Lieberkuehnia wageneri Claparède et Lachman, 1859
A short history
Lieberkuehnia wageneri is a freshwater foraminifer; it is an organic-walled monothalamid. The first freshwater representative of this group was described by Dujardin (1841). He collected an organic-walled monothalamous foraminifer from water plants in the river Seine (France) and called it Gromia fluviatilis. In 1837 he had already described G. fluvialis from the same location, but this was obviously a filose species (De Saedeleer, 1934). Some years later Claparède and Lachmann (1859) described and depicted another monothalamous species after a single specimen that they found in a bottle of water. This specimen had a thin flexible ovoid test, 160 µm large, with a clearly visible pseudopodial peduncle. They named it Lieberkuehnia wageneri in honor of two other researchers, Lieberkühn and Wagener, who had found a similar specimen.
In 1876 Cienkowski collected an almost identical species from a freshwater marsh in Russia and described it as Gromia paludosa. Penard (1907) transferred that species to the genus Lieberkuehnia and gave emended descriptions of both L. wageneri and L. paludosa. He found both species together in submerged mosses in a marsh near Bernex, Switzerland, and distinguished both species based on overall size, thickness of the organic wall, number and length of pseudopodia, number, size and structure of the nuclei and the presence of large granules in the cytoplasm.
Leidy (1879) was the first who described a terrestrial organic-walled monothalamous foraminifer, G. terricola. He found this species “among moist moss in the crevices of pavements, in shaded places, in the city of Philadelphia”. A similar terrestrial allogromiid, Edaphoallogromia australica, has been described from tropical forest litter by Meisterfeld et al. (2001) based on both morphological and molecular data.
Problems concerning Lieberkuehnia wageneri
L. wageneri has always been a debatable species, because since there has been little or no consensus between observers about several aspects like habitat, nuclei and size. It was reported from marine habitat (Welsh coast, Siddall 1880), freshwater (e.g. Penard 1907; Verworn 1889; Wailes and Penard 1911) and soil (Mvra 2009). Siddall (1880) doubted whether the original habitat was correct, because “in English books it is invariably stated to have been originally found in unknown fresh water from Berlin” (italized by Siddall). This habitat is also mentioned by Mvra (2009), but Claparède and Lachmann (1859) didn’t mention whether they found their specimen in marine or freshwater as they found it “à Berlin, dans une petite bouteille qui renfermait de l’eau de provenance inconnue” (= “in Berlin, in a small bottle that contained water of unknown origin”).
Claparède and Lachmann didn’t observe any nuclei in their specimen. Siddall (1880) gave, according to Penard (1907), a vague and confusing description of a large number of “vesicular nuclei” each 13 µm in diameter (quotes by Siddall). Maupas (1882) described L. wageneri as multinucleated, without giving any details, except for their diameter (4 µm). Verworn (1889) has never seen any nuclei and doubted their presence. Penard (1907) was the first to give a detailed description and drawings of the nuclei and the nucleoli. Netzel (1971) noted that “nucleoli were not present in every stadium”.
Another point of confusion was the difference in size. Penard mentioned 32-200 µm and Awerinzew (1906) 6-900 µm, as cited in Hoogenraad and De Groot (1940) who considered this enormous difference in size “mind blowing, if not a misprint”.
In an attempt to end this discussion, Mvra (2009) proposed an improved diagnosis of this species including all available data. His improved description of L. wageneri appears to be a compilation of all known descriptions of L. wageneri. Based on our recent -but unpublished- research, we now know that there are different species that appear morphologically similar to L. wageneri, but are genetically different. One indication is the presence of nuclei with different structures in different types. Penard already noted the difference between L. wageneri and L. paludosa in the structure of the nuclei. Mvra has found three specimens in moss in Slovakia and describes their nuclei as spherical with a central nucleolus.
Identification and classification problems
Until recently monothalamous foraminiferal identification and classification was exclusively based on morphological characters and very difficult because of incomplete or poorly defined type descriptions and the lack of appropriate criteria (Meisterfeld et al. 2001; Siemensma et al. 2017), a problem that is not restricted to monothalamids (Kosakyan et al, 2013). Since the nineties, the advent and rise of molecular systematics changed the traditional view of foraminiferal diversity tremendously and led to a revision of foraminiferal classification. Especially diversity surveys based on environmental DNA have dramatically changed this view by revealing an unexpected diversity of naked and organic-walled lineages as well as detecting foraminiferal lineages in soil and freshwater environments (Pawlowski et al. 2014). These advances were very helpful in constructing a phylogeny tree, resulting in the establishing of at least four clades of monothalamids in freshwater and soil (Lejzerowicz et al. 2010). However, that led to a situation in which numerous new species are known genetically, but no one has any idea how they look like morphologically and vice versa. That makes identification problematic for ecological field research, biogeography and systematics (Wylezich 2014). Detailed combined morphological and molecular studies of protist groups remain rare (Kosakyan et al. 2013). Until now, only six species of freshwater and soil monothalamids are represented by both morphological and genetical data: Limnogromia sinensis, Lacogromia cassipara, “Lieberkuehnia” sp., Reticulomyxa filosa, Haplomyxa saranae and Dracomyxa pallida.