Sea Thong is brown seaweed of with a threadlike appearance: it has up to 5 meter long strap-like reproductive fronds.
Sea thong has a two stage morphology. Small button-like thalli are first produced. These thalli are submerged and attached to the rocky seabottom.
After two years the seaweed is mature and is able to reproduce, the second stage.
Sea Thong reproduction
To reproduce it starts producing the long fronds at the start of the spring.
These fronds releases gametes from June until the winter, after which it starts to decay.
Thongweed dies as soon as it has released its gametes, so the total age of this seaweed is most 2 or 3 years.
Himanthalia elongata is the only member of its genus, Himanthalia Lyngbye and the only member of its family, Himanthaliaceae. Although it may resemble other seaweeds it is not closely related to the kelps or the wracks.
But there are other seaweeds that have long strap-like blades like dead man's rope or sea lace or Chorda filum, which is a very common seaweed but has no button-like thalli.
Chorda filum is unbranched, darker and generally the plants are twisted together.
'Sea Spaghetti', edible thongweed
The young receptacles can be eaten: they are harvested early in the summer, air-dried, cut into finger-like lengths and packaged.
They are used in (seafruit) salads. It has a very mild taste.
The thalli op Sea thong or sea spaghetti. The color is olive green, the underside of this button is the hold fast of Himanthalia elongata.