› Continue reading]]> Comparison of HQI and LED lighting systems on Coral Growth

Lighting systems and absorption spectra

Lighting is crucial to life and calcification of corals. It allows the photosynthesis by symbiotic dinoflagellates (zooxanthellae). This involves the use of a set of molecules including photosynthetic pigments like chlorophyll a and c2 and carotenoids. These molecules absorb some radiations efficient for photosynthesis (PAR for Photosynthetically Active Radiation) (Figure 1).

Figure 1. Absorption spectra of chlorophyll a, c2 and carotenoids (after Fawley, 1989 and http://www.snv.jussieu.fr/bmedia/Photosynthese/exp233.html).

These spectra indicate that the dinoflagellates are particularly well suited to wavelengths between 450 and 500 nm, corresponding to blue waves. This explains why these dinoflagellates are brown: the color that maximizes the absorption of blue. While deep corals use more effectively the blue spectrum, those in shallow waters are suitable for the entire solar spectrum. Indeed, by photo-acclimation, dinoflagellates induce cellular changes that optimize the collection and use of light energy up to five times.

Measurement of Photosynthetically Active Radiation (PAR)

According to the Stark-Einstein law, photosynthesis begins when a photon excites an electron. In 1972, Keith Mc Cree discovers that counting photons of light radiation can measure the rate of photosynthesis. While this measure expressed in lumens (lm) is a very good indicator of the light intensity perceived by the human eye, the photosynthetic yield is evaluated with a PAR meter (PAR for Photosynthetically Active Radiation). This instrument measures the number of photons between 400 and 700 nm, which can be absorbed by photosynthetic organisms. The measure provides a rough indication of the photosynthetic efficiency of a light source, but it has limitations. Indeed, the PUR (Photosynthetically Usable Radiation) or radiation used for photosynthesis, is the fraction of PAR actually absorbed by dinoflagellates.

Different lighting technologies

There are currently three major lighting technologies for aquaculture: the so-called “HQI” lamps, the “LED” ramps and fluorescent tubes. As part of this research, only the first two are developed.

The HQI are recognized since the 90s by aquarists raising hard corals as the best lighting available. An HQI (Hydrargyrum Quartz Iodide) lamp is a glass bulb filled with a gas called metal halide, powered by a transformer discharge. An AC voltage applied across the electrodes gives rise to an electric field therebetween. The rare gas allows the discharge regime and the arc is established.

As shows on Figure 2A, the spectrum of a metal halide lamp designed for reef tanks (here a GiesmannTM Marine Megachrome 12 500°K) has a peak between 400 and 450 nm, promoting photosynthesis. However, this type of light source has a non-continuous spectrum. It comprises narrow wavelengths bands giving a non natural light.

Figure 2. Emission spectrum of the HQI 150 watts from GiesmannTM (A) et LED from AlphéusTM (B).

LED (Light Emitting Diode) appeared a few years ago and started to become affordable for individuals holding coral reef aquarium. A LED is an electronic component capable of emitting light when traversed by an electric current. The emission spectrum has two peaks, a narrow one at around 455 nm (Figure 2B) and a wider one from 500 to 650 nm. Unlike the HQI, the spectrum is continuous, emitting all wavelengths, offering a more natural light.

The short background from the use of LED does not allow to objectively evaluate their effectiveness on the growth of corals in captivity. The purpose of this pilot study is to compare the growth rates of corals subjected to these two light sources. The buoyant weight technique was used to follow the coral growth because of its sensitivity to any changes in the system.

Experimental setup

To study the influence of HQI and LED technologies on the growth of Acropora spp and Pocillopora spp, two 80-liter tanks were installed and each equipped with one type of lighting. These two pools were connected to the same filtration system, guaranteeing identical water quality in both experimental conditions. A 150W HQI bulb from GiesemannTM (Marine Megacrome 12 500°K) and a LED ramp from AlpheusTM (double ramp 11m1001) were used. The LED ramp has a theoretical yield of 66 lm/W, which is 12% higher than the HQI (59 lm/W). Thus, the power of the LED lighting has been deliberately reduced by 12% to emit the same light intensity than the HQI. To get a first approach to the photosynthetic capacity of these two technologies, the PAR quantities were measured in each system using a PAR meter (ApogeeTM). We measured an average of 94.42 ± 11.56 mmol/m²s and 223.08 ± 39.89 mmol/m²s for HQI and LED units respectively.

