RT info:eu-repo/semantics/article T1 Mesophyllum sphaericum sp. nov. (Corallinales, Rhodophyta): a new maërl-forming species from the northeast Atlantic A1 Afonso Carrillo, Julio A1 Peña, Viviana A1 Adey, Walter H. A1 Riosmena-Rodríguez, Rafael A1 Jung, Moon-Yung A1 Choi, Han-Gu A1 Bárbara, Ignacio A2 BotánicaEcología y Fisiología Vegetal A2 Botánica Marina AB Mesophyllum sphaericum sp. nov. is described basedon spherical mae¨rl individuals (up to 10 cm) collected in a shallow subtidal mae¨rl bed in Galicia(NW Spain). The thalli of these specimens areradially organized, composed of arching tiers ofcompact medullary filaments. Epithallial cells haveflattened to rounded outermost walls, and they occurin a single layer. Subepithallial initials are as long as,or longer than the daughter cells that subtend them.Cell fusions are abundant. Multiporate asexual conceptacles are protruding, mound-like with a flattenedpore plate, lacking a peripheral raised rim. Filaments lining the pore canal and the conceptacle roofare composed of five to six cells with straight elongate and narrow cells at their base. Carposporangialconceptacles are uniporate, protruding, and conical.Spermatangial conceptacles were not observed.Molecular results placed M. sphaericum near toM. erubescens, but M. sphaericum is anatomically closeto M. canariense. The examination of the holotypeand herbarium specimens of M. canariense indicatedthat both species have pore canal filaments with elongate basal cells, but they differ in number ofcells (five to six in M. sphaericum vs. four inM. canariense). Based on the character of pore canalfilaments, M. canariense shows similarities withM. erubescens (three to five celled). The outermostwalls of epithallial cells of M. canariense are flaredcompared to the round to flattened ones of M. erubescens, the latter being widely accepted for the genusMesophyllum. The addition of M. sphaericum as newmae¨rl-forming species suggests that European mae¨rlbeds are more biodiverse than previously understood. PB Phycological Society of America YR 2011 FD 2011 LK http://riull.ull.es/xmlui/handle/915/28261 UL http://riull.ull.es/xmlui/handle/915/28261 LA en DS Repositorio institucional de la Universidad de La Laguna RD 25-abr-2024