Something totally different is featured, Marther presents a discussion on why Xenia pulse, and there is heaps of things happening in the Park.

Editorial

Welcome to another issue of OZ REEF Press. Sorry that the issue from March was missed for those of you who look forward to reading this each month. But I just ran out of spare time with which to spend on it. As you can see though, I have found the time this month, it is amazing what you can do with the odd long weekend. I am also not sure how I will be going for time in the coming next twelve months. It is starting to approach crunch time with my Ph.D., and things are not quite going how they should be. Anyway, I enjoy working on OZ REEF, both the electronic and real version, so I will be trying to keep things moving along and not drop things all together.

I have been planning for quite awhile to add some more Lysmata amboinensis, cleaner shrimp. The idea behind this was to build up a group of reproducing shrimp that would supply a great source of zooplankton to the reef community. I am going to aim for about a group of 6 in total, but will have to wait and see what the interactions are actually like with this number. Along the way I hoped to observe the interesting interactions between the shrimp that would occur along the way. The addition of another would have been very interesting to follow, would they form a threesome and mate with each other, would they new shrimp displace one of the original pair, or out it stay as a loner? So about a month ago I purchased a new cleaner shrimp to add, and then everything went wrong, with the end result being three dead cleaner shrimp :-( That was not a good week at all, and expensive reef food too ;-( You will have to read the Bereavement Notices for full details.

About three weeks later I then purchased another two cleaner shrimp. They were by no means a pair in the tank at the store, I just picked out the two that looked the most healthy. This included their response to things outside and inside the tank, number of legs, length of their antennae, and exoskeleton colouring. They are not quite as large as the previous pair, being about 2/3^rds the length. The settled in very quickly into OZ REEF and quite amazingly they took up residence in the same area of the reef structure as the previous pair had. It is obviously a great place for shrimp to live, located at the right hand side of the back of the reef under a small overhang.

After the cleaner shrimp had been living in OZ REEF for around two weeks the larger of the two molted and mated right before my eyes. So I suppose staying up late at night correcting undergraduate student's reports is not such a bad thing after all, though the reports are still terrible ;-). The molting was almost before my eyes, it most likely occurred about 5 minutes before I spotted the molt separated. The shrimp that molted did not act at all reclusive, with both being out in the open by the same amount, even the next day. While I was watching the two formed a simple cross position placing the front section of both their tail sections together. There was no obvious courting by either shrimp, they just moved rapidly together and it was all over within 5 seconds. About a week later the other cleaner shrimp also molted. So it seems like they are both on the way to being a breeding pair and hopefully now that I am learning how to keep algae and rotifer cultures I might have a good chance of raising them.

Staying on the shrimp line of thought, the female golden headed coral banded shrimp is carrying another batch of eggs again. One thing about this particular species of coral banded shrimp is that I would not recommend them for a system that has a very closely packed reef structure or lots of tunnels which you cannot see into. If this were the case, then you would never see them as they are a very shy shrimp. The furthest that I have every seen them from their little crevice in the reef structure is 15 cm. During the day you are lucky to spot them outside of it, and if so they are usually feeding and at the most 10 cm from the crevice. Another interesting thing is that while there were no cleaner shrimp present, the pair actually moved into the same spot where the cleaner shrimp hang out. But as soon as the new two cleaners were introduced they moved back to their original crevice. The good thing about them is that they don't hassle anything else, including the cleaner shrimp. They can almost walk past each other and not even "give a sideways look".

Some more good news is that a small purple, with olive green polyps, Acropora sp. fragment is doing great. I am yet to take a good photograph of it that shows how purple it actually is, but I am working on it. The way it is growing is a little strange, well it was to me initially but after talking to a few people that have kept various Acropora for quite sometime. They said the some colonies like to get a very good base attachment to the rock before they start to commence branching. Anyway, what it is doing is sending out laminar grows over the epoxy putty that it is attached with. I suppose that is not entirely unusual, but so far I have not had one go so far without sending out branches. Also at the point where the putty starts to head vertically downwards, and the amount of light reaching it is not as strong, the colony has started to grow out horizontally into the water column. So far it has grown about 5mm into the open water with no rock underneath it. There are also a couple of polyps on the surface that are slightly raised above the others, but these are not actual branches. How ever it turns out, it will be interesting to see what happens over the next 6 months.