The buoyant weight technique

The mass of corals cultured under LED or HQI lighting were measured each week and conversed in average daily growth rate (%.d-1). The immersed weight is defined as the result of two opposing forces, the mass and buoyancy. These two forces are compensated for the living tissues having the same density as seawater. Their mass immersed in sea water is close to zero. Conversely, limestone skeleton has a positive apparent mass. Thus, the extent of the submerged mass is primarily a measure of the mass of the skeleton in salt water.

Results and discussion

No significant difference was observed between HQI and LED in terms of coral growth rate (Figure 3). It is worth to notice that these corals have not been fed during the whole comparison period. This indicates that lighting systems could fulfil the majority of the energy demands required for the physiology and growth of corals. Indeed, a daily growth rate indicates the use of the calcification process. However, the photosynthetic product is mainly used by corals to their breathing, with only a small proportion to their growth. These lights thus provide optimal energy production for breathing and also for growth.

  Figure 3. Comparison of HQI and LED lightings on the growth of Pocillopora spp (A) and Acropora spp (B). The results express the average daily growth rate (%.d-1) ± Standard Deviation. Data obtained from four coral frags for each experimental condition during follow-up of 35 days.

This study revealed a quantity of PAR 2-fold higher for LED than HQI lighting in spite of an equivalent intensity in lumen. This is probably explained by the fact that LEDs have a continuous spectrum, unlike HQI which has narrow stripes neglecting certain wavelengths measured by the PAR-meter. The results obtained in this study show similar growth rates for both types of lighting. This suggests two possible explanations. Either the actual amount of radiation used in photosynthesis (PUR) provided by the two lights is substantially equivalent, or the dinoflagellates have the ability of photo-acclimatization to compensate the PAR difference. The darker appearance of coral frags placed under HQI (Figure 4A vs. 4B) suggests a photo-acclimation resulting in an increase in the concentration of cell pigments, as it has been previously described in several works (see additional references).

  Figure 4. Pocillopora spp under HQI (A) and under LED (B).

Both lighting types providing mainly blue wavelengths (Figure 2). This experiment confirms the importance of this color and photo-acclimation ability of dinoflagellates under artificial light. Dinoflagellates have chlorophyll pigments that absorb red wavelengths (Figure 1). Thus, a light emitting a significant amount of red wavelengths in addition to blue wavelengths would likely have a significant positive impact on coral growth in captivity.

To assist in the selection of the most suitable type of lighting for aquaculture, it is necessary to take into account the difference in energy consumption. LED technology has a higher energy efficiency than the HQI. In addition to being “green” and less expensive to use, it has many other features such as longer service life. In addition, the flexibility of LED is made possible thanks to computer control. It allows the creation of lighting effects, with the ability to easily mimic natural conditions by increasing and decreasing the intensity gradually or creating cloudy weather.

Special thanks to Jean-Louis Cuquemelle, designer of Alphéus ramps, for very kindly attended and for his expert collaboration in the field of LED lighting. Jeremy Berthelier, student in Biology, is also warmly thanked for all the work he has done in this study, the establishment of experimental systems to growth monitoring as well as its participation in the writing of this article.

Additional references

Allemand D., Ferrier-Pagès C., Furla P., Houlbrèque F., Puverel S., Reynaud S., Tambutté E., Tambutté S., Zoccola D., 2004. Biomineralisation in reef-building corals: from molecular mechanisms to environmental control, Palevol, 3:453–467.

