Climacosphenia scimiter A. Mann, 1925

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 scimiter A. Mann, 1925

Figs 29 , 30

Reference.

Mann 1925, p. 59, pl. 12, fig. 4.

Description from literature.

Cells tapering uniformly and strongly curved, the septa “delicate,” very narrow, "and showing at the middle either obscurely or not at all the break or sutural division common to specimens of this genus." Length 414 µm, width at apical pole 28 µm, stria density not specified.

Materials examined.

GUAM: GU52U-2!, GU52AH!, GU44Z-15!. F.S.M.: Chuuk: TK28!.

Observations.

Specimens fitting this description have been found in Guam and Chuuk, often together with C. elegantissima . Colonies on branched mucilaginous stalks, the nucleus near the apical pole between two of the widely spaced craticular bars (Fig. 29A ). Length 390-612 µm, maximum width 25-26 µm near apical pole, 8-10 µm across basal pole (Fig. 29A, B ). Stria densities outside the annulus 21 in 10 µm in lower part, 29 in 10 µm at apical pole; striae within annulus at basal pole about 16 in 10 µm, areolae more, or less aligned (Fig. 29C-E vs Fig. 30A ). Maximum distance across annulus 10 µm (Figs 29B, D , 30A ). While annulus appears discontinuous in SEM, phase contrast suggests continuity (Fig. 29C ). Valves delicate except at basal pole, apical striae hard to resolve in LM even with phase contrast (Fig. 29C, E ), costae not developed on either vimines or annulus, except near basal pole (Fig. 29D ). Two spines on apical pole of valve (Fig. 30A, D ). Two girdle bands present, both broad and with regular striae, but at different densities, valvocopula 20 in 10 µm, copula 24 in 10 µm (Fig. 30D ). Valvocopulae fimbriate with narrow, widely spaced craticular bars, unions all seamless (Fig. 30E-G ).

Taxonomic comments.

Observations are completely in accord with Mann’s (1925) description of specimens from the Philippines (Mann noted that data on the locations of the dredge samples were lost). Given also that this species was discovered not far from Micronesia, we are confident in the identification. We cannot accept that this is merely a curved C. moniligera , as suggested by Round (1982), because of the great difference in septum characters and differences in stria densities. Whether there exist straight versions of this species, or curved C. moniligera populations, remain open questions.

Figures

Figure 29. Climacosphenia scimiter, all from GU 52 X- 1 A colony of living cells on branched mucilage stalk B valve and valvocopula of cleaned material, LM-DIC, showing consistently narrow craticular bars C, E valve in phase contrast LM, showing more strongly silicified basal pole in C and weakly silicified apical portion in E, along with difference in stria density; note appearance of annulus at basal pole (arrow, C) D basal pole in SEM, oblique view, showing shallow mantle and very weak costae and apparently discontinuous annulus. Scale bars: 50 µm (A, B); 10 µm (C-E).

Figure 30. Climacosphenia scimiter, cont. All GU 52 X- 1 except D, GU 52 U- 2 A apical pole of valve, exterior view, showing stria density and spines B detail of valve internal aspect, showing absence of costae C detail of external valve face at basal pole, showing more scattered areolae inside annulus D whole mount of frustule, apical pole, showing spines and girdle bands E-G valvocopulae showing consistently seamless craticular bars. Scale bars: 100 µm (E); 10 µm (A, C, D, F, G); 5 µm (B).