University of Hawai`i

Botany Department

          Marine Algae of Hawai`i

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Caulerpa sertularioides

 (Gmel.) Howe 1905




Class Order Family
Chlorophyta Ulvophyceae Bryopsidales Caulerpaceae

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Caulerpa sertularioides is a small delicate green alga found only in O‘ahu and Kaua‘i. This species closely resembles C. taxifolia, the invasive "killer weed" of the Mediterranean.





















Caulerpa sertularioides attached to hard substrate
on the reef flat.



Branches, feather-like, flattened, and upright, 3 - 5 cm high, rising from a creeping stolon (runner), 1 - 2mm in diameter, anchored by rhizoids to the substrate. Branchlets oppositely attached to midrib, flattened, slightly curved upwards and tapered at both base and tip. Midrib is slightly flattened, appearing oval in cross-section.  Light green to yellow green.


This species resembles another native Hawaiian Caulerpa species, C. taxifolia. C. sertularioides is more delicate and the branchlets are rounded, compared to the flattened branchlets of C. taxifolia. The rising branches are also more rounded toward apices, compared to the more angular, squared-off branches of C. taxifolia.


Structural Features

Thallus non-septate, coenocytic, traversed by trabeculae, which are extensions of cell wall; reproduction vegetative and sexual, latter anisogamous. Gametes liberated through papillae that develop on frond or occasionally on frond.



This delicate plant is usually found in warm, quiet waters in tide pools or on sandy, calm reef flats. It anchors to sandy bottoms or coral rubble by the creeping rhizoids.



Hawai‘i:  Northwest Hawaiian Islands, O‘ahu, Kaua‘i.

Mechanism of Introduction:  Indigenous to Hawai‘i.

Worldwide:  Pacific Mexico, Caroline Islands, Micronesia, North Marianas, Marshall Islands, Gilbert Islands, New Caledonia, Solomon Islands, Japan, China, Australia, Philippines, Tahiti, Indonesia, Indian Ocean, Caribbean to Brazil.



Little information has been recorded on Caulerpa sertularioides. This green alga is a native of Hawai‘i, and is quite common throughout the world. The Hawaiian version is small and delicate and grows in small patches in quiet, warm waters on reef flats.


This species is an unassuming, uncommon alga that can easily be mistaken for C. taxifolia.  C. taxifolia is on invasives lists elsewhere in the world because of its highly invasive nature. Though not an invasive in Hawaiian waters, C. taxifolia communities should be watched for invasive tendencies. For this reason, it is important to differentiate between the two species.


The extensive rhizoid system of C. sertularioides aids in nutrient acquisition from sediments. Similar to other Caulerpa species, recruitment primarily occurs by fragmentation, but C. sertularioides also reproduces sexually.



Abbott, I.A., 2001, unpublished manuscript.

Eubank, L.L., 1946. Hawaiian Representatives of the Genus Caulerpa. University of California Publications in Botany, V. 18 : 409-432.

Larned, S.T., 1998. Nitrogen- versus phosphorus-limited growth and sources of nutrients for coral reef macroalgae. Marine Biology, 132: 409-421.

Littler, D.S. and Mark M., 2000. Caribbean Reef Plants. OffShore Graphics, Washington, D.C.

Magruder, W.H, and J.W. Hunt, 1979. Seaweeds of Hawai‘i. Oriental Publishing Company, Honolulu, Hawai‘i.


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