Haslea crucigeroides var. australis Cefarelli, Simonato & Mascioni 2018, var. nov.
Creators: name: Cefarelli, Adrián O.
name: Mascioni, Martina
name: Simonato, Julián
name: Almandoz, Gastón O.
name: Vernet, Maria
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Chromista
Ochrophyta
Bacillariophyceae
Naviculales
Naviculaceae
Haslea
Haslea crucigeroides
Haslea crucigeroides var. australis cefarelli, simonato &amp; mascioni

description: Haslea crucigeroides var. australis Cefarelli, Simonato & Mascioni, var. nov. (Figs 2–18, 22–32)   
 LM observations (Figs 2–18): The cells are solitary and have two apically elongated chloroplasts, one on each side of the girdle, visible in valve view (Fig. 2). The frustules are rectangular with rounded corners in girdle view, height ca. 26 μm (Figs 3, 4). The valves are lanceolate to linear with a narrow pseudostauros and acute apices. Length 68.0–172.0 μm, width 8.2–23.5 μm (n = 83) and a highly variable length-to-width ratio (between 4.5 and 10.3) (Figs 5–18). The valve face is domed without a clear distinction from the mantle (Fig. 4). The raphe sternum is central, narrow and straight over the full length of the valve, with a small central area. Transverse striae 20–23 in 10 μm, longitudinal striae 19–24 in 10 μm (n = 29), both of them discernible with LM under an oil immersion objective.   
 SEM observations (Figs 22–32): Externally, the tegumental layer presents continuous longitudinal fissures demarcating longitudinal strips, except on the valve margin (Figs 22, 23). The central raphe fissures are shaped as enlarged droplets and are deflected towards the same side (Fig. 23). The terminal raphe fissures are strongly deflected to the same side of the valve (Figs 24, 25). The cingulum consists of a valvocopula (ca. 6 μm wide) and a narrower copula, both unperforated (Fig. 22).   
Internally, the basal layer is composed of transverse and longitudinal bars, crossed at a right angle delimiting the areolar foramina, the transverse and the longitudinal striae (Figs 26, 27, 29). The foramina, occluded internally by hymenes (Fig. 28), are generally square, except at the valve margin where they become rectangular in transapical direction (Fig. 27). The pseudostauros, with a thickening of about one central transverse bar, is attached to a short ridge on one side of the central nodule and to a longer ridge on the other side; the latter overlaps the raphe in almost its entire length except for the straight helictoglossae (Figs 29, 30). The two layers of the valve are joined by perforated saepes (Figs 31, 32), except at the valve margin where they are fused (Figs 27, 31).  
 Distribution: Haslea crucigeroides var. australis was found during the entire study period in the three sampling sites of the Beagle Channel, at a water temperature of 4.2–9.0°C. It reached a maximum concentration of 720 cells L- 1 at station BF in August 2016 (austral winter, Fig. 1, Table 1). It was also found with low frequency from net samples near icebergs in Antarctic waters (stations 37 and 100a, Scotia Sea, Table 1) during winter 2008 at water temperatures between -0.68 and -0.26°C and salinities from 34.09 to 34.14.   
 Holotype: ARGENTINA. Tierra del Fuego Province, Beagle Channel, Almirante Brown Bay (54°51’32.6’’S – 67°30’26.4’’W), plankton sample. Specimen in slide LPC 15222, illustrated in Fig. 5, located using England Finder between coordinates G31(2) and G32(1) (Herbarium of the División Ficología, Facultad de Ciencias Naturales y Museo, La Plata, Argentina).   
 Etymology: the varietal epithet “australis” (austral, southern) refers to the finding of this taxon in the Southern Hemisphere.
description: Published as part of Cefarelli, Adrián O., Mascioni, Martina, Simonato, Julián, Almandoz, Gastón O. & Vernet, Maria, 2018, Haslea crucigeroides var. australis, var. nov. (Bacillariophyta), a new marine diatom from southern South America and Antarctica, pp. 179-188 in Phytotaxa 357 (3) on pages 181-183, DOI: 10.11646/phytotaxa.357.3.2, http://zenodo.org/record/13706033