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Gonipora Success!?

By Rob Toonen. Posted to Reefkeepers emailing list, Saturday the 18th of December 1999.

The article that everyone is discussing is Julian's "Is there really something special about Goniopora, Alveopora and Heliofungia?" (Marine Fish and Reef USA 2000 -- Fancy Pubs). I must say that I really dislike the unknown pathogen idea, and frankly think that blaming an unknown pathogen for our widespread failure with this species is the easy way out. People continue to blame an "unknown pathogen" or "unknown toxic factor" for a variety of failures, but I really think that this is a cop-out, and this is certainly the easiest explanation for failure because it doesn't require any knowledge or advice on the part of the experts -- an off the cuff. "too bad -- you have an unknown pathogen. Maybe it's Vibrio!" will suffice...

Several coral biologists have recently published reviews of the coral disease literature and pointed out that there are only so many ways a coral can die, and a similar pattern of decline or "symptoms" does not necessarily imply a similar cause of coral demise. The best of these reviews, IMO, argues that unless the same criteria are applied to coral disease as we apply to human disease we will never gain a proper understanding of diseases in corals, and the "unknown pathogen" hypothesis is a long way from the isolation, identification and reinfection model upheld for human and veterinarian medicine.

I say that it is the "easy way out" because it is always simpler to blame some nasty little bug that we can't see, isolate or control for our failures than to figure out what the real root of the problem is. I so often see people attribute difficulties of all sorts to unknown pathogens, but the fact is that even the studies on natural coral disease outbreaks typically find that foreign organisms, such as bacteria, fungi, algae and protozoans, are only occasionally found in diseased coral tissues. Eric Borneman and Jonathan Lowrie review the literature on coral disease and propose a new hypothesis for the root of RTN in their "Invertebrate Immune System" series in the Aquarium.Net archives ( http// and http// ).

The reason that I most strongly disagree with Julian's conclusions in that article is that despite the differences in the sump relative to the tank, he still proposes a disease is likely to be the root cause of the problem. Personally, I think that a disease does not make much sense given the typical pattern of decline reported by the vast majority of hobbyists (other than the obvious "brown jelly" problem over the short-term), and my guess for the standard "thriving for 4-6 months followed by decline and death around 1 year" pattern reported for these corals is starvation. The reports, like Julian's as well as that of Inland Aquatics (Morgan Lidster), in which the animals are doing well, are usually in a lagoonal setting, typically with a well-established sandbed, and lots of "refugium-type" fauna in the system. I have thought that feeding was the logical answer for a long time, and I think it explains my success with these coral and that of the other people to whom I have spoken that have observed growth and asexual reproduction in their corals.

However, until now I have had nothing other than a gut feeling (and the same feeling of a bunch of other people like Eric Borneman and Morgan Lidster) to support my idea. That just changed, however -- I have recently been corresponding with Meredith Peach, and have gotten a copy of her unpublished thesis research on Goniopora (before she switched her field of research from coral biology to shark physiology). She published only 1 paper (on the structure and function of sweeper polyps in Goniopora) from her Masters Degree on the feeding and growth of Goniopora, but the rest of her research was even more fascinating (at least to me). She did a research project at One Tree Island in Australia and suggested that the corals may not be capable of supporting themselves on photosynthesis alone, and *worse* when deprived of food, she found that photosynthetic rate (as estimated from CN ratios of zooxanthellae) actually *dropped*. A similar effect has been found in several other coral species in which the translocation of nitrogen from the digestion of zooplankton prey by the coral leads to significant increases in the photosynthetic rate of the symbiotic zooxanthellae (host starvation resulted in decreased chl-a content, density & mitotic indices of zooxanthellae), but this makes the feeding all the more critical to the health and survival of the coral.

Feeding attempts with newly hatched brine shrimp were unsuccessful, and despite repeated contact with the tentacles, these prey were far too large for the animals to actually ingest. In fact, repeated contact with the tentacles led to the tentacles retracting and therefore an end to feeding rather than the animals actually being fed. Gut content analyses of polyps excised from wild colonies revealed that the majority of the prey were microcrustaceans (copepods and their larvae, juvenile mysids, barnacle cyprids and such) but much of the diet appeared to consist of a mixture of phytoplankton and other tiny non-crustacean plankton (such as polychaete and mollusc larvae, ciliates, and rotifers) of the same size range. Turns out that phytoplankton was found in the guts of every animal examined and probably accounts for a significant proportion of the nutrient uptake by these corals, and was the only prey type that showed significant variation in capture rate by tidal regime or day versus night-time sampling.

Given the results of Meredith's research, it is not surprising that the occasional reports we see for the maintenance and growth of these corals tend to be lagoonal or refugium-type systems with intense lighting and plenty of opportunity for the capture of tiny plankton and invertebrate larvae. It is also not surprising that a typical pattern of apparent health last for some months before the animal begins to show the signs of starvation (due to both deprivation of planktonic prey and the resultant decrease in photosynthetic ability) followed by a decline and eventually the death of the colony occurs in the majority of reef tanks (in which these type of prey are rarely provided in sufficient numbers). The animals do not need a lot of prey -- Meredith found that supplementing the feeding of wild colonies did not significantly increase growth rate, suggesting that the animals are not prey limited at natural feeding rates (roughly 50% of the polyps contained prey items of the sort outlined above at any given time), but decreasing the amount of prey captured obviously has a strong negative impact. These results explain the observation that adding declining animals to a well-stocked and highly productive deep sandbed system (such as Morgan's at IA) typically results in a complete recovery of the colony, because the renewed capture of phytoplankton and invertebrate larvae in addition to providing nutrition to the colony, in turn should lead to the increase of zooxanthellar output and both contribute the revival of the colony.

After seeing this thread and reading the article which started it, I think I'll try to write a rebuttal article when I have some time. I think that the information presented in that article is the easy way out on explaining why we continue to fail with these organisms, and it simply seems unlikely to me that everyone in every tank around the world has gotten the "unknown pathogen" that prevents survival of Goniopora beyond 12-18 months in an aquarium, but allows them to thrive in the wild. I'm not sure why that seems like a reasonable explanation to anyone, and after picking up a copy of FAMA last night (my new sandbed article just came out in it), I see that Julian is using that article as supporting evidence that a bacterial infection is likely to be the root cause of the poor success rates observed with Goniopora and Elegance Corals recently.... Frankly, I think that answer is a cop-out and I think that this new research from One Tree Reef supports another hypothesis (namely starvation) that makes much more intuitive sense that is also consistent with the observations of general decline in divergent systems, and the occasional "unexplained" success....

I also suggest readers check Eric's article at http// for more information regarding the debate about successfully keeping these enigmatic corals in aquaria...

Created by liquid
Last modified 2006-11-24 18:42