Sexual reproduction of the invasive green alga Caulerpa racemosa var. occidentalis in the Mediterranean Sea

Since the beginning of the 1990s, a pan-tropical species Caulerpa racemosa var. occidentalis has been recorded on the numerous new locations throughout the Mediterranean, specifically on its northwestern part where until then it had never been observed. Such extensive spreading is probably supported by successful sexual reproduction. Field observations of fertile plants and synchronous gamete release of C. racemosa var. occidentalis were carried out in Saronikos Gulf (Greece, Aegean Sea) at the beginning of July 1999. The fertile plants were detected due to reticulate depigmented protoplasmic masses and cylindrical papillae. The alga is monoecious. The both sex gametes were released synchronously from all the fertile plants approximately 14 min before sunrise and formed a green gamete cloud. Although both sex gametes were present, low gamete compatibility was noted during the laboratory examination. (C) 2001 Ifremer/CNRS/IRD/Editions scientifiques et medicales Elsevier SAS.