Falkowski P. G., Dubinsky Z, 1981. Light-shade adaptation of Stylophora pistillata, a hermatypic coral from the Gulf of Eilat. Nature, 289 :172-174.

Falkowski P. G., Dubinsky Z., Muscatine L., Porter J. W, 1984. Light and the bioenergetics of a symbiotic coral. BioScience, 34 :705-709.

Falkowski P. G., Jokiel P. L., Kinzie R. A. III, 1990. Irradiance and corals. Ecosystems of the world #25: coral (ed Dubinsky Z.), Elsevier Press., 89-106.

Fawley, Marvin W., 1989. A New Form Of Chlorophyll C Involved In Light-Harvesting. Plant Physiol., American Society of Plant Biologists, 91:727-732.

Grosjean Ph., Spirlet Ch., Jangoux M., 1999. Comparison of three body-size measurements for echinoid, Echinoderm Research (ed M.D. Candia Carnevali et F. Bonasoro), 31-35.

Jokiel P. L., Maragos J. E., Franzisket L., 1978. Coral growth: buoyant weight technique. UNESCO, Coral reefs: research methods, 529–541.

Mass T., Kline D. I., Roopin M., Veal C. J., Cohen S., Iluz D. and Levy O., 2010. The spectral quality of light is a key driver of photosynthesis and photo adaptation in Stylophora pistillata colonies from different depths in the Red Sea. The Company of Biologists Ltd, The Journal of Experimental Biology, 213:4084-4091.

› Continue reading]]> Colin Foord recently co-authored a peer-reviewed scientific paper on four new species of Zoanthids in Florida waters. The zoanthids were discovered by expeditions undertaken by Coral Morphologic and several of the new species are occasionally offered on the Caribbean livestock specialist.

An english version about this topic is available on two blogs:

Reef builder at

http://reefbuilders.com/2012/10/08/species-zoanthids-florida-waters/ # ixzz2D3FH4cTc

and Coral morplogic at

http://coralmorphologic.com/b/2012/10/04/coral-morphologic-confirms-4-undescribed-species-of-zoanthids-from-south-florida

› Continue reading]]> Olivier Detournay, an immunologist who recently joined Coral Biome, is working closely with the team of Virginia Weis at the Oregon State University (OSU) and the Hawaiian Institute of Marine Biology (HIMB), addressing fundamental questions on the symbiotic relationship between zooxanthellae and corals.

“Unity is strength”. This proverb is probably much older than previously thought. Corals applied this principle millions years ago through their association with zooxanthellae to provide the energy needed to build coral reefs. The deal is simple: the coral plays host to the zooxanthellae, thereby providing physical protection and, in exchange the algae provide sugars, amino acids and lipids to the corals through photosynthesis. Although this symbiotic relationship was described long ago, large gaps persist in our understanding of the cellular mechanisms ensuring peace in the household. These issues are of paramount importance since the climate changes has taught us that the coral-zooxanthellae relationship, believed to be stable, may be disrupted, resulting in bleaching events observed throughout the world, and even in our aquariums.

Tentacles of Aiptasia pallida in confocal microscopy. One sees zooxanthellae in red.

What intrigued Olivier and his colleagues was not to know why corals bleach, but why they do not when everything goes well! After all, it is logical to think that an animal (corals) gets rid of microbes (zooxanthellae) through activation of its immune system. In fact, the role of the immune system is trickier than the simple destruction of any “foreigner”. Its role is to ensure the integrity of the animal by implementing mechanisms at play to destroy pathogens and to tolerate beneficial organisms. The assumption is that the zooxanthellae are capable of inducing immune tolerance in coral tissue. This mechanism is known for many years in medicine. Many cancers force their own tolerance. The agent of malaria, Plasmodium falciparum, is another example of tolerance induction allowing parasites evade the immune system of its host.

