What is that all about? The world is full of beautiful, exciting, warm places with a lot of stuff I haven´t seen. It seems quite overkill to return to Lembeh again and again, and even again.
The first reason is that I find coral dives beautiful, but quite unexciting. It is nice every now and then to do “landscape” dives, seeing the views of the underwater world, the beautiful colors and the schools of fish, and even the magnificent visibility on some of the coral reef spots around the world. After some days, however, I find that kind of dives a little repetitive. The excitement of searching through a rubble patch and suddenly seeing an eye or a small movement, and finding out what it is, is much more exciting and probably even to some extent addictive.
The second reason is that I really like some of the common animals here. Emperor shrimp, coconut octopus, long-armed octopus, flamboyant, pygmy seahorses, thorny seahorses, carrier crabs, Cymothoa parasites, Coleman shrimp, zebra crabs and so many different species that otherwise are quite uncommon can more or less be expected to be seen on your next dive if you ask your guide to show you one. On top of my favorite “common”list, are a couple of things that you do not even need a guide for. First of all, the strait is littered with flasher scorpion fish of different colours. Their clumsy walk over the sea bed is always a joy to watch.
Second, who does not like frogfish? On this trip we have seen five to ten frogfish every day. That is really hard to beat. Furthermore, the frogfish have been really active; walking, yawning and feeding, giving us ample opportunity to get pictures a little bit out of the ordinary.
Third, coming in as number one on the “common”list is the devilfish! They are all over the place, hiding in sea weeds, burying in the sand or just lying around looking like anything but a fish. Getting closer, it is hard to imagine anything more ugly, mean looking and plain weird than those fish.
The third reason I like to come is that there are quite a number of things here that are rare here and very rare everywhere else. This time hairy octopus was a first for me, and I also saw a crab buried in a Litophyton soft coral that I never have seen before, not even on pictures.
Also, Ambon scorpion fish are not to common around other places I dive, Here, however, there are common enough that I actually find them myself now and then.
And then there are the xeno crabs. Coolest among crabs, those denizens of wire corals rule!
Finally, I like to come here because there are so many different subjects to shoot that there is always something new to try. I will end this blog series with a picture quite rare for me, a wide angle horrid stonefish on Aer Bajo.
It has really been fun to be here this time. This blog series has benefitted from divebuddying, pointing out stuff and comments from Greg Bang, John Davies, Steven Parkinson, Kristin Anderson, and, most of all, Belinda Parkinson. First and foremost, the excellent dive guides Paulus and Joni are responsible for finding a lot of cool critters just waiting to be photographed. And, of course, all the people at NAD has as always been very helpful, kind and nice that I am looking very much forward to my next visit.
Commensalism requires one animal, the host, to accept the presence of another, without receiving anything for it, which, in itself, is not very complicated from an evolutionary point of view. Mutualism requires one animal to give advantages to another while at the same time receiving benefits from the other. At first sight this probably seems as easy to understand as commensalism. However, evolution will favor animals receiving more for less, thus probably putting a strain on most mutualisms. Mutualisms could probably be understood as standoffs, where both parties try to minimize their cost and maximize their benefits. Parasitism, on the other hand, has interesting complications. Parasites receive benefits from another animal, while the other animal, the host, incurs a cost. Thus, the host will want to get rid of the parasite. The parasite, while wanting to get as much benefit as possible from the host, does have to be a prudent consumer. If the parasite is to costly for the host, the host will die, leaving the parasite in a really problematic situation, as new hosts are often hard to find.
So which are the parasites we can see here in Lembeh? First of all, many of the crustaceans living on echinoderms would be parasitic to some extent. Coleman shrimp, for example, live exclusively on fire urchins and feed on the tube feet of the urchin. Even if urchins are good at regenerating lost body parts, there will at least be an energetic cost to the removal and regeneration of the tube feet caused by the feeding of the Coleman shrimp.
Another crustacean parasite, more common than the Coleman shrimp, that divers looking for gobies on wire corals will see a lot, is the copepods that attach to the wire coral gobies. These copepods look like normal crustacean larvae when pelagic, but when they settle on a goby, the copepods sink their mouthparts into the skin of the goby and changes morphology dramatically. The resulting individual will be composed of the mouth stuck in the goby, a digestive system converting fluids from the goby to new eggs, and the egg sacks looking like corkscrew curls.
