Neidium collare, Hamilton & Savoie & Sayre & Skibbe & Zimmermann & Bull, 2019

Hamilton, Paul B., Savoie, Amanda M., Sayre, Cynthia M., Skibbe, Oliver, Zimmermann, Jonas & Bull, Roger D., 2019, Novel Neidium Pfitzer species from western Canada based upon morphology and plastid DNA sequences, Phytotaxa 419 (1), pp. 39-62 : 52-55

Neidium collare sp. nov. Figs 45–68

Individuals examined for morphological analyses: n = 31, examined for molecular analysis: n = 1.

Valves elliptic lanceolate to lanceolate with rostrate to broadly apiculate apices ( Figs 45–55 ). Valve length 44–96 μm, width 14.5–20.0 μm. Striae oblique to mildly convergent at apices, 14–18 in 10 μm. Areolae round to elliptical, 16–19 in 10 μm. Voigt faults on secondary side of valve. Central area transapically expanded, covering 1/3 to 1/2 valve width. Axial area linear from mid-valve to apex. In LM, raphe filiform and linear-elliptical. One large longitudinal canal present along each margin. Central raphe ends deflected extending ½ to ¾ across central area. Terminal ends forming bifurcate lacinia.

In SEM external view, raphe linear, curving to secondary side of valve close to apex ( Figs 56, 60, 61 ). Proximal raphe ends deflected, not hooked on small central mound ( Fig. 57 ). Distal raphe ends form a small triangular lacinia ( Figs 60, 61 ). Axial area straight to linear-elliptic with no surface depressions ( Figs 56, 57 ). One longitudinal canal along each margin with a single row or linear elliptic areolae ( Fig. 58 ). Areolae round to elliptic with no cribra formation evident ( Fig. 59 ). One round to elliptic areola opening from the longitudinal canals all the way to the apex. ( Figs 60, 61 ). Copulae open bands with two rows of pores (Figs, 58, 60, 61). Internal valve: Central area elevated with weak ghost striae. Central helictoglossae offset with silica interconnection ( Figs 62, 65, 66 ). Terminal helictoglossae forms vertically (not recurved) at edge of small terminal nodule ( Fig. 64 ). Canal along each margin elevated from valve face, extending from apex to apex with a single row of linear elliptic areolae ( Figs 63, 64, 67 ). Areolae opening recessed from valve face and covered by hymenes ( Fig. 67 ). Areolae chambered with transapical interconnections ( Fig. 68 , on mantle). Renilimbia around areolae along axial area, and longitudinal canals. Renilimbia also randomly scattered around areolae on the valve face ( Fig. 66 , arrows).

Type:— CANADA. British Columbia: Vancouver, VanDusen Botanical Garden, J. Holmes, December 28, 2016. Small stream at the end of Livingstone Lake (pond) (holotype: CANA! 126257-4, fig. 49 holotype specimen, circled on slide. Isotype ANSP GC65326 (specimen circled on slide). Genbank # See Table 2.

Etymology:—The specific epithet ( collare ), refers to the narrow neck of the valve approaching the apices.

Registration: http//phycobank.org/102031

Observations:—The elliptic lanceolate valve form with rostrate to apiculate rounded apices is represented in a number of Neidium species. Plastid rbc L DNA sequence, size (47–92 μm long), valve outline, one prominent longitudinal canal, weak to no ghost striae along the margins of the central area and formation of the proximal helictoglossae identifies this taxon. Neidium collare can be compared with N. ligulatum Liu et al. (2017: 22) and N. affine var. amphirhynchus ( Ehrenberg 1843: 417) Cleve (1894: 68) sensu Liu et al. (2017: 22 , figs 204, 207, 216–220). There is a continuum of shape changes from narrowing apiculate ( N. collare ) to rostrate apices ( N. affine var. amphirhynchus sensu Liu et al. ). Both of these comparable taxa have two clear helictoglossae at the central nodule while, N. collare has a merged helictoglossae formation. The distal helictoglossae are vertically projected against the terminal nodule in N. collare , while N. ligulatum and N. affine var. amphirhynchus sensu Liu et al. have recurved helictoglossae. Neidium ligulatum is at the smaller end of the size spectrum (47–64 μm long) with a slightly lower stria count (14–18 in 10 μm), while N. affine var. amphirhynchus sensu Liu et al. has a slightly higher stria count (18–20 in 10 μm). Genetic studies are required to delineate the relationship between these taxa.

Neidium collare can also be compared to N. oblique-striatum var. nipponicum Skvortzow (1936: 30 , as var. nipponica ) and N. oblique-striatum var. rostratum Skvortzow (1936: 30 , as var. rostrata ). The Skvortzow taxa have distinct oblique striations with rostrate and sagittate apices. N. oblique -striatum var. nipponicum is much broader (20–25 μm wide) and N. oblique-striatum var. rostratum has a higher stria count (24 in 10 μm). The single line drawing limits the understanding of the phenotype expression of these taxa.

In North America, N. collare can be compared with the smaller (36–53 μm) N. statuarium Siver & Hamilton (2005: p. 364) although N. collare has a lower stria count, more lanceolate valve and no extensive valve surface sculpture.

Figures

FIGURES 45–55. Neidium collare sp. nov. LM. Fig. 49, holotype. Scale bar = 20 μm.

FIGURES 56–61. Neidium collare sp. nov. SEM, external view. Fig. 56. Whole valve. Fig. 57. Central valve with longitudinal canal and transapical central area. Proximal raphe branches deflected. Fig. 58. Valve face mantle junction with epivalve, hypovalve and copula band. Fig. 59. Valve face with developed areolae. Areolae without finger-like cribra. Fig. 60. Apex with open bands of copulae. Copulae with 2 rows of pores. Lacinia weakly developed. Fig 61. Apex showing no apparent lacinia. Longitudinal canals extend to the tip of the apex. Scale bars = 30 μm: Fig. 56; 5 μm: Figs 57, 58, 60; 3 μm: Fig. 61; 2 μm: Fig. 59.

FIGURES 62–68. Neidium collare sp. nov. SEM, internal view. Fig. 62. Whole valve. Figs 63, 67. Recessed areolae and longitudinal canals at mid-valve and close to apex. Figs 65, 66. Central area with offset forming interconnected helictoglossae. Very weak surface depressions (ghost striae) present in the central area. Remnants of renilimbia present (arrows). Fig. 64.Apex showing an erect helictoglossa at terminal nodule and single longitudinal canal extending to the apex. Fig. 68. broken valve showing the canal. Scale bars: 20 μm: Fig. 62; 5 μm: Figs 64, 65; 3 μm: Figs 63, 66, 67; 1 μm: Figs 68.