frogfish and one common sea horse were found.

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That was just the start. After that, less than 5 meters apart, a flamboyant cuttlefish was hunting,

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a hairy frogfish came walking by, and, finally,

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a coconut octopus did his (or her) amazing show with a couple of beautiful shells, hiding, digging, watching me and walking around with the shells.

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So, TK, I am officially sorry for my negative attitude. TK after this climbs significant steps on my favorite dive site list. Simultaneously, my wow for this trip of concentrating the photo shooting to a few of the best subjects on each dive, was blown to pieces. But what can you do, this was like letting kids loose in a candy store, Danes loose in a beer pub, Djengis Khan loose in a village of pacifists or Simon loose in a camera store!

Masters of disguise

Well, as Lembeh must be the frogfish capital of the world, and frogfish are some of my favourite critters, I think that frogfish actually merits another blog entry. So here it is.

Juvenile painted frogfish

Frogfish are probably most known for their built in bait, an illicium or “fishing rod” that is topped with the esca, the worm- or shrimplike lure it self. The illicium and esca are formed from the foremost rays of the anterior dorsal fin, and can be moved in different directions in front of the mouth when prey comes close enough.

Striated frogfish using its lure

Frogfish belong to the family Antennariidae in the order Lophiiformes, which among others also include the supercool deep water anglerfish with lures that are shining with light. With a few exceptions, the most notable being the Sargasso frogfish, frogfish are mostly shallow water fish, living among rubble, sea weed, coral heads and other underwater structures that can aid the frogfish in hiding their outline from prey and predators.

Orange painted frogfish in orange sponge

In Lembeh strait a number of species are found. I have seen eight or nine species in Lembeh, but there are probably one or two more around.

Scarlet frogfish. I think.

Frogfish are notoriously hard to determine to species. Many species come in different colors, so color is at best a weak clue to what they are. Colors seem to change with background, making camouflage excellent, but on the other hand not helping very much in species determination.

Probably a spotfin frogfish

A combination of habitat, body shape, and, maybe most important, characteristics of the lure can most often be used to at last narrow it down to a couple of likely names. A few, however, such as the hairy frogfish with it´s wormlike lure and the warty frogfish with it´s warty exterior are very characteristic and often easy to name. Others, such as the hispid, the painted and the giant (also called Commersons) frogfish are not to hard to determine if the lure is visible.

Probably giant frogfish

Then there are a number of frogfish with lures that are hard to see and quite similar markings that I find pretty hard to determine to species underwater.

Well, it is a frogfish! More than that, I have no idea.

And finally, Lembeh is home to at least one undescribed species, which has not been named by scientists yet.

An undescribed frogfish. Isn´t that cool!

The lure of the frogfish indicates that frogfish are specializing on fish as prey. With a few exceptions, fish is exactly what frogfish eat. When a small fish comes close to the frogfish, the lure is waved in an enticing way in front of the mouth of the frogfish. The prey fish will often be conned into believing that it is the luckiest day in its life, which most often is the last feeling the prey fish will have. When the prey comes close enough, the frogfish extends its enormous mouth, inhaling a lot of water and a small, and highly likely very surprised, fish. The mouth movement of the frogfish is so quick that scientists have problems explaining how that speed is even possible.

Large volume of striated frogfish mouth

The teeth of frogfish are very pointed and directed backwards towards the interior of the mouth. Thus, anything caught by a frogfish will have a really hard time escaping, while the direction of the teeth will allow the frogfish to move the prey inside the mouth. Frogfish are extremely elastic, being able to swallow prey as large as themselves.

Teeth of hispid frogfish

Frogfish have three ways of moving. First, like most fish, they can swim through the water column using their caudal fin. They can also use a water jet by expelling water through the small gill openings behind the pelvic fins. Finally, frogfish can more or less gallop over sandy bottoms, in a rather ungraceful running motion resembling what a cross between a sea lion, a football and a horse would look like in full speed.

Speeding striated frogfish

So, now I am of running an ecology/photo course in the Red sea. Those of you that follow this series will probably have the next entry available in a couple of weeks.

Juvenile striated frogfish. Quite cute!

Commensal Bryaninops gobies

For some reason certain animals are on the “cool” list that everyone wants to see and photograph and others are placed on the “not so cool” list and get ignored by most divers and photographers. Scarcity and cuteness seems to be two important factors determining the popularity of an animal. Despite not really ticking either the scarce or the cute box, due to their interesting life style the gobies of the genus Bryaninops have a long time been on my favourite list, and I more or less never pass a wire coral without checking it out for a goby or two.

Goby on wire coral

Few other divers seem to find them very interesting, so I mostly get to have the wire corals and the gobies more or less for myself. This time in Lembeh, Paulus, my excellent guide, knowing about my interest in parasites, in the beginning of my stay showed me a couple of Bryaninops with the characteristic copepod parasites that many of these gobies carry, with the gobies living on other animals that I did not normally associate the gobies with.

Goby with a heavy load of copepod parasites on sponge

During the weeks I stayed, I found gobies on a lot of different sedentary animals, more or less always colour matching the animal the goby associate with.

Goby on soft coral

The Bryaninops gobies are found as commensals on different coral groups as well as sponges, sea squirts, sea stars and even on Halimeda algae.

Goby on Halimeda algae

The pelvic fins of the gobies are more or less adapted to be a disc capable of sucking the goby to its host during currents.

Goby on sea star

They never move far from their host, and can often be seen moving quickly around on the surface of the host, feeding on small zooplankton drifting by in the current.

Goby on tube sponge

Being commensal means that the interaction between two animals are neutral for one of the, in this case the host. The other partner, in this case the goby, of the interaction receives some benefit of being in a commensal relationship. There is no doubt that commensal gobies receive benefits by living on their hosts. The gobies settle as small larvae on their hosts and change colour to match the host during ontogeny.

Goby on soft coral

Obviously such a colour match leads to some kind of concealment for the goby which otherwise has no protection against predators. When detected the gobies also use their hosts as hiding place, moving quickly to the other side of the host.

It is, however, not really clear that the hosts are unaffected by the interaction. At least one of the species, the common and wide spread wire coral goby Bryaninops yongei, lays their eggs on a patch of the wire coral where the gobies have cleared the coral from living polyps. Thus, at least in this case, it is unlikely that the coral is not negatively affected, and the relationship then should rather be classified as a parasitic interaction. On the other hand the goby might protect the coral from coralivores, thus mitigating the cost of the lost polyps somewhat.

Goby tending eggs (the black spots beside the goby) on soft coral

Many new species of those gobies are now being recorded by goby experts from different parts of the world. The diversity of commensal gobies in Lembeh is probably quite high judging by the number of different gobies of slightly different shapes I saw on a number of different hosts during my two week stay, and I would not be surprised if there was one or two undescribed species among them. It will require a goby specialist to really understand what species are present here in Lembeh, so at least I, not that much into goby taxonomy, will have to enjoy the active and often quite beautiful fish without really knowing what specific species it is. On the other hand, with many other groups of high diversity in Lembeh, that happens quite often here, so one just have to get used to it!

Probabably Bryaninops yongei

Win free spot for Underwater.kr Shoot-Out @ NAD Lembeh

As mentioned before NAD Lembeh will host a UW Photo Shoot-Out organized by Underwater.kr this december (8-15). The whole resort will be blocked for the Shoot-Out – prices are over 35.000 US$ Value and include Cash Prices! Now Underwater.kr announced a Online Photo Competition to win a free spot for the Shoot-Out (Value: 965 US$). Please check the Competition Page for Details. Good luck to all participants!