A somewhat similar parasite is found inside the gill covers of shrimp. Shrimp, such as emperor shrimp, with this parasite gets a very distinct hump on the side where the parasite is attached. On some of the translucent shrimp it is actually possible to see the parasite eggs inside the gill cover of the shrimp.
One of my favorite parasites is the blue shells that parasitize Linckia sea stars. Linckia sea stars sometimes reproduce asexually by releasing an arm or two, letting the arm regenerate to a new sea star. A single arm, however, has a significantly greater risk of dying than a whole sea star. The shell takes control over this process and shuts down the release of arms, minimizing the risk that the shell gets caught on a single arm.
Finally, my absolute favorite among animals, is the so called tongue eating parasite, Cymothoa exigua, that lives in a number of fishes mouths, apparently eating the tongue of the host, replacing the function of the tongue. In Lembeh they are commonly seen in the mouths of anemone fish, especially the saddlebacks residing on sand bottoms in large carpet anemones.
It should, however, be emphasized that most of the current information on the Cymothoa is purely anecdotal and much more research will be needed before the interaction between fish and alleged tongue eater is understood.
Mutualisms are close, long-term relationships between two species where both species benefit from the relationship. Mutualisms can, just as commensalisms, be obligate or facultative. They can also be endosymbiotic, that is one species living inside another, or ectosymbiotic, which is one species living on the surface of the other.
One relationship that during a long time has been viewed as a proper endosymbiotic mutualism is that of corals and their algal symbionts, the zooxanthellae. Zooxanthellae are small, unicellular algae that after being ingested by reef building corals are transferred to cells just under the surface of the coral. The zooxanthellae then translocates photosynthetic products to the coral, while the coral in turn provides the zooxanthellae with inorganic nutrients.
This relationship has been widely studied during the last couple of decades due to the decline of coral reefs over large areas. There is now some discussion of the exact form of the relationship between coral and algae, as the algae seem to be have a much slower reproduction rate inside corals than outside on their own, corals ingest a fair number of the zooxanthellae and the coral can expel the zooxanthellae during periods of distress. The later is called bleaching and is a subject of much concern, believed to worsen in years to come, when surface temperatures in the oceans rise, and maybe even more problematic, when the acidity of oceans rise in response to the increase in atmospheric CO2-levels. Currently, you are not likely to see much bleaching in Lembeh, but there are single colonies here and there showing the white skeleton of the coral.
Many other animals use zooxanthellae to cover parts of their energy requirements. Some sponges, giant clams, anemones, jellyfish and nudibranchs have this symbiosis.
However, for the nudibranchs it is pretty clear that the relationship is not mutualistic, as the zooxanthellae do not get any benefit from being held within the mollusk. The solarpowered nudibranch, as an example, initially gets their zooxanthellae from their soft coral prey.
Anther recently disputed relationship is that of anemone fish and their host anemones. The conventional wisdom has for many years been that the relationship is mutualistic, with the anemone fish receiving protection from predators by the stinging tentacles of the anemone, while anemone fish protect their hosts from butterfly fish and provide inorganic nutrients through the waste of the fish. There is now some doubt on whether the anemone actually gets any benefit from the relationship.
So are there no classic nice mutualistic stories left to tell? Well, some still seem to meet the requirements. The small crabs that sit in branching corals actually do benefit the coral, cleaner fish actually are very important for reef fish, and, finally, the partnership between gobies and burrowing shrimp seems to be essential to both goby and shrimp. The shrimp are blind, or at least do not see very well, while the goby has nowhere to hide on the sandy areas they both reside. In a remarkable partnership, the goby keeps watch over the surroundings while the shrimp tends to their common burrow. When outside the burrow, using its very long antennae, the shrimp always has direct contact with the posterior dorsal fin of the goby. The goby use different vibration frequencies of the fin to inform the shrimp about the level of danger and the shrimp responds accordingly. When there is no danger, the shrimp works quite far from the burrow, when there is a medium risk work is performed in the burrow opening, and when it gets too scary, the shrimp bolts into the burrow; at night, when the eyesight of the goby is of no use, the goby enters the burrow and the shrimp closes for the night from the inside by using small shells and pebbles, leaving both safe for the night.
On my day job part of my time is used to teach ecology for undergraduates in biology. Maybe not such a surprise, many of the best examples of interactions between species that I use in my teaching come from marine ecosystems. This is especially true when dealing with symbiosis theory.
