Pyramimonas australis sp. nov. (Prasinophyceae, Chlorophyta) from Antarctica: fine structure and molecular phylogeny

Abstract

An undescribed marine Pyramimonas, P. australis Andreoli et Moro, sp. nov., forming a bloom in a hole of Terra Nova Bay (Ross Sea, Antarctica) sea ice, was collected, but could not be cultured. Consequently, the description of this new species is based on light and electron microscope observations on samples that were fixed or stored at -80 degreesC, and its phylogenetic position inferred from nuclear-encoded small-subunit ribosomal DNA (SSU rDNA) and chloroplast-encoded rbcL gene sequences. This is the third Antarctic species described for this genus. The ultrastructure of the cell is consistent with species of the subgenus Trichocystis McFadden, but differs in that it has unique body and cyst scales. and a different encystment procedure. The outermost layer of body scales is formed by flat box scales with peripheral perforations oriented parallel to the four edges and with a further eight central perforations oriented perpendicular to the peripheral ones. Crown scales, which in many other species of the genus form the outermost layer over the entire cell body, were observed in this species in the flagellar pit over the box scales. The flagella are covered by a pentagonal underlayer of scales and by limuloid scales with two subsidiary spines, in addition to the central one. Encystment begins in the flagellate form resulting in a cyst with an irregular wall bearing spine scales. Ultrastructural and molecular data confirm that P. australis belongs to the subgenus Trichocystis

Pleomorphism in the Antarctic flagellate Pyramimonas gelidicola (Prasinophyceae, Chlorophyta)

“…The Pyramimonas cyst formation began with the motile single‐celled quadriflagellate (van den Hoff et al. 1989; Daugbjerg 2000; Moro et al. 2002), but cysts could also be the product of the multilobed stage observed in culture, because we saw on one occasion a multilobed form containing a thickened internal cyst‐like wall structure, a single nucleus and a diffuse mass of DNA.…”

Seasonal changes in phytoplankton on the north-eastern shelf of Kangaroo Island (South Australia) in 2012 and 2013

“…The green alga Pyramimonas was also abundant in the north-eastern shelf of Kangaroo Island. It is a highly diverse genus which has been frequently reported in polar waters (Balzano et al, 2012;Bell and Laybourn-Parry, 2003;Moro et al, 2002) but was also previously observed in south-eastern Australia (McFadden et al, 1986) and in the Gulf Saint Vincent .…”

Taxonomy and phylogeny of Pyramimonas vacuolata sp. nov. (Pyramimonadales, Chlorophyta)

“…To amplify 18S rDNA, the conditions were as follows: initial denaturation at 948C for 3 min followed by 35 cycles of 948C for 30 s, 508C for 30 s, 728C for 1-2 min and a final extension at 728C for 10 min. For rbcL, the conditions were from Moro et al (2002). PCR products were purified and sequenced at Macrogen Japan (Tokyo, Japan).…”