Pelvetia

Pelvetia canaliculata, the channelled wrack, is a very common brown alga (Phaeophyceae) found on the rocks of the upper shores of Europe. It is the only species remaining in the monotypic genus Pelvetia.[1][2] In 1999, the other members of this genus were reclassified as Silvetia due to differences of oogonium structure and of nucleic acid sequences of the rDNA.[3]

Pelvetia
Close-up
Growing on the side of a slipway
Scientific classification
Clade: SAR
Phylum: Ochrophyta
Class: Phaeophyceae
Order: Fucales
Family: Fucaceae
Genus: Pelvetia
Decne. & Thur.
Species:
P. canaliculata
Binomial name
Pelvetia canaliculata
Synonyms [1]
  • Fucus canaliculatus L.
  • Halidrys canaliculata (L.) Stackhouse
  • Fucodium canaliculatum (L.) J.Agardh
  • Ascophyllum canaliculatum (L.) Kuntze
  • Ascophylla canaliculata (L.) Kuntze
  • Fucus excisus L.

Description

Pelvetia grows to a maximum length of 15 centimetres (6 in) in dense tufts, the fronds being deeply channelled on one side: the channels and a mucus layer help prevent the seaweed drying (desiccation) when the tide is out. It is irregularly dichotomously branched[4] with terminal receptacles,[5] and is dark brown in colour. Each branch is of uniform width and without a midrib. The receptacles are forked at the tips.

It is distinguished from other large brown algae by the channels along the frond. It has no mid-rib, no air-vesicles and no cryptostomata. It forms the uppermost zone of algae on the shore growing at or above high-water mark.[6] The reproductive organs form swollen, irregularly shaped receptacles at the end of the branches. The conceptacles are hermaphrodite and borne within the receptacles. at the apices.

Reproduction

Both sexes occur in the same plant, the reproductive structures develop at the apices.[7] The receptacles are swollen during the summer and are yellowish-green at maturity.[8]

Ecology

Pelvetia canaliculata is the only large algae growing on rocks forming a zone along the upper shore at the upper littoral zone, on the shores of the British Isles. It tolerates a wide range of exposure conditions.[9] It needs periods of exposure to the air, and sometimes grows so high up a beach that coarse grass and other longshore angiosperms grow among it. If it is submerged for more than six hours out of 12 it begins to decay.[10]

Distribution

Pelvetia canaliculata is common on the Atlantic shores of Europe from Iceland to Spain, including Norway, Ireland, Great Britain, the Netherlands, France and Portugal.[11] In Ireland, collection of Pelvetia canaliculata (Irish: dúlamán) has been recorded as a source of sustenance during times of famine.[12] A popular Irish folk song, Dúlamán, describes events transpiring between two people who collected the seaweed as a profession.

References
  1. M. D. Guiry & G. M. Guiry. "Genus: Pelvetia". AlgaeBase. National University of Ireland, Galway. Retrieved April 24, 2012.
  2. Fernando G. Cánovas, Catarina F. Mota, Ester A. Serrão & Gareth A. Pearson (2011). "Driving south: a multi-gene phylogeny of the brown algal family Fucaceae reveals relationships and recent drivers of a marine radiation". BMC Evolutionary Biology. 11: 371. doi:10.1186/1471-2148-11-371. PMC 3292578. PMID 22188734.CS1 maint: uses authors parameter (link)
  3. Ester A. Serrão, Lawrence A. Alice & Susan H. Brawley (1999). "Evolution of the Fucaceae (Phaeophyceae) inferred from nrDNA-ITS" (PDF). Journal of Phycology. 35 (2): 382–394. doi:10.1046/j.1529-8817.1999.3520382.x. hdl:10400.1/4045. Archived from the original (PDF) on 2015-09-23. Retrieved 2013-06-10.CS1 maint: uses authors parameter (link)
  4. W. E. Jones (1962). "A key to the genera of British seaweeds". Field Studies. 1 (4): 1–32.
  5. L. Newton (1931). A Handbook of the British Seaweeds. British Museum, London.
  6. C. I. Dickinson (1963). British Seaweeds. The Kew Series.
  7. Bunker, F.StP. D., Brodie, J.A., Maggs, C.A. and Bunker, A.R. 2017 Seaweeds of Britain and Ireland. Second Edition. Wild Nature Press, Plymouth, UK. ISBN 978-0-9955673-3-7
  8. Dickinson, C.I. 1963. British Seaweeds. The Kew Series
  9. J. R. Lewis (1964). The Ecology of the Rocky Shores. The English Universities Press Ltd. London.
  10. D. Thomas (2002). Seaweeds. Life Series. London: Natural History Museum. ISBN 978-0-565-09175-0.
  11. M. D. Guiry & Wendy Guiry (October 25, 2006). "Pelvetia canaliculata (Linnaeus) Decaisne & Thuret". AlgaeBase.
  12. Doreen McBride (1994). "When Hunger Stalked the North".
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