Currently I am working on establishing algae and rotifer cultures, and this is not exactly a trivial task. This is the first step in being able to raise any larvae that I can catch from OZ REEF. And once this part has been mastered, then the actual raising of the larvae can be focused on. I have been lucky enough to find a good source of the algae cultures to start mine off. Here at the University of Melbourne, where I am studying, the Botany School has a collection of 70 different marine algae species. And there are several there that are suitable to act as a food source for rotifers and larvae. All I have to do now is set up the equipment to maintain the cultures and then get an inocculum to start it off. I plan to keep a minimum of two different species cultures to diversify the food source. As I develop the details of the cultures, equipment etc I will add them to OZ REEF Marine Park.

I have been noticing lately that there is beginning to be more emphasis placed on feeding your reef tank well, mainly from the couple of emailing lists I am following and the reports coming back from the Western Marine Conference. And as a result I am planning to diversify and increasing the volume current feed program, which I believe is more than what the average hobbyist uses anyway. Currently I feed my seafood mixture, that can be found in the DIY Plans section, once a day and flake/pellet food at the opposite part of the day. Every two days frozen rotifers are added to the seafood mix. Alternating yeast and newly hatched brine shrimp are added nightly, mainly to feed the filter feeders and corals with smaller tentacles that feed at night. About 1 teaspoon of yeast is used, and the amount of newly hatch brine shrimp is only a small limited amount. I want to expand this to include green water (or algae culture) and live rotifers or similarly small sized zooplankton to the system. That way there will be a much more natural and diverse food supply over the current totally synthetic food sources. To help with the feeding program, I might have to invest in an automatic feeder. This would be to feed the flake and pellets in the morning as I am not around when the lights come on anymore and are therefore not always able to perform two feedings per day.

Now it is time for the bad stuff for this month ;-( I seem to be having some long term problems with keeping starfish alive, particularly the Linkia family. I currently have a Linkia laevigata, or Blue Linkia Starfish, which seems to be on the way out. This is the second one that I have had, the previous one was a Linkia sp. that was multi-coloured, and both have gone the same way. What is happening is the top end of each of the arms is appearing to erode and fall apart. If this follows that of the previous starfish, it will start to consume the entire arms, then work its way to the oral disc before it just all falls into a pile of starfish flesh. It appears to be something to do with not being able to supply the correct food requirements, as before they start to fall about the body appears to shrink a little from the time of purchase. But this puzzles me a little, as starfish of the Linkia family are meant to be the best for a reef tank, being strict detrivores that can be supplemented by seafood. I have also attempted to feed the starfish with various types of seafood, but it always just cruises over the top, actually retracting its tube feet to avoid contact. On several occasions I have noticed that they would park themselves on a section of the rock for a day or so, with the oral disc tightly pressed against the rock. This appeared to be feeding behavior, but I have never been able to identify what was in the spots before it stopped there. The first death I thought was due to some sort of ionic shock cause when I added some live sand. But things have been very stable in the Park for the last 3 months, there have been no dramatic changes in any of the measurable parameters that I test for. For the moment anyway, I am going to stay clear of starfish until I can work out what is happening here.

I am sure most of you out there do it to, no matter how much you deny it. That's right, I am on to you. You name your fish!!! Come on, be a big person about it, you can admit it to me, I wont tell .... too many people. ;-) And don't worry, well may be you should because you do name them, but I have also named all my fish. Just to get this all of my chest fully and be a bit more neighborly, I thought I should go through and introduce everybody by their real name and a little about why.

Stuart and Mandy

This is my pair of Orange Spotted Gobies, Valenciennea puellaris, named after a couple of friends of mine that should be a couple. ;-)

Ben

He is a Lawnmower Blenny,Salarias fasciatus, named as such because 'Ben the Blenny' sounds cool.

The Shadow

The Pacific Sailfin Tang, Zebrasoma veliferum, got this name because he "shadowed' Edgar for the first two weeks after he moved in.

Dan

Dan the Bi-Colored Blenny, Ecsenius bicolor, named after a friend of my fiance and don't ask me why cause I don't know.

