Delicatophycus porosus Mironov, Chudaev & Jüttner, 2022

Mironov, Andrei, Chudaev, Dmitry & Jüttner, Ingrid, 2022, Cymbelloid diatoms from the River Adegoy, Krasnodar Territory, Russia, with a description of a new species Delicatophycus porosus sp. nov. (Cymbellaceae, Bacillariophyta), Phytotaxa 548 (1), pp. 26-38 : 31

Delicatophycus porosus Mironov, Chudaev & Jüttner , sp. nov.

LM description ( Figs 46–61 ):— Valves dorsiventral, semi-lanceolate, with moderately arched dorsal margin and slightly convex to almost straight ventral margin. Ends obtusely rounded and barely protracted. Valve dimensions (n=65): length 16.0–29.5 μm, width 5.0–6.0 μm, maximum length/width ratio 5.0. Axial area narrow-lanceolate, becoming wider in center of valve. Central area absent on ventral side and only sometimes slightly widened dorsally, and irregular, bordered by shortened striae of different length. Raphe clearly lateral and bent to ventral side near proximal ends. Central raphe ends simple. Terminal raphe fissures curved towards dorsal side. Striae slightly radiate, 17.5–20.5 in 10 μm. Areolae not discernible in LM.

SEM external valve surface ( Figs 62–67 ):— Terminal fissures deflected to dorsal side of the valve. Small notch present on dorsal side of each terminal fissure ( Figs 66–67 , white arrows). Striae undulate, areolae appear to be tildeshaped. APFs present, pores small round to oval, hence differ from tilde-shaped areolae in external view. APF divided by distal raphe fissure into two unequal sections. Dorsal part of APF ( Figs 66–67 , white arrowheads), composed of only two rows of pores, much smaller than ventral part ( Figs 66–67 , black arrowheads). Thus, the new species appears to have Type II APFs ( Liu et al. 2022).

SEM internal valve surface ( Figure 68–77 ):— Proximal raphe ends covered by dorsally curved flap ( Figs 71– 73 , white arrows). Central area irregular, with 1–2 shortened dorsal striae ( Figs 72–73 , black arrowheads). Raphe terminates with helictoglossae adjacent to the last striae ( Figs 74–77 , white arrows). Internal openings of areolae located in distinct transapical grooves with small stubs on margins ( Figs 71–73 , white arrowheads). Areola density 40.0–44.0 in 10 µm. Virgae much broader than striae, becoming narrower towards valve ends. APFs composed of pores occluded by convex tubercle ( Figs 74–77 ).

Type: — RUSSIA. Krasnodar Territory: Adegoy River, vicinity of Afonka Khutor , on mosses, 44.72580° N, 37.93992° E, 176 m asl, D. A . Chudaev , 27th May 2016 (Holotype: MW-D! slide 501s1 = Fig. 54 ; isotypes: slides LE A0000300 , LE A0000303 ) .

Etymology: —The specific epithet refers to the possession of apical pore fields.

Distribution and ecology: —The species is so far only known from the River Adegoy (samples 501, 502, 506, 507, 508, 509, 510). In the type material it is associated with several unidentified species in Achnanthidium Kützing (1844: 75) , Diatoma moniliformis ( Kützing 1834: 580) D.M. Williams (2012: 260) , Encyonopsis cesatii ( Rabenhorst 1853: 39) Krammer (1997b: 156) , Gomphonella olivacea ( Hornemann 1810: fasc. 24, pl. 1429) Rabenhorst (1853: 61), Gomphonema tergestinum (Grunow in Van Heurck 1880: pl. 25, fig. 40) Fricke in A. Schmidt (1902: pl. 234, figs 39–43), Navicula cryptotenella Lange-Bertalot in Krammer & Lange-Bertalot (1985: 62) and Nitzschia media Hantzsch (1860: 40) .

Figures

FIGURES 46–61. Delicatophycus porosus sp. nov. LM, type material, slide MW-D 501s1. Fig. 46 represents the post-initial cell. Fig. 54 represents the holotype. Scale bar = 10 µm.

FIGURES 62–67. Delicatophycus porosus sp. nov. SEM, type material, sample MW-D 501. External valve surface. 62–64. Entire valve. 65–67. Details of Fig. 62, note central area slightly widened dorsally (65); small notch on the dorsal side of each terminal fissure (66–67, white arrows); APFs divided by terminal fissures into two unequal sections, dorsal (66–67, white arrowheads) much smaller than ventral (66–67, black arrowheads). Scale bars = 5 µm (Figs 62–63), 2 µm (Fig. 64), 1 µm (Figs 65–67).

FIGURES 68–73. Delicatophycus porosus sp. nov. SEM, type material, sample MW-D 501. Internal valve surface. 68–70. Internal view of entire valves. 71–73. Inner valve center, note dorsally curved flap (71–73, white arrows); irregular central area bordered by shortened dorsal striae (72–73, black arrowheads); slit-like areolae openings with adjacent marginal stubs (71–73, white arrowheads). Scale bars = 2 µm (Figs 68–70), 1 µm (Figs 71–73).

FIGURES 74–77. Delicatophycus porosus sp. nov. SEM, type material, sample MW-D 501. Internal view of valve apices and APFs. Distal raphe fissures terminate with helictoglossae (white arrows); dorsal APF sections (white arrowheads) smaller than ventral (black arrowheads) and covered by convex tubercle. Scale bars = 0.5 µm (Figs 74, 76, 77), 1 µm (Fig. 75).