One of the mechanisms involved in immune tolerance is based on the increase of a soluble anti-inflammatory factor (TGFbeta) induced in the host by the parasite. This anti-inflammatory activity promotes the proliferation of parasites to trigger the disease. It is worth to note that from an evolutionary perspective, the zooxanthellae are very close cousins of Plasmodium, both belonging to the group of Alveolata. The idea is therefore that the zooxanthellae could use a similar mechanism of tolerance induction to ensure symbiotic relationship with coral.

The first discovery of Olivier and his colleagues is that the vast majority of genes involved in the activation of anti-inflammatory factor TGFb are very old and are present in corals.

In addition, functional experiments in Aiptasia pallida anemones, a model widely used in coral physiology studies, have strengthened their hypothesis. Indeed, it is possible to prevent the bleaching of anemone subjected to a 34°C-heat shock after treatment with TGFb factor (Fig. 1). This shows that TGFb pathway is crucial for the maintenance of the symbiosis.

Figure 1. Left, Aiptasia pallida bleached after heat shock. On the right, the pretreatment of Aiptasia pallida with 100 ng / ml of TGFb decreases the bleaching of anemones after a heat shock.

Conversely, an inhibition of TGFb induces the disruption of the symbiotic relationship, leading to rejection of zooxanthellae (Fig. 2).

Figure 2. Addition of anti-human TGFb sensu stricto to putatively block a TGFb pathway increases NO production and reduces infection success in A. pallida. Aposymbiotic anemones were incubated in: vehicle only control, rabbit isotype control (IgG) or rabbit anti-human TGFb sensu stricto, for 1 h prior to being inoculated overnight with symbionts. (A) NO-dependent DAF-FM DA fluorescence expressed as mean fluorescence intensity (MFI) at 24, 72 and 144 h post infection. NO production was significantly higher in animals incubated in anti-TGFb sensu stricto compared to control animals at 72 and 144 h after inoculation. (B) Relative infection success in the same anemones at the same time points, expressed as percentage of pixels displaying fluorescence at 600-700 nm. Animals incubated in anti-TGFb sensu stricto were significantly less infected than control animals at 72 and 144 h after inoculation (For A and B: points represent means + SD; n=3 anemones. t-tests: values of NO levels and infection success of anti-TGFb-incubated animals different from isotype controls at a given timepoint by * Ptentacles, from animals incubated in the three treatments 144 h post-infection. DAF-FM DA fluorescence is colored yellow and symbiont autofluorescence is colored red.

This study paved the way to a better understanding of symbiotic relationships, including those of corals facing climate changes. On a medium term, we can even expect that this kind of work could provide solutions to make corals more resistant to bleaching. Moreover, the characterization of such complex immune mechanisms such as those orchestrated by the TGFb signaling pathway has perhaps found a new animal model. Applications out of these findings are numerous, including the identification of molecules to improve the prognosis of Graft Versus Host Disease (GVDH), the effectiveness of vaccines or in the fight against cancer. Case to follow very closely…

Reference
Detournay O, Schnitzler CE, Poole A, Weis VM. Regulation of cnidarian-dinoflagellate mutualisms: Evidence that activation of a host TGFβ innate immune pathway promotes tolerance of the symbiont. Developmental & Comparative Immunology. 2012 Sep 22.

› Continue reading]]> One of us recently visited Coral Morphologic’s Miami Lab. Our good friends Colin Foord and Jared McKay expanded their livestock list and recently added new Caribbean gorgonians.

Collected in the respect of the environment (very few fragments are cut off from the wild colonies), selected for the best colors, mounted on normalised plugs, and cultured in a Green house these trademarked gorgonians named ‘Eco-Gorgs‘ are a very welcome new product to the aquarium trade, showing that is possible to sell corals and to work together for the conservation and the valorisation of the marine biodiversity.

The ‘Eco-Gorgs’ farm located in the Florida Keys is one of the latest projects by Coral Morphologic. The set up is as simple as possible and well equipped to grow a broad diversity of corals. The whole system is under a greenhouse and the corals grow under natural lighting. No heating or cooling elements are used beside some big fans to remove heat which remains below the plastic roof. Water filtration is provided by a single sandbed filter and liverock. Also the system can be opened and washed up with natural sea water from the lagoon. Most of the water movement is driven by air pumps and air lifters as an inexpensive and energy-friendly alternative to water pumps, besides this method also has the benefits of oxygenating the water.