Edgar

Now this Banded Goby, Amblygobius phalaena, managed to get its name in a really round about way. Because he is a goby, he goes around the tank like a vacuum cleaner, sucking things up. There is a brand of vacuum cleaner here called Hoover, and then there is a famous person called Edgar J. Hoover. Strange way of naming a fish I hear you thinking, but strange things happen when you sit in front of a reef tank for long periods of time. ;-)

Freddy

My Psychedelic Mandarin, Synchiropus picturatus, is the favorite of the tank. He managed to get this name after everybody exclaimed that he looked like a frog, so it is 'Freddy the Frog'.

The Boyz

How could you get a much better name than this for a school of Blue Chromis, Chromis viridis. And I am not quite far enough gone to name each one. ;-)

Well, I must say I know feel much better having put that out in the open. So, when are you going to face up to it and let the world know? ;-)

The only other things on the site that I have had time to work on since the last issue is the WWW links. There are quite a few good ones that I have recently added, many which are to do with breeding of marine organisms which I am now starting to get very interested in. I would like to give one particular site a plug right here, as I believe it is offering a wonderful service. It is The Breeders Registry. This non-profit, volunteer organisation has been around for about 5 years. It was formed to allow better communication between people that are working on the breeding of marine organisms, from corals to fish. Located on the site are some good articles relating to some part of breeding and most importantly a database of reports of breeding activity in aquariums. The database reports are all of varying degrees of detail and of how far the reporter reached with raising the larvae. This I believe is the strong point of this site, you can find some specific details on a particular species or family that you are looking to breed. If you join the organisation then you also get access to a quarterly Journal and an emailing list. I have personally learnt a lot over the last month on the emailing list in how to maintain algae and rotifer cultures. If you ever happen to have some breeding activity in your tank, then please document it and send the report to The Breeders Registry. And also if you are interested in the breeding side of reef keeping, then I strongly recommend you join and support this organisation. The costs and how to join can be found on the site.

That is all for this month, catch ya,
DBW

Welcome OZ REEF's New Residents

• 2 x Xenia sp., Waving Hand Coral. Now these two corals are spectacular. They are not pulsing at all, but look terrific. I believe they are more like what most US people talk about when they say Xenia. The first colony that moved in is very different. They are doing very well too, and are both only about 50mm across when fully expanded.
• 3 x Lysmata amboinensis, Cleaner Shrimp. One moved in to watch the social interactions of adding another shrimp to the existing pair, which ended up killing all of them, see Bereavement Notices for details. The next two are to replace the lost breeding pair, and were not purchased as a pair as such. They were just two cleaner shrimp in the same dealer's tank. They have since paired up and are now breeding again.
• 1 x ????, Sea Fan. A small yellow fragment about 8cm long and 4 cm wide. It was just in the bottom of one of the dealer's tanks and got it thrown in for nothing. It had broken off a larger colony and had been sitting there the last couple of times that I had dropped in there. Will be interesting to see if there is enough fine food particles that will sustain it, and I will be trying to provide this for it.

Resident of the Month

Dear Marther ReefKeeper

Dear Marther,

Why is it that soft corals that are members of the family Xenia pulse?

From,
Curious Xena (WP)

Dear Curious Xena (WP),

This is actually not yet known, why it is that Xenia corals pulse. I thought that I could best discuss why Xenia pulse by presenting a discussion, of those more in the know than me, that was held on recently on one of the reef keeping emailing lists. Thanks to Eric Borneman and Daniel Knop who were the major contributors to the discussion, and all the others that participated. (Note that some of the discussion has been edited to fix grammatical and spelling errors and maintain better coherence of the discussion in this format.)

DBW:
Just bit of a pet theory I have that I thought I should bounce off some people that should be in the know or have some experience with it. Why is it that Xenia pulse? To me it appears that the advantage of a polyp to pulse is that it improves mass transfer. That is the transfer of nutrients and wastes, whether dissolved or as particulates, to and from the coral tissue surface. The act of pulsing will also consume energy that otherwise could be used to grow or reproduce, replication, which is the fundamental goal of living organisms. The fact that it does pulse indicates that it must give the pulsing coral an advantage over not pulsing. This is most likely a net energy gain caused by pulsing, that is most likely linked to the transfer of nutrient and waster to and from the coral. Therefore if the mass transfer and energy excess is optimised i.e. at it's highest level, then the polyp has no reason to pulse. If it did start pulsing it would be just a waste of energy, with the amount of energy gain due to the pulsing being less than the energy expended in the act of pulsing. From this, it then follows that a polyp would be much more likely to pulse in low current, laminar flow regimes and if exposed to high current, turbulent regimes then the pulsing should stop or even slow down.

