Pyramimonas octopora L. Haraguchi, Moestrup, H.H. Jakobsen & Lundholm, 2022

Haraguchi, Lumi, Moestrup, Øjvind, Jakobsen, Hans Henrik & Lundholm, Nina, 2022, Phytoflagellate diversity in Roskilde Fjord (Denmark), including the description of Pyramimonas octopora sp. nov. (Pyramimonadales, Chlorophyta), Phycologia 61 (1), pp. 45-59 : 49-51

publication ID	https://doi.org/10.1080/00318884.2021.2000285
persistent identifier	https://treatment.plazi.org/id/03A61274-1759-0E3E-5F2D-FF217A9E7F50
treatment provided by	Felipe
scientific name	Pyramimonas octopora L. Haraguchi, Moestrup, H.H. Jakobsen & Lundholm
status	sp. nov.

Treatment

Pyramimonas octopora L. Haraguchi, Moestrup, H.H. Jakobsen & Lundholm sp. nov.

Figs 28–42 View Figs 28–31 View Figs 32–42

DIAGNOSIS: Elongated cells with average cell length 9.5 ± 1.2 µm and width 7.2 ± 1.1 µm. The eyespot comprises two rows of carotenoid droplets, near the apical end of the cell in two adjacent chloroplast lobes. The four flagella are slightly longer than the cell. Each flagellum is covered by a layer of small pentagonal scales, in addition to limuloid scales and hair scales. A layer of box scales covers the cell body, each box scale with eight round irregular perforations in the base plate, arranged in a rounded square around the centre of the base plate. Crown scales have a squared base with pointed edges. A cross-shaped structure is formed by struts from the middle of each side of the outer rim and meeting in the centre. In each quadrant defined by the cross-shaped structure, the outer parts of the rim are connected by two smaller structures arranged at about 45 degrees in relation to the cross, forming a complex pattern. From each corner, a tubular structure rises upward, all four meeting at the top, from where a central tubular column connects to the base plate centre.

HOLOTYPE: A fixed and plastic-embedded sample of culture Poct _06 is deposited at C, the herbarium at the Natural History Museum of Denmark (museum number C-A-99692) ( Fig. 35 View Figs 32–42 illustrates the holotype). Accession number MW451603 View Materials for the SSU sequence of the holotype strain.

TYPE LOCALITY: Type material was collected at the inner portion of Roskilde Fjord , Denmark (55°41 ʹ N, 12°5 ʹ E) in June 2016. Salinity was 13.1 and temperature 19.8 GoogleMaps ° C.

ETYMOLOGY: Latin adjective octoporus, -a, -um, eight pores, referring to the box scale with eight round irregular perforations in the base plate.

Morphology

LIGHT MICROSCOPY

The cells have an average length of 9.5 ± 1.2 µm and a width of 7.2 ± 1.1 µm (n = 27, mean ± s). The apical portion of the cell is truncated, but some notches can occasionally be observed, corresponding to the four anterior lobes of the cell. Cell morphology varies from inverse pyramidal to U-shaped ( Figs 28, 29, 31 View Figs 28–31 ). The single chloroplast is bright light green, and cup-shaped with four anterior lobes ( Figs 29, 31 View Figs 28–31 ). The pyrenoid is excentric and located in the antapical part of the cell ( Figs 28, 29, 31 View Figs 28–31 ). Four thick flagella emerge from the flagellar pit, which is about ⅓ of the cell length ( Fig. 31 View Figs 28–31 ). The flagella are slightly longer than the cell. The two eyespots are located near the cell apex, often at the edge of a cell corner ( Figs 28–31 View Figs 28–31 ).

TRANSMISSION ELECTRON MICROSCOPY

This species presents morphological characteristics common to species of Pyramimonas subg. Vestigiferae McFadden, D.R.A. Hill & Wetherbee. These include two bi-layered eyespots ( Figs 32, 34 View Figs 32–42 ), an excentric pyrenoid with invading thylakoids ( Figs 28, 29 View Figs 28–31 ), a square synistosome ( Fig. 37 View Figs 32–42 ), and square underlayer scales ornamented with perforations ( Fig. 42 View Figs 32–42 ).

