Climacosphenia elegantissima Lobban & Ashworth, 2022

Lobban, Christopher S., Ashworth, Matt P., Camacho, Terance, Lam, Daryl W. & Theriot, Edward C., 2022, Revision of Ardissoneaceae (Bacillariophyta, Mediophyceae) from Micronesian populations, with descriptions of two new genera, Ardissoneopsis and Grunowago, and new species in Ardissonea, Synedrosphenia and Climacosphenia, PhytoKeys 208, pp. 103-184 : 103

Climacosphenia elegantissima Lobban & Ashworth sp. nov.

Figs 26 , 27 , 28

References.

? Hustedt 1914 in Schmidt et al. 1874-1959, pl. 308, figs 5-10;? Hustedt 1931-1959, fig. 626; Navarro and Lobban 2009, p. 136, figs 64, 65 (all as C. elongata Bailey).

Diagnosis.

Differing from C. elongata in the greater length, especially in the stem, and narrower, linear apical portion, and from C. truncata Hustedt ex Simonsen in the shape of the wide part of the valve.

Description.

Cells attached in small groups to stout, branched mucilage stalks (Fig. 26A, E ), at least 110 µm wide at the base and up to 2 mm long. Frustule generally deeper than wide, especially where stem first narrows below the apical pole, ratio there about 15 µm deep to 5 µm wide (Fig. 27A ). Nucleus situated between two more-widely spaced craticular bars about 120 µm from apical pole (Fig. 26A, D ); plastids lenticular. Valves 750-1305 µm long, linear toward apical pole, 22-24 µm wide, then tapering to a long linear stem, 5 µm wide, expanding to 10 µm at the pole (Figs 26A-C , 27A ). Stria density 27-28 in 10 µm through most of the valve but 18-21 in 10 µm near basal pole, sparser and more scattered inside annulus near basal pole (Fig. 27D, E, G ). There was a crescent of scattered areolae at top of mantle at apical pole (Figs 27D, G , 28A ) (noticed in Climacosphenia spp. by Round 1982: figs 15, 16, 25). Annulus apparently open at basal pole, sides ± parallel in the wide area, 8.3 µm apart, in the stem 2.3 µm apart, expanded to 5 µm at the basal pole (Fig. 27C-G ). Two or more stout spines on external apical pole (Figs 27D , 28A ), shallow transapical costae throughout except near basal pole (Fig. 27F, G ). Pseudoseptum absent (Fig. 27F, G ). Two girdle bands (Fig. 28A ): valvocopula (Figs 26B, F , 27B, C, F, I , 28A-C ) with fimbriate inner edge (Fig. 28B ), stria density 19 in 10 µm (Fig. 28A, B ) but increasing around foot pole, where there was also a row of pores on pars interior (Fig. 27I ). Craticular bars widely spaced in wide part of the cell, with widest space corresponding to the location of the nucleus (Figs 26B , 27B ); in the stem becoming much closer together (Figs 26B , 28C ), often paired with the two bars apparently growing from opposite sides (Fig. 28C ). In one specimen from culture, we observed porous bands of silica around several craticular bars near the apical pole (Fig. 28D ). Copula fimbriate, more densely striated than the valvocopula but less than the valve, 22 in 10 µm (Fig. 28A, E ). A search of abundant girdle views in whole mounts showed no sign of a pleura.

Holotype

(designated here). Specimen at 16.1 mm E, 12.8 mm S of the mark on slide 1861; deposited at Academy of Natural Sciences, Drexel University, Philadelphia, accession number ANSP GC20108. Fig. 27B .

Registration.

Phycobank http://phycobank.org/103246.

Type locality.

Guam: Apra Harbor, Scuba Beach, 13.464°N, 144.656°E, epiphytic on filamentous red algae in farmer fish territory, collection number GU52U-2, 10 May 2015. C.S. Lobban and M. Schefter leg.

Additional materials examined.

