Cavinula scutelloides Lange-Bertalot

• Main Authors: Cvetkoska, Aleksandra, Levkov, Zlatko, Hamilton, Paul B., Potapova, Marina
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2014
• Subjects: Biodiversity; Taxonomy; Chromista; Bacillariophyta; Bacillariophyceae; Naviculales; Cavinulaceae; Cavinula; Cavinula scutelloides; Tundra; Alaska
• Online Access: https://doi.org/10.5281/zenodo.5149459; http://treatment.plazi.org/id/8A5C9F1CA463FF9D1DA98C612097F80D

Cavinula scutelloides (W. Smith) Lange-Bertalot (Figs 101–106, 165–171) Basionym: Navicula scutelloides W. Smith 1856 (in Synopsis of British Diatomaceae, Vol. 2, 107, figs: 32–60, 61–62) Valves elliptical, to round in smaller specimens with widely rounded apices. Valve length 12–26 µm, width 9.5–20 µm. Striae radiate, 8–10 in 10 µm, uniseriate with coarse elliptic to rounded areolae. Areolae internally occluded with hymen. Central area can be transversely expanded on one side. A few short striae present around valve center; all striae continue on mantle. Axial area narrow, linear-lanceolate. Raphe system linear; externally, proximal raphe features tear-drop like on valve face. Distal raphe fissures bent in the same direction, question mark-like, terminating on the valve mantle. Internally, raphe positioned on elevated sternum. Proximal raphe features curved in same direction, hook-like, and distal raphe features terminate with helictoglossae. Type :––Omersby, Norfolk, United Kingdom. Here presented in Figs 103, 104 (type material). Observations:— This taxon is identified (Figs 103, 104 from type material) based on shape, size and the enlarged areolae on the valve face. The closest taxon to compare with would be C . pseudoscutiformis , however they are separated by shape of proximal raphe fissures, length of alternating striae around the central area, and areolae size, and orientation. In addition, C . scutelloides and C . pseudoscutiformis are found under different water acidity conditions. Distribution:— Currently this taxon is recognized as a cosmopolitan species across the temperate zone of the northern hemisphere, and relatively absent from the northern tundra with the possible exception of a small deep lake from northern Alaska (Foged 1971). C. scutelloides was identified in 26 samples in the CANA database. According to those identifications, this taxon is present in the central part of North America e.g. the province of British Columbia, Ontario, Quebéc (Canada) and New York and Massachusetts (USA). The ...