Mike:
Does pulsing give these Xenia species an evolutionary advantage over similar, non-pulsing species, allowing it to grow in calmer areas where others can't survive?

DBW:
Well, to start with it must have an evolutionary advantage because the Xenia family still exists, they are not yet a dead end family. Most evolutionary features are there for a reason, giving the organism an advantage in its niche environment enabling it to our compete others found within that same environmental zone. Otherwise it would not be selected out as a feature to be passed on to the next generation, thus giving that generation a better chance of dominance. Though the flaw of this particular argument is that not all evolutionary changes have a purpose as such, they could just be a side product of some sort. To illustrate this, think of a controlled experiment with two species of birds both with the same number of individuals, reproduction rate etc. The only difference between the two different species is that one is wingless with a prominent plume on its head, the other with wings and no plume. With each generation of birds you throw all the birds, both species, off a cliff. After several generations you will most likely end up with a bird population that consists of only winged species with no plume. Now if you then look at the fact that the species having a plume died out, can you attribute the fact that it died out to the fact that it has a plume?

Back to whether it gives them an advantage. If the pulsing of the polyps can accelerate the mass transfer in calm waters, then there will be nutrients and wastes carried to and from the polyps much more quickly. Therefore the coral can use up the nutrients and produce wastes at a faster rate. This will then lead to an accelerated growth and reproduction rate and will make it much more likely to out compete other species.

Has anyone had experience of this happening, in particular with the pulsing Xenia? For example if you move the coral to a high current area, does the pulsing reduce or stop.

Eric:
No...good thought, but colonies of Xenia in my tanks pulse in both flow regimes. Although some colonies getting really "whipped" around are hard to see pulse since they flail so. The pulsing in high flow is every bit as strong, though the outward expansion of the tentacles remains more contracted, pulsing in a "tight" formation.

John:
If this truly were the reasons, then wouldn't that make Xenia the most "advanced" coral in the evolutionary ladder? And if you wanted to ponder that thought for a moment, how about this...if there was an evolutionary ladder in corals, why wouldn't SPS be the highest rung? Seeing how they are the fastest and seemingly most efficient reef builder. Survival of the fittest! Any thoughts?

DBW:
Firstly one thing that people have to get away from is the idea of an evolutionary ladder. This give a wrong idea of how it, evolution, all works. The idea of an evolutionary ladder is how some few people thought things happened: bacteria evolves into an ascidian, an ascidian into a cnidarian etc....., and an ape into man as the end product. (This is just a rough example showing how it progresses) This is not the way that it occurs. The best way to illustrate evolution is to think of it as like a huge, every growing, every dying and branching tree. Along all parts of the tree it grows out, dies or splits into more branches. When it grows out a species is changing or evolving, when it dies then this is when the species becomes extinct and when it splits into more branches then this is when speciation occurs i.e. two populations of what was the same species can no longer breed with each other.

The thing with this also, is that there are a multitude of differing environments or zones present with the region of a reef. As yet there is no single organism that can populate all of these environmental niches that occur. There are zones that are as vastly different in conditions as a cave to the reef crest. The former has very low currents that are laminar with very little light penetration, and the latter high, surging, turbulent water flow with very intense light. These are only the most obvious differences, but you can see from this example that it would be very difficult for a single species to have the upper hand in both i.e. out compete all other species trying to live in those zones. What actually happens is each species finds a position in the community where it can maintain a sustained population. For this to happen it has to have an advantage over other species present in the same niche, and out compete them. If this was not the case, then they would die out.

That is why Xenia is still around, it has advantages over other species in its particular niche of the environment. Until some other species appears that is better adapted, or the niche disappears, then Xenia will remain.

