UC specimens and range limits for Rhizoclonium riparium

• Blue markers: specimen records
• Yellow marker: type locality, if present
• Red markers: endpoints of range from literature

View map from the Consortium of Pacific Northwest Herbaria

Notes: Widely distributed.

Status: Rhizoclonium riparium var. implexum (Dillwyn) Rosenvinge (type locality: Ireland) and Rhizoclonium tortuosum (Dillwyn) Kützing (type locality: Wales) have also been reported for California. Species boundaries for California specimens have not been determined with molecular methods; this complex needs study, and specimen determination is unreliable. Rhizoclonium tortuosum was included in the Monterey flora by Smith (1944), but his records were referred to R. riparium by Abbott & Hollenberg (1976). Blair (1983), however, cited collections of R. tortuosum from San Mateo, Monterey, and Los Angeles counties. As circumscribed by Blair, R. tortuosum includes Chaetomorpha capillare (Kütz.) Børg., emphasizing the intermediacy of this species between Rhizoclonium and Chaetomorpha. Scagel et al. (1986) assigned their material of Rhizoclonium tortuosum to Chaetomorpha "because it has numerous small nuclei per cell." The California populations need to be studied in this regard.

It should be pointed out that within the context of the synonymy given by Blair, the correct name for Rhizoclonium tortuosum when assigned to Chaetomorpha is C. capillaris rather than C. tortuosa (Dillwyn) Kleen 1874, a spurious combination that under any circumstance is a later homonym of C. tortuosa Kützing 1849, which in turn is a superfluous name for Rhizoclonium capillare. The explanation of this involved nomenclature offered by Christensen (1955: 255) is lucid, in sharp contrast to that offered by Blair (1983: 201).

Habitat: Mid-intertidal, on other algae or mud

Life History: Alternation of isomorphic phases, with quadriflagellate zoospores and biflagellate isogametes (Bliding 1957); parthenogenetic recycling of gametophytic stage also observed (Nienhuis 1974; Migita 1967).

Search Sequences in GenBank

Rhizoclonium Kützing 1843

Thalli of uniseriate filaments with or without short, simple rhizoidal branches, the filaments forming small entangled masses on other algae, on wood, or on flowering plants, or forming larger masses on mud, or free-floating. Cells multinucleate; chloroplast reticulate, with few to many pyrenoids. Cell length/width ratio used as primary taxonomic character but unreliable. Vegetative reproduction by fragmentation. Asexual reproduction by quadriflagellate zoospores, akinetes, and biflagellate zoospores from unmodified vegetative cells. Sexual reproduction by biflagellate isogametes. Zygotes developing directly into sporangial plant. Life stages isomorphic.

Rhizoclonium riparium (Roth) Harv.

Conferva riparia Roth 1806: 216. Rhizoclonium riparium (Roth) Harvey 1846-51 (1849): 238; Scagel 1966: 74. R. tortuosum sensu Smith 1944: 62.

Thalli in tangled masses, dark green to pale yellowish-green. Uniseriate filaments sometimes twisted or contorted, usually with numerous short, tapering, irregular rhizoidal branches, these nonseptate or composed of 2-5 cells; filaments 35-50(70) µm diam., 1-3(6) times longer; chloroplast coarsely reticulate, with 10-12(24) pyrenoids.

Locally abundant, in skeinlike masses on various substrata including pilings and clay banks, upper and midtidal, Alaska to Chile. Widely distributed in temperate regions. Type locality: Germany.

Excerpt from Abbott, I. A., & Hollenberg, G. J. (1976). Marine algae of California. Stanford University Press, Stanford, California. xii [xiii] + 827 pp., 701 figs.

Notes: See Notes tab.