Scrippsiella acuminata (Ehrenberg) Kretschmann, Elbrächter, Zinssmeister, S. Soehner, Kirsch, Kusber et Gottschling

Lewis, Jane, Taylor, Joe D., Neale, Klaire & Leroy, Suzanne A. G., 2018, Expanding known dinoflagellate distributions: investigations of slurry cultures from Caspian Sea sediment, Botanica Marina (Warsaw, Poland) 61 (1), pp. 21-31 : 27

Scrippsiella acuminata (Ehrenberg) Kretschmann, Elbrächter, Zinssmeister, S. Soehner, Kirsch, Kusber et Gottschling

( Figures 26–28 )

Cells were brown in colour with a pale central nucleus ( Figure 26 ) and 21–26 µm long and 20–28 µm wide. Cells had a conical epitheca and a rounded hypotheca and were circular when seen in apical view ( Figures 26 and 27 ). The cingulum was median and only slightly offset. Characteristic cysts were formed in one isolate ( Figure 28 ). One Caspian and one Black Sea isolate were successfully sequenced and placed in the tree alongside Scrippsiella trochoidea (F. Stein) Loeblich III (considered a heterotypic synonym of S. acuminata by Kretschmann et al. 2015) from the Lafeyette River in the USA ( Figure 32 ). Two other Scrippsiella species are of note to review here – S. plana and S. spinifera Honsell et Cabrini. In their paper describing S. plana from the Caspian Sea for the first time, Luo et al. (2016) clearly illustrate both species which each have characteristic motile cells. Scrippsiella plana has a distinctive flattened morphology and S. spinifera an elongate morphology with small antapical spines. The cultures developed in this study did not show these thecal morphologies; furthermore, a sequenced isolate formed characteristic S. trochoidea cysts. The taxonomy of Scrippsiella sensu lato remains enigmatic with further resolution awaiting sequencing of key species ( Luo et al. 2016).

Figures

Figure 32: Molecular phylogeny of dinoflagellates isolated from the Caspian and Black Sea sediments inferred from partial large-subunit rDNA (LSU rDNA) sequences based on the maximum likelihood (ML) method. Oxyrrhis marina was used as an outgroup. Numbers on branches represent ML bootstrap values for that node; bootstrap values>50% are shown. Sequences from isolates in this study are indicated in bold. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. Scale bar = nucleotide substitutions per site. The analysis involved 42 nucleotide sequences. Sequences generated in this study are available from GenBank, Accessions KY921615-KY921624. There were a total of 503 positions in the final dataset.

Figures 2–31: Light micrographs of Caspian Sea dinoflagellates grown in culture from sediments. (2–6) Gonyaulax baltica, culture CS-ST1-005. (2) Lateral view of cell showing cingulum offset. (3) Dorsal view of cell showing general shape and wide cingulum. (4) Antapical view of cell showing broad sulcus. (5) Ecdysed cell showing antapical spines. (6) Hypotheca of cell showing plate reticulation, smooth sulcus and intra plate growth bands. (7–10) Gonyaulax sp., culture CS-ST2-001. (7) Lateral view of cell showing general shape, cingulum offset, apical horn and antapical spine. (8) Ventral view of cell showing broad offset cingulum. (9) Dorsal view of cell in outline showing pronounced apical horn and definite shoulders. (10) Ecdysed theca showing solid antapical spine and heavy plate reticulation. (11–14) Gymnodinium aureolum. (11–13) Culture CS-ST7-009. (14) Culture A3. (11) Cell showing overall shape, central nucleus and radiating chloroplasts. (12) Ventral view of cell showing sulcal-cingulum arrangement. (13) Dorsal view of cell. (14) Cells in duplet. (15–20) Kryptoperidinium foliaceum. (15 and 19) Culture CS-ST1-007. (16 and 18) Culture CS-ST1-001. (17 and 20) Culture A6. (15) Ventral view of cell showing leaf-like curvature, central nucleus, median cingulum and eyespot. (16) Lateral view of cell showing dorsoventral flattening and eyespot. (17) Theca stained with trypan blue. (18) Cysts in ventral view. (19) Cyst in lateral view. (20) Cysts in mucoid capsule. (21–25) Lingulodinium polyedra. (21 and 23) Culture CS-ST1-002. (22) Culture CS-ST1-004. (25) Culture CS-ST1-003. (21) Ventral view of cell showing cingulum offset and first apical plate. (22) Dorsal view of cell showing horse-shoe shaped nucleus. (23) Ecdysed hypotheca showing distinctive polyhedral shape and plate reticulation. (24) Squashed cell showing thecal plates. (25) Cyst from Station 1 sediment. (26–28) Scrippsiella acuminata. (26) Culture CS-ST2-006. (27–28) Culture D10. (26) Outline view of cell. (27) Outline view of cell. (28) Cyst formed in culture. (29–30) Woloszynskia sp. (29) Culture D3 showing cell with eyespot. (30) Cell showing general outline from culture D4. (31) Impagidinium caspienense from palynological preparation (core CS03/1 at 32 cm) showing archeopyle. Scale bars = 10 µm.