Eric:
In a sense, they are. However, evolution favors species which are able to reproduce successfully in their niche environment, of which the coral reef is limited. Acropora are highly specialized, from intra-colonial transport channels, to axial corallites, to ease of asexual reproduction through breakage.... However, Platygyra is also "recent" on an evolutionary scale... Survival of the fittest does not necessarily mean over all other corals, it means in the environment, and Acropora is dominant in many areas... However, Leptoseris is dominant at 200 feet down, soft corals can be dominant over Acropora where they exist together. Tubastraea is dominant in caves, Goniastrea is dominant on rocky shores, etc...Xenia is a primary colonizer that thrives in high nutrients, like many zoanthids...as such, it may well soon be dominant everywhere if we keep polluting like we do! :-) It also "walks" into uncolonized areas by detachment and drift or by branch attachment/detachment. Just because a species is relatively "new" in an evolutionary sense, does not mean it is better, advanced, or more "fit." Simply that there are presently conditions in which it is able to "fit" for either a comparatively short or long time.... I would not consider humans to be "evolutionarily superior" either....and we are really recent and working really hard to become extinct, so it would seem. Look at chitons, cockroaches and blue green algae...almost as old as the earth itself and still doing really well... That, in my opinion, is an evolutionary winner.

The function of pulsing in the xeniids is still a mystery It was originally thought to aid in nutrient transport, then in gas exchange...neither have proved to be conclusive in experiments. What is certain is that Xenia occurs in some fairly large colonies in the wild, and that the pulsing in unison of a whole colony can significantly alter the hydrodynamics around a colony. They don't feed, so prey capture is not an issue. What about anti-predation? Maybe, but most xeniids (except perhaps Anthelia) produce a lot of soft coral compounds, with some Cespoitularia being highly toxic. Nutrient absorption? Doesn't make a lot of sense as they are often found near sewage discharge...obviously enough nutrients that pulsing would not be necessary. Gas exchange? What kind of gas? Carbon dioxide? Not for calcification...even sclerites are almost totally absent...for zooxanthellae? Why? Tissue is thin, animal is producing it...not logical...oxygen? Why? Oxygen is near or at saturation in many areas they are found, including our tanks where they pulse or don't pulse. Is it an old evolutionary function? Like an appendix? Maybe.

DBW:
What about a combination of many of the above points? Nutrient and waste transport. If the colony becomes so big, then a lot of water movement is required to get nutrients to and waste away from the internal parts of the colony.

The idea that is just an evolutionary side product could be possible. But the idea that it is partaking in an energy wasting movement (which it would be if it serves no function) does not sit well with me. Organisms do not just waste energy for the hell of it.

Eric:
It doesn't sit well with me, either, but it does happen.... We "evolved" humans have a number of such traits besides appendices..... Vestigial traits are the rule, not the exception, though this is clearly a very prominent attribute of these corals... I would have to agree that it probably does or did serve a significant function...but a function observable to us may be a little crazy! For all we know, its a method of increasing mucus levels to attract surface bacteria.... The fact that some studies have been done to look for the "obvious" and came up empty makes me think we are looking at this in our distinctively logical manner, and could likely be way off base... I'm dying to know though, huh? !!!! :-)

Daniel:
Why do Xenia pulse? Interesting question. I'm asking that to myself for more than 10 years...;-)

I absolutely agree to your [DBW's] hypothesis about the Xenia pulsing, and from earlier observations, I also have got the impression that it pulses stronger in weaker water current. (and strong illumination, and availability of trace elements and CO₂. If one of those is missing for a longer time, to my observation the pulsing gets weaker).

I am remember having read that Xeniidae have a reduced digestive tract and are not able to catch prey and digest. So they rely to the uptake of dissolved matter and to their zooxanthellae to a bigger extent than other corals, e.g. Nephtheidae. But as far as I know, with Stoloniferans it's similar to the Xeniidae, meaning that they also cannot catch prey and also strongly rely to zooxanthellae and uptake of dissolved matter.

So, for quite a while I have asked myself one question: Why did other coral families not develop the same strategies of pumping? If birds and fishes separately can discover the advantages of living in a school and evolve similar strategies, I think that polyps living in the same habitat and being somehow closely related to each other (well, relatively closed) like Xeniids and Stoloniferans should well be able to develop similar strategies.

