Green Alga Caulerpa Taxifolia Research Articles

Closing the Wound

PLANT BIOLOGY In the normal cut and thrust of everyday life, nonfatal injuries are common, and organisms rely on rapid repair mechanisms to stanch the loss of fluids. Adolph et al. have studied the invasive tropical green alga Caulerpa taxifolia , which lives as single polyploid multinucleated cells. In the early 1980s, Caulerpa invaded the Mediterranean, and its mechanism of wound repair may have contributed to its high growth rates. When the algal cells are mechanically broken, a gelatinous material consisting of cross-linked proteins rapidly plugs the wound and results in two cells, each with a full genomic inheritance. Polymer formation depends on the enzymatic unmasking of caulerpenyne, the dominant secondary metabolite of the alga. Its 1,4-bis-enoylacetate moiety is transformed into a dialdehyde, which reacts with nucleophilic groups of algal proteins, forming a life-saving plug. — SMH Angew. Chem. Int. Ed. 44 , 10.1002/anie.200462276 (2005).

Differences between native and invasive Caulerpa taxifolia: a link between asexual fragmentation and abundance in invasive populations

The tropical and subtropical marine green alga Caulerpa taxifolia has invaded several temperate regions throughout the world, including southeastern Australia. In this study, I examined how invasive C. taxifolia from temperate southeastern Australia differed from native C. taxifolia from subtropical Moreton Bay, Australia, in the traits proposed as being important to its invasion success: thallus size and density, levels of asexual reproduction (fragmentation) and total biomass. Against the prediction of a large size for invasive C. taxifolia, native populations from Moreton Bay had larger stolons and fronds than invasive populations. However, invasive populations consistently had much higher densities of stolons, fronds and fragmented fronds; and a greater biomass compared to native populations. Average densities at invasive sites exceeded 4,700 stolons and 9,000 fronds/m2 and were as high as 27,000 stolons and 95,000 fronds/m2, whichare the highest reported for C. taxifolia anywhere. Average densities of fragmented fronds at invasive sites were as high as 6,000/m2 and up to 45% of all stolons at invasive sites could be directly linked to asexual recruitment via fragmented fronds. Importantly, at invasive locations there was a strong association between asexual reproduction and abundance demonstrated by positive correlations between the density of fragmented fronds and total biomass. These findings are the first to describe quantitative differences between native and invasive C. taxifolia and to demonstrate a link between the high levels of asexual reproduction and high abundance in invasive populations. Although the causes and consequences of high levels of asexual reproduction remain to be explored, this study suggests that changes in demographic and life-history traits during the invasion by C. taxifolia into temperate habitats may contribute to its success there.

New records of marine benthic algae from New South Wales, eastern Australia

SUMMARY Twenty-four species of marine macroalgae are recorded from the mainland coast of New South Wales for the first time. One species, Laurencia platyclada Boergesen, represents a new record for Australia and the Pacific Ocean. Included in these new records is the introduced, invasive and cold-tolerant strain of the green alga Caulerpa taxifolia, which was formerly known only as native, non-invasive populations from Lord Howe Island. Based on published accounts, the composition of the marine benthic algae for the state of New South Wales now stands at 131 green, 140 brown and 449 red macroalgae. This baseline information adds significantly to our knowledge of the overall marine biodiversity of the state, as well as to the phycogeography of the southwestern Pacific region.

Intracellular compartmentation in the biosynthesis of caulerpenyne: study on intact macroalgae using stable-isotope-labeled precursors.

The biosynthesis of caulerpenyne 1 was studied in the invasive green alga Caulerpa taxifolia. The investigation was performed on intact algae with stable-isotope-labeled precursors administered under mixotrophic growth conditions. According to the labeling pattern, after incorporation of 1-(13)C-acetate and (13)CO(2), respectively, the biosynthesis of the sesquiterpene backbone occurs in the chloroplast and follows the methyl-erythritol-4-phosphate (MEP) pathway. In contrast, the acetyl residues of caulerpenyne 1 are derived from a cytosolic resource. [structure: see text]

Aliens on the shores.

