Mallomonas dimorphus, Kim & Lee, 2022

Kim, Han Soon & Lee, Jae Hak, 2022, Silica-scaled chrysophytes from Mt. Sinbul wetland in South Korea, Journal of Species Research 11 (4), pp. 253-265 : 258

Mallomonas dimorphus sp. nov.

Han Soon Kim ( Figs. 15-20 )

Description. The cells are small (16.5-18 × 22-24 μm), subglobose or ellipsoid with a rather short protruding collar. Its scales are arranged in transverse rows. Each scale is overlapped with the scales positioned behind them in the same row and by the scales in the row above and below them ( Fig. 15 ). Three types of scales were found, the base plate of all of which are perforated with small and evenly spaced pores. All of them possess an upturned posterior rim encircling half the scale. (i) 5-6 apical scales are asymmetric and, elongated-oblong, with one lateral edge being concave, a relatively large and flat dome, the anterior part slightly narrowed, and the apex projected with short papillae ( Fig. 16 , arrowhead). Its shield is divided into anterior and posterior parts by a well-developed longitudinal rib that connects to an anterior submarginal rib ( Fig. 16 , arrow). The anterior half is covered with well-developed straight or irregularly curved parallel or reticulated ribs, most of which continue with those of the dome. The posterior half is marked with irregularly fine and sparse ribs and large reticulation ribs. (ii) Body scales are broad elliptical to oval with a proximal rim, variously developed ribs and a relatively small flat dome. Its shield area enclosed by continuous submarginal ribs is covered with ribs in various thicknesses and patterns; and is separated into anterior and posterior areas by a slight to strongly hooded V-shaped rib (some scales with a round or Ushaped rib) continues with submarginal ribs. The rib patterns of the anterior half including the dome consist of labyrinth-like systems of semicircular ribs and straight or irregularly curved ribs, most of which continue with those of the dome. The distal portion of the continuous submarginal ribs is marked with small papillae ( Fig. 17 , arrow). In the proximal area, thick ribs form 3-6 large meshes or pores which are subdivided by less prominent ribs ( Fig. 18 , arrows). Short ribs extend at 90° angles onto the flange along two-thirds of the continuous submarginal ribs in the proximal area. (iii) The following is present: two types of smaller body scales, symmetric scales with circular ribs instead of a V-rib structure ( Fig. 19 , arrow) and only smaller-sized asymmetric scales ( Fig. 20 , arrow) similar to body scales.

Its cells are mostly covered with bristles, which are short (11-12 μm long), slightly curved, smooth and, strongly tapering to a fine point ( Fig. 20 ).

Dimension. Cells 16.5-18 × 22-24 μm, Apical scales 4-4.2 × 5.3-5.5 μm, Large body scales 3.2-4.2 × 5-6 μm, Small body scales 2-2.7 × 3.7-5 μm, Bristles 11-12 μm long.

Type locality. Mt. Sinbul wetland, Sangbuk-myeon , Ulju County, Ulsan Megacity, South Korea (129°00.03′E, 35°25.32′N, sea level 745 m, pH 5.5-6.2, water temperature 0-9.1℃, EC 15.2-44.8 μS cm -1) .

Holotype. Fig. 15 (iconotypus) from materials collected on March 27, 2020 deposited at the Herbarium of Kyungpook National University ( KNU), Daegu (KNUSBW2020 0327).

Etymology. The specific epithet “ dimorphus ” refers to the fact that the ornamentation of the shield has two types of patterns.

Sectio Torquatae Momeu & Péterfi

Series Doigonianae Asmund & Kristiansen

Figures

Figs. 13-15. Silica-scaled chrysophytes from Mt. Sinbul wetland, 13. Mallomonas striata, 14. M. tonsurata, 15. Whole cell of M. dimorphus sp. nov. Scale bars=13, 14(1 μm), 15(5 μm).

Figs. 16-20. Mallomonas dimorphus sp. nov., 16.Apical scales with short papilla(arrow head) and longitudinal rib (arrow), 17. Body scales showing flat dome marked with irregularly ribs such as labyrinth, perforated base plate and small papillae (arrow) on the anterior submarginal rib, 18. Body scales showing hooded V-shaped rib, large meshes or pores and strutted posterior flange, 19, 20. Showing the small scales(arrows) with circular ribs and short, smooth needle like bristles. Scale bars=1 μm.