Haslea clevei, 2015

Sterrenburg, Frithjof A. S., Tiffany, Mary Ann, Hinz, Friedel, Herwig, Wulf E. & Hargraves, Paul E., 2015, Seven new species expand the morphological spectrum of Haslea. A comparison with Gyrosigma and Pleurosigma (Bacillariophyta), Phytotaxa 207 (2), pp. 143-162 : 152-155

H. clevei Hinz, Hargraves & Sterrenburg , sp. nov. ( Figs 18 : LM, 47–57: SEM)

Type:— “ E251, Finnmark, Maasö, a, P. T. Cleve, 12.1881, von E. Weissflog ”, geographic coordinates 71°00’ N, 24°00’E. Holotype BRM ZU9 /89, slide coordinates 10.2 E, 2.3 S. This material is a subsample of Cleve & Möller 312, “ Finnmark, Maasö”.

Valve ( Figs 18 , 47, 48 ) delicate, inconspicuous in LM even with contrast enhancement, slender lanceolate, 85–110 μm long, 10–12 μm wide, apices acute. Striae perpendicular, transverse circa 23, longitudinal circa 30 in 10 μm. Most of the transverse striae are offset, the striae on one side of the raphe ridge aligning with the interstriae on the other ( Fig. 47 , inset). Axial and central area so narrow as to be inconspicuous in LM. In SEM, the tegumental layer shows little surface relief ( Figs 50, 51 ). External raphe fissures slightly undulating in the centre, central external raphe endings extremely approximate and depressed as two tiny pits so close together that they tend to fuse ( Fig. 50 and inset; Fig. 56 , horizontal arrow), terminal raphe fissures long and curved ( Fig. 51 ). Internally, the raphe ridge is not markedly twisted sideways ( Fig. 49 ). Central bars highly variable: from an elevated central bar on one side and two elevated small ridges on the other ( Fig. 49 ) to only one vestigial bar ( Fig. 57 ). At the apices, there is a prominent projecting helictoglossa ( Fig. 52 ). Basal layer: foramina practically square, transverse bars of the grate clearly wider than the longitudinal ( Figs 49, 57 ). The two layers of the valve sandwich are joined by longitudinal upright saepes with large perforations ( Fig. 53 inset, Figs 54, 55, 56 oblique arrows). These perforations are located underneath (in Fig. 53 ) the transverse bars of the basal layer grate.

Etymology:— named after P.T. Cleve, as the sample is part of the collection Cleve & Möller.

Habitat:— littoral-marine sediment.

Distribution:— The type locality is now known as Måsøy, Norway. Rare in the type material, less so in a sample from the Indian River Lagoon, Florida, see under Observations.

Observations:— In several slides of Cleve & Möller 312 examined, no additional specimens have been seen, but the species is so delicate that we may simply have overlooked it. Samples (collection Hargraves) from the Indian River Lagoon, Florida, USA, contained specimens matching the type, including the central external raphe endings in “pits” (horizontal arrow in Fig. 56 ), but the central bars ( Fig. 57 ) are obviously as variable as in Gyrosigma and Pleurosigma . In several specimens observed ( Figs 54–56 ) valve development is not yet complete: the basal layer and saepes are fully formed, the fissures in the tegumental layer are being filled in. All perforations of the saepes are located on top (in the figure!) of the transverse bars of the basal layer.

The offset of the striae on either side of the raphe ridge has not so far been described in Haslea and is not limited to H. clevei . It is also evident in H. salstonica , see Massé et al. 2001: Plate II, figure E, and H. provincialis sp. inedit., see Gastineau et al. 2014, Fig. 15.3 , but is not mentioned in the texts of these publications.

Of the smaller ostrearia -like taxa, H. hyalinissima superficially resembles H. clevei , but the latter is almost double the size of the former and has much coarser transverse striae (23 as against 27–28 in 10 μm). H. crystallina also has finer transverse striae (26 in 10 μm) than H. clevei and is longer and broader.

Figures

FIGURES 10–20. New Haslea species, LM images (DIC).All bars = 10 μm. All except Fig. 11 are stacks of 12–22 separate images. FIGURES 10, 11. H. staurosigmoidea sp. nov. Fig. 10. Holotype, Fig. 11. Isotype, aspect in normal DIC corresponding to what is seen on visual inspection.

FIGURES 47−57. H. clevei sp. nov., SEM. figs 47–53. Type material, Finnmark, Norway. figs 54–57. Material from Florida, USA. SEM. Fig. 47. General aspect, exterior, bar = 20 μm. Inset: detail, magnified 4x, showing offset striae. Fig. 48. General aspect, interior, bar = 20 μm. Fig. 49. Centre, interior, bar = 2 μm. Note vestigial central bar. Fig. 50. Centre, exterior, bar = 2 μm. Inset (2x enlargement): central raphe endings in “pits”, almost fused. Fig. 51. Apex, exterior, bar = 2 μm. Fig. 52. Apex, interior, bar = 2 μm. Note prominent helictoglossa. Fig. 53. Interior view of valve where basal and tegumental layer have separated, bar = 2 μm. Inset (2x enlargement): saepes with large perforations (arrow) located underneath the transverse basal layer bars. Figs 54, 55.Apex, exterior, 2 different specimens, bars = 1 μm. Valve morphogenesis not yet finished, longitudinal fissures still to be filled in.Arrows mark perforations in saepes. Fig. 56. Centre, exterior of developing valve, longitudinal fissures still to be filled in. Horizontal arrow marks raphe endings in “pits”, oblique arrows mark perforations in saepes. Bar = 3 μm. Fig. 57. Centre, interior. Vestigial central bar, compare with Fig. 49 for variability. Bar = 2 μm.