C. taxifolia is light green[3] with stolons (stems) on the sea floor, from which sparsely-branched upright fronds of approximately 20–60 cm (8–24 in) in height arise.[6] Algae in the genus Caulerpa synthesize a mixture of toxins[7] termed caulerpicin, believed to impart a peppery taste to the plants.[8] The effects of the specific toxin synthesized by C. taxifolia, caulerpenyne, have been studied,[9][10] with extracts from C. taxifolia being found to negatively affect P-glycoprotein-ATPase in the sea spongeG. cydonium.[11]
Like all members of the genus Caulerpa,C. taxifolia consists of a single cell with many nuclei. The algae has been identified as the largest known single-celled organism.[12] Wild-type C. taxifolia is monoecious.[13]
Use in aquaria
Caulerpa species are commonly used in aquaria for their aesthetic qualities and ability to control the growth of undesired species.[14]C. taxifolia has been cultivated for use in aquaria in western Europe since the early 1970s.[15] A clone of the alga that was resistant to cold was observed in the tropical aquarium at the Wilhelma Zoo in Stuttgart[16] and further bred by exposure to chemicals and ultraviolet light.[17] The zoo distributed the strain to other aquaria, including the Oceanographic Museum of Monaco.[16]
The aquarium strain is morphologically identical to native populations of the species.[3] However, a 2008 study found that a population of the aquarium strain near Caloundra, Australia exhibited markedly reduced sexual reproduction, with only male plants present during some reproductive episodes.[13] The aquarium strain can survive out of water for up to 10 days in moist conditions, with 1 cm fragments capable of producing viable plants.[18]
Status as invasive species
Outside its native range, C. taxifolia is listed as an invasive species.[19][20] It is one of two algae on the list of the world's 100 worst invasive species compiled by the IUCN Invasive Species Specialist Group.[5] The species is able to thrive in heavily polluted waters,[21] possibly contributing to its spread in the Mediterranean.[22]
Presence in the Mediterranean Sea
The presence of C. taxifolia in the Mediterranean was first reported in 1984[23] in an area adjacent to the Oceanographic Museum of Monaco.[24] Alexandre Meinesz, a marine biologist, attempted to alert Moroccan and French authorities to the spread of the strain in 1989,[16] but the governments failed to respond to his concerns.[25] The occurrence of the strain is generally believed to be due to an accidental release by the museum,[3][26] but Monaco rejected the attribution and instead claimed that the observed algae was a mutant strain of C. mexicana.[25] By 1999, scientists agreed that it was no longer possible to eliminate the presence of C. taxifolia in the Mediterranean.[25]
A study published in 2002 found that beds of Posidonia oceanica in the Bay of Menton were not negatively affected eight years after colonization by C. taxifolia.[27] Other published studies have shown that fish diversity and biomass are equal or greater in Caulerpa meadows than in seagrass beds[28] and that Caulerpa had no effect on composition or richness of fish species.[29]
Studies in 1998[15] and 2001[23] found that the strain observed in the Mediterranean was genetically identical to aquarium strains, with similarities to an additional population in Australia.
Presence in Australia
A 2007 study found that a native bivalvemollusc species was negatively affected by the presence of C. taxifolia, but that the effect was not necessarily different from that of native seagrass species.[30] A 2010 study indicated that the effect of detritus from C. taxifolia negatively impacted abundance and species richness.[31]
C. taxifolia may become entangled in fishing gear and boat propellers.[4]
Control methods
C. taxifolia may be controlled via mechanical removal, poisoning with chlorine, or application of salt.[6] Researchers at the University of Nice investigated possible use of a species of sea slug, Elysia subornata, as a possible natural control method, but found that it was not suitable for use in the Mediterranean due to cold winter water temperatures and insufficient population density.[38]
^Nielsen, Peter G.; Carlé, Jørgen S.; Christophersen, Carsten (January 1982). "Final structure of caulerpicin, a toxin mixture from the green alga Caulerpa racemosa". Phytochemistry. 21 (7): 1643–1645. Bibcode:1982PChem..21.1643N. doi:10.1016/S0031-9422(82)85032-2.