And now it gets interesting. If you take a closed look at some Xeniids you will see that sometimes they don't really do a full pumping action but just roll up one of their tentacles. I've seen that at night, for example, when the illumination was turned off and I had the feeling that those Xeniids are "about to go to sleep". Then I have examined the polyps of some Stoloniferans, and I am absolutely sure to have seen the same "rolling up of single tentacles", in several polyps, and different aquaria. It was not just a single observation. Not regular, just occasionally and just in some single polyps. Could it somehow be connected to the fact that they rely more on their algal symbionts and the uptake of dissolved matter than other coral families that also catch prey?

But if so, I still don't have any idea about whether the pumping action is connected to the transportation of dissolved nutrients or waste products, or to the supply of their zooxanthellae ;-)

DBW:
Interesting, Xenia pulse weaker if there is absence of strong illumination and trace elements/CO₂? I would think may be that it would pulse harder to try and facilitate better transport of such things to the coral tissue. Then again, it may be starting to get low on energy reserves, and the action of pulsing may put too much of a drain on it without giving enough back. A couple of thoughts anyway.

Eric:
That is also correct...Xeniids maintain the ability to actively pump, not pump, vary the rate of their "pump", bend or twist their stalk, or move individual tentacles. They can exert control over this on their own, as you have seen, but I feel that we influence this ability negatively somehow in captivity.

Daniel:
Definitely. And if we can really find out what has a negative effect on their pumping activity, maybe we would come closer to the answer to that question why they pump. For example, I have observed that they reduce pumping when CO₂ is missing and the pH gets too high. John Newton has observed and also cited Julian's and Charles' vol. 2 that Xeniids reduce pumping action when the pH gets too low, which could well be caused by an excess of CO₂. Maybe we are all right. Maybe it's just a problem for those Xeniids if the pH leaves the proper range between value X and value Y.

If that would be the case, it could possibly help a little in coming nearer to the answer.

Dave:
..... how about this for a hypothesis. If memory serves Xenia often inhabit lagoonal areas where there may be some degree of turbidity. Perhaps their pumping serves to discourage sedimentation. Then again it could be as Daniel suggests and it could be enhancing photosynthesis in the same way the swaying of kelp exposes all portions of the kelp to light thus maximizing surface area.

Daniel:
....the assumption that the Xeniids might pump to rid themselves of sediments. I doubt that. I think nature always goes the least energy consuming way to solve problems. If a coral wants to rid itself of sediments, it can be done pretty easy with a secretion, as many soft corals do. The pumping action of Xeniids is surely consuming lots of energy. So I think that it just makes sense for the polyps if their gain of energy is bigger than their expense. So, whatever purpose it serves, it must be one that is contributing a considerable amount to their energy supply.

Eric:
Agree...and they already have a good mucus coat for absorption and bacteria... H. fuscecens is a bacteria farm (Ducklow and Mitchell, 1979)...it would be a waste of their time, in my opinion, to pulse for sediment rejection.

Daniel:
For example (I'm just theorizing) it could benefit the zooxanthellae, which could get a higher supply of something they need. This could enable the Xeniids to have a higher zooxanthellae density than a not pumping species, for example. I remember that in the giant clams, Carmen Belda found a 10 times higher zooxanthellae density compared to the same tissue surface of a coral. Just due to their zooxanthellae tubular system! What if those pumping Xeniids have found a way to supply their zooxanthellae with more nutrients and enhance their gas exchange by the pumping action, which could have enabled them to "breed" more zooxanthellae and cultivate it in higher density? As soon as the environmental conditions are leaving the optimum range, it might be a limiting factor. The zooxanthellae density will not be able to exceed a certain point, and furthermore it will not make sense for the polyp to invest energy into the pumping action because the gain of energy from that pumping is smaller than the investment of energy.

Eric:
Interesting...and there are many compounds which some species coral animal or the zooxanthellae might need. Example are amino acids that must be taken up from the environment, provided by surface micro-layer bacteria, etc. I'm with you on the energy part.... I think that is a very widespread characteristic of many marine animals ..they live on the edge...limited resources, limited energy budgets...a very keen area of interest for me.. as you said, we see in it anemones. I am fairly convinced that it is a major reason why all of us with vibrantly healthy tanks are not seeing more sexual reproductions.. allocations of energy budgets...and at some point, something's gotta give.

