Craticula molestiformis (Hust.) Mayama 1999

Novis, Phil M., Braidwood, Jasmine & Kilroy, Cathy, 2012, Small diatoms (Bacillariophyta) in cultures from the Styx River, New Zealand, including descriptions of three new species, Phytotaxa 64 (1), pp. 11-45 : 36-37

Craticula molestiformis (Hust.) Mayama 1999 ( Figs 148–159 , 164 )

Frustules elliptic-lanceolate in valve view, 11.9–12.5 µm long, 3.1–3.8 µm wide, biraphid. Valve faces and margin curved, with narrow copulae ( Fig. 158 ). Striae transverse except for a slight radial tilt around the narrow central area, composed of longitudinally aligned areolae that are slightly elongate longitudinally, except adjacent to the central area, where they are laterally elongated; 33–35 in 10 µm. Raphe linear, with straight and slightly widened central endings ( Fig. 159 ), and apical endings turned towards the primary side of the valve. Sternum pronounced and thickened.

References: — Krammer & Lange-Bertalot 1986, p. 130, figs 45:1–9; Mayama 1999, p. 2, figs 1, 2.

Specimens examined: —CHR618420! (cleaned frustules made from culture LCR-S:44:2).

Distribution: — Craticula molestiformis is widespread, but has seldom been reported from New Zealand. There are two unpublished records: 7 frustules seen in Lake Aviemore, February 2002, and 1 frustule seen in Lake Pupuke, March 2002.

Molecular data:— Two German strains were very close matches (p-distance=0.001) to the Styx strain: Craticula molestiformis strains AT-36.klein, isolated from a river in Weser, and AT-5Nav02, isolated from a canal in Maschinenfleet. The Styx strain formed a robust clade with these strains in both Bayesian and MPB analyses ( Fig. 164 ). The full dataset was 1745 bp long, with 104 variable sites (65 parsimony-informative, 32 occurring within our 822 bp fragment). The model selected using BIC and included in the Bayesian analysis was T92+G+I.

Observations: —The Styx strain agrees well with the description and illustrations given by Mayama (1999). In particular, the narrow central area bounded by laterally elongated areolae and the narrow copulae are almost identical. We also did not observe any “craticulate” internal valves in our specimens. The striae were often difficult to discern by LM, but the thickened sternum was always very obvious. The length variation of our specimens was far less than that reported by Krammer and Lange-Bertalot (9.5–22 µm).

Figures

FIGURE 164. Bayesian phylogenies of Craticula and Fistulifera strains from the Styx River, for 18S rDNA (left) and rbcL (right). Support numbers above branches are Bayesian posterior probabilities / Maximum Parsimony bootstrap values. Scale bar = 0.1 subsitutions/site. See text for substitution models and description of data sets.

FIGURE 148–159. Craticula molestiformis, strain LCR-S:44:2, CHR618420. Scales: Fig. 148, 10 µm; Fig. 152, 5 µm (use in Figs 152–157); all others 1 µm. Figs 148–151. Live cells viewed by LM, showing lobed plastids (girdle view in Fig. 151). Figs 152–157. Cleaned frustules viewed by LM, showing thickened raphe/sternum and transverse striae. Figs 158, 159. Cleaned frustules viewed by SEM. Fig. 158, valve with intact margin, showing longitudinally aligned, slightly elongated areolae, narrow central area bordered by laterally elongated areolae, and narrow copulae; Fig. 159, valve with intact central raphe termini.