Eunotioforma synedraeformis (Hust. 1952: 137) Kociolek & Burliga, 2013

Burliga, Ana Luiza, Kociolek, John Patrick, Salomoni, Saionara Eliane & Figueiredo, Daniela, 2013, A new genus and species in the diatom family Eunotiaceae Kützing (Bacillariophyceae) from the Amazonian hydrographic region, Brazil, Phytotaxa 79 (2), pp. 47-57 : 53-55

Eunotioforma synedraeformis (Hust. 1952: 137) Kociolek & Burliga , comb. nov.

Basionym:— Eunotia synedraeformis Hust. (1952: 137) . TYPE:— BRAZIL. Lago Jurucui (Holotype: BRM L4 /41, Simonsen 1987: Pl. 566, figs 1–8)

Eunotioforma conversa (Hust. 1952: 136) Kociolek & Burliga , comb. nov.

Basionym:— Eunotia conversa Hust. (1952: 136) . TYPE:— BRAZIL. Lago Jurucui (Holotype: BRM 318 /24, Simonsen 1987: Pl. 565, figs 1–8)

Eunotioforma curvula (Hust. 1952: 137) Kociolek & Burliga , comb. nov.

Basionym:— Eunotia curvula Hust. (1952: 137) . TYPE:— BRAZIL. Rio Ereri-Tal (Holotype: BRM L4 /48, Simonsen 1987: Pl. 568, figs 1–5)

Eunotioforma elongata (R. M. Patrick 1940: 3) Kociolek & Burliga , comb. nov. et stat. nov.

Basionym:— Desmogonium rabenhorstianum var. elongatum R. M. Patrick (1940: 3) . TYPE:— BRAZIL. Municipio de Belém — Drouet 1315 (Holotype: ANSP AGC 25415)

Eunotioforma genuflexa (Nörpel-Schempp in Lange-Bertalot & Metzeltin 1996: 50) Kociolek & Burliga,

comb. nov.

Basionym :— Eunotia genuflexa Nörpel-Schempp in Lange-Bertalot & Metzeltin (1996: 50). TYPE:— FINLAND. Julma Ölkky bei Kuusamo – Dorn (Holotype: Eu-SF 117, J. W. Goethe—Universität Frankfurt) .

Eunotioforma weisingii (Lange-Bert. 1993: 40) Kociolek & Burliga , comb. nov.

Basionym:— Eunotia weisingii Lange-Bertalot (1993: 40) .

Eunotioforma recta (Hust. ex Simonsen 1987: 38) Kociolek & Burliga , comb. nov.

Basionym:— Eunotia recta (Hust. ex Simonsen 1987: 38) . TYPE:— USA. Columbia River, Oregon (Lectotype: BRM L3/5, Simonsen 1987: Pl. 37, figs 1–6).

In terms of placing the genus Eunotioforma in a phylogenetic context of the eunoitioid diatoms, it may form an early branch within the Eunoticaeae, sharing the putative synapomorphy of asymmetry about the apical axis with all the members of the family except Peronia . Berg (1948) considered the evolution of the raphe system in pennate diatoms. He took the approach that the earliest known fossil species of Eunotia would have the most primitive raphe type, concluding that the raphe in eunotioids evolved independently from the other raphid diatoms, an approach also taken in Simonsen’s (1979) consideration of diatom phylogeny. In most cases, for example, “ Eunotia mauiensis A. Berg ” (a diatom illustrated by Berg 1948, Fig. 4 , but apparently never formally described—it is absent from Van Landingham 1969 and Fourtanier & Kociolek 2011), the raphe is similar to most extant species in the genus and in Trachysphenia Petit in Folin & Périer (1877:190), where the majority of the raphe is positioned on the valve mantle and there is only a short portion of the external distal raphe end evident on the valve face ( Berg 1948). It is interesting to note that Trachysphenia baltica A. Berg (1948:3) appears to have a central sternum, where the interruption of striae is in the middle of the valve, similar to most other diatoms, raphe-bearing and rapheless taxa.

Hustedt (1952) took a different tack in his consideration of the raphe system in this group. Hustedt reasoned that the split between the eunotioid diatoms and naviculoid diatoms occurred with a taxon similar to Peronia , and that further evolution of the raphe system in the eunotioid line was from this primitive form (with the raphe positioned in or near the centre of the valve), with more derived forms represented by more “typical” members of the genus Eunotia . Hustedt made this conclusion in part by considering a number of Brazilian species, which he perceived to be intermediate between the raphe of Peronia and most Eunotia species.

Mann (1984) in considering the evolution of the raphe system in general, made the assumption that the raphe system was homologous amongst all raphe-bearing taxa. According to Mann, the primitive raphe type was positioned in the centre of the valve along the longitudinal axis, and that in eunotioid diatoms, the raphe rotated towards and onto the valve mantle. Interruption of the striae also shifted towards the ventral margin in his consideration of raphe evolution.