^Pesando, Danielle; Lemée, Rodolphe; Ferrua, Corine; Amade, Philippe; Girard, Jean-Pierre (October 1996). "Effects of caulerpenyne, the major toxin from Caulerpa taxifolia on mechanisms related to sea urchin egg cleavage". Aquatic Toxicology. 35 (3–4): 139–155. Bibcode:1996AqTox..35..139P. doi:10.1016/0166-445X(96)00013-6.
^Mozzachiodi, R; Scuri, R; Roberto, M; Brunelli, M (November 2001). "Caulerpenyne, a toxin from the seaweed Caulerpa taxifolia, depresses afterhyperpolarization in invertebrate neurons". Neuroscience. 107 (3): 519–526. doi:10.1016/s0306-4522(01)00365-7. PMID11719006. S2CID40312176.
^Müller, Werner E.G.; Koziol, Claudia; Wiens, Matthias; Schröder, Heinz C. (2000). "Stress Response in Marine Sponges: Genes and Molecules Involved and Their use as Biomarkers". Environmental Stressors and Gene Responses. Cell and Molecular Response to Stress. Vol. 1. pp. 193–208. doi:10.1016/S1568-1254(00)80016-9. ISBN978-0-444-50488-3.
^"Caulerpa taxifolia". Invasive Species Compendium (CABI International). Archived from the original on 2017-07-23. Retrieved Jan 24, 2021.
^"Caulerpa taxifolia". Center for Aquatic and Invasive Plants (University of Florida). Archived from the original on 2017-08-06. Retrieved Jan 24, 2021.
^Houngnandan, Fabrice; Kefi, Sonia; Deter, Julie (October 2021). "The joint influence of environmental and anthropogenic factors on the invasion of two alien caulerpae in northwestern Mediterranean". Biological Invasions. 24 (2): 449–462. doi:10.1007/s10530-021-02654-w.
^ abWiedenmann, J.; Baumstark, A.; Pillen, T. L.; Meinesz, A.; Vogel, W. (19 February 2001). "DNA fingerprints of Caulerpa taxifolia provide evidence for the introduction of an aquarium strain into the Mediterranean Sea and its close relationship to an Australian population". Marine Biology. 138 (2): 229–234. Bibcode:2001MarBi.138..229W. doi:10.1007/s002270000456. S2CID84150417.
^Jaubert, Jean M.; Chisholm, John R. M.; Ducrot, Danielle; Ripley, Herb T.; Roy, Laura; Passeron-Seitre, Gilles (December 1999). "No deleterious alterations in Posidonia beds in the Bay of Menton (France) eight years after Caulerpa taxifolia colonization". Journal of Phycology. 35 (6): 1113–1119. Bibcode:1999JPcgy..35.1113J. doi:10.1046/j.1529-8817.1999.3561113.x. S2CID85127610.
^Relini, G., M Relini, and G. Torchia. (1998) Fish biodiversity in a Caulerpa taxifolia meadow in the Ligurian Sea. Italian Journal of Zoology 65 Supplement:465-470.
^Francour, P.; Harmelin-Vivien, M.; Harmelin, J. G.; Duclerc, J. (1 March 1995). "Impact of Caulerpa taxifolia colonization on the littoral ichthyofauna of North-Western Mediterranean sea: preliminary results". Hydrobiologia. 300 (1): 345–353. doi:10.1007/BF00024475. S2CID23445784.
^Wright, Jeffrey T.; McKenzie, Louise A.; Gribben, Paul E. (2007). "A decline in the abundance and condition of a native bivalve associated with Caulerpa taxifolia invasion". Marine and Freshwater Research. 58 (3): 263. doi:10.1071/MF06150.
^Thibaut, Thierry; Meinesz, Alexandre; Amade, Philippe; Charrier, Stéphane; De Angelis, Kate; Ierardi, Santina; Mangialajo, Luisa; Melnick, Jennifer; Vidal, Valérie (June 2001). "Elysia subornata (Mollusca) a potential control agent of the alga Caulerpa taxifolia (Chlorophyta) in the Mediterranean Sea". Journal of the Marine Biological Association of the United Kingdom. 81 (3): 497–504. Bibcode:2001JMBUK..81..497T. doi:10.1017/S0025315401004143. S2CID85066136.
Further reading
Peplow, Mark (23 March 2005). "Algae create glue to repair cell damage". Nature: news050321–11. doi:10.1038/news050321-11.