Himanthalia elongata

Himanthalia elongata is a brown alga in the order Fucales, also known by the common names thongweed, sea thong and sea spaghetti. It is found in the north east Atlantic Ocean and the North Sea.^[1]

Himanthalia elongata
Scientific classification
Domain:	Eukaryota
Clade:	Sar
Clade:	Stramenopiles
Phylum:	Ochrophyta
Class:	Phaeophyceae
Order:	Fucales
Family:	Himanthaliaceae
Genus:	Himanthalia
Species:	H. elongata
Binomial name
Himanthalia elongata (Linnaeus) S.F. Gray[1]
Synonyms[1]
Fucus elongatus Linnaeus, 1753 Fucus loreus Linnaeus, 1767 Fucus pruniformis Gunnerus, 1772 Fucus tomentosus Hudson, 1778 Funicularius tuberculatus Roussel, 1806 Himanthalia lorea (Linnaeus) Lyngbye, 1819

According to the World Register of Marine Species Himanthalia elongata is the only member of its genus, Himanthalia Lyngbye, 1819 ^[2] and the only member of its family, Himanthaliaceae (Kjellman) De Toni, 1891.^[3]

Description

Thongweed at Rossnowlagh, Ireland.

Himanthalia elongata is a common brown alga of the lower shore. The thallus is at first a small flattened or saucer-shaped disc up to three centimetres wide with a short stalk. In the autumn or winter, long thongs grows from the centre of this, branching dichotomously a number of times. They grow fast and can reach up to two metres by the following summer when they become mature. They bear the conceptacles, the reproductive organs, and begin to decay when the gametes have been released into the water. The discs live for two or three years.^[4][5]

Young thallus of Himanthalia elongata

Distribution and habitat

Himanthalia elongata is found in the Baltic Sea, the North Sea and the north east Atlantic Ocean from Scandinavia, through Ireland, and south to Portugal.^[6] It is found on gently shelving rocky shores in the lower littoral zone and the sublittoral zone particularly on shores with moderate wave exposure. It is sometimes abundant and forms a distinct zone just below the Fucus serratus zone.^[4][5]