The flagella are covered by an underlayer of pentagonal scales about 40 nm wide (usually 38–42 nm) overlain by nine rows of limuloid scales. Each limuloid scale is 260–300 nm long and 170–190 nm wide, with a longitudinal spine directed anteriorly ( Figs 33, 42 View Figs 32–42 , 45 View Figs 43–45 ). At least two ribs diverged from the centre of the scale towards the margins, one located close to the spine base and the other more posteriorly ( Figs 33, 42 View Figs 32–42 , 45 View Figs 43–45 ). Three perforations of irregular size are found in the anterior part of the scale, one very close to the base of the longitudinal spine and the other two near the anterior end ( Figs 33, 42 View Figs 32–42 , 45 View Figs 43–45 ). Hair scales are present ( Fig. 33 View Figs 32–42 ) but were not examined in detail.

The cell body is covered with a layer of square box scales ( Figs 35, 41, 42 View Figs 32–42 ), in which the only ornamentation are eight perforations on the base, arranged in a square with round corners around the centre. The perforations are irregular in shape and size and occasionally very small. Each box scale is about 200 nm wide and about 80 nm high ( Figs 41, 35 View Figs 32–42 ). The crown scales, situated on top of the box scales ( Fig. 41 View Figs 32–42 ), have a square base with pointed edges, with a cross structure from the middle portion of each side of the outer rim, meeting at the centre. In each quadrant defined by the cross, the two parts of the rim were connected by two smaller structures arranged at an angle of c. 45 degrees in relation to the central cross, forming an intricate pattern on the base of the crown scale ( Fig. 39 View Figs 32–42 ). From each corner, a tubular structure rises upwards, the four structures meeting at the top, from where a central tubular column connects to the centre of the base ( Figs 35, 41 View Figs 32–42 , 44 View Figs 43–45 ). A layer of small square scales with perforations ( Fig. 38 View Figs 32–42 ) is present only in the flagellar pit ( Fig. 41 View Figs 32–42 ). Footprint scales can be found between the box scales and measure approximately 60 nm in length when measured in thin sections, one end being slightly thicker than the rest ( Fig. 40 View Figs 32–42 ).

Cell motion

In culture, cells usually swim forward in a straight line, rotating along the cell axis. To turn to a new direction, the cells stop, turn and then resume swimming. Cells can also be found with their flagella attached to a surface and moving in circles.

Phylogenetic analyses

Phylogenetic trees were based on alignments of 1683 positions of the SSU rDNA ( Fig. 46 View Fig ). The genus Pyramimonas made up a monophyletic clade, weakly supported (67/-/- as NJ/MP/ML), to which ‘Prasinopapilla vacuolata’ was the closest sister taxon ( Fig. 46 View Fig ). The designation ‘Prasinopapilla vacuolata’ was not validly published (no description) and no further information on the organism was found, except what was mentioned in GenBank. Pyramimonas octopora clustered within the Vestigiferae clade, which was monophyletic and highly supported (98/88/83). The clade Vestigiferae appeared as sister to the clade Punctatae , with no statistical support. Within the Vestigiferae clade, three main clades were observed: the basal clade included P. disomata Butcher ex McFadden, D.R.A. Hill & Wetherbee and received high bootstrap values (98/88/93 as NJ/MP/ML), whereas the two other clades were supported by the moderate bootstrap values 96/66/- (NJ/ MP/ML). The second clade comprised P. octopora , an unidentified Pyramimonas (strain RCC1987 from the Beaufort Sea; JN934670 View Materials ) and an uncultured chlorophyte (clone CCW80 from rRNA library-based sample from Cape Cod, US; AY180034 View Materials ). The third clade comprised the cold-water species P. diskoicola Harðardóttir, Lundholm, Moestrup & T.G. Nielsen and P. gelidicola McFadden, Moestrup & Wetherbee , and a few unidentified organisms ( Fig. 46 View Fig ).