Symbiosis means “together living”, and describes animals or plants living together with a tight relationship with each other. It is reserved for animals or plants of different species, but the exact definition is under some discussion. I will use it in its general sense, including obligate (the different species need each other) and facultative (at least one species affects the other species, but the interaction is not essential for either). Used in this sense, symbiosis includes commensalism, mutualism and parasitism. Today´s entry will be on the least exciting of the three, commensalistic interactions.
Commensalism describes the relationship between two organisms where one organism benefits without affecting the other. Many such examples are found in marine environments. One likely example is the small porcelain crabs residing on soft corals. The porcelain crabs get a perch to sit on and protection among the arms of the soft coral, while the soft coral is unaffected.
Another example would be the gobies that live on many other animals in the sea, often changing colour to closely resembling their host. It is likely that the host in most circumstances are rather unaffected by the gobies seeking shelter.
The gobies and the porcelain crabs exemplify commensalistic interactions where one species lives on the other species, which is a true symbiosis. They are probably also more or less obligate, as predators quickly would kill both gobies and porcelain crabs without the shelter of the hosts . Commensalism doesn´t have to include symbiosis. This was clear when we were in a slight current on Hairball, watching a box crab rip a smaller crab to pieces. Box crabs are messy feeders, so a lot of the bits and pieces of the crab were swept down current out of reach of the box crab. However, it was not just lost, as a couple of big flounders quickly placed themselves behind the crab and ate the morsels coming with the current, benefitting the flounders without harming the box crab.
Finally, one part of the pair can already be dead when the commensalistic interaction takes place. Hermit crabs, having to find shelter for their soft anterior parts, need empty shells in order to hide the unprotected part of their body. Different snails provide these shell after the snails are dead, which means that the hermit crabs are benefitted by the presence of snails, while snails are unaffected by hermit crabs.
Update 1. In the blog on cephalopods I mentioned that we still had a couple of species to be seen. Not so now, we saw an algae octopus yesterday and on this morning’s first dive, not one but two hairy octopus were found. I guess that´s it for the cephalopods! Maybe not if we get really picky about the number of bluering species in the area, but as even experts seem to have quite some trouble defining that, we will just leave it at bluering for now.
Update 2. In the blog on seahorses and relatives, there was a blaring omission. No pictures of the pygmy seahorse itself, the Hippocampus bargibanti. No such omission now, here is a bargibanti from today. Interestingly enough, I have a distinct feeling that there are way more bargibanti in the area now than a couple of years go when I first came here.
Update 3. The seahorse blog did not have a picture of a pregnant ghost pipefish. Here is a pregnant female with the extended pelvic fins holding the eggs.
Update 4. There was some discussion here at NAD on whether frogfish lack gills, lack gill covers or neither. Frogfish have gills, have no proper gill covers but exhale the water exchanging gasses over their gills through a little hole at the base of their front “feet” (“arms”, “legs”?). The holes can be used as water jets, propelling the frogfish along quite like a cephalopod.
Talking about frogfish, there will soon be a new batch of small hairy frogfish around. A couple of hairy frogfish, where the female is very full of eggs, seems to be having a cozy day in the strait today, spending some quality time together. The couple will probably heat up the action tonight, so look out for a floating egg masses in the strait tomorrow. Judging by the size of the female, it will be a big one!
Lembeh is a very good place for seahorse hunting. Not only does Lembeh have several “proper” seahorses, which is medium-sized fish, looking like a seahorse should look like but also at least three pygmy seahorses, a number of pipefish and the almost iconic Lembeh sea dragon as well as their relatives, ornate ghost pipefish and the sea moths.
The coolest and maybe best known feature of the seahorses and pipefish is that the males takes care of the eggs. Why is this such a big deal? Well, as we define the two sexes, males produce tiny mobile sex cells called sperm numbering gazillions, while females make a few energetically expensive, immobile sex cells called eggs. Thus, males can get to father a lot of offspring by getting their sperm placed in contact with eggs, while females are limited to much fewer offspring. Of course the mean number of offspring for the two sexes will be the same, indicating that some males have great success, and others none, while females have much less variance in their number of offspring than males. Also, in most cases, as females have a large investment in each mating, females may often be more motivated to invest in offspring.
