Fine structure and taxonomy of two species of the marine diatom genus Climaconeis (Berkeleyaceae, Bacillariophyta): C. silvae sp. nov. and C. riddleae sp. nov. from the Caribbean Sea and Florida bay, USA

Resumo

Two new species of marine biraphid diatoms of the genus Climaconeis, C. silvae, collected from several localities in Puerto Rico (Caribbean Sea), and C. riddleae, from two localities in Florida Bay, USA, are described by light and scanning electron microscopy. Climaconeis silvae is characterized by long arcuate cells (132-298 ?m long and 5-10 ?m wide) with extremely fine striae (28-35 in 10 ?m), transapically elongated poroid areolae, biarcuate eccentric raphe, both polar and central raphe endings externally deflected toward the ventral side, 8-20 H-shaped plastids, and absence of central stauros and associated pores. Climaconeis riddleae is characterized by arcuate, asymmetrical cells, 4 plastids, valves measuring 82-182 ?m long and 4-6 ?m wide, transapical striae 24-27 in 10 ?m, each stria composed of single row of squarish poroid areolae, and an almost central raphe. Climaconeis silvae and C. riddleae closely resemble only three other arcuate species, C. inflexa, C. ghurbensis and C. koenigii, in valve shape and in structure and arrangement of the striae but differ from them in stria density, number of plastids, valve dimensions, and some fine structural detail. They are compared with other members of the genus, including the generitype, C. lorenzii. A revised synoptic key to the 13 known species of Climaconeis is presented.