Invasion HistoryFirst Non-native North American Tidal Record: 1961
First Non-native West Coast Tidal Record: 1961
First Non-native East/Gulf Coast Tidal Record:
General Invasion History:
Caulacanthus ustulatus (Kutzing 1843) was described from Cadiz, Spain, but was believed to have a cosmopolitan range in the Eastern Atlantic (France-South Africa) and the Indo-West Pacific (South Africa-Japan, and east to Australia, New Zealand, and Hawaii). A molecular analysis indicates that this 'species' contained two major lineages, an Indo-West Pacific lineage and an Atlantic lineage (Zuccarello et al. 2002). The name C. okamurae Yamada 1933 was used for populations from the Northwest Pacific by many Asian workers, but there was doubt about the validity of the name, and the distinctiveness of the species. Observations of the reproductive structures of C. okamurae support its status as a separate species (Choi and Nam 2001; Choi et al. 2001; Verlaque et al. 2015; Guiry and Guiry 2017). Caulacanthus okamurae is known from Japan, China, Korea, Taiwan, and Yonaguni Island, a Japanese island near Taiwan (Choi et al. 2001; Zuccarello et al. 2002; Guiry and Guiry 2017).
North American Invasion History:
Invasion History on the West Coast:
Caulacanthus okamurae is an invader in the Eastern Pacific, being found in the Gulf of California in 1944; Pacific Baja California in 1961; British Columbia in 1974; San Pedro, California (CA) in 1999; and Prince William Sound, Alaska sometime from 1989-1996 (Gabrielson and Scagel 1999; Lindstrom et al. 1999; Rueness and Rueness 2000; Whiteside and Murray 2004; Miller et al. 2011). In southern California, Caulacanthus has been observed at numerous sites during the last decade (S. Murray, personal communication), but was not recorded 30 years ago during extensive intertidal surveys sponsored by the government (Murray & Littler, 1981), nor 40 years ago when E.Y. Dawson conducted extensive surveys (Dawson, 1959). This alga was found at Point La Jolla and Dana Point, CA in 2004 (Maloney et al. 2006); Corona del Mar and Point Fermin, CA in 2010 (Smith et al. 2014); and Elkhorn Slough, CA (deRivera et al. 2005; Blanchette et al. 2008). It is also known from locations in central California, including: Santa Cruz, San Francisco Bay (Miller, 2004), and Tomales Bay (specimens from the University of California); and it appears to be spreading northward (Miller et al. 2011).
In the Strait of Georgia, it is known from the Redondo Islands, Pendrell Sound, British Columbia (first reported in 1974; Gabrielson and Scagel 1989) to the San Juan Islands, Washington (first reported in 1995; Zucarello et al. 2002). In surveys run from 1989 to 1996 in Prince William Sound, Alaska, C. okamurae (as C. ustulatus) was found at one location – Hogg Bay (Lindstrom et al. 1999). Vectors on the West Coast probably include hull-fouling, ballast water, and oyster-culture.
Invasion History Elsewhere in the World:
Caulacanthus okamurae was reported in 2004 in Brittany, France. Populations of C. ustulatus from Brittany were grouped with the Pacific lineage in the plastid and mitochondrial DNA analysis (Rueness and Rueness 2000; Zuccarello et al. 2002). Subsequently, populations of C. okanmurae were found in Belgium in 2011 (Kerckhof et al., in ICES Advisory Committee on the Marine Environment 2012), the Netherlands in 2005 (Stegenga and Karremans 2015), and the south coast of England in 2000-2005 (Brodie et al. 2016). In the Mediterranean, C. okamurae was found in Marseille in 2004 and later at Toulon, with its identity confirmed by molecular methods (Mineur and Maggs 2005; Verlaque et al. 2015).
Caulacanthus okamurae reaches 20-30 mm in height, forming dense, low turf in the intertidal zone. The branching is irregular to sub-dichotomous, with the smallest branches curved or spine-like. The plants are attached by multicellular holdfasts to the substrate. Cystocarps (fruiting structures in haploid female plants, 300-500 µm in diameter) occur on the tips of the finest branchlets. The cystocarps of C. okamurae lack the spines which occur in C. ustulatus. Diploid tetrasporophyte plants have tetrasporangia, which occur as swellings in the spine-like branchlets (Choi and Nam 2001; Verlaque et al. 2015). Identification of C. okamurae, and distinction from C. ustulatus, requires microscopic and/or molecular examination.
