Wikipedia
Caulerpa
Caulerpa is a genus of seaweeds in the family Caulerpaceae (among the green algae). They are unusual because they consist of only one cell with many nuclei, making them among the biggest single cells in the world. A species in the Mediterranean can have a stolon more than 3 metres (9 ft) long, with up to 200 fronds.
Referring to its thalli's crawling habit, the name means ‘stem (that) creeps’, from the Ancient Greek (, ‘stalk’) and (, ‘to creep’).