Palusphaera probertii Archontikis & Jer.R. Young, 2021

Archontikis, Odysseas A. & Young, Jeremy R., 2021, A reappraisal of the taxonomy and biodiversity of the extant coccolithophore genus Palusphaera (Rhabdosphaeraceae, Prymnesiophyceae), Phycologia 60 (6), pp. 589-602 : 596

Palusphaera probertii Archontikis & Jer.R. Young sp. nov.

Figs 12–16

PREVIOUS RECORDS UNDER MISAPPLIED NAMES: Rhabdosphaera longistylis J. Schiller sensu Reid (1980, p. 157 , pl. 4, fig. 3). Palusphaera vandelii sensu Cros (2002, p. 36, pl. 9, fig. 3); Cros & Fortuño (2002, pp 24-25, fig. 22A); Yang et al. (2003, p. 38, pl. IV, fig. 1); Young et al. (2003, pp 56-57, pl. 25, fig. 8); Kahn & Aubry (2006, p. 334, pl. 2, figs 4-6); Andruleit (2007, p. 43, fig. 6d); Kahn (2007, p. 38, pl. 2, figs. 4-6); Wang et al. (2012, p. 5, pl. 2, fig. H).

DESCRIPTION: Coccosphere, monomorphic and spherically shaped, but usually seen collapsed, composed of c. 45–60 BCs. BCs broadly elliptical to subcircular in plan view, with narrow rims and nearly flat bases. Rim with typical Rhabdosphaeraceae rim structure. Central area filled by a lamellar cycle of numerous rod-shaped, slightly overlapping crystal segments; no radial cycle is observed. Central process bears a thin, hollow, styliform spine with no collar; spine structure composed predominantly of numerous elongate elements arranged parallel to the axis of the spine. The spine is remarkably long compared to the coccosphere diameter. The proximal planolith side has three robust angular nodes around the central pore.

DIMENSIONS: Coccosphere diameter c. 7–8 μm excluding processes and c. 13–18 μm with processes. BCs c. 1.5 μm × c. 1.1 μm; rim c. 0.2 μm in length and width. Spine is typically c. 5–8 μm long.

HOLOTYPE: 118-55 (specimen illustrated in Fig. 12 ), stub no. 257/0, deposited at the collections of the Natural History Museum, London under the designation PM NF 4591 118-55 .

PARATYPES: 212-09 (stub no. 511/3, designation PM NF 4875 212-09 ); 188- 03 (stub no. 459/2, designation PM NF 4814 188-03 ); 297-77 (stub no. 729/ 0, designation PM NF 4928 297-77 ); 212-19 (stub no. 511/3, designation PM NF 4875 212-19 ). Specimens of these stubs are illustrated by Figs 13–16 .

TYPE LOCALITY: North-eastern Atlantic Ocean (29°45.7'N, 17°55.8'W, depth 25 m, 24 September 1997, P 233B Expedition, Station P233b-2).

DISTRIBUTION: Subtropical waters.

NUMBER OF SPECIMENS STUDIED: Ten.

ETYMOLOGY: After Dr. Ian Probert (Station Biologique de Roscoff) in recognition of his many contributions to extant coccolithophore biology and physiology.

REMARKS: The species is similar to P. vandelii but with noticeably smaller BCs that present a more broadly elliptical shape. The outer rim of the BCs on the distal side is usually narrower than that of P. vandelii , and the styliform central process is hollow and predominantly composed of a single set of very long elements aligned parallel to the long axis. This clearly opposes the spine structure of P. vandelii , which is formed by numerous shorter (c. 1 μm) elements in a spiral arrangement.

Figures

Figs 12–16. SEM micrographs of Palusphaera probertii sp. nov. Fig. 12. Holotype and complete coccosphere specimen. Scale bar = 2 μm. Fig. 13. Detailed view of a specimen with broadly elliptical planoliths showing a central pore and three angular nodes on the proximal side (a) and clockwise imbrication on the distal side (b); broken spine (c) is long and thin, formed of crystallites arranged parallel to the spine axis. Scale bar = 2 μm. Fig. 14. Collapsed coccosphere. Scale bar = 5 μm. Fig. 15. Incomplete coccolith in distal view; crystal elements show dextrogyral curvature (arrow). Scale bar = 1 μm. Fig. 16. Detailed view of a broadly elliptical coccolith, small in size, and its broken styliform process. The lath-like crystal segments of the spine are arranged parallel to its long axis (see arrow). Scale bar = 1 μm.