Phyllospadix torreyi / P. scouleri Silvetia compressa / S. deliquescens
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Silvetia compressa (J. Ag.) Serrão, Cho, Boo, & Brawley (Previously known as Pelvetia fastigiata and Pelvetia compressa) / Silvetia deliquescens Silva (Previously known as Pelvetia fastigiata f. gracilis) |
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General Description (from Abbott and Hollenberg 1976 and Kendall et al. 2002): |
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Silvetia compressa: Thalli perennial and up to 90 cm long; dark olive green to yellow brown; thick, narrow, dichotomous fronds that often appear irregularly branched because of axis breakage; lacking a midrib; receptacles on ends of branches containing eggs and sperm which are produced in tiny pits called conceptacles Silvetia deliquescens: Thalli slender relative to S. compressa, with more branches |
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Habitat and Range (from Abbott and Hollenberg 1976): |
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Silvetia compressa: Locally abundant, forming beds on rocks somewhat protected from open surf; midtidal; Horswell Channel, British Columbia to Punta Baja, Baja California Silvetia deliquescens: Pebble Beach (Monterey Co.) and Channel Islands, where it is abundant and replaces S. compressa |
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Silvetia compressa |
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Silvetia deliquescens (Photo: Teri Denis) |
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Silvetia compressa receptacles containing conceptacles |
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Biology: |
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Silvetia is a dominant perennial alga that provides habitat and shelter for algae and many animals, allowing them to live higher up the shore by creating a moist microhabitat (Hill 1980; Gunhill 1983). Like other rockweeds, reproductive structures are produced in swollen branch termini called receptacles. Unlike Fucus and Hesperophycus, these are rarely inflated with gases. Gametangia occur in pits (conceptacles) that dot the surface of fertile receptacles. Gametes are released during receding tides and dispersal is very limited (Johnson and Brawley 1998). Although Silvetia is tough and long-lived, it is slow-growing, recruitment is irregular and survivorship is low (Gunhill 1980). Silvetia is susceptible to trampling (Denis 2003) and oiling because of its midtidal height and recovery from disturbance is believed to be long (Hill 1980; Vesco and Gillard 1980). |
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Silvetia compressa |
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Can be confused with: Fucus gardneri, Pelvetiopsis limitata, and Silvetia compressa. In California, Fucus has broader fronds and lacks closely spaced white hairs along the midrib. Fronds of Silvetia and Pelvetiopsis lack a midrib. |
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References: |
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Abbott IA and Hollenberg GJ (1976) Marine algae of California. Stanford Univ Press, Stanford, CA Denis T (2003) Title. Master of Science Thesis, California State University, Fullerton, California Gunnill FC (1980) Demography of the intertidal brown alga Pelvetia fastigiata in southern California, USA. Mar Biol 59:169-179 Gunnill FC (1983) Seasonal variations in the invertebrate faunas of Pelvetia fastigiata (Fucaceae): effects of plant size and distribution. Mar Biol 73:115-130
Johnson LE and Brawley
SH (1998) Dispersal and recruitment of a canopy-forming intertidal alga: the
relative roles of propagule availability and post-settlement processes. Oecologia
117: 517-26 Kendall A, Kusic K, Maloney E, Williams M (2002) List of species to be discussed at the 2002 MMS Taxonomic Workshop Vesco LL and Gillard R (1980) Recovery of benthic marine populations along the Pacific Coast of the United States following man-made and natural disturbances including pertinent life history information. U.S. Department of the Interior, Bureau of Land Management Service, POCS Reference Paper No. 53-4
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Updated: 12/9/2004 |