Daniel:
For example, let's assume that the Xenia polyp lives in an aquarium that lacks CO₂, from whatever reason. Let's furthermore assume that the metabolic CO₂ supply coming from the polyp is not sufficient to supply all the zooxanthellae if their density exceeds a certain value. That could result in a decrease of zooxanthellae density in the polyp tissue because the polyp might not be able to maintain the maximum zooxanthellae density. The coral will have a reduced gain of energy coming from the symbionts. That could make it necessary for the polyp to reduce their investment of energy, by reducing their pumping action.

Eric:
Push this a step further.... coral has less carbon being translocated of which the majority goes into mucus production and as quick energy source... translocated carbon is mostly unused for growth.. goes into metabolic expenditures....... and less mucus means less bacteria and POM/DOM uptake.... and even less energy in these corals... increasing cycle happening.

Daniel:
The loss of pumping action somehow reminds me of what Julian and Charles have written about the "stickiness" of anemones in their vol. 2. It's very energy consuming for them to maintain their cnidocysts. But they need those cnidocysts to catch prey and supply themselves with energy. So, if the anemone in captivity starves from missing nutrition, their gain of energy is reduced and they can furthermore "not afford to invest" energy into maintaining all the cnidocysts. As a result, the "stickiness" will slowly get lost ( I hope that I have cited them correctly. I even cannot say the exact pages of this, I just remember it from translating it).

Eric:
Now.. here's some more fuel for the fire.. not all of it corroboratory, maybe?

1. Dissolved CO₂ is used for calcification. Not a big deal in Xenia since they even pretty much lack inclusions. Therefore CO₂ is likely a more important metabolic need for these guys than Scleractinia or heavily spiculed Octocorals. Uptake could theoretically be more important for them.
2. Problem... pulsing has been observed frequently to cease in high nutrient water. I am not sure at all of the directness of the correlation, because high nutrient when it comes to aquaria is kind of irrelevant compared to the ocean. But high nitrates and phosphates and other nutrients acquired through direct uptake are available to the algae first...they use this for increasing their numbers. If C02 was limiting, would they be capable of increasing densities? Probably not...so maybe that explains why the high nutrient thing doesn't wash with what is observed in the wild and with tank observations.
3. If there is a lack of CO₂ by the animal in Scleractinia, carbon released from calcification can be used as a secondary source to the zooxanthellae...this isn't happening in Xenia.
4. High nutrients in water decrease the efficiency of photosynthate translocation and photosynthesis through various means, lowering overall, metabolism and success of the symbionts. Another increasing counterproductive cycle, high nutrients, less photosynthesis and translocation
5. Under normal conditions in the ocean, Xenia self-regulates behavior, maximizing _______? Energy cost, like cnidicytes/aggression/normal heterotrophic feeding etc. is determined by prevalent ambient conditions. In aquaria, light/nutrient/carbon source balance is shifted, behavior changes, at some point, pulsing ceases to be energetically favorable given limited energy resources. Energy state decreases till no longer feasible...OK.. I like the hypothesis

Problems....

1. What about long term Xeniids that do not pulse but continue to grow or survive? Is it hanging on? Well, why would energy be shunted to reproduction and growth in such cases?
2. Generally, areas of high nutrients tend to have high CO₂ from microbial action, even in nature. Acidification problems, red tides, low redox, etc... Xenia are found here. Sure would be nice to know some respective wild and captive levels of a couple parameters, wouldn't it?

John:
One more factor to throw out here I have both read (The Reef Aquarium, Delbeek and Sprung, vol 2) and observed in my tank that the pulsing increases as pH increases and tends to stop if the pH is too low.

