Caulerpa racemosa is a type of edible green alga, also known as seaweed, that belongs to the family Caulerpaceae.
It’s commonly called Sea Grapes, just like its relative Caulerpa lentillifera. This seaweed is found in many shallow sea areas around the world.
There are different forms and varieties of Caulerpa racemosa, and one of them, which appeared in the Mediterranean Sea in 1990, is causing concern because it’s invasive.
What Is the Taxonomy of Caulerpa racemosa?
There are about 75 species of Caulerpa, and many of them show different growth forms in different habitats, making it hard to identify them.
Caulerpa racemosa, Caulerpa laetevirens, and Caulerpa peltata form a species complex.
There are several forms and varieties of Caulerpa racemosa, but more study is needed to understand their exact relationships to each other.
How Does Caulerpa racemosa Look Like?
A Caulerpa racemosa plant has many branches connected to stolons, which are anchored to the sandy ground by rhizoids.
The branches can grow up to 30 centimeters (12 inches) tall and are a few centimeters apart.
Many round or oval side-shoots branch off from the main branches, giving the seaweed its name of Sea Grapes.
This plant is unique because it’s made up of a single enormous cell with many nuclei.
The chloroplasts containing chlorophyll can move freely within the plant, and there is a network of fibrous proteins that helps in this movement.
Where Is Caulerpa racemosa Found?
Caulerpa racemosa is found in shallow temperate and tropical seas around the world.
In 1926, a new form of the alga was reported off Tunisia, possibly coming from the Red Sea. This form later spread to much of the eastern Mediterranean Sea.
In 1990, a larger form with two vertical rows of branches on opposite sides of the stem was found off Libya.
This form, known as var. cylindracea, has spread throughout the Mediterranean Sea and may have come from Australian waters.
In America, Caulerpa racemosa is found in shallow water in the Caribbean Sea, around Bermuda, and along the eastern seaboard from Florida to Brazil.
How Does Caulerpa racemosa Grow and Reproduce?
In the Mediterranean, the growth of Caulerpa racemosa starts in April when new stolons develop, and erect branches begin to grow.
This growth continues until December, after which the plants decline and become dormant.
Caulerpa racemosa can reproduce by breaking into pieces, which then develop into new plants. Even small pieces of tissue can do this.
The plant can also reproduce sexually by using all of its cytoplasm to create male and female gametes, leaving only a husk behind.
The male and female gametes are produced by the same plant and are released into the water where they join to form round zygotes.
These zygotes settle and, after five weeks, produce germ tubes that grow and branch into new plants.
Sometimes, mass spawnings happen in the Caribbean Sea and the Mediterranean Sea, usually just before dawn.
These events release a green cloud of gametes into the water, making it hard to see.
The gametes can move for about 60 minutes, and mass spawning helps increase the chances of fertilization.
What Is the Ecology of Caulerpa racemosa?
Caulerpa species, including Caulerpa racemosa, have secondary metabolites like caulerpenyne that are toxic and deter animals from eating them.
Some herbivores, like sea breams, sea urchins, and other grazers, can still feed on these plants.
However, the total amount they eat is not enough to control the growth of invasive species like Caulerpa racemosa var. cylindracea.
What Are the Uses of Caulerpa racemosa?
Caulerpa racemosa, just like its relative Caulerpa lentillifera, is edible and widely consumed in salads in Japan, Fiji, the Philippines, and Thailand.
It’s also eaten by local fishermen in Malaysia and Indonesia.
This seaweed is rich in fiber, proteins, minerals (calcium and magnesium), folic acid, ascorbic acid, vitamin A, and vitamin B1, while being low in fat.
Apart from its nutritional qualities, Caulerpa racemosa also has antibacterial and antioxidant properties, although these are not yet fully explored.
These properties might come from a strain of rare endophytic actinomycetes that live in symbiosis with the plant.
Extracts of Caulerpa racemosa are being tested for potential treatments for various diseases, including cancer, multi-drug resistant uropathogens, diabetes, and herpes.
Caulerpa racemosa Characteristics
| Care Level: | Easy |
| Growth Rate: | Fast |
| Nutrient Uptake: | Excellent |
| Required Lighting: | Moderate High |
| Required Water Flow: | Moderate High |
| Is Palatable? | Somewhat |
| Maximum Size: | 8 in (20.3 cm) |
Scientific Classification
| Kingdom: | Plantae |
| Order: | Bryopsidales |
| Family: | Caulerpaceae |
| Genus: | Caulerpa |
| Scientific Name: | Caulerpa racemosa |
| Also Known As: | Coarse Sea Grapes |
| Conservation Status: | Unknown |