Figure 1
Cocconeis subantarctica. SEM. monospecific clump (possibly in a fecal pellet). Scale bar: 20 μm
Table 1
List of materials examined, including locality, geographical coordinates
| Locality | Island | Date | Material | Zonation | Latitude | Longitude |
|---|---|---|---|---|---|---|
| Mayès I. | Kerguelen | 20.01.1991 | sediment | 20 m deep | 49°28′20″S | 69°55′55″E |
| Pointe Bizet | 18.01.1991 | intertidal | 49°31′12″S | 69°54′36″E |
Figure 2a-i
Cocconei subantarctica. LM (Pointe Bizet, Kerguelen Main Island). Complete frustule (a-b); often subdiscoid (d-e, g); elliptic small specimen with SVVC without fimbriae (c arrowhead); SVs with one virga slightly larger on one side of the valve (d-e arrowheads), SV areolae are not arranged in a regular axial pattern (d-e); small elliptic SV with pearl-like marginal areolae (f); RVs (g-i) with one virga slightly larger on one side (h arrowhead), and RV areolae arranged along axial rows. Note the marginal hyaline rim and large marginal areolae. Scale bar: 10 μm
Figure 3a-g
Cocconeis subantarctica. SEM (Pointe Bizet, Kerguelen Is.). SV in the external view, note the subround shape (an illustration of the holotype); small elliptic SV with oblong complex marginal areolae separated from the rest of the stria by a hyaline rim (b framed arrow), and SVVC possibly open at both apices (b arrowheads); SV convex and flat (c); SV apex with 4 cingular bands (numbered 1-4), from which several are open; note a ligula (d arrowhead); one SV virga larger on one side (e arrowhead); detail of SV ornamentation with a kind of hymenate pierced rotae (f arrowhead), detail of the marginal complex and larger areolae (g). Scale bars: 5 μm (a-b), 3 μm (e), 2 μm (c), 500 nm (f), 400 nm (g)
Table 2
Morphometrics and features of 1) C. subantarctica sp. nov. (Kerguelen Is., present study), 2) C. stauroneiformis (cf. Riaux-Gobin & Romero 2003, Kerguelen Is.) and 3) C. stauroneiformis sensu Romero (1996, diverse origin)
| Cocconeis subantarctica sp. nov. present study n = 80 | Cocconeis stauroneiformis (W.Smith) Okuno sensu Riaux-Gobin & Romero (2003) | Cocconeis stauroneiformis (Rabenh.) Okuno sensu Romero (1996) | Cocconeis scutellum var. posidoniae M.De Stefano, D.Marino & L.Mazzella (2000) | |
|---|---|---|---|---|
| Valve face | subround to elliptic | elliptic | elliptic to elliptic-lanceolate | elliptic |
| Length (µm) min-max | 12-18 | 15-32 | 9.6-36 | - |
| 14.6 ± 1.0 | ||||
| Width (µm) min-max | 8-15 | 8-21 | 5.5-27 | - |
| 10.3 ± 1.3 | ||||
| SV stria density min-max | 11-14 | 8-9 | 6-11 | 12-14 |
| 12.6 ± 0.9 | ||||
| uniseriate, rotate and reniform hymenate occlusions | wavy transapical rows, externally complex, internally uniseriate | externally tetra- to pentaseriate, internally uniseriate | uniseriate, transapical rows of areolae with axial bar, rotate or not | |
| RV stria density min-max | 12-14 | 8-10 | 6-12 | 18-23 |
| 13 ± 0.6 | ||||
| uniseriate, hymenate reniform occlusions | biseriate in mid-valve, complex on the margin | biseriate, tetra- to pentaseriate at the margin | uniseriate | |
| SV sternum | straight, relatively large | straight, narrow, externally depressed (thickened internally) | straight, narrow, concave | straight, narrow |
| SV fascia | one virga larger on one side | absent | absent | absent |
| Marginal SV areolae | transapical to quadrangular group of hymenate reniform occlusions | undifferentiated from the other areolae | - | biseriate to triseriate occlusions |
| SV marginal rim | often present | absent | absent | absent |
| SV internal virgae | large, flat | thickened | elevated | narrow, not elevated |
| SVVC | with short undulations, possibly open at both ends | short fimbriae | reduced fimbriae, open at both ends | digit fimbriae |
| RV fascia | often assymetrical | more or less wide | present | absent |
| RV marginal rim | present | robust | present | present |
| Marginal RV areolae | transapical and complex large group of concentric hymenate reniform occlusions | apically elongated group of hymenate reniform occlusions | group of hymenate reniform occlusions | striae biseriate on the mantle |
| RVVC | open, without fimbriae | - | short fimbriae, open at one apex | fused fimbriae |
| Biogeography | Kerguelen Is. | Kerguelen Is. | diverse origin | Ischia I. (Italy) |
x ± σ (mean and standard deviation when available) - (not specified)
Figure 4a-d
Cocconeissubantarctica. SEM (Pointe Bizet, Kerguelen Is.). SV in the internal view. Eroded SV in the internal view with flat virgae (a arrow); SVVC with undulating edge (b arrowhead), flat virgae, and SV areolae with a kind of pierced rota (b arrow); broken frustule showing RV marginal large and complex areolae (c arrow), SVVC still in place, with undulating short fimbriae (c arrowhead); detail of marginal complex areolae with domed hymenes still in place (d arrowhead) and low virgae (d arrow). Scale bars: 3 μm (a), 1 μm (b), 500 nm (c-d)
Figure 5a-e
Cocconeis subantarctica. SEM (Pointe Bizet, Kerguelen Is.). RV in the external view, note the round shape (a) with oblong complex marginal areolae and the presence of a larger asymmetrical virga (a-b arrowheads); detail of the marginal row of complex areolae with a kind of pegs (d arrowhead); apex void of areolae (c framed arrow), and close proximal raphe endings (c arrowhead); detail of a terminal raphe ending (e arrowhead). Scale bars: 5 μm (a), 3 μm (b), 1.8 μm (c), 1 μm (d), 700 nm (e)
Figure 6a-d
Cocconeis subantarctica. SEM (Pointe Bizet, Kerguelen Is.). RV in the internal view. Marginal rim and subtle helictoglossa (6 arrowheads) and narrow RVVC with no fimbriae (a twin arrowheads); central area, with proximal raphe endings bent in opposite directions (b arrowheads). Entire valve with the cingulum, note the axial rows of areolae (c); detail of an apex with subtle helictoglossa, complex marginal areolae (d arrowhead) and open copula (d arrows). Scale bars: 3 μm (a, c), 1 μm (b, d)
Figure 7a-g
Cocconeis scutellum var. stauroneiformis W.Smith (1852: Supp. Pl. 30, fig. 34 β) (a). Cocconeis scutellum Ehrenberg in Smith (1852: pl. 3, fg. 34) (b). Cocconeis scutellum var. stauroneiformis W.Smith in Van Heurck (1880: fgs 10-11) (c). Cocconeis scutellum var. stauroneiformis Sm. in Peragallo & Peragallo (1897-1908: pl. 4, fg. 4) (d). Cocconeis paniformis Brun and allied, in Schmidt et al. (1874-1959: pl. 189, fgs 16-20, see text) (e). Cocconeis scutellum var. y in Roper (1858: pl. 3, fg. 9) (f). Cocconeis scutellum Ehrenberg f. parva in Peragallo & Peragallo (1897-1908: pl. 4, fg. 3) (g). Scale bars: 20 μm. Refer to Roper (1858) and Schmidt et al. (1874-1959) for other illustrations.