Sea Grapes

A plant of C. racemosa consists of a number of branches linked to stolons which are anchored to the sandy substrate by rhizoids. The branches are a few centimetres apart and can grow to a height of 30 centimetres (12 in). Many spherical or ovate side-shoots branch off these and give the seaweed its name of sea grapes. Like other members of the order Bryopsidales, each C. racemosa plant consists of a single enormous cell with a large number of nuclei. The chloroplasts containing chlorophyll are free to migrate from any part of the organism to another and there is a network of fibrous proteins that helps movement of organelles.

C. racemosa is widely distributed in shallow temperate and tropical seas. In 1926 a new form of the alga was reported off Tunisia, possibly an immigrant from the Red Sea, and this later spread to much of the eastern Mediterranean Sea. In 1990, a new, larger form with two vertical rows of branches on opposite sides of the stem was found off Libya. It spread widely, invading much of the Mediterranean Sea and becoming more widespread than the invasive species, Caulerpa taxifolia. It is known as var. cylindracea and may have originated from Australian waters. In America C. racemosa is found in shallow water in the Caribbean Sea, around Bermuda and along the eastern seaboard of America from Florida to Brazil.

Caulerpa species contain secondary metabolites that are cytotoxic, of which caulerpenyne is the most abundant. These deter animals from consuming the plants. A study has been done on herbivores that graze on meadows of the invasive C. cylindracea in the north west of its range in the Mediterranean. The sea breams Boops boops and Sarpa salpa were found to feed on the algae, as did the sea urchins Paracentrotus lividus and Sphaerechinus granularis. Other herbivores also grazed occasionally, but the total amount consumed was compensated for by the rapid growth of the plant and it was considered that these organisms were not likely to play a valuable role in bio-control of the plant. C. taxifolia and C. racemosa show the great influence of substratum on their spatial distribution with a high colonization of the dead matte of the seagrass Posidonia oceanica C. racemosa and C. taxifolia are both invasive Lessepsian migrants. Caulerpenyne content is lesser in C. racemosa than in C. taxifolia.

Like the closely related C. lentillifera, C. racemosa is edible. It is consumed widely in salads in Japan, Fiji, the Philippines, and Thailand. It is also eaten by local fishermen in Malaysia and Indonesia. They are rich in fiber, proteins, minerals (calcium and magnesium), folic acid, ascorbic acid, vitamin A, and vitamin B1 while also being low in fat. In addition to the nutritional qualities of C. racemosa, it also has anti bacterial and anti-oxidant properties but these characteristics are not yet fully explored. These different biological activities provide a glimpse of biomedical innovations for the future. The properties are believed to come from a strain of rare endophytic actinomycetes that lives in symbiosis with C. racemosa and more particularly of the secondary metabolites produced (flavonoids and alkaloids). Extracts of C. racemosa are already tested to reduce different types of cancer but also to fight against multi-drug resistant uropathogens (as K. pneumoniae and P. aeruginosa). The multi drug resistance is a major public health problem because by 2050 (World Health Organization WHO), 10 million people could die each year as a result of this evolution of bacteria against the current families of antibiotics. Moreover, a multitude of potential treatments for various pathologies have been identified, particularly for diabetes and herpes.

== References ==