In the early 1980s, a biologist at the tropical aquarium in Stuttgart, Germany, noticed that the beautiful green alga Caulerpa taxifolia (Fig. 1) would make an ideal aquarium decoration. It does not wither, it is fast growing and it withstands cool temperatures. In the following years, many aquariums acquired Caulerpa plants from Stuttgart, among them the Oceanographic Museum of Monaco, from which it escaped into the Mediterranean Sea. In 1984, the alga covered an area of around 1 m2 on the coast of Monaco. Since then, it has invaded large areas of the French and Italian coasts and has spread as far as the coasts of Spain, Croatia and North Africa. The alga grows everywhere, from the surface to the lower limits of underwater vegetation, forming huge monocultures that displace other plant species and, being highly toxic to many fish species, also threatens aquatic fauna wherever it roots. > Invasive species are the second biggest cause of loss of biodiversity after habitat destruction Figure 1. The green alga Caulerpa taxifolia In the summer of 1999, New York City witnessed an unusual spate of bird deaths, particularly of crows. During the same summer, on August 23, a physician from a hospital in northern Queens reported two encephalitis patients to the New York City Department of Health, and further surveillance identified other cases. A month later, scientists from the Centers for Disease Control and Prevention (CDC) in Atlanta, GA, USA, identified the link between these seemingly unrelated events. They discovered that the causative agent was the West Nile virus, which had never before been seen in North America. To contain the outbreak and prevent transmission of the virus by mosquitoes, New York's mayor, Rudy Giuliani, ordered the spraying of whole neighbourhoods in New York with pesticides. It was in vain. During 2001, 149 cases …

Use of amplified fragment length polymorphism (AFLP) as a new tool to explore the invasive green alga Caulerpa taxifolia in Australia

Caulerpa taxifolia is a high profile introduced alga in the Mediterranean Sea and California. It is native to tropical and subtropical regions of Australia. However, during 2000/01, 7 locations with abundant C. taxifolia were discov- ered in temperate waters around Sydney. To overcome limita- tions of resolution in previous studies using ITS (internal tran- scribed spacer) rDNA sequencing, we developed amplified fragment length polymorphism (AFLP) markers for C. taxi- folia, using 4 primer combinations. With this technique we found a close relationship between isolates from Moreton Bay (native) and Lake Conjola (introduced). The Mediterranean samples, which previously could not be separated from the other isolates, formed a discrete cluster supported by high bootstrap values. AFLP had greatly improved resolution over other molecular markers, making it a promising technique for further studies on the population structure of C. taxifolia and the assignment of source populations.

Re-evaluation of the extent of Caulerpa taxifolia development in the northern Mediterranean using airborne spectrographic sensing

There has been significant concern over development of the tropical green alga Caulerpa taxifolia in the Mediterranean Sea. Reports dating back to 1991 predicted that the species would expand exponentially on all types of substrata and displace major components of the coastal benthic flora, in particular the dominant native seagrass Posidonia oceanica. A pilot study of the Bay of Menton, SE France, where C. taxifolia has been established since at least 1989, indicated that these predictions might not be correct and that more sophisticated methods might be needed to gain a bet- ter estimate of the alga's abundance. We thus surveyed 44% of the total area reportedly colonized by C. taxifolia to a depth of 20 m on the south coast of France by compact airborne multispectral imag- ing and validated our maps by an extensive underwater survey. Our data indicate that the cover of C. taxifolia has been overestimated by at least 1 order of magnitude and that C. taxifolia has not sub- stantially impacted the cover of P. oceanica. They also indicate that exponential expansion of the alga is only likely to have occurred on substrata situated in the vicinity of sewage outfalls and storm water drains, suggesting that it principally occupies partially vacant niches in stressed environments. In the light of these results, we consider that the risk to most endemic species should be considerably lower than formerly predicted.

Genetic polymorphism in Caulerpa taxifolia (Ulvophyceae) chloroplast DNA revealed by a PCR-based assay of the invasive Mediterranean strain

Abstract An invasive, cold-tolerant strain of the tropical green alga Caulerpa taxifolia was introduced recently in the Mediterranean Sea and along the Californian coast. We screened 50 aquarium and open-sea C. taxifolia specimens for the presence/absence of an intron located in the rbcL gene of chloroplast DNA. We also reanalysed a total of 229 sequences of the Internal Transcribed Spacer (ITS) of ribosomal DNA, combining previously published sequences from different studies with 68 new sequences to complement rbcL data. The introduced Mediterranean strain was found to be characterized by the absence of the rbcL intron and by the occurrence of a particular monomorphic ITS type. A PCR assay based on rbcL gene was developed to detect new introductions of the invasive strain of C. taxifolia. This rapid and inexpensive test could be useful to assist environment managers in the preservation of coastal marine ecosystems.

