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Chlorophyta, Green Algae

Codium decorticatum (Woodw) Howe =Codium elongatum (Turner) C. Agardh

Chlorophyta,  Order: Caulerpales; Family: Codiaceae.


Codium, means ‘sheep’, and, indeed, the alga resembles sheepskin, due to its softness and the hair around the thallus. The previous species name, elongatum, hints at the species long arms. The present name, decorticatum, means ‘exposed’ or ‘peeled’, ‘that has lost its covering’, possibly due to the fact that the species is smoother and less hairy than other Codium species.


The Codium decorticatum resembles the Codium vermilara but is structurally more delicate. Its dichotomous branches are thin and cylindrical; the inner sides of the dichotomous branching are wider giving the branches a more rounded appearance. The alga is dark and attaches to the substrate using a flat holdfast.


The branches of the Codium grow to a length of 20 cm and sometimes more. Their diameter is around 4 mm.


The Codium decorticatum is dark green. Often, individuals found in the field are covered with epiphytes and seem somehow ‘dirty’.

Special features

The Codium decorticatum resembles the Codium vermilara, and if the two aren’t compared coincidentally, or unless one is not well familiarized with both, confusion comes easily. The Codium vermilara’s branches are cylindrical and not flattened. They are more delicate, and a comparatively wide straddle occurs at the point of branching.


The Codium decorticatum appears in rocky habitats and less so in polluted areas. Often, two species of Codium can be found in the same potholes. The Codium decorticatum apparently is found in the darker part of the pothole.

Biology and reproduction

The Codium decorticatum undergoes sexual reproduction. Reproductive cells develop in small protrusions at the edge of cysts and resemble dark spots when observed through a magnifying glass. For additional information on the genus, see the description under Codium vermilara.

Seasonality and distribution

The alga is common throughout the year, usually along rocky shores but also along sandy shores. The species can be found in the Atlantic Ocean, the Canary Islands, the Indian Ocean and the Mediterranean.

Additional species

The Codium decorticatum has several synonyms, most of which probably refer to the same species. However, there may be other species present in the Mediterranean. Here, too, more extensive research will advance our knowledge. Several species reported in the region include:

Codium bursa (Linnaeus) C. Agardh Codium effusum (Rafinesque) Delle Chiaje Codium tomentosum (Hudson) Stackhause sensu G. Hamel Codium vermilara (Olivi) Delle Chiaje.

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