Not so among seahorses and pipefish. Seahorse and pipefish males, for some reason, are the caretakers of the eggs during development. In seahorses eggs are transferred to a pouch on the males abdomen and the male there fertilizes the eggs. Eggs are kept in the pouch until they hatch and the small seahorses, that look like miniature versions of the adults, are expelled by the male by contractions of the pouch. Pipefish on the other hand, do not have a pouch and “glue” their eggs to either their abdomen or to the base of the tail. As most seahorses and pipefish are monogamous, it does make sense for the pair to let the male take care of the eggs and juveniles, as the female then can invest all surplus food in a new batch of eggs. As far as I know, little is known about the sex roles of the pygmy seahorses, but researchers are currently working on both their ecology and their systematics.
Ghost pipefish females in contrast take care of the eggs. The eggs are held between the pelvic fins of the female and held until they hatch. The male, often much smaller than the female, hangs around and waits for the eggs to hatch.
Quite common here in the strait are the sea moths, close relatives to the seahorses. They are almost always found in pairs, with the more distinctly coloured male leading their walk around their territory in search of food.
Finally, it is interesting that there still are both a number of known but scientifically undescribed species, and news species that are found on a continuous basis. In the north Sulawesi region the Pontohi seahorse and the Lembeh seadragon have been found during recent years. It is highly likely that more species will be found here in the years to come. In fact, the first of the pygmy seahorses were found not too long ago by a sea fan researcher, that took a sample of a particular sea fan into his laboratory, and there much to his surprise, saw the small, pink Bargibanti seahorses swim around the fan.
Invertebrates are in general stupid animals. Mussels, snails, and most other members of the mollusk group would certainly score pretty low on any scale of creative brightness, but their life style on the other hand does not require a brilliant mind. The only exception is the cephalopods, translated from greek as headfoot, such as the squid, cuttlefish and octopus. The cephalopods are highly adaptable animals, making creative use of their environment when hiding and hunting prey. Cephalopods are bright animals, with some of the octopus being significantly smarter than even some vertebrates. An octopus ability to learn mazes is in the range of that of a rat (which is good at learning mazes!), and octopus learn to open glass jars with screw on lids very quickly and do remember how for a long time. One of the octopus, the coconut octopus, is the only invertebrate currently being classed as being able to use tools. Coconut octopus live on sand flats and would be very easy prey for medium-sized and larger fish when the octopus is up and moving around in search of prey. Coconut octopus solve this problem by placing different objects such as empty shells or coconut husks on certain places in their territory, and use those objects to hide in when in danger.
During the week I have been here in Lembeh, we have during just a couple of days seen flamboyant cuttlefish, coconut octopus, reef squid, broadclub cuttlefish, pygmy cuttlefish, wunderpus, bobtail squid, starry night octopus, blue ringed octopus (at least 5!), mototi octopus, algae octopus, mimic octopus as well as reef octopus. It seems that we only got one left on the list now, the hairy octopus, which seems to be very seasonal, and not here now. (See update here.)
On proper coral reefs only a couple of cephalopods can be found. The much larger diversity of cephalopods here in Lembeh is due to the mosaic of habitats that can be found. Mototi and blue-ringed octopus, as an example, prefer to live in rubble. Mimic octopus live in sand, while bobtails and flamboyants live in siltier conditions. Wunderpus prefers a mixture of sand and rubble, while most squid and cuttlefish, being more or less living in the water column, are found over different bottoms.
More or less everyone seems to be well aware of the powerful toxin used as a defense by blue-ringed octopus. Less known is that most, if not all, octopus have toxins in their saliva that are injected when the octopus bites something or someone. Mototi seem to be in the range of the blue-ringed, while most other octopus seem to be less dangerous, but great care should be taken not to be bitten by any octopus. Some of the cuttlefish, such as the flamboyant cuttlefish are poisonous enough to quickly kill any predator brave enough to ignore the flamboyants flashing of warning colours, deterring most predators from even trying.
Most cephalopods have the ability to change colour and skin texture very rapidly, thus being able to melt in in the environment while moving around. The many pygmy cuttlefish we see here now are prime examples of that feature. They look like sponges, sand, coral and even crinoids.
Juveniles of broadclub cuttlefish like to hang around soft corals and change colour and to some extent skin structure to resemble the coral colony.
No molluscs tomorrow, the nudis will have to wait a day or two. It is highly likely that the sea horses and their relaitves will be the subject for tomorrows entry, but, as always, something could get in the way during the mornings dives.