General morphology of Lacogromia cassipara. ah – apertural hyaloplasm; p – peduncle; e – entosolenian tube; g – granuloreticulopodia; n – nucleus; m – membrane; x – xenosomes; c – cap of adhering bunch of xenosomes.

Class ‘Monothalamea’ (Pawlowski et al. 2013)

Diagnosis: Foraminifera with single chamber (monothalamous) test with an organic or agglutinated wall.

Remarks: Monothalamid foraminifera are widely distributed in marine and brackish habitats. Some members of this class occur in fresh water, but are rare. The main reason is probably that light microscopically these tests are hard to discover between debris, despite of their relatively large size (average 250 µm, but up to 1 mm). Usually the amoebae spread out their pseudopodial network up to several mm when kept on microscope slides in moist chambers or in culture dishes.

Recent environmental DNA surveys revealed the presence of four major phylogenetic groups or clades of freshwater foraminifera. However, only from one genus in each group its light microscopical morphology could be linked to environmental DNA:

Clade 1: Lieberkuehnia
Clade 2: Reticulomyxa
Clade 3: Lacogromia
Clade 4: Limnogromia

Ecology: Freshwater foraminifera seem to be rare, given the very scarce microscopic records over the years. However, molecular data show a rich diversity of freshwater and soil foraminiferans (Holzmann and Pawlowski 2002; Holzmann et al. 2003; Lejzerowicz et al. 2010). The close relationship between Lieberkuehnia sp. and L. sinensis with environmental sequences suggests that the same morphotypes might also live in the Geneva basin. Members of clades 3 and 4, represented by Lacogromia and Limnogromia, respectively, seem to be present in all types of habitats tested molecularly (lake, small and big river, pond, soil) in the Geneva area. Groups 3 and 4 are represented by more sequences than groups 1 and 2 (Apotheloz-Perret-Gentil, unpublished), which suggests that the species described by Penard might still occur in the Geneva basin.

Lacogromia cassipara, morphotype B; a adult specimen; b young specimens, just 24 hours after schizogony – drawing and micrograph Ferry Siemensma (1982)
Lacogromia cassipara, four young specimens, just 24 hours after schizogony (Siemensma, 1982)
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