Caulerpa racemosa

Lore & Background

Caulerpa racemosa consists of a single enormous cell with many nuclei, with branches linked to stolons anchored by rhizoids. It exhibits polymorphism, making identification difficult, and forms a species complex with C. laetevirens and C. peltata. A new form reported off Tunisia in 1926, possibly from the Red Sea, later spread in the eastern Mediterranean. In 1990, a larger form with two vertical rows of branches, known as var. cylindracea and possibly from Australian waters, was found off Libya and became more widespread than the invasive Caulerpa taxifolia. In the Mediterranean, growth begins in April and continues until December, after which plants decline and become dormant. It reproduces vegetatively by fragmentation, with small pieces capable of developing into new plants, and sexually via holocarpy, where all cytoplasm is used for gametes. Mass spawnings occur in the Caribbean and Mediterranean, often just before dawn, with no relation to tidal or lunar cycles.

Reader's Guide

Caulerpa racemosa is significant both as an edible seaweed and as an invasive species. It is consumed widely in salads in Japan, Fiji, the Philippines, Thailand, Malaysia, and Indonesia, and is rich in fiber, proteins, minerals, folic acid, ascorbic acid, vitamin A, and vitamin B1, while being low in fat. It also has antibacterial and antioxidant properties, believed to come from endophytic actinomycetes producing flavonoids and alkaloids. Extracts are being tested against cancers and multi-drug resistant uropathogens such as K. pneumoniae and P. aeruginosa, with potential treatments for diabetes and herpes identified. However, its invasive form, var. cylindracea, has spread widely in the Mediterranean, colonizing dead matte of the seagrass Posidonia oceanica. Herbivores like sea breams and sea urchins graze on it, but their consumption is compensated by rapid growth, making biocontrol unlikely. The alga contains the cytotoxic secondary metabolite caulerpenyne, though in lesser amounts than C. taxifolia.

Did You Know?

• Each Caulerpa racemosa plant is a single enormous cell with many nuclei.
• The invasive form var. cylindracea may have originated from Australian waters.
• Mass spawnings of C. racemosa can reduce underwater visibility to less than one meter.
• Extracts of C. racemosa are being tested against multi-drug resistant uropathogens.