Krammer and Lange-Bertalot (1991), in their consideration of the genus Eunotia in European freshwaters, recognized 3 major subgroups within the genus. One of these subgroups, (their “Schlüsselgruppe C”) has species where the raphe is quite curved (the group is reflected in the updated work by Lange-Bertalot et al. 2011 as “Key Group A” or taxa with a “U-turn raphe” p. 24) and has a significant proportion of the raphe on the valve face, relative to other subgroups within the genus. A small portion of the axial area is found in the centre of the valve, but the majority of the interruption of the striae is positioned near the ventral margin.

Kociolek (2000) reviewed many of the species described by Hustedt (1952) with SEM, as well as other members of the Family. He confirmed Hustedt’s observations (illustrating the position of the raphe, striae interruptions, rimoportulae, etc.), and suggested the scenario of Hustedt (1952) was congruent with the observations based on SEM.

The evolutionary scenario depicted in Figure 5 is not only congruent with the hypothesis of non-raphid pennae lineages branching before the Eunotiophycidae, and the rest of the raphid diatoms branching afterwards (as suggested by Kociolek 2000) but is identical with the phylogenetic analysis of diatoms with molecular data ( Sims et al. 2006; Theriot et al. 2011). This supports the idea of a single origin of the raphe system in the diatoms, and its rotation towards the ventral margin (and in some cases the reduction or complete loss of the raphe) in the eunotioid lineage Wetzel et al. (2012). Reduction in the raphe in the eunotioid diatoms has support from fossil evidence as well ( Novitski & Kociolek 2005; Siver & Wolfe 2007). An alternative scenario was published by Williams and Reid (2006a) where Amphora Ehrenberg ex Kützing (1844:107) and Eunophora Vyverman, Sabbe & Mann in Vyverman et al. (1998:96) were considered in the analysis of the Eunotiophycidae. Two outcomes were offered. One showed Amphora basal to the clade of rimoportula-bearing eunotioid diatoms (including Eunophora ) ( Williams & Reid 2006a, figures 1, 2), and the other showed the situation where the naviculoid raphe (being continuous and nearly straight or arched on the valve face) must be both primitive (in the case of Peronia ) and derived (in Eunophora ). In the case of Eunophora , the raphe would have secondarily arose after being reduced in more “typical” Eunotiaceae . Molecular data ( Sims et al. 2006; Theriot et al. 2010) do not support sister-taxon relationships between Amphora and the Eunotiophycidae, and the secondary (re)appearance of a naviculoid raphe in Eunophora is, to us, highly untenable. These results call for further work on the enigmatic genus Eunophora to better help understand its position in the diatom tree of life.

In the present report, our new genus lacks the features of the majority of the raphe being positioned on the valve mantle, and interruption of the striae near the ventral margin, features suggested by Mann (1984) to be derived and found in Eunotia ( Round et al. 1990) , Actinella ( Kociolek et al. 2001) , Amphicampa (Ehrenberg) J. Ralfs in Pritchard (1861:765) ( Kociolek 2000), Semiorbis Patrick in Patrick & Reimer (1966:162) ( Moss et al. 1978), Amphorotia Williams & Reid (2006a) , and Colliculoamphora Williams & Reid (2006b) . The interpretation of the phylogenetic relationships of these taxa relative to the symmetry and raphe features presented in Figure 5 , shows Eunotioforma to be a distinct, early branch in the eunotioid lineage. This interpretation is aligned with the suggestions of Hustedt (1952) and Mann (1984) on the evolution of the raphe in this family. Further segregating Eunotioforma from other eunotioid diatoms is the observation that it also lacks pseudosepta, a feature illustrated (but rarely reported or discussed) in Brazilian species of Eunotia (e.g. Metzeltin & Lange-Bertalot 1998) and Actinella ( Kociolek et al. 2001) . Further examination of eunotioid diatoms from Brazil, as well as those species in subgroup “C” of Krammer and Lange-Bertalot (1991) is expected to provide insights into the diversity of morphology and species in this interesting lineage of raphid diatoms, which may lead to the inclusion of other species in this new genus.

Figures

FIGURES 4A–E. SEM, valve interior. Fig. 4A. Valve view. Scale bar = 20 µm. Figs 4B-D showing apex of valve with raphe branch, helictoglossa and rimoportulae evident. Fig. 4E. Central portion of the valve with interruption of striae evident in the center of the valve. Scale bars = 2 µm for figures 4B–D.

FIGURE 5. Phylogenetic hypothesis of the evolutionary relationships within the Eunotiophycidae, and to other pennate groups. Short, horizontal bars indicate putative synapomorphies for the particular level of evolutionary branching.