Eco-Gorgs include some beautiful Eunicea including the purple Eunice and Hazel Eunice, two colourful Pseudopterogorgia pinnata sea plume, as well as the emblematic Purple blade Pterogorgia guadalupensis.

The Eco-Gorgs available at Aquascapers and Coral Biome web sites. A- Purple Blade Eco-Gorg™ (Pterogorgia guadalupensis). B- Hazel Eunice Eco-Gorg™ (Eunicea calyculata). C- Purple Plume Eco-Gorg™ (Pseudopterogorgia bipinnata). D- Narrow Eunice Eco-Gorg™ (Eunicea succinea). E- Golden Plume Eco-Gorg™ (Pseudopterogorgia bipinnata). F- Purple Candelabra Eco-Gorg™ (Plexaura flexuosa). G- Black Candelabra Eco-Gorg™ (Plexaura homomalla). H- Purple Eunice Eco-Gorg™ (Eunicea sp.). 

Check out the new web site of Morphologic: Aquascapers.com

Read more: http://reefbuilders.com/2012/07/18/aquascapers/#ixzz27rWNnH9c

› Continue reading]]> Palytoxins are back under the spotlight! Coral Biome breeds in its facility some potentially toxic zoanthids. To get the bottom of it, we carried out a study based upon the same protocol described by Jonathan Deeds and his colleagues in the “Plos One” journal in 2011, a publication previously discussed on our blog.

First, we investigated the phylogenetic relationships of some species including the famous Palythoa grandis, a rare endemic species living in deep waters of the Gulf of Mexico. The determination of the phylogenetic relationships of this species is important because, according to Deeds and coll., it exists a close link between the membership of a species to a given clade and its potential toxicity. Therefore we analyzed the DNA sequence coding for the large subunit mitochondrial ribosomal RNA (rRNA16S) of P. grandis. Our phylogenetic reconstruction suggested the potential toxicity of this species. Indeed, P. grandis grouped with P. heliodiscus, a species known for its high concentration of palytoxin and listed among the most toxic zoanthids in the Deeds study.

To confirm the toxicity of P. grandis, we performed a liquid chromatography analysis of a mixture from a polyp from P. grandis in ethanol. One other unknown species of Palythoa sp. have also been analyzed as well as one specimen of Zoanthus sp. from the Vice Zoa complex.

Chromatography principle is to separate different molecules from a mixture. In our study, the detection of molecules was achieved by UV at a wavelength of maximum absorption for palytoxin (263 nm). The material and method used were similar to the Deeds and coll. protocol. These authors observed a retention time for palytoxin about 13 min, a duration we also observed in our analysis for P. grandis (A). A result consistent with its phylogenetic position and its close relationships with the known toxic species P. heliodiscus. The second specimen belonging to an indeterminate species of Palythoa sp. also showed a peak of palytoxin (B) while the Zoanthus Vice Zoa (C) did not. The absence of peak for Zoanthus considered here as a negative control confirms the higher toxicity of Palythoa versus Zoanthus as previously shown in the Deeds and coll. study.

Therefore, P. grandis likely contains a concentration of palytoxin potentially dangerous for Human. Some cultured species in our tanks exhibit high rates of palytoxin, important enough to justify elementary precautions when handling them: use of gloves and protective goggles.

Special thanks to Robert at the University of Aix-Marseille for his help in chromatographic analysis. This work was directed by Pierre Maziani, undergraduate student of Biology. A big thank to its availability, its rigor … and good humor!

› Continue reading]]> What’s more surprising than a short walk on a coral reef near… Marseilles! This incredible situation is indeed possible because of the main feature of hard corals: a carbonate skeleton that fossilizes easily.

