Plocamium pacificum

Plocamium pacificum Kylin

Type locality: Biological Station at Friday Harbor  (UW).

Etymology: Plocamium, from Greek = curled (Druehl 2000). Pacificum, adjective (Latin) pertaining at Pacific Ocean.

Common name: Sea comb (Druehl 2000). Comb weed, Cockscomb (Braune 2000).

1. Taxonomy

Class: Florideophyceae

Order: Gigartinales

Family: Plocamiaceae

 2. Identification

Thalli is narrow, tufted-erect, tough and cartilaginous, with a length ranges from 4 to 45 cm tall. The thalli is typically deep red or purplish-red to pink (Fig. 1). P. pacificum lives in clumps or singly, but it is not mat-forming (Fig. 1). The principal axes arises from stoloniferous branches (Fig. 2; Abbott & Hollenberg 1976). Branches are arranged and compressed. Branchlets are straight or slightly curving outward in groups of 3 or 4 and successively pectinate (Fig. 3; Abbott & Hollenberg 1976). Tetraesporangia are borne in 2 rows in swollen tips of mostly compound stichidia (Fig. 4; Abbott & Hollenberg 1976).

The medulla is composed of large pseudoparenchymatous cells. In cross-section, it is possible to see the medulla throughout the plant. The medulla is composed of large isodiametric cells among which are chains of small cells (Fig. 5; Gabrielson et al. 2012).

3. Distribution:

 This specimen was collected at Mosquito Pass, dredged at depth of 10-20 m (48° 35’ 44.66’’ N; 123° 10’ 30.1’’ W). Usually, it is possible to find P. pacificum in exposed to sheltered habitats on middle to low intertidal zone, occasionally in tide-pools and subtidal to 20 m (Abbott & Hollenberg 1976; Gabrielson et al. 2012).

P. pacificum has been registered and collected in North America (British Columbia, Washington, California (1, 2; Much smaller and more delicate forms of this species occur along with coarser forms throughout California; Abbott & Hollenberg 1976), Baja California, Central America (Islas Revillagigedo) and South America (Galápagos Islands) (see Guiry & Guiry 2013). Specimens of this genus have been deposited at Friday Harbor Laboratories Herbarium. However, all specimens were first identified as P. cartilagineum subsp. pacificum (Kylin) P.C. Silva and then it has been determined as P. pacificum by Sandra C. Lindstrom (27/October/1993). In Washington State, the regional distribution of this species is focused in sites on San Juan Island (some sites near or around San Juan Island) such as: Point no Point (West of Sooke, Vancouver Island), West Beach (near Partridge Point, west side Whidbey Island WA), Salmon Bank, Mitchell Bay, Partridge Point (Whidbey Island, WA), David Bay, Mitchell Bay, American Camp Beach, Cattle Point, and between American Camp Beach and Eagle Cove (Specimen deposited at Friday Harbor Laboratories Herbarium).

4. Vouchers.

Number specimens that were prepared in the development of this page: #1

Preservation: Herbarium Marine Algae Course Summer 2013.

ID PHYKOS: #00123

5. Research Notes

 Currently, there is little information on ecological and biological aspects about this species (see link of search). However, laboratory studies of habitat selection (nursery) by early benthic juvenile lobsters Panulirus interruptus suggest their preference for P. pacificum (amongst other types of algae; Castañeda-Fernández et al. 2005). This indicates the importance that this alga species could have in the formation process of microhabitat for marine invertebrates on the North Pacific Coast.

This species name (P. pacificum) is currently regarded as a taxonomic synonym of P. cartilagineum subsp. pacificum (Kylin) P.C. Silva.  In this context, chemical variation between individual plants has been reported for the red alga P. cartilagineum in response to a potential risk of consumption by herbivores (Hay & Fenical 1988). Further, it has been reported as an epiphytic alga on Chondracanthus chamissoi (C.Agardh) Kützing and Gracilaria chilensis C.J. Bird, McLachlan & E.C. Oliveira (Gonzalez et al. 1993, Vásquez & Vega 2008). Other species of the genus Plocamium (e.g. Plocamium hamatum J.Agardh) causes tissue necrosis in soft corals upon physical contact due to allelo-pathic effects of the monoterpene chloromertensene (de Nys et al. 1991).

As anecdotal data, between the uses of this species, extracts with a red color have been used for the cosmetic purposes in ancient Rome (Braune 2000).

 6. Literature Cited

Abbott, I.A. and Hollenberg, G.J. 1976. Marine algae of California. Stanford University Press. Stanford.

Braune, W. 2011. Seaweeds. A colour guide to common benthic green, brown and red algae of the world’s oceans. Koeltz Scientific Books, Germany.

Castañeda-Fernández de Lara, V., Butler, M., Hernández-Vásquez, S., Guzman del Próo, S. and Serviere-Zaragoza, E. 2005. Determination of preferred habitats of early benthic juvenile California spiny lobster Panulirus interruptus, on the Pacific coast of Baja California Sur, Mexico. Mar Freshwater Res 56: 1037-1045.

Druel, L.D. 2000. Pacific Seaweeds. A guide to common seaweeds of the West Coast. Harbour Publishing, Canada.

de Nys, R., Coll, J.C., Price, I.R. 1991. Chemically mediated interactions between the red alga Plocamium hamatum (Rhodophyta) and the octocoral Sinularia cruciata (Alcyonacea). Mar. Biol. 108: 315–320.

Gabrielson, P.W., Lindstrom, S.C. and O’Kelly, C. 2012. Keys to the seaweeds and seagrasses of Southeast Alaska, British Columbia, Washington, and Oregon. Phycological Contribution Number 8. Hillsborough, North Carolina.

Gonzalez, M.A., Barraler, H.L., Candia, A. and Cid, L. 1993. Spatial and temporal distribution of dominant epiphytes on Gracilaria from a natural subtidal bed in central-southern Chile. Aquaculture 116: 135-148.

Guiry, M.D. and Guiry, G.M. 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.

Hay M.E. and W, Fenical. 1988. Marine Plant-Herbivore Interactions: The Ecology of Chemical Defense. Ann. Rev. Ecol. Syst. 19: 111-145.

Vásquez, J.A. and Vega, J.M.A. 2001. Chondracanthus chamissoi (Rhodophyta, Gigartinales) in northern Chile: ecological aspects for management of wild populations. J. Appl. Phycol. 13: 267-277.

7. Links to additional resources

For more information:

For molecular data:

8. Page Authors & Affiliations

Author: Mauricio H. Oróstica

Affiliations: 1) Ecology Marine Lab ( Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Larrondo 1281, Coquimbo, Chile. 2) Universidad de Atacama-CRIDESAT. Copayapu 485, Copiapó, Chile ( Email:

PlocamiunFigure 1. Specimen dredged at 10-20 m depth identified as P. pacificum Kylin.

stolonFigure 2. Stoloniferous branches of P. pacificum Kylin.

pectinateFigure 3. Branches successively pectinate of P. pacificum Kylin (10x).

TetraesporangiaFigure 4. Tetraesporangia of P. pacificum Kylin (20x).

cross-sectionFigure 5. Cross-section thalli of P. pacificum Kylin (20x).