Using genetic techniques to investigate the sources of the invasive alga Caulerpa taxifolia in three new locations in Australia

The invasive green alga Caulerpa taxifolia has gained a high profile due to `outbreaks' in the Mediterranean and California. During the year 2000 three new discrete locations colonised by abundant C. taxifolia were discovered in New South Wales (NSW), Australia. Sequencing of the internal transcribed spacer (ITS) region of the ribosomal DNA was used to explore the source(s) of these new records, which is an important prerequisite for subsequent environmental management responses. Our results indicate that the NSW C. taxifolia originated from several sources and, hence, through different invasion events. For two of the new records (Port Hacking, Careel Bay) it can be excluded that they are derived from the so-called “aquarium strain” of C. taxifolia, closely related to the invasive Mediterranean populations. Port Hacking is likely to have originated from tropical native populations. However, samples from Lake Conjola cannot be sufficiently distinguished with the applied technique from native C. taxifolia in Moreton Bay and the Mediterranean/“aquarium strain”.

Caulerpenyne from Caulerpa taxifolia has an antiproliferative activity on tumor cell line SK-N-SH and modifies the microtubule network

Caulerpenyne, the major secondary metabolite synthesized by the green marine alga Caulerpa taxifolia, is cytotoxic against several cell lines. To identify possible targets of this toxin, we investigated the effect of caulerpenyne on the neuroblastoma SK-N-SH cell line. Caulerpenyne induced an inhibition of SK-N-SH cell proliferation with an IC 50 of 10 ± 2 μM after 2 hr of incubation.We observed no blockage in G 2/M phase and an increase in cell death. On immunofluorescence microscopy, caulerpenyne affected the microtubule network in SK-N-SH cell line; we observed a loss of neurites and a compaction of the microtubule network at the cell periphery. In vitro, after 35 min of incubation, caulerpenyne inhibited the polymerization of pig brain purified tubulin or microtubule proteins, with an IC 50 of 21 ± 2 μM and 51 ± 6 μM respectively. Analysis by electron microscopy indicated that caulerpenyne induced aggregation of tubulin, which may be responsible for inhibition of microtubule polymerization and bundling of residual microtubules.

Modeling the Ultimate Seaweed Expansion

Since 1984 the green tropical alga Caulerpa taxifolia (Chlorophyta), of aquarium origin, has spread rapidly along the north-western Mediterranean sea coast. This alga was recently discovered on the Mediterranean south coast (Tunisia) and the west coast of the United States. This paper presents modeling efforts to simu late Caulerpa taxifolia expansion. Three different mod els were built; the first model is based on stochastic discrete event simulation coupled with a geographical information system. The second model uses a neural network, trained with simulation data and is consid ered as a metamodel. The third is a multimodel de signed to simulate a biocontrol. Indeed, to control Caulerpa overhang, it may be possible to use special ized predator of C. taxifolia such as Elysia subornata (Mollusca, Ascoglossa). Simulation was mandatory before any introduction to estimate the potential re duction of the colonization by C. taxifolia. Encourag ing results concerning the use of E. subornata are pre sented.

The Introduced Green Alga Caulerpa Taxifolia Continues to Spread in the Mediterranean

The tropical green alga Caulerpa taxifolia in the Mediterranean has spread steadily since its introduction in 1984. At the end of 2000, approximately 131 km2 of benthos had been colonized in 103 independent areas along 191 km of coastline in six countries (Spain, France, Monaco, Italy, Croatia and Tunisia). Large regions neighboring the invaded areas appear favorable to further colonization, and there is thus no reason to believe that spreading will slow down in the years to come.

Invasive alga reaches California.

The alga has been identified that threatens to smother Californian coastal ecosystems. The recent discovery of the marine green alga Caulerpa taxifolia on the Californian coast1,2 has raised public concern about the potential danger of a new invasion similar to the one endured by the Mediterranean Sea over the past decade. A small colony of C. taxifolia introduced into the Mediterranean in 19843,4 from a public aquarium5 has spread to more than 6,000 hectares today, outcompeting native species and seriously reducing diversity in areas of the northwestern Mediterranean6. This invasive strain of C. taxifolia differs from tropical populations in that it is much larger, grows more vigorously, does not rely on sexual reproduction, and is resistant to low temperatures4,6,7. Here we evaluate the risk of invasion by Californian C. taxifolia by comparing it genetically with the Mediterranean and aquarium strain, as well as with native tropical populations. Our results show that the Californian alga is the same as the invasive Mediterranean strain, calling for its rapid eradication to prevent a new invasion.

