Alveolophora jouseanа (Moisseeva) Moisseeva emend. Usoltseva, 1971

Usoltseva, Marina V., 2022, Morphological variability of Alveolophora jouseana (Bacillariophyta) from type material, Phytotaxa 533 (4), pp. 194-204 : 195-196

Alveolophora jouseanа (Moisseeva) Moisseeva emend. Usoltseva

Emended description:— The frustules in valve view are round ( Figs 1–3 , 17–25 ), 8–31 µm in diameter. Most frustules in a girdle view are short straight cylinders, 2.2 – 7.0 μm in height ( Figs 4–6 , 8–16 ). The areolae are arranged on the mantle in straight single rows, 8 – 12 in 10 μm ( Figs 8 – 16 ), with 3 – 7 areolae in each row (8 – 15 in 10 μm of a row). The areolae are rounded. The linking spines are triangular shape with slight bicuspidate ends ( Figs 10, 16 ), or spatulate– shaped, broadened ( Fig. 15 ). The separating spines are pointed ( Figs 9, 11–14 ). The collar is structureless or thin ribbed at the edge ( Figs 11, 12, 16 ).

The valve face has round areolae ( Figs 1, 2 , 17–20 ). They are located over the entire surface ( Figs 17, 18 ), along the periphery in 1–3 rows of areolae ( Figs 1, 2 , 19, 20 ), or being completely absent ( Figs 3 , 21, 22 ). Sometimes the external valve face has granules at the centre ( Figs 19, 20 ) or one ring of granules near the periphery ( Figs 21, 22 ). The ringleiste is deep or narrow ( Figs 22–37 ).

The complex-chambered alveolae and pseudoalveolae can be observed from the inside of the valves. The valves with alveolae are very rare ( Fig. 26 ). More often, valves with pseudoalveolae are noted ( Figs 27–30, 36 ). Sometimes, alveolae can be observed among pseudoalveolae on the same valve ( Fig. 27 ). They are separated by longitudinal costae. Sometimes, there are no robust costae and pseudoalveolae, but there are longitudinal and transverse thickenings ( Figs 31, 32 ). Figures 33, 35 , and 37 display valves with micropseudoalveolae. The rimoportulae are very small, sessile, and located at the base of the costae ( Figs 26–34, 36 ). The channel of rimoportulae is straight ( Figs 30, 32, 36 ). The external openings of rimoportulae are small, round, and open in the first row of areola ( Figs 10, 11, 13, 16 ).

Figures

FIGURES 1–7. LM images of type material of Alveolophora jouseanа from the Miocene sediments of the Kizi strata (Lake Toni, Primorye, Far East, Russia). 1–3. External view of valves showing areolae position. 4–6. External view of mantle. 7. External view of valves showing costae and Ringleiste. Scale bars: 10 µm.

FIGURES 17–25. SEM images of type material of Alveolophora jouseanа from the Miocene sediments of the Kizi strata (Lake Toni, Primorye, Far East, Russia). 17–22. External valve face view showing areolae and granules. 23–25. Internal view of valves showing costae and Ringleiste. Scale bars: 10 µm.

FIGURES 8–16. SEM images of type material of Alveolophora jouseanа from the Miocene sediments of the Kizi strata (Lake Toni, Primorye, Far East, Russia). 8. General view of the sample. 9. Valves in external view showing variability of height and diameter. 11–14. Valves showing areolae rows and separating spines. 13. Valve with auxospora in girdle view showing areolae rows and external opening of rimoportulae (arrows). 10, 15–16. Valves in girdle view, showing linking spines, areolae rows and external opening of rimoportulae (arrows). Scale bars: 50 µm (Fig. 8), 10 µm (Figs 9–16).

FIGURES 26–37. SEM images of type material of Alveolophora jouseanа from the Miocene sediments of the Kizi strata (Lake Toni, Primorye, Far East, Russia). 26–37. Internal view of valves showing alveolae (alv), pseudoalveolae (p-alv), micropseudoalveolae (mpa), longitudinal costae (lc), transverse costae (tc), rimoportulae (arrows), rimoportulae chanels (r-ch) and Ringleiste (R). 37. Fragment of auxospora valve with micropseudoalveolae. Scale bars: 10 µm (Figs 27–29, 31–35, 37), 1 µm (Figs 26, 30, 36).