Phycological Research 2007; 55: 42–46 Blackwell Publishing AsiaMelbourne, AustraliaPREPhycological Research1322-08292006 Japanese Society of PhycologyDecember 20065514246Original Article Verosphacela silvae sp. nov.G. Alongi et al. *To whom correspondence should be addressed. Email: g.furnari@unict.it Communicating editor: K. Kogame. Received 2 March 2006; accepted 12 June 2006. doi: 10.1111/j.1440-1835.2006.00445.x Verosphacela silvae sp. nov. (Onslowiaceae, Phaeophyceae) from the Mediterranean Sea Giuseppina Alongi, Mario Cormaci and Giovanni Furnari* Department of Botany, University of Catania, via A. Longo 19, 95125 Catania, Italy SUMMARY We describe Verosphacela silvae sp. nov., from the Mediterranean Sea. It consists of horizontal filaments living on the lower face of the red alga Peyssonnelia rubra (Greville) J. Agardh, from which erect filaments up to 1.5 mm high rise and grow upright after passing through the thallus of the supporting species. There are both horizontal and erect filaments growing by apical cells. In the subapical cells, 1–2 longitudinal divisions occur (more frequently in the erect filaments) but no secondary transverse divisions occur. Erect filaments bear lateral propagules on a stalk of one to three (rarely more) cells. Propagules, with neither apical cells nor arms, consist of seven cells. Zoidangia are borne at the apex of erect laterals. The new species differs from V. ebrachia Henry mainly in habit, propagules and zoidangia. In addition, distinct from V. ebrachia, fila- ments of V. silvae never penetrate between the cuticle and the cell wall of the supporting alga. Moreover, propagules of V. silvae consist of seven cells, whereas those of V. ebrachia consist of 9–13 cells, and zoidan- gia are terminal on laterals in V. silvae, whereas in V. ebrachia they are sessile on both axes and laterals. Key words: Aeolian Islands, Mediterranean Sea, Onslo- wiaceae, Phaeophyceae, Verosphacela silvae. INTRODUCTION The monotypic genus with the species Verosphacela ebrachia (Onslowiaceae, Phaeophyceae) was described by Henry (1987) for a brown alga, collected at Vero Beach, Florida, USA, superficially endophytic in Spato- glossum schroederi (C. Agardh) Kützing. It showed ‘branched filaments growing by prominent apical cells, subapical cells becoming divided by one or two longi- tudinal divisions, and propagules without an apical cell or arms, usually germinating from a basal cell’. Accord- ing to Henry (1987), the genus Verosphacela is related to the genus Onslowia Searles (Searles & Leister 1980), from which it differs mainly in its propagules, which lack an apical cell (whereas propagules of Onslowia have four meristematic apical cells). Searles placed Onslowia in the Sphacelariales because of the apical mode of growth, occasional longitudinal division of veg- etative cells and the production of propagules, and in the Sphacelariaceae because of the occurrence of lon- gitudinal vegetative cell divisions (Searles & Leister 1980). However, Henry (1987) placed both Onslowia and his new genus Verosphacela in the Choristocar- paceae (Sphacelariales) since they share with Choristo- carpus a simple vegetative construction and propagules without the peculiar lenticular apical cell (always present in the development of propagules of Sphacelaria). Prud’homme van Reine (1982) opposed the inclusion of Choristocarpaceae within the Sphacelariales, but in 1993 (Prud’homme van Reine 1993) he placed the family in the ‘Sphacelariales (s.l)’, ‘because at the moment no other place in the classifi- cation system of brown algae can be suggested.’ De Reviers and Rousseau (1999) considered Choristo- carpaceae incertae sedis. Finally, Draisma and Prud’homme van Reine (2001), on the basis of the molecular phylogenetic study by Draisma et al. (2001) in which it was demonstrated that Onslowia and Verosphacela are not monophyletic with the Choristo- carpaceae, proposed placing these two genera in the new family Onslowiaceae. This new family differs from Choristocarpaceae in the occasional occurrence of lon- gitudinal cell walls in the filaments (filaments strictly uniseriate in Choristocarpaceae) and in propagules lacking a large conspicuous apical cell (propagules with a large conspicuous apical cell in Choristocarpus). Moreover, Draisma and Prud’homme van Reine (2001) considered both Choristocarpaceae and Onslowiaceae incertae sedis ‘until additional DNA sequences resolve their currently obscure systematic position’. However, these families may both require accommodation in a separate order (Draisma 2002; Draisma et al. 2003). In the course of our floristic research on Mediterra- nean macroalgae, some specimens of a brown alga showing characteristics of the genus Verosphacela were