Neurotoxic effects of caulerpenyne

1. 1. In this paper the authors tested the effect of caulerpenyne (CYN), a sesquiterpene synthesized by the green alga Caulerpa taxifolia onto the central nervous system of the leech Hirudo medicinalis. Investigations have been performed with three different approaches: neuroethological, electrophysiological and neurochemical techniques. 2. 2. CYN application mimics the effect of a nociceptive stimulation (brushing), eliciting a clear-cut potentiation of the animal swim response to the test stimulus (non associative learning process such as sensitization). This effect is similar to that one induced by the endogenous neurotransmitter serotonin (5HT). 3. 3. CYN strongly reduces the after-hyperpolarization (AHP) recorded from T sensory neurons. This effect overlaps that one produced by 5HT, but it is not affected by the serotonergic antagonist methysergide. 4. 4. The decrease of AHP amplitude due to CYN application is observed also in presence of apamin, a blocking agent of Ca ++-dependent K + channels, suggesting that CYN is acting through the inhibition of the Na + K + electrogenic pump. 5. 5. The depression of the AHP driven by CYN is not prevented by application of MDL 12330A, an adenylate cyclase inhibitor. On the other hand MDL 12330A counteracts the reduction of AHP due to 5HT application. 6. 6. Incubation of the leech central nervous system with CYN induces the phosphorylation of proteins of 29, 50, 66 and 100 kDa. This pattern of phosphorylation is similar to that one elicited by 5HT treatment. 7. 7. The data demonstrate that CYN exerts remarkable effects on leech neurons by acting onto specific molecular targets such as the Na + K + ATPase. This effect may influence important neural integrative functions and may explain the sensitizing action produced by the toxin on swim induction. Finally, caulerpenyne does not act through the pathways involved in the 5HT action, and its effect is not mediated by the second messenger cyclic AMP. The mechanism of action of CYN are still under investigations.

Synchronous release of male gametes of Caulerpa taxifolia (Caulerpales, Chlorophyta) in the Mediterranean Sea

Fifteen years after the first report of the presence of the tropical green alga Caulerpa taxifolia (Chlorophyta) in the Mediterranean Sea off the shores of Monaco, this alga is now present in the waters of five Mediterranean countries. This rapid, broad dissemination is believed to have occurred solely by thallus fragmentation, because sexual reproduction, common in tropical Caulerpa species, has not been demonstrated in Mediterranean C. taxifolia. Here, we report field observations of the synchronous formation and release of male gametes by the Mediterranean strain of C. taxifolia. As in related species living in tropical regions, gamete release was synchronized by light intensity. Despite the prolific release of male gametes, sexual reproduction apparently does not occur, because female gametes are absent.

Effect of low water temperature on metabolism and growth of a subtropical strain of Caulerpa taxifolia (Chlorophyta)

The cold tolerance capacity of samples of the marine green alga Caulerpa taxifolia, ob- tained from Moreton Bay, Brisbane, Australia, was investigated by exposing samples to seawater tem- peratures of 9 to 15°C, for periods of 4 to 10 wk, after maintenance at 22°C. Residual effects of cold wa- ter exposure were evaluated by re-acclimating samples to 22°C. Phenotypic expression and survivorship were monitored throughout both cold treatment and re-acclimation phases. Measurements of photo- synthesis and respiration were made toward the end of the cold treatments and after re-acclimation. Samples exposed to 9 and 11°C water exhibited retraction or loss of chloroplasts (or chlorophyll) from the mid-rib regions of the pseudo-fronds. After 4 wk of exposure to 9°C the only green coloured regions of the fronds were the extremities of the pinnules; 1 to 2 wk later these samples began to decompose. Sam- ples kept at 11°C retained the bulk of their photosynthetic pigments and survived throughout experi- ments. The stolons of samples tended to grow upward toward the seawater surface rather than parallel to the substratum. Samples at all treatment temperatures tended to become progressively detached from the substratum through stolon extension without intermittent rhizoid attachment. Several samples be- came fragmented and covered with mucilaginous epiphytes during re-acclimation, such that those lack- ing rhizoid anchorages, rose to the seawater surface, buoyed by metabolic gases trapped in the mu- cilage. During cold treatment, the maximal rates of gross and net photosynthesis (Pm g and Pm n ), normalised to dry weight or tissue protein content, and the ratio of Pm g to dark respiration (-R) varied directly with temperature. The irradiance required for compensation (Ic) varied inversely with temperature. The rate of dark respiration increased with cold exposure. Calculation of whole day net production indicated that rates of photosynthesis among samples incubated at 13°C or below were insufficient to maintain exist- ing tissue biomass. There were no residual effects of cold exposure after re-acclimation, except that 11°C samples failed to increase in relative protein content as a function of ambient irradiance, perhaps due to nitrogen limitation. Results indicate a cold-tolerance threshold of 9 to 11°C, thus genetic modification does not need to be invoked to explain the occurrence of C. taxifolia in the northwest Mediterranean.

