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Haplomyxa
Fig. 1: Main cell body of specimen A, partly hidden by debris

Haplomyxa sp.

Three specimens were observed in a Petri dish, along with two specimens of an unidentified organic-walled foraminifer resembling a Lieberkuehnia or Claparedellus species. These three specimens were difficult to observe because they were hidden and attached to debris. Only the pseudopodial network was visible. A part of the cell mass of one specimen was visible; it was sausage-shaped and an estimated 600 µm long (fig. 1). A second and much smaller specimen emerged from the debris and extended to the bottom of the dish with some very long granuloreticulopodia (Fig. 2-4). Unfortunately, the stretched cell returned to the debris within minutes and was hidden again. Only a few long strains of granuloreticulopodia remained visible. A third, and also a small one, was also hidden by debris (Fig. 6). It showed a very large network of extremely fine pseudopodia (Fig. 5; video).

I found this naked foraminifer in material scraped from submerged basalt blocks at the foot of the northern dike of Gooimeer (Lake Gooi), Netherlands, May 2020 (52° 18’17.7 “N 5° 18’51.6” E). The material was divided into 40 Petri dishes. Foraminifera were present in only one Petri dish, three naked and two organic-walled. Two naked specimens were isolated, transferred to 50 µl Guanidin each and sent to Maria Holzmann in Geneva for phylogenetic analysis. Both specimens were found to belong to the genus Haplomyxa. The third specimen was lost and could no longer be found.

Haplomyxa
Fig 2: Specimen B. The cell body is hidden by and attached to debris; some pseudopodia are arrowed
Haplomyxa
Fig 3: Specimen B. The cell has left the debris, forming a reticulate plasmodium
Haplomyxa
Fig 4: Specimen B. The cell stretched out as a network with some long granuloreticulopodia
Haplomyxa
Fig 5: Specimen C. Detail of very fine network (image inversed for better visibility)
Haplomyxa
Fig 6: Specimen C. The cell body is surrounded by debris. The pseudopods can easily break off from the main body if there is even a slight movement of the water, for example when the Petri dish is shifted.
Haplomyxa
Fig 7: This Haplomyxa species was collected between these basalt blocks at the base of a dike.