Caulerpa racemosa is a species of edible green alga, a seaweed in the family Caulerpaceae. It is commonly known as sea grapes (along with the related Caulerpa lentillifera) and is found in many areas of shallow sea around the world. There are a number of different forms and varieties, and one that appeared in the Mediterranean Sea in 1990, which is giving cause for concern as an invasive species. Caulerpa a grappoli Caulerpa racemosa alga algae intotheblue.it
There are about 75 species of Caulerpa. Many of them exhibit polymorphism, showing different growth forms in different habitats which makes them difficult to identify. Caulerpa racemosa, C. laetevirens and C. peltata form a species complex. A number of forms and varieties for C. racemosa are listed but further study is needed to clarify their exact phylogenetic relationships.
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 C. racemosa 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.
In the Mediterranean, growth begins in April when new stolons develop and erect branches start growing, and continue till December, after which the plants decline and become dormant.