Table 4.
Comparison of morphological features of Gomphonema zapitaja sp. nov. and related species.
| G. zapitaja sp. nov. | G. cymbelliclinum | G. angustatum | |
|---|---|---|---|
| Outline | clavate, asymmetrical to the longitudinal axis | slightly heteropolar, linear to linear-lanceolate | lanceolate to rhombic lanceolate, larger specimens less club-shaped than the smaller |
| Headpole | acutely rounded | rostrate to subcapitate | wedge-shaped, blunter to more pointed |
| Footpole | narrowly rounded | rostrate | barely narrower in larger specimens |
| Axial area | narrow but expands near the central area | very narrow, linear | narrowly linear |
| Central area | formed by shortening of the central striae | large, asymmetric, wider on the side opposite to the isolated pore, bordered on each margin by a single shortened stria | usually extending over more than half of the valve by strong unilateral shortening of the central striae |
| Valve length (μm) | 13.5–34.5 | 16.0–37.5 | 16–48 |
| Valve breadth (μm) | 5–7 | 4.5–6.7 | 5.3–6.7 |
| Striae number in 10 μm, | 11–13 | 9–16 | 10–14 |
| Areolae type | occluded by large c-like semilunar siliceous flaps, merged with the areolar surface | not occluded | occluded by large c-like or reniform semilunar siliceous flaps, merged with the areolar surface |
| Areolae number in 10 μm | ≈40 | 30–35 | 35–40 |
| Internal opening of isolated pore | slit-like | slit-like | slit-like |
| Distribution | Russia, Baikal | Europe | Europe |
| References | This study | [55,57] | [54,55] |