Some of us probably know the little port of Carry-le-Rouet, located about thirty kilometers from Marseilles (France).

A continuous succession of continental and marine sediments of late Oligocene (28 MY) to early Miocene (20 MY) age is exposed along the coast of this very typical Mediterranean village. The Carry-le-Rouet sedimentary succession is an excellent climatic archive. Just after the port, when you start to walk along the rocky shores, it is easy to remark the very usual aspect of a ‘reef’ which extends along the shore over more than 1 kilometer.

One can quickly realize that all the rocks are full of fossils and it is easy to recognize some ‘best-sellers’ such as Acropora or Caulastrea species! The most diversified coral community occurred during the warmest period of the Aquitanian (23My). The diversity consists of in-life-position, coalescent or scattered, massive colonies of poritids and faviids, bundles of mussids, dendrophyllids and of fragments of branching acroporids (Galloni, 2003).

Porites

Turbinaria

Tarbellastrea

Mussismili

Caulastrea

Acropora

The alternation of branching acroporitids fragments and muddy sediment suggests episodic storm-deposition in a relatively deep lagoon, as observed nowadays in the Caribbean (Demory et al. 2011). 

Associated organisms are molluscs (gastropods and lamellibranches), echinoids (scutellids), red coralline-algae. 

Mollusc assemblage

Lamellibranch deposit

Gasteropod shells

Coralline red algae

It is well known by palaeontologists that the Mediterranean shores exhibit a large number of fossil corals including different reef types. During the Oligocene and Miocene age, shallow-water of the Mediterranean region were rich in scleractinian corals, their diversity is considered to be strongly controlled by changes in sea-surface water temperature. Indeed, coral reefs occurrences match the glacial to interglacial transition and the most diversified coral environment matches the warmest period. Thus within an increasing need of data for better understanding the response of reef corals to climate change, the Mediterranean fossil reefs represents a unique paleontological database for investigating spatio-temporal changes in reef ecosystems.

References

GALLONI F (2003) Organisation sédimentaire et anatomies récifales des systèmes carbonatés à silicoclastiques oligo-miocènes inférieurs de Provence et du bloc corso-sarde. – PhD Thesis, Université of Provence, Marseille, 300 p.

FRANÇOIS DEMORY, GILLES CONESA, JULIEN OUDET, HABIB MANSOURI, PHILIPPE MÜNCH, JEAN BORGOMANO, NICOLAS THOUVENY, JULIETTE LAMARCHE, FRANCK GISQUET and LIONEL MARIÉ (2011) Magnetostratigraphy and paleoenvironments in shallow-water carbonates: the Oligocene-Miocene sediments of the northern margin of the Liguro-Provençal basin (West Marseille, southeastern France). Bull. Soc. géol. Fr., t. 182, no 1, pp. 37-55

› Continue reading]]> Today, it is well known that the anthropogenic rise in atmospheric CO2 is changing not only the climate but also the chemistry of the world’s oceans. First, global warming is causing massive coral bleaching. But a rise in coral disease by undermining their ability to build reefs is also produced by the mixing of anthropogenic CO2 in seawater. Indeed, a large amount of the CO2 produced by the human activities is taken up by the oceans. As CO2 dissolves in the sea water, it takes part in chemical reactions leading to a decrease in pH. This has led to changes in the physiology of a wide variety of organisms and the ecology of all oceans. For increasing our understanding of the natural history of stony corals and the effect of climate change, biologists are testing acidic sea water on their growing, palaeontologists are exploring the fossil records and mass extinctions to uncover clues of ancient episodes of ocean acidification, while phylogeneticists are elucidating their evolution with DNA.

