Mallomonas divida Nĕmcová & Kreidlová, 2013

Němcová, Yvonne & Kreidlová, Jana, 2013, Two new species of Mallomonas (Chrysophyceae: Synurales): Mallomonas temonis and Mallomonas divida, Phytotaxa 87 (1), pp. 11-18 : 14

Mallomonas divida Nĕmcová & Kreidlová sp. nov. ( Figs 2A–K )

Type:— FRANCE. Aquitaine: unnamed lake south of the Reserve Naturelle Marais d'Orx , 43° 34.398´N, 1° 23.464´W, 23 m a.s.l., sample collected by Y. Nĕmcová & J. Kreidlová, 27 March 2011. Figure 2E .

Collar, body, and rear scales are discerned. Collar scales, surrounding the flagellar pore (3.1 – 3.3 × 1.9 – 2.1 µm), are of trapezoid shape and relatively broad at the base ( Figs 2A – D ). The large and suboval dome has a small peak that rises as the extension of the dorsal submarginal rib. The dome is partly reticulated by circular meshes and possesses a ridge dorsally marked with delicate struts ( Figs 2B – C ). The submarginal rib is distinctly developed at the dorsal part of the scale. The flange is smooth, forming a prominent elongated protrusion on the dorsal edge of the collar scale adjacent to the dome ridge. A proximal border circulates the posterior and dorsal parts of the scale. The submarginal rib is smooth and less prominent at the ventral part of the scale. The shield of the scale is covered by more or less regularly arranged delicate papillae, and divided by one or several rows of more distinctive papillae ( Fig. 2D ). At the articulation, the submarginal rib window (depression without secondary layer) possesses the row of 3−5 pores. Body scales (2.6 – 2.9 × 1.7 – 2.0 µm) are rhomboid and domeless ( Figs 2E – H ). The posterior submarginal rib is not prominent; it is more flattened and smooth. There is no anterior submarginal rib; the anterior flange and shield are not distinctly separated. There are rows of papillae outlining the outer surface of the anterior scale part, whereas the posterior flange is smooth. The ornamentation of the shield is similar to the collar scales. Posteriorly on the shield, a window with 2 – 3 pores is present. Rear scales (2.2 – 2.5 × 1.2 – 1.5 µm) are asymmetric with one anterior flange considerably longer than the other, and possessing a short spine ( Figs 2I– J ). The rearmost scales (1.1 × 0.8 µm) are oval with a spine ( Fig. 2J ). Bristles not observed. Cyst unknown. Dimensions of the cell unknown, first row is formed by approximately 5 – 6 collar scales ( Fig. 2K ).

Habitat:— Mesotrophic lake.

Distribution:— France, the species was only found in the type locality.

Etymology:— The epithet refers to shield divided by one or several rows of more distinctive papillae.

Observations:— Selected environmental variables were measured during the sampling: pH 6.6, conductivity 395 µS⋅cm -1, surface water temperature 16.1°C.

Figures

FIGURE 2. Mallomonas divida. A–D, collar scales with different shield patterns. The dome is partly reticulated by circular meshes; A–C, scales viewed in a transmission electron microscope (TEM); D, a scale viewed in a scanning electron microscope (SEM). The pattern on the shield is formed by one or several rows of more distinctive papillae; E–H, body scales with different shield patterns; E–G, scales viewed in TEM; H, a scale viewed in SEM; I, a rear scale with one anterior flange considerably longer than the other; J, two rearmost scales possessing spines; K, the scales comprising the scale case. Bar = 0.5 µm, if not stated otherwise. A–J are shown at the same magnification.