Variation of heavy metal contents of the green alga Caulerpa Taxifolia (VAHL) C. Agardh in its area of expansion in the French Mediterranean Sea

Concentrations in cadmium, copper, mercury, nickel, lead and zinc were determined by atomic absorption spectrophotometry in 72 samples of the green alga Caulerpa taxifolia collected in its area of expansion in the French Mediterranean Sea. The data obtained was used to carry out a statistical study on the two main parts of the thallus (pseudo‐stolons and pseudo‐leaves), in regard to the seasons, the geographical and bathymetrical localisations and the distance from sources of pollution. The highest concentrations were those of copper and zinc, followed by lead and nickel, then by cadmium and mercury to a lesser extent. The samples collected near the most heavily populated places such as Monaco and Menton harbours, showed the highest concentrations of heavy metals. It seems that pseudo‐leaves concentrate metals more than pseudo‐stolons and that the metallic charge increases with the depth. However, these results are significant only for some of the metals. The presence of heavy metals in rather large quantities in this alga may carry a toxicological risk for the fauna that feeds on it and may be a hindrance for a possible industrial exploitation. But, it is difficult to assess the degree of this risk. Thanks to its ability to concentrate metals, however, Caulerpa can be used as a biological indicator in the "in situ”; assessment of the metallic pollution of the sea.

NO DELETERIOUS ALTERATIONS IN POSIDONIA BEDS IN THE BAY OF MENTON (FRANCE) EIGHT YEARS AFTER CAULERPA TAXIFOLIA COLONIZATION

High‐resolution multispectral imagery, aerial photography, and SCUBA diving surveys were used to determine if there had been any significant alteration in the dimensions of Posidonia oceanica beds in the Bay of Menton, French Riviera, since colonization of the green alga Caulerpa taxifolia began in the late 1980s. After 8 years of direct contact, there was no evidence of a decrease in the abundance of P. oceanica. On the contrary, the integrity of a seagrass bed had increased in the first area colonized by Caulerpa taxifolia on the eastern side of Cape Martin and, in a more recently colonized central part of the bay, established tufts of Posidonia were isolated from the alga by well‐defined exclusion zones.

Neural-network metamodelling for the prediction of Caulerpa taxifolia development in the Mediterranean sea

This paper addresses the use of neural networks as a metamodelling technique for discrete event stochastic simulation to reduce significantly the computational burden involved by the simulations. A sophisticated computer model has been developed to anticipate the propagation of the green alga Caulerpa taxifolia in the northwestern Mediterranean sea. The simulation model provides reliable predictions, a couple of years in advance, of the covered surfaces. To reduce the heavy computational burden involved by the simulation, a neural network was successfully trained on artificially generated data provided by the simulation runs to provide accurate forecasts 12 years in advance, along with associated confidence intervals. The neural-network metamodel is competitive in accuracy when compared to the simulation itself and, once trained, can operate in nearly real time.

Wedding connectionist and algorithmic modelling towards forecasting Caulerpa taxifolia development in the north-western Mediterranean sea

We discuss the use of supervised neural networks as a metamodelling technique for discrete event stochastic simulation in order to reduce significantly the computational burden involved by discrete simulations. A sophisticated computer model, coupling a geographical information system with a stochastic discrete event simulator, has been developed to anticipate the propagation of the green alga Caulerpa taxifolia in the north-western Mediterranean sea. The simulation model provides reliable predictions, a couple of years in advance, of: (i) the local expansion patterns of the alga; (ii) the increase of C. taxifolia biomass and (iii) the covered surfaces. However because the algorithmic model accounts for spatial interactions and anthropic dispersion/activities such as eradication, introduction of specific predators etc., simulations are extremely time and memory consuming. Therefore, to reduce the computational burden, a neural network was successfully trained on artificially generated data provided by the simulation runs to provide accurate forecasts 12 years in advance along with associated confidence intervals. The ability of the neural networks to capture the underlying physics of the phenomena is clearly illustrated by several preliminary experiments on a large coastal area. The neural network is able to construct, on this site, estimates of the Caulerpa taxifolia expansion 12 years in advance in good agreement with the simulation trajectories.