GU44AI-5! (culture), GU44BM-7!, GU52G-B!, GU52X-1!, GU52Y-3B!, GU52AI-1!.

Etymology.

Superlative of elegans, with reference to the slender appearance of the extremely long cells.

Taxonomic comments.

The width of the apical pole and especially the distance between the annular lines are narrower than in C. elongata (Table 5 ) and the stem is also narrower, though the basal pole is inflated and slightly wider than C. elongata . Hustedt’s (1914) drawings of C. elongata have the greatly extended stems that are present in our new species, but the apical portions of his cells are generally elliptical rather than linear. However, the valvocopula ( Hustedt 1914, pl. 308, fig. 6) is notable in having parallel sides as far as the large space (i.e., where the nucleus would have been), so it is possible they represent C. elegantissima . Climacosphenia truncata from Borneo is also illustrated there (pl. 308, figs 1-4); it also has a very long stem but possesses an essentially triangular blade with a bluntly rounded apical pole. C. elegantissima is common as an epiphyte on filamentous seaweeds in Guam farmer fish territories and such habitats around the western Pacific/ IndoPacific may yield new material of C. truncata and other Climacosphenia spp.

Round (1982) showed porous bands of silica on craticular bars near the basal pole of both species only found in Hawaiian material. We saw them only once on apical bars in C. elegantissima . Their distribution and function are unknown.

Figures

Figure 26. Climacosphenia elegantissima sp. nov., (GU 52 AI- 1 except B from GU 52 U- 2) A, D living cell, showing extreme length and location of nucleus (arrow) B acid-cleaned complete valvocopula, emphasizing the very long, narrow stem C portion of colony, showing cells attached to mucilage stalk; the two cells to right of middle are 1300 µm long E detail of mucilage stalk with bases of attached cells. Scale bars: 250 µm (A-C); 50 µm (D, E).

Figure 27. Climacosphenia elegantissima sp. nov., cont. GU 52 AI- 1, except GU 52 U- 2 (B) and GU 52 X- 1 (G, H) A whole mount of colony in SEM, showing contrasting width versus depth of frustule in the stem (arrows at approximately same distance from apical poles) B portion of holotype in LM; although specimen is broken in two places, the basal pole of the valvocopula is also present, total length ca. 835 µm C apical pole of valve and valvocopula in LM, showing parallel sides of annulus and some misaligned unions in the craticular bars D SEM of external valve surface at apical pole, showing annulus (double-headed arrow) continuing around apical pole, two spines, and crescent of scattered areolae at top of mantle (arrow) E external valve surface at basal pole, showing variation in areola density and alignment within the annulus, apparent discontinuity of annulus at pole, and width of basal pole relative to stem (cf. H at same scale) F internal aspect of basal pole of valve and valvocopula, showing absence of pseudoseptum (arrow) and associated structure in valvocopula G, H internal aspect of valve at apical pole, showing crescent of scattered areolae (arrow) and in the narrow stem, respectively I oblique view of basal pole with valve and valvocopula, showing increase in areola density on the valvocopula around the pole (arrow) and short row of pores on pars interior (arrowhead). Scale bars: 200 µm (A); 50 µm (B); 10 µm (C-H); 5 µm (I).

Figure 28. Climacosphenia elegantissima sp. nov., cont. GU 52 U- 2 (A), GU 52 X- 1 (B, C), GU 44 AI- 5 culture (D), GU 52 AI- 1 (E) A whole mount of frustule apical pole in girdle view, showing two girdle bands, patch of irregular areolae on the valve mantle (arrow), spines (arrowheads) B part of valvocopula broken away and showing a solid circular cross-section of the craticular bar (arrowhead) and well-developed fimbriae (arrow) C portion of valvocopula from stem, showing double craticular bars, ingrowths from opposite sides D apical pole with valvocopula showing porous bands of silica around several craticular bars E detail of copula showing stria density and fimbriate margin on pars interior. Scale bars: 10 µm (A, D, E); 5 µm (B, C).