Most populations of Caulacanthus spp. have been traditionally identified as C. ustulatus (Kutzing 1843) described from Spain, and widespread on Eastern Atlantic shorelines. A distinct form from Japan (C. okamurae Yamada 1933) was found elsewhere in the Northwest Pacific (Choi and Nam 2001; Choi et al. 2001). The status of C. okamurae has been disputed, partly on nomenclatural grounds, but a genetic analysis found that Northwest Pacific populations were genetically distinct from those in the Atlantic (Zuccarello et al. 2002). Reproductive structures, needed for comparison of the populations, are rare in Asian populations, possibly by stress due to seasonal typhoons. However, cultured specimens show morphologically distinct structures (Choi and Nam 2001; Choi et al. 2001). Extenisive mitdochondrial DNA analysis found that Caulacanthus sp. from Moss Landinfg were conspecific with specimens from Korea, France, and Spain (Hartnell College Genomics Group et al. 2020),
Potentially Misidentified Species
Described from Cadiz, Spain, broad Eastern Atlantic distribution
Caulacanthus okamurae has a two-phased life cycle, with haploid gametophytes, producing carpospores, and diploid tetrosporophytes, producing haploid tetrospores. However, in Korea, where it is native, the reproductive stages are rarely seen, and most of the plants reproduce vegetatively. In culture, temperatures above 19°C were required for sexual reproduction, but in the field, in Busan, South Korea, these temperatures were reached only in September, a season of extensive typhoons, which severely damaged the plants (Choi and Nam 2001; Choi et al. 2001).
Caulacanthus okamurae is a low-growing mat-forming red alga that can grow in dense turfs on the mid-to-upper intertidal zone of exposed rocky coasts as well as in sheltered areas (Gabrielson and Scagel 1989; Choi and Nam 2001; Choi et al. 2001; Whiteside and Murray 2004; Smith et al. 2014). Caulacanthus okamurae grew well at 13-27°C, at 8 to 16 hours of light per day, and 20-16 µE m-3s-1 (Choi and Nam 2001).
|General Habitat||Oyster Reef||None|
|General Habitat||Marinas & Docks||None|
|Salinity Range||Polyhaline||18-30 PSU|
|Salinity Range||Euhaline||30-40 PSU|
|Tidal Range||Mid Intertidal||None|
Tolerances and Life History Parameters
|Maximum Temperature (ºC)||27||Highest tested, in culture, Korea (Choi and Nam 2001)|
|Minimum Reproductive Temperature||19||For sexual reproduction, in culture, Korea (Choi and Nam 2001)|
|Maximum Height (mm)||30||Cho and Nam 2001|
|Broad Temperature Range||None||Cold temperate-Warm-temperate (Introduced from)|
|Broad Salinity Range||None||Polyhaline-Euhaline|
General ImpactsTurf-forming algae are common in the intertidal zones of tropical regions, but are rare in temperate regions. Caulacanthus okamurae has become a local dominant in mid-intertidal algal turf communities in southern California (Whiteside and Murray 2004; Blanchette et al. 2008; Smith et al. 2014). This dense, low turf habitat decreased the number of larger intertidal fauna (periwinkles, limpets, barnacles), but favored meiofauna (copepods and ostracods) and larger fleshy seaweeds by retaining water and decreasing desiccation (Whiteside and Murray 2004; Smith et al. 2014).
|NEP-VI||Pt. Conception to Southern Baja California||Ecological Impact||Habitat Change|
|Caulacanthus okamurae has become a local dominant in mid-intertidal algal turf communities in southern California (Whiteside and Murray 2004; Smith et al. 2014.) Blanchette et al. (2008) found that C. okamurae had an average of ~5-10% cover at sites from Paradise Cove to Point Fermin, but did not note its occurrence elsewhere in a survey of rocky intertidal communities from San Diego to Alaska. At five sites in southern California (Dana Point, Shaw's Cove, Corona del Mar, Point Fermin, and Point Fermin North), C. okamurae often formed dense patches of low turf exceeding 40% cover. This turf displaced macroinvertebrates, such as limpets, periwinkles, and barnacles, but supported an increased number of copepods and ostracods, and of fleshy seaweeds, including Ulva, Gelidium, and Chondracanthus. The dense turf may restrict movements of larger animals, and settlement and feeding of barnacles, but also retains water and reduces desiccation (Smith et al. 2014).|
Regional Distribution Map
|Bioregion||Region Name||Year||Invasion Status||Population Status|
|NEP-VI||Pt. Conception to Southern Baja California||1961||Def||Estab|
|NEP-I||Alaska north of the Aleutians||1996||Def||Estab|
|NEP-III||Alaskan panhandle to N. of Puget Sound||1974||Def||Estab|
|NEP-V||Northern California to Mid Channel Islands||2003||Def||Estab|
|P056||_CDA_P056 (Los Angeles)||1999||Def||Estab|
|P027||_CDA_P027 (Aliso-San Onofre)||2004||Def||Estab|
|P022||_CDA_P022 (San Diego)||2004||Def||Estab|
|P090||San Francisco Bay||2003||Def||Estab|
|P292||_CDA_P292 (San Juan Islands)||1995||Def||Estab|
|P105||_CDA_P105 (Tomales-Drakes Bay)||2015||Def||Estab|
|P058||_CDA_P058 (San Pedro Channel Islands)||2019||Def||Estab|
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