Eric:
This is a common report, but so is the use of small amounts of granulated carbon, the use of Biotrace, Lugol's, no Lugol's, high nutrients, low nutrients, currents, etc. In my experience, it is too anecdotal to be meaningful. Too many exceptions....and the biggest exception is, in my experience, the differences in species, genera, and wild vs. captive colonies. I have Anthelia of the same colony that pulses in one tank, does not pulse in another and twists a tentacle only at night in a third, all substantially similar in pH, and by coin-kee-dink, the non-pulser is in the tank with the highest pH. I have had colonies that both applied and contrasted virtually every anecdote reported in these corals And because they have been good growers, I have been able to eliminate the "different colony, different collection location" variable, merely transplanting colonies from one tank to another. Without question, the Xenia which have continued to pulse in virtually all conditions have all been captive bred. Without question, almost every wild collected Xenia I have owned has ceased to pulse after changes in environment or irrespective of environment. What does *that* mean? I haven't the foggiest!

Marther:
And this is the explanation that I like the most, and I think shots all the other arguments/reasoning to the ground ;-)

Daniel:
Here is another assumption about that topic. We are always trying to find a scientific explanation for the pumping action of the Xenia polyps. We always try to examine their physiology and anatomy. But maybe we should remember that they are called "waving hand polyps". Maybe they are just trying to say "Hi!" to us...;-)

Marther:
And a final note from Eric....

Eric:
....Xenia is a hard coral that is found at 600 feet of depth in the Arctic circle....

Marther:
Now whatever is Eric talking about here, are we sure that he is the same person that co-wrote "The Practical Guide to Corals"?!?! Opps, Eric told me not to quote that line about what he thinks Xenia is ..... I'm in trouble now ..... hehehehehe

From,
Marther ReefKeeper

Special Feature

You Wouldn't Believe It!

..... a large part of waste organic material from a reef community is repeatedly recycled by fish in the water column and corals on the reef surface. Most of what is not recycled in the short term is then transported into fine sediment in regions such as lagoons or the deep fore reef. This can then be returned to the reef by the action of other organisms such as grunts. These fish work sediment in lagoon areas at night, sifting out worms and detritus from the sand. This provides a way for nutrients to be returned to the reef community even after it has left the proximity of the main reef structure.

..... parrot fish are a highly developed grazer of the reef. They have developed strong calcified, fused teeth that is used to scrape off coralline algae and the calcareous surface that most algae live on. Some species will also scrape off living corals while feeding. Because of this scraping of the calcareous surfaces and algae they are one of the major sources for the fine calcareous silt found around a reef. They are also one of the major animal components of the degradation of the hard reef structure.

Bereavement Notices

3 x Lysmata ambionensis, Cleaner Shrimp
Now I think this must be the most depressing deaths that I have had so far, more so than the flame angle, and actually ends up being the most expensive too. I decided to purchase another cleaner shrimp, and it was acclimatised and added without any problems at all. Two days later I found the new shrimp looking a little worse for wear, and then about 6 hours after that it was dead. Now that was bad enough as it was, had I not acclimatised him properly, been beaten by something else, or been injured when purchased? Well, the none of them held up, he looked fine and nothing was giving him a hard time. So I just took it as one of those things that tends to happens, but then the next day one of the original pair was dead. Now this is starting to get very worrying, and then another two days later the last one died. I did not have the opportunity to examine the bodies, as they are quickly taken to by hermits and the fish, nut all looked outwardly healthy. Luckily it stopped there, and what ever it was did not spread to the breeding pair of golden headed coral banded shrimp. What it appears like is that the new shrimp introduced a disease into the Park and it is specific to the Lysmata family, if not Lysmata ambionensis in particular. Everything else was normal, nothing out of the ordinary in behavior or appearance. That was not a good week at all, anyway it seems like the new pair is doing fine and I hope that I don't come across something like this again. What makes it so depressing is that the original pair had been in OZ REEF for around 9 months and were regularly breeding. Poof, there goes $135 just like that ;-(

Sea pen
This is the sea pen that I got about two months ago off Christian when he moved north. It was going OK in the sand, but then the gobies started to stir things up a bit too much around him. Then one morning I found that it was trapped underneath a rock in a bottom corner. And to no avail I could not dislodge it. Over the next week or so it got buried and unburied several times. If I wanted to reach it, it would entail pulling apart at least 1/2 of the reef structure, and I was not about to do that. I now realise that I should have placed it in the sump, where there is a thick bottom layer of sand, gentle currents and no large organisms to dislodge it from the sand. If ever I do come across one again, it will go in there, it should be a great place for a suspension feeder to live.

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