Alaria Greville, 1830, nom. cons.

Lectotype species: Alaria esculenta (Linnaeus) Greville

Original publication: Greville, R.K. (1830). Algae britannicae, or descriptions of the marine and other inarticulated plants of the British islands, belonging to the order Algae; with plates illustrative of the genera. pp. [i]-lxxxviii, [1]-218, pl. 1-19. Edinburgh & London: McLachlan & Stewart; Baldwin & Cradock.

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Type designated in: De Toni, G.B. (1891). Systematische √úbersicht der bisher bekannten Gattungen der echten Fucoideen. Flora 74: 171-182.

The most recent alteration to this page was made on 2015-10-19 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Gender: This genus name is currently treated as feminine.

Most recent taxonomic treatment adopted: Silberfeld, T., Rousseau, F. & Reviers, B. de (2014). An updated classification of brown algae (Ochrophyta, Phaeophyceae). Cryptogamie Algologie 35(2): 117-156, 1 fig., 1 table.

Comments: A number of species are recognized: between 5 (Petrov 1973) and 14 (Widdowson 1971a). The genus has a circumboreal distribution and is most commonly found close to low water mark where there is some surf. It is usually a dominant in this habitat. Petrov and Widdowson both identify plants in this habitat as A. esculenta in the Atlantic, A. marginata in the northeast Pacific, and A.crassifolia (Petrov would say A. ochotensis) in Japan. A. fistulosa forms floating canopy kelp beds in the north Pacific. The center of variation, with the most species, is in the north Pacific. Using restriction mapping of rDNA, Mroz (1989) tended to support Widdowson's suggestion of hybridization between A. marginata and A. nana (midintertidal exposed coasts) and A. tenuifolia (sheltered coasts). However, Mroz found the genotypic differences between these "species" to be very small. Sea temperature of 16%C is limiting for Alaria and is related to its 4 southern limits. The effect of this temperature is quite distinct on transplanted A. esculenta (Sundene 1962, Munda and Luning 1977). In other species, the non-reproductive sporophyte may survive a few degrees higher and reproduce in a cooler season (Niihara and others 1987 -- A. crassifolia; Druehl and Hsiao 1973 -- A. tenuifolia). The limiting effect of these temperatures has been confirmed by laboratory experiment (Luning and Freshwater 1988). Alaria has disappeared from much of the English Channel in the past century, perhaps because of increased sea temperatures. Alaria has been shown to be similar to other kelps in life cycle and gametophyte structure (Robinson and Cole 1971b); ultrastructure of sperm and meiospores (Henry and Cole 1983a and b); and in the light and temperature requirements of gametophytes (Luning and Neushul 1978). Haploid chromosome number is "probably" 28 for A. esculenta (Evans 1965), 22 for A. crassifolia (Yabu 1957), 22 for A. praelonga in Japan (Yabu 1964b), "approximately" 24 for A. praelonga in Alaska (Robinson and Cole 1971a as A. grandifolia), and approximately 14 for A. fistulosa, A. taeniata (a mainly north Pacific species), A.marginata, A. nana, and A. tenuifolia (Robinson and Cole 1971a). The mature sporophyte varies in length from 15 cm (A. nana) to 15 m (A. fistulosa). It consists of a ramified holdfast, an unbranched stipe, and a blade with a percurrent midrib strongly emergent in cross-section. Sori of sporangia and paraphyses occur on short-lived sporophylls born on the distal part of the stipe in the plane of the blade. In A. paradisea (Kurile Is.) some sporophylls are replaced by vegetative blades with midrib. Sori sometimes appear on the vegetative blade, either spontaneously or because of amputation of the sporophylls (Pfister 1991). The kelp beds of A. fistulosa are seasonal, but in most species the sporophyte is perennial, with heavy mortality in the first two years. Anatomy is similar to other kelps (Schmitz and Srivastava 1975). The primary source of photosynthate is the meristoderm of the distal parts of the blade and the primary sink is the meristem at the base of the blade, with sporophylls and holdfast secondary. Longitudinal transport is localized in the medulla of the midrib (Buggeln 1981, Schmitz 1984). While the normal flow of photosynthate is from source to sink, this flow can be reversed experimentally (Schmitz and Srivastava 1975). The sporophylls have more phenolic compounds thought to discourage herbivores (Steinberg 1984) and less antimicrobial activity (Hornsey and Hide 1985) than the rest of the plant.

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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 19 October 2015. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 17 June 2024

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