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Chlorophyta, Green Algae

Caulerpa scalpelliformis (Borwn and Turner) C. Agardh

 Chlorophyta, Order: Caulerpales; Family: Caulerpaceae.


Caulerpa, means ‘crawling stalk’. The scientific name of the species refers to the dented shape of the thallus, which resembles a knife or a scalpel.


The Caulerpa scalpelliformis thallus resembles flat, emarginate ‘leaves’ that are uniformly separated by indentations into lobes. The indentation depth reaches a third of the thallus width. Microscopic examination reveals lateral and vertical fibres that support the thallus. The thallus itself is a single, multi-nuclear cell with many chloroplasts and no walls (coenocyte).


The leaf-like thallus reaches 10-20 cm in length and sometimes more. Its width is about 1 cm, and the indentations between the lobes are a third of the thallus width.


The body of the alga is grass-green, and the rhizoids are usually transparent.

Special features

The Caulerpa scalpelliformis may be mistaken for the Caulerpa mexicana. In the Caulerpa scalpelliformis indentations are about a third of the thallus length, whereas those of the Caulerpa mexicana are much deeper.


The species has been found in a variety of habitats, upon rocky, sandy or silt substrates. It appears in the wave- breaking area, in tidal pools and in potholes in the intertidal zone and at depths of up to 50 m in the open sea.

Biology and reproduction

Fertile individuals of Caulerpa scalpelliformis appear in December. Individuals that have been torn from their substrate can, in some cases, complete their growth pattern.

Seasonality and distribution

The Caulerpa scalpelliformis can be found year round. Individuals usually appear in the same place each year. Remnants of alga bases remain in the area, and so, apparently, do the rhizoids in the rock. The algal global

distribution includes the Mediterranean, the Atlantic Ocean and the Pacific Ocean.


In many countries, the Caulerpa scalpelliformis popular name is ‘Marine sensitive-plant’ (timid/shy mermaid, shy mermaid), since upon returning the dried plant to the water, it only reabsorbs water from one side and folds in on the other. Caulerpa species are consumed by humans in several countries, especially in northeast Asia.

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