Actinella leontopithecus-rosalia

Tremarin, Priscila I., Kim, Kwang I. M. B., Marra, Raquel C. & Ludwig, Thelma A. V., 2016, Additional data on morphology of Actinella leontopithecus-rosalia Costa (Bacillariophyta, Eunotiaceae), Phytotaxa 247 (4), pp. 259-266 : 260-264

Actinella leontopithecus-rosalia Costa, Iheringia 46: 64, fig. 18, 1995 emend. Tremarin, Kim & T. Ludwig.

Synonym: Actinella lange-bertalotii Kociolek in Jahn et al., Studies on Diatoms, p. 148, figs 46–50, 99‒103, 2001, syn. nov.

Frustules clavate in girdle view. Valves dorsiventral and heteropolar, 18.1–90.3 μm long, 2.6–4.6 μm wide at median region. Dorsal margin convex and ventral margin concave. Headpole subcapitate, 1.4–2.8 μm wide, slightly dorsal bent in the larger valves. Footpole rounded, 1.4–2.0 μm wide. Raphe reduced at the ventral margin of valve, with external distal ends hook-like on the valve face. Helictoglossa distinct. Striae parallel in the center of the valve becoming radiate towards the poles, 16–19 in 10 μm, composed by continuous rows of rounded areolae, 3–5 in 1 μm. One small spine at the headpole of each valve. A single rimoportula per valve on headpole or footpole, oriented parallel to apical axis. Cingulum composed of 3–4 open bands perforated by two rows of puncta.

Type:— BRAZIL. Rio de Janeiro: Reserva Biológica de Poço das Antas, Juturnaíba reservoir, station IV, 24 April 1990 (Lectotype here designated: HAS!, slide n° 4283)

Costa (1995) described Actinella leontopithecus-rosalia as distinctly heteropolar, with round poles, long and thin valves, 45–74 μm long, 3.0–3.5 μm wide, and having 18–19 striae in 10 μm. Spines were not observed and a single specimen was illustrated in phase contrast. The author designated a permanent slide (slide n° 4283) as holotype and cited two sampling stations as type locality: station I corresponding to marginal puddles at EF-103 railroad, and the station IV, to Juturnaíba reservoir. We examined the holotype slide 4283 assigned to station IV, and we concluded that this is the correct type locality.

The analyzed population of A. leontopithecus-rosalia is here illustrated in valve and girdle views based on several specimens. The morphometric range (length, width and striae density) found is greater than that recorded by Costa (1995) ( Table 2). In addition, we expanded the description of the species with information about the ultrastructure of frustule in SEM.

In their review of Actinella from South America, Kociolek et al. (2001) proposed A. lange-bertalotii Kociolek in Kociolek et al. (2001: 148), based on samples from Surinam as locus typicus and Brazil (Jurucuí lake), comparing the species with A. leontopithecus-rosalia . Both species are distinguished by the smaller length, smaller width and fewer striae density in A. lange-bertalotii . Kociolek et al. (2001) examined the type slide (n° 4283) of A. leontopithecus-rosalia stating that no specimens were found that fit in the species circumscription. Costa had shown only one individual and maybe it has hindered the real recognition of the species.

We examined the paratype material and Guaraguaçu river specimens related to A. leontopithecus-rosalia under SEM and noticed no differences between this species and A. lange-bertalotii , except for the rimoportula which can occur at both extremities of the valve, and not only in the footpole as cited by Kociolek et al. (2001). Therefore, we propose the synonymization of A. lange-bertalotii with A. leontopithecus-rosalia .

Many Actinella described from tropical regions may differ in relation to the occurrence of marginal spines ( Siver et al. 2010). Species may have spines around the entire valve margin [as A. punctata Lewis (1864: 343) ], only small apical spines [as A. manguinii Kociolek, Rhode & Williams (1997:186) ] or are totally devoid of spines [as A. aotearoaia Lowe, Biggs & Francoeur in Sabbe et al. (2001: 324), A. indistincta Vyverman & Bergey in Sabbe et al. (2001: 328– 329) and A. muylaertii Sabbe & Vyverman in Sabbe et al. (2001: 329)]. The small apical spine of A. leontopithecus-rosalia may be observed in SEM and LM when frustules are in girdle view.

The genus Actinella is described presenting two rimoportulae per valve, one at each apex ( Round et al. 1990). However, A. australis (Manguin in Bourrelly & Manguin 1949:167) Kociolek, Rhode & Williams (1997: 184–185), A. manguinii Kociolek, Rhode & Williams (1997:186) and many species described in Australasian countries ( Sabbe et al. 2001) have only a single rimoportula per valve, and this character is also seen in A. leontopithecus-rosalia .

Actinella modesta Moser, Lange-Bertalot & Metzeltin (1998: 86–87) described from New Caledonia ( Table 2) is comparable to A. leontopithecus-rosalia , differing by the small spines around the valve margin, the striae with irregular distribution of areolae, and the terminal raphe end being more distant from the headpole than in A. leontopithecus-rosalia ( Moser et al. 1998) .

This study provides more information concerning the geographic distribution of A. leontopithecus-rosalia to tropical and subtropical regions of South America. We believe that the intraspecific phenotypic variation here documented will light the recognition of the taxon and will allow its geographic expansion.