Caulerpa taxifolia

Scientific name

Caulerpa taxifolia (Vahl) Agardh (Mediterranean strain)

Common names

caulerpa, killer alga

Family

Caulerpaceae

Similar genera

Fissidens and other feather-like Caulerpa spp., e.g., C. mexicana, C. veravalensis Thivy & Chauhan (Arabian Sea), C. scalpelliformis (Brown ex Turner), as well as C. ashmeadii Harvey, and C. sertularioides. Also, C. racemosa and varieties of C. racemosa v. macrophysa and C. microphysa (W.V. Bosse) Feldmann, with their grape-like morphologies, can be confused.

Native distribution

(of noninvasive strain) Caribbean, Indo-Pacific, the Red Sea, Australia

Species cultivated

Caulerpa ashmeadii Harvey

C. brachypus Harvey

C. cupressoides (Vahl) C. Agardh

C. mexicana Sonder ex Kützing

C. paspaloides (Bory) Greville

C. prolifera (P. Forsskal) Lamouroux

C. racemosa (Forsskal) J. Agardh

C. serrulata (Forsskal) J. Agardh

C. sertularioides (S.G. Gmelin) Howe

C. taxifolia (Vahl) C. Agardh

U.S. Federal Noxious Weed: Caulerpa taxifolia

Identification: The distinctive, frond-like morphology of Caulerpa taxifolia (under high sunlight conditions) can be distinguished from the other Caulerpa species to which it is most similar by the nature of its frondfrond:
(n) (1) a term used to describe the leaves of, e.g., ferns, palms, or duckweeds; (2) a leaf-like organ (as in .e.g. some algae, such as <em>Caulerpa</em>)
pinnules and its stolonstolon:
(n) an above-ground stem growing more or less horizontally and often forming adventitious roots at the nodes
. Caulerpa mexicana fronds reach an average length of 6 cm, with pinnules that are wide and short, and C. scalpelliformis fronds are about 10-20 cm long with pointed pinnules, whereas C. taxifolia pinnules are constricted at the base (where they attach to the midribmidrib:
(n) the main or central vein, line or rib in a leaf or perianth segment
of each frondfrond:
(n) (1) a term used to describe the leaves of, e.g., ferns, palms, or duckweeds; (2) a leaf-like organ (as in .e.g. some algae, such as <em>Caulerpa</em>)
), curve upwards, and taper at the apexapex:
(n) the point farthest from the point of attachment; the tip (often pointed)
. Caulerpa veravalensis is similar to C. taxifolia but differs in the shape of the stolonstolon:
(n) an above-ground stem growing more or less horizontally and often forming adventitious roots at the nodes
. DNA tests are necessary to distinguish the invasive Mediterranean strain from native C. taxifolia. Additionally, in weak sunlight conditions C. taxifolia and other species of Caulerpa grow in a more amorphous form and can only be distinguished from one another through DNA typing. Due to the morphological plasticity of Caulerpa, morphological identification is considered by some to be unreliable.

See Caulerpa taxifolia disseminule fact sheet.

Adventive distribution

Caulerpa taxifolia: Mediterranean Sea, Australia, Japan, the United States; C. racemosa: Mediterranean Sea, Australia, Canary Islands

Weed status

Caulerpa taxifolia is an aquatic weed on the U.S. federal noxious weed list. Caulerpa racemosa var. cylindracea is also an invasive strain. Other species of Caulerpa have been considered weeds as well.

Habit

submersed, stoloniferous marine alga

Brief description

Amorphous growth form in low sunlight conditions. In relatively high sunlight: dark to bright green, flattened, feather-like branches (also called fronds) 5-65 cm long; leaf-like pinnules oppositely attached to midribmidrib:
(n) the main or central vein, line or rib in a leaf or perianth segment
, flattened, slightly curved upwards, tapered at both base and tip. Branches extend upward from horizontal stolons; stolons to 3 m long and 1-2 mm in diameter, attached to underwater surfaces such as rocks, mud, or sand via root-like rhizoids.

Caulerpa does not have true fronds or stolons. The branches, though leaf-like, and the "stolons" are actually parts of an algal vegetativevegetative:
(adj) (1) pertaining to or to the growth of plant organs or plant parts that have nonreproductive functions, such as leaves, roots, stems, etc.; (2) concering non sexual propagules such as tubers, turions, stem fragments, root crowns, rhizomes
body that is non-septate and coenocytic (multinucleate, not separated by cell walls).

Natural habitat

tropical and temperatetemperate:
(adj) of the climatic zone between boreal and tropical
coastal lagoons to ocean waters; usually in water to 50 m deep but can grow in water as deep as 150 m or possibly deeper, though with a different morphology under low light conditions

Additional comments

The invasive strain of Caulerpa taxifolia is genetically distinct from the noninvasive form. It grows more rapidly, tolerates cooler water, and grows at greater depth than the native species. This strain was probably released from an aquarium into the Mediterranean in 1984 and spread rapidly, covering thousands of acres of underwater surfaces. This algaalga:
(n) (sing. alga) photosynthetic, eukaryotic, unicellular or complex multicellular organisms, mainly aquatic, lacking true stems, roots, leaves, conducting vessels, and complex sex organs
can become the dominant species, altering native algal and marine animal communities. There is no sexual reproduction; propagation is purely vegetativevegetative:
(adj) (1) pertaining to or to the growth of plant organs or plant parts that have nonreproductive functions, such as leaves, roots, stems, etc.; (2) concering non sexual propagules such as tubers, turions, stem fragments, root crowns, rhizomes
. Branch and stolonstolon:
(n) an above-ground stem growing more or less horizontally and often forming adventitious roots at the nodes
fragments as small as a half inch can grow into a new algaalga:
(n) (sing. alga) photosynthetic, eukaryotic, unicellular or complex multicellular organisms, mainly aquatic, lacking true stems, roots, leaves, conducting vessels, and complex sex organs
. These fragments are easily transported by boating and fishing activities. Populations of the Mediterranean aquarium strain discovered in 2000 in California were declared eradicated in 2005. A number of species of Caulerpa are native to the United States.