Cocconeis subantarctica sp. nov. from Kerguelen Archipelago (Austral Ocean) and comparison with Cocconeis stauroneiformis (W.Smith) Okuno

Riaux-Gobin, Catherine; Witkowski, Andrzej

doi:10.1515/ohs-2017-0036

Figures & Tables

Cocconeis subantarctica. SEM. monospecific clump (possibly in a fecal pellet). Scale bar: 20 μm

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

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)

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)

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)

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)

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.

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	Kerguelen	18.01.1991	sediment	intertidal	49°31′12″S	69°54′36″E

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	-
Length (µm) min-max	14.6 ± 1.0	15-32	9.6-36	-
Width (µm) min-max	8-15	8-21	5.5-27	-
Width (µm) min-max	10.3 ± 1.3	8-21	5.5-27	-
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)

Cocconeis subantarctica sp. nov. from Kerguelen Archipelago (Austral Ocean) and comparison with Cocconeis stauroneiformis (W.Smith) Okuno

Figures & Tables

Figure 1

Figure 2a-i

Figure 3a-g

Figure 4a-d

Figure 5a-e

Figure 6a-d

Figure 7a-g

List of materials examined, including locality, geographical coordinates

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)

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