Gomphonema correntinum Frenguelli (1933: 422

Guerrero División Ficología, José M., 2025, Lectotypification of Gomphonema correntinum Frenguelli (Gomphonemataceae, Bacillariophyceae), Notulae Algarum 369, pp. 1-4 : 1-2

Gomphonema correntinum Frenguelli (1933: 422 , pl. IV [4]: figs 24, 25) ( Figs 2 –17)

Lectotype (here designated): slide 261(4) Frenguelli Diatom Collection at LPC. Fig. 8 (Finder: O/40) represents the lectotype.

Registration (lectotypification): http://phycobank.org/105478

Type locality: Argentina, Corrientes province, Estero Carambola (28° 27' 22.7" S, 57° 49' 14.9" W). On aquatic macrophytes, 8.xii.1923, leg. J. Frenguelli.

Description: Valves clavate-lanceolate, with the widest part at the middle or slightly towards the apiculate headpole. Footpole slightly protracted and acutely rounded. Valve dimensions (n=14): length 28–42 μm, width 8.5–10 µm. Axial area straight and narrow, occupying about one sixth of the valve width. Central area unilateral and rectangular, delimited by a very shortened stria opposite to the rounded stigma. Raphe filiform and somewhat sinuous. Central raphe endings slightly drop-like expanded. Terminal raphe fissures bent to the same side, in opposite direction to the stigma. Striae uniseriate, parallel at centre becoming radiate towards the apices, 14–15 in 10 µm at the centre, 16–17 in 10 µm at the poles, continuous onto the valve mantle. Areolae with C- or 3-shaped volate occlusions, 40 in 10 μm, hardly discernible with LM. Internally, areolae with round foramina. Apical pore field located on the mantle, at the footpole only, composed of several rows of rounded poroids, divided in two areas by the raphe fissure. Mantle low, in right angle to the valve face. Girdle composed of open copulae, with one row of small poroids, 40 in 10 μm.

No. 369 (10 April 2025)

ISSN 2009-8987

Notes: In contrast to our measurements, Frenguelli (1933: 396) reported in his original description greater valve dimensions (length 41–57 μm, width 13 μm) and a lower stria density (10–12 in 10 μm). These discrepancies in morphometrics are usual when re-examining Frenguelli’s original materials (see Vouilloud & al. 2022 and references therein). Later records of G. correntinum are scarce but all come from subtropical areas in NE Argentina: Frenguelli (1953) reported this species from a basalt quarry in Misiones province and Herbst & Maidana (1983) found it in the flood plain of Paraná River in Chaco province.

Gomphonema Ehrenberg is one of the most taxon-rich genera of diatoms ( Radhakrishnan & al. 2020) with more than 930 recognised species ( Guiry & Guiry 2025). While many species possess clavate valves, only a handful have an apiculate apex and an acutely rounded footpole. We compared G. correntinum with the most similar species G. perapicatum Metzeltin & Lange-Bertalot and G. graciloides Hustedt to assess whether it should be considered a valid species.