MESOPHYLLUM SPHAERICUM SP. NOV. (CORALLINALES, RHODOPHYTA): A NEW MAËRL-FORMING SPECIES FROM THE NORTHEAST ATLANTIC

Authors

  • Viviana Peña,

    1. Laboratorio de Algas Marinas, Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de A Coruña. Campus de A Zapateira, S/N. A Coruña. E-15071, Spain
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  • Walter H. Adey,

    1. Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, D.C., 20560, USA
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  • Rafael Riosmena-Rodríguez,

    1. Departamento de Biología Marina, Universidad de Baja California Sur (UABCS). Apartado postal 19-B, km. 5.5 Carretera al sur, La Paz, B.C.S. 23080, Mexico
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  • Moon-Yung Jung,

    1. Division of Life Sciences, Korea Polar Research Institute, KORDI, 7-50 Songdo-dong, Yeonsu-gu, Incheon 406-840, Korea
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  • Julio Afonso-Carrillo,

    1. Departamento de Biología Vegetal (Botánica), Universidad de La Laguna, La Laguna, Canary Islands, E-38271, Spain
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  • Han-Gu Choi,

    1. Division of Life Sciences, Korea Polar Research Institute, KORDI, 7-50 Songdo-dong, Yeonsu-gu, Incheon 406-840, Korea
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  • Ignacio Bárbara

    1. Laboratorio de Algas Marinas, Departamento de Biología Animal, Biología Vegetal y Ecología. Universidad de A Coruña. Campus de A Zapateira, S/N. A Coruña. E-15071, Spain
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    • Present address: Facultad de Ciencias, Universidad de A Coruña, Campus de A Zapateira, S/N, 15071 A Coruña, Spain.


  • Received 27 November 2009. Accepted 2 February 2011.

Abstract

Mesophyllum sphaericum sp. nov. is described based on spherical maërl individuals (up to 10 cm) collected in a shallow subtidal maërl bed in Galicia (NW Spain). The thalli of these specimens are radially organized, composed of arching tiers of compact medullary filaments. Epithallial cells have flattened to rounded outermost walls, and they occur in 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 flattened pore plate, lacking a peripheral raised rim. Filaments lining the pore canal and the conceptacle roof are composed of five to six cells with straight elongate and narrow cells at their base. Carposporangial conceptacles are uniporate, protruding, and conical. Spermatangial conceptacles were not observed. Molecular results placed M. sphaericum near to M. erubescens, but M. sphaericum is anatomically close to M. canariense. The examination of the holotype and herbarium specimens of M. canariense indicated that both species have pore canal filaments with elongate basal cells, but they differ in number of cells (five to six in M. sphaericum vs. four in M. canariense). Based on the character of pore canal filaments, M. canariense shows similarities with M. erubescens (three to five celled). The outermost walls of epithallial cells of M. canariense are flared compared to the round to flattened ones of M. erubescens, the latter being widely accepted for the genus Mesophyllum. The addition of M. sphaericum as new maërl-forming species suggests that European maërl beds are more biodiverse than previously understood.

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