Two similar red algal species, Melanamansia glomerata and Amansia rhodantha (Rhodomelaceae, Ceramiales), from the north-western Pacific Ocean

Two different entities have been included in the alga passing under the name of Melanamansia glomerata (C. Agardh) R. Morris or Amansia glomerata C. Agardh in the north-western Pacific Océan. An alga, which is characterised by the production of two pseudopericentral cells that are eut off from two dorsal pericentral cells towards the centre of the thallus and surround the axial cell together with five pericentral cells, is referred to genuine M. glomerata. Another alga, which lacks such pseudopericentral cells, is referred to Amansia rhodantha (Harvey) J. Agardh. The two species are also distinguished by two further features: 1) thallus colour, dark brown in M. glomerata and dark red in A. rhodantha; and 2) the absence or presence of conspicuous midribs, absent in M. glomerata and present in A. rhodantha. However, diagnostic features between the genera Melanamansia and Amansia besides the presence/absence of pseudopericentral cells, such as development of serrations, the presence/absence of trichoblast capsules and transverse-sectional profiles of tetrasporangial stichidia, may vary in both genera and overlap each other. The pseudopericentral feature is only a reliable taxonomic criterion that distinguishes these two genera. These facts strongly indicate that Amansia and Melanamansia are congeneric, at least M. glomerata should be put back in Amansia, although it is desirable to conduct further studies including molecular analysis for reassessment of the status of the genus Melanamansia.