Scleractinian corals, commonly named stony corals (or hard corals), developed during Paleozoic but became extinct massively in the Permian. They suddenly reappear in fossil records in the middle of the Triassic, several millions years later. One of the primary hypotheses regarding such a crisis is that a decrease of the sea water pH altered the ability of stony corals to form their calcite skeleton. To explain the sudden reappearance of scleractinians in the Triassic, when ocean conditions came back to normal, it has been proposed that they survived perhaps in a different form, a form lacking a skeleton, the so-called “naked coral” (Stanley and Fautin 2001). That seems far fetched, but we must keep in our mind that coral reefs have survived millions of years to sea level change, to chemical disturbance of sea water as well as to massive extinctions of other living organisms.

Laboratory experiments showed that two species of stony corals (the scleractinian Mediterranean species Oculina patagonica and Madracis pharencis) can survive long periods of low pH (Fine and Tchernov 2007). After 1 month in acidic sea water, first morphological changes resulted in polyp elongation, followed by dissociation of the colony and complete skeleton loss. All polyps maintained their algal symbionts and the biomass of the solitary polyps under acidic conditions was three times as high as the biomass of polyps cultured under normal conditions. After 12 months, when transferred back to normal pH, the solitary polyps calcified and rebuild colonies! This important experimental result supports the “naked coral” hypothesis.

The second set of observations supporting the “naked coral” is based on morphological similarities between scleractinians and corallimorpharians, for instance the presence of paired mesenteries in both groups. Also cnidoms and sperm ultrastructure were identified as features that may be synapomorphies for uniting scleractinians and corallimorpharians in a same clade.

Finally, the phylogenetic analysis of mitochondrial genome from nine scleractinians, six corallimorpharians and six soft corals as outgroups (three octocorallians, two actiniarians and one zoanthidean) clarified our understanding of the stony corals natural history (Medina et al 2006). Indeed, the results unambiguously indicated that the corallimorpharians are true members of scleractininians, so that the later should include the formers to refer to a natural group. Thus, scleractinians are likely ancestral to the nonmineralized corallimorpharian which are able to adapt to higher CO2 levels. The skeleton was likely lost in the ancestry of corallimorpharians which originated between -110 and -132 Ma, coinciding with high levels of oceanic CO2.

The Oceans are currently experiencing an increase in CO2 concentration similar to what occurred in the Cretaceous when multiple calcifying scleractinians went extinct. In such a context, the “naked coral” hypothesis represents an important and promising field of research for understanding the response of the coral reefs to ocean acidification due to human activities.

Stanley GD Jr, Fautin DG. Paleontology and evolution. The origins of modern corals. Science. 2001 Mar 9;291(5510):1913-4

Fine M, Tchernov D. Scleractinian coral species survive and recover from decalcification. Science. 2007 Mar 30;315(5820):1811

Medina M, Collins AG, Takaoka TL, Kuehl JV, Boore JL. Naked corals: skeleton loss in Scleractinia. Proc Natl Acad Sci U S A. 2006 Jun 13;103(24):9096-100

› Continue reading]]> DNA evidence suggests that the genera Palythoa and Protopalythoa are actually all members of a single genus.

The taxonomic status of the Zoanthid genera Palythoa and Protopalythoa has been under question by biologists for almost a century. Previous morphological and histological studies have separated these two genera on the basis of the shape of their polyp and colony, the size of their nematocysts and the number and position of septa in their body cavity.

During the last decade, Dr Jame Davis Reimer who is one of the best specialist about zoanthid systematics in the world has published important genetic studies on Zoanthids. To determine the phylogenetic relationships of the Palythoa and Protopalythoa  Zoanthids at the molecular level, Dr Reimer and his team from the Japan Agency for Marine-Earth Science and Technology sequenced two mitochondrial genes (coding for the cytochrome oxydase I and small-subunit ribosomal RNA) from different specimens belonging to these genera.

The phylogenetic analyses carried out by the team showed only 0.0-0.1% divergence among the Palythoa and Protopalythoa species, a level similar to that seen among the species of the genus Zoanthus. The authors concluded that Protopalythoa specimens cannot be differentiated from Palythoa genetically.

“The phylogenetic trees for both COI and 16S rDNA from Palythoa and Protopalythoa show four monophyletic groups (designated Palythoa tuberculosa, Palythoa heliodiscus, Palythoa mutuki 1, and Palythoa mutuki 2), with levels of sequence divergence (COI and 16S rDNA divergence approximately 0.0 similar to 1.1%) similar to or lower than that previously found among congeneric species within the closely related genus Zoanthus”.

In conclusion, the molecular genetic evidence provided by the Japanese Team strongly suggests that Palythoa and Protopalythoa are not truly separate genera. Protopalythoa is likely erroneous nomenclature.

After Reimer JD, Ono S, Takishita K, Tsukahara J, Maruyama T. Molecular evidence suggesting species in the zoanthid genera Palythoa and Protopalythoa (Anthozoa: Hexacorallia) are congeneric. Zoolog Sci. 2006 Jan;23(1):87-94.

› Continue reading]]> Recently, Jonathan Deeds and his collaborators published a very interesting study about one of our favourite animals in the open access journal ‘Plos One’. They reported the case of a zoanthid colony from a home aquarium which was responsible for a severe respiratory reaction due to palytoxin when a hobbyist attempted to eliminate the colonies using boiling water. Sample from the home tank was found to contain approx. 600 mg of palytoxin per g of wet zoanthid, which is enough to kill several thousands of mice!

Some of the deadliest toxins known to man such as palytoxin or maitotoxin come from the sea and are often produced by tropical marine dinoflagellates. However, these toxins can also be found in many more species due to accumulation through trophic chain or symbiosis relationships, such as in fishes, crustaceans or zoanthid corals. This is the reason why palytoxins are one of the few marine compounds that pose a risk to humans through ingestion (consumption of contaminated seafood), inhalation (exposure to palytoxin containing aerosols), and dermal (exposure to select marine zoanthids) routes of exposure.

Thus, to assess the availability and potential exposure of palytoxin to marine aquarium hobbyists, Deeds and coll. analyzed zoanthid samples collected from local aquarium stores for palytoxin using liquid chromatography and high resolution mass spectrometry. In addition, because zoanthids are proved difficult to identify to the species level on the basis of their appearance, specimens were also identified through genetic analysis of 16S and cytochrome c oxidase genes.

During this investigation, it was shown that many of the zoanthids commonly sold in the home aquarium trade are non-toxic or weakly-toxic, but a highly toxic variety of Palythoais indeed available. The authors found four specimens of the same apparent species which was responsible for a severe respiratory reaction in a home aquarium available in three aquarium stores. The most closely related species to the toxic specimens based on DNA analysis were Palythoa heliodiscus, showing that the most potent non-protein compounds ever discovered is present in dangerous quantities in a species of zoanthid commonly sold in the home aquarium trade.

Numerous poisonous and venomous animals are traditionally available at your local pet store for instance the lionfish (family Scorpaenidae), puffer fish (family Tetraodontidae), sea urchin (Astropyga spp.)and the blue ringed octopus (Hapalochlaena spp.). However, well documented cases of human poisonings due to exposure to zoanthids in home aquaria are limited, leaving hobbyists often unaware of the deadly poisons they are being exposed to. We therefore encourage everybody to take all necessary precautions when handling zoanthids.

Representative specimens for Palythoa spp. (both toxic and non-toxic/weakly-toxic) and Zoanthus spp. (all non- or weakly-toxic) collected from aquarium stores. [Red Box] Visually and genetically consistent with Palythoa heliodiscus and containing high concentrations of palytoxins. [Green Box] Visually and genetically consistent with Palythoa mutuki and Palythoa tuberculosa but non- or weakly-toxic. [Blue Box] visually and genetically consistent with Zoanthus sansibaricus, close to Zoanthus sociatus, and non- or weakly-toxic. Bar represents 1 cm.

After Deeds JR, Handy SM, White KD, Reimer JD. Palytoxin found in Palythoa sp. zoanthids (Anthozoa, Hexacorallia) sold in the home aquarium trade. PLoS One. 2011 Apr 4;6(4):e18235.