Palmaria palmata

Palmaria palmata (L.) Kuntze, also called dulse, dillisk, dilsk or creathnach, is a red algae (Rhodophyta) previously referred to as Rhodymenia palmata (Linnaeus) Greville. It grows on the northern coasts of the Atlantic and Pacific oceans. It is a well-known snack food, and in Iceland, where it is known as söl, it has been an important source of fiber through the centuries.

Additional recommended knowledge

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History

The earliest record of this species is of St Columba's monks harvesting it 1,400 years ago.^[1]

Description

Dulse grows attached by its discoid holdfast to the stipes of Laminaria or to rocks. It has a short stipe, the fronds are very variable and vary in colour from deep-rose to reddish-purple and are rather leathery in texture. The flat foliose blade gradually expands and divides into broad segments ranging in size to 50 cm long and 30 - 8 cms in width which can bear flat wedge-shaped proliferations from the edge.^[2] [1]

The reference to Rhodymenia palmata var.mollis in Abbott & Hollenberg (1976),^[3]is now considered to refer to a different species: Palmaria mollis (Setchel et Gardner) van der Meer et Bird.^[4][2]

Dulse is similar to another seaweed Dilsea carnosa (Schmidel) Kuntze, [3] Dilsea, however, is more leathery with blades up to 30cms long and 20cms wide. Unlike Palmaria palmata it is not branched and does not have proliferations or branches from the edge of the frond. The older blades may split however.^[5]

Life history

The full life-history was not fully explained until 1980.^[6] Tetraspores occur in scattered sori on the mature blade, which is diploid. Spermatial sori occur scattered over most of the frond of the haploid male plant. The female gametophyte is very small stunted or encrusted, the carpogonia apparently occurring as single cells in the young plants. The male plants are blade-like and produce spermatia which fertilize the carpogonia of the female crust. After fertilization the diploid plant overgrows the female plant and develops into the tetrasporangial diploid phase attached to the female gametophyte. The adult foliose tetrasporophyte produces tetraspores meiotically.^[2] It is therefore usually the diploid tetrasporic phase or the male plant which is to be found on the shore.^[7]

Ecology

Palmaria palmata is to be found growing from mid-tide of the intertidal zone (the area between the high tide and low tide) to a depths of 20 m or more in both sheltered and exposed shores.^[7]

Food

Dulse is a good source of minerals and vitamins compared with other vegetables and it contains all trace elements needed for humans with a high protein content.^[1]

It is commonly found from June to September and can be collected by hand when the tide is out. When collected, small snails, shell pieces and other small particles can be washed or shaken off and the plant then spread to dry. Some collectors may turn it once and roll it into large bales to be packaged later. It is also used as fodder for animals in some countries.

Dulse is commonly used in Northern Ireland [4], Iceland and Atlantic Canada both as food and medicine. It can be found in many health food stores or fish markets and can be ordered directly from local distributors. In Ballycastle, Northern Ireland it is traditionally sold at the Ould Lammas Fair. A variety of dulse is cultivated in Nova Scotia and marketed as Sea Parsley, sold fresh in the produce section. Dulse is now shipped around the world. In Northern Ireland it is particularly popular along the Causeway Coast region. Although a fast dying tradition, there are many who still gather their own dulse although waste pipes have spoiled some sites.

Dulse can be found in some dietary supplements, where it is often referred to as "Nova Scotia Dulce", it is a good source of dietary requirements, a handful will provide more than 100% of the daily amount of Vitamin B6, 66% of Vitamin B12, a day's supply of iron and fluoride, and it is relatively low in sodium and high in potassium.[5]

Fresh dulse can be eaten directly off the rocks before sun-drying. Sun-dried dulse is eaten as is or is ground to flakes or a powder. In Iceland the tradition is to eat it with butter. It can also be pan fried quickly into chips, baked in the oven covered with cheese, with salsa, or simply microwaved briefly. It can also be used in soups, chowders, sandwiches and salads, or added to bread/pizza dough. Finely diced, it can also be used as a flavor enhancer in meat dishes, such as chili, in place of monosodium glutamate.

Distribution

Palmaria palmata is the only species of Palmaria found on the coast of Atlantic Europe. It is to be found from Portugal to the Baltic coasts also on the coasts of Iceland and the Faeröes (Faroes).^[8] It also grows on the shores of Arctic Russia, Arctic Canada, Alaska, Japan and Korea.^[7]The records from California are of Palmaria mollis which is considered a different species.[6]

Infections, galls, malformations and diseases

Galls, possibly produced by nematodes, copepods and bacteria are known to infect these plants. They were recorded as "outgrowths of tissue produced by the presence...of an animal."^[9][7]

References

1. ^ ^{a b} Indergaard, M. and Minsaas, J. 1991. 2 Animal and human nutrition. in Guiry, M.D. and Blunden, G. 1991. Seaweed Resources in Europe: Uses and Potential. John Wiley & Sons. ISBN 0 471 92947 6
2. ^ ^{a b} Hoek, C.van den, Mann, D.G. and Jahns, H.M. 1995. Algae: An Introduction to Phycology. Cambridge University Press, Cambridge. ISBN 0 521 30419 9
3. ^ Abbott, I.A. and Hollenberg, G.J. 1976. Marine Algae of California. Stanford University Press, California. ISBN 0 8047 0867 2
4. ^ Mondragon, J. and Mondragon, J. 2003. Seaweeds of the Pacific Coast. Sea Challengers, California. ISBN 0 930118 29 4
5. ^ Hiscock, S. 1986. A Field Key to the British Red Seaweeds. Occasional Publications No.13. Field Studies Council, Dorset Press, Dorchester ISBN 1 851538136
6. ^ van der Meer, J.P. and Todd, E.R. 1980. The life-history of Palmaria palmata in culture. A new type for the Rhodophyta. Can. J. Bot. 58: 1250 - 1256
7. ^ ^{a b c d} Irvine, L.M. 1983. Seaweeds of the British Isles. Volume 1. Part 2A. Cryptonemiales (sensu stricto) Palamriales, Rhodymeniales. British Museum (Natural History), London. ISBN 0 565 00871 4
8. ^ Borgesen, F. 1903. Botany of the Faeröes...Part II. Copenhagen (reprint 1970)
9. ^ Barton,E.S. 1891. On the occurrence of galls in Rhodymenia palmata Grev. J.Bot. Lond. 29: 65 - 68

Further reading

• Grubb, V.M. 1923. Preliminary note on the reproduction of Rhodymenia palmata, Ag. Ann. Bot. 37 : 151 - 152.

• Pueschel, C.M. 1979. Ultrastructure of the tetrasporogenesis in Palmaria palmata (Rhodophyta). J. Phycol. 15: 409 - 424.
• South, G.R. and Hooper, R.G. 1980. A Catalogue and Atlas of the Benthic Marine Algae of the Island of Newfoundland. p. 1 - 136. Memorial University of Newfoundland Occasional Papers in Biology.