Neidium lavoieanum, 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 : 56-57

Neidium lavoieanum sp. nov. Figs 69–82

Individuals examined for morphological analyses: n = 27, examined for molecular analysis: n = 1.

Valves linear to linear-elliptic with capitate apices ( Figs 69–74 ). Valve length 58–70 μm, width 14.–15.0 μm. Striae mildly oblique throughout, 20–22 in 10 μm. Areolae elliptical, 15–18 in 10 μm. Voigt faults on secondary side of valve. Central area transapically expanded, covering ½ to ¾ valve width. Axial area linear to linear elliptic from mid-valve to apex. In LM, raphe filiform and linear-elliptical. One 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, proximal raphe ends deflected and hooked on small central mound ( Fig. 77 ). Raphe with small thickened ridges mid-way across valve. Distal raphe ends form small triangular lacinia extending to base of mantle ( Fig. 78 ). Axial area straight to linear-elliptic with no surface depressions ( Fig. 76 ). One longitudinal canal along each margin, extending to base of terminal raphe fissure ( Fig. 78 ). Longitudinal canal with two external pores, one on valve face, one on mantle ( Fig. 75 ). Areolae round to elliptical, no cribra occlusions evident. Internal view, helictoglossae at raphe ends not, deflected up, not recurved ( Figs 79, 81, 82 ). Terminal apex without prominent pseudosepta ( Fig. 82 ). Central helictoglossae separate, in linear alignment ( Fig. 81 ). Central area broad with recessed coverings between virgae. Areolae chambered ( Fig. 80 ). Areolae openings round to linear-elliptic, covered by hymenae ( Fig. 80 , arrow). Renilimbia scattered, primarily around longitudinal canals and axial area ( Figs 81, 82 ). Longitudinal canal with single row of elliptical areolae covered with hymenae.

Type:— CANADA. British Columbia: Vancouver, VanDusen Botanical Garden, J. Holmes, December 28, 2016. Small stream at the end of Livingstone Lake (pond) (holotype: CANA! 126257-1, fig. 71 holotype specimen circled on slide.). Isotype ANSP GC65329 (circled specimen on slide). Genbank # See table 2.

Etymology:—The specific epithet ( lavoieanum ) is presented in honour of Dr. I. Lavoie for her exceptional work on ecosystem modelling, diatom ecology, toxicology and teratology.

Registration: http//phycobank.org/102032

Observations:—The linear to linear-elliptic valve form with capitate apices is represented in a number of Neidium species. At present plastid rbc L DNA sequence, size (59–70 μm long), one prominent longitudinal canal, and formation of the proximal helictoglossae identifies this taxon. Neidium lavoieanum can be compared with N. longiceps (W.Greg. 1856: 8) R. Ross (1947: 210) from North America ( Lefebvre et al. 2017), but separated by larger size ( N. longiceps 28–47 μm long, 8–12 μm wide), and lower stria count ( N. longiceps 30–36 in 10 μm), and a distinct difference in the rbc L gene. All other morphological features are similar between the two taxa. Another similar taxon is N. angustatum Liu et al. (2017: 11) , but N. angustatum is narrower (10–11 μm), with a higher stria count (25–27 in 10 μm), different striae orientation and the apices are more rostrate than capitate. No DNA metrics are available for comparison.

Genetic Analysis

The maximum-likelihood (ML) analyses of rbc L sequence data present a broad taxonomic tree across the genus Neidium ( Fig. 83 , Supplement B). Interestingly, the rbc L genetic divergence among the Neidium taxa examined was relatively low (<1%), however the genetically identified clades separate well with morphology, indicating that rbc L is conserved among taxa of this genus. The new species described here were between 0.4 to 0.96% different from their nearest neighbour. For example, Neidium collare (n=1) was 0.96% (6 bp different over 625 bp) different from N. bisulcatum (Lagerst. 1873: 31) Cleve (1894: 68) . Neidium lavoieanum was separated from N. cf. productum (W.Sm. 1853: 51) Cleve (1894: 69) (Czarnecki culture, UTEX collection) with the smallest difference, 0.40% (3 bp over 751 bp). Neidium iridis was also present in the creek sample (Lake Victoria, VanDusen Botanical Garden) and was 0.67% different (5 bp over 750 bp) from N. lavoieanum . These differences are in line with established Neidium species, for example N. fossum and N. longiceps are 0.51% different (6 bp over 1168 bp). In the ML analysis, the genus Neidium was monophyletic relative to the outgroup taxa included ( Neidiomorpha , Luticola and Scoliopleura ) and had medium bootstrap support (84%, Fig. 83 ). Neidiomorpha binodis and N. binodeformis were associated with Luticola ventricosa and sister to S coliopleura peisonis . Within the genus Neidium , N. hitchcockii was sister to the other species included in this study. A clade including N. fossum Lefebvre & P.B.Hamil. (2015, 214), N. longiceps , N. sacoense Reimer (1959: 29) ( Patrick & Reimer 1966: 402, pl 37: 3), and N. promontorium Lefebvre & P.B.Hamil. (2017: 696, 697) had high support (98%), while many of the other relationships between species were poorly supported in this analysis ( Fig. 83 ).

Figures

FIGURES 83. RaxML phylogenic tree construction showing boostrap (BS) confidence levels using the gene rbcL for selected taxa within the genus Neidium.

FIGURES 69–74. Neidium lavoieanum sp. nov. LM. Fig. 71, holotype. Scale bar = 10 μm.

FIGURES 75–78. Neidium lavoieanum sp. nov. SEM, external view. Fig. 75. Half valve. Fig. 76. Surface areolae with no occlusions and axial area mid-way along the valve. Fig. 77. Elevated central area with elongated areolae along the margin and recurved proximal raphe endings. Fig. 78.Apex showing lacinia and longitudinal canals extending to the apex. Scale bars = 10 μm: Fig. 75; 3 μm: Figs 76–78.

FIGURES 79–82. Neidium lavoieanum sp. nov.SEM, internal view.Fig. 79. Half valve showing valve outline.Fig. 80. Brokenlongitudinal canal with areoale and internal valve face areolae. Arrow indicates renilimbia. Fig. 81. Internal central nodule with a covering over the verminae along the margin. Helictoglossae separated and aligned. Fig. 82. Apex, showing longitudinal canal extending to the apex and an erect helictoglossa next to hyaline thickened apex. Scale bars = 10 μm: Fig. 79; 5 μm: Fig. 81; 3 μm: Figs 80, 82.