First record of the green alga Acetabularia caliculus from Greece

Abstract

The green alga Acetabularia caliculus Lamouroux, commonly known as the umbrella alga, is reported for the first time from Greece. Specimens were detected at depth of 4 m in Nea Kallikrateia, Thermaikos Gulf (North Aegean Sea; 40.30488°N, 23.07694°E) in September 2018. Several individuals were found growing in clusters on dead shells of Callista chione, on sandy bottom. The cup-shaped disk (upturned umbrella) and the number of rays per disk (<40) distinguish the species from the similar species Acetabularia acetabulum (Linnaeus) Silva, which is commonly found in Greece. First described from Western Australia, Acetabularia caliculus is commonly found in the tropical and subtropical coasts of the Atlantic and Indo-Pacific Ocean. In the Mediterranean Sea, it is only known from Spain, Egypt, Israel and Morocco. We consider the species as cryptogenic, pending molecular investigation of it.