Morphology of three benthic diatoms from a tropical mangrove in Hainan Island, China: Gyrosigma centropunctatum sp. nov., G. dongzhaiense sp. nov. and G. orbitum Thaler et Kaczmarska

Abstract

Three benthic Gyrosigma species isolated from sediments of a tropical mangrove in Hainan Island, China, are described using light, scanning and transmission electron microscopy: G. centropunctatum sp. nov., G. dongzhaiense sp. nov. and G. orbitum Thaler et Kaczmarska. Gyrosigma centropunctatum is a tube-dwelling species possessing a unique row of pores on either side of the central area. Gyrosigma dongzhaiense differs from congeners by a combination of small cell size, linear-sigmoid outline, and higher stria density. Gyrosigma orbitum is another tube-dwelling species, which possesses two remarkable oval pits on the external central area. This study expands our knowledge of the marine species diversity and distribution of Gyrosigma in the tropical Western Pacific. We discuss the taxonomic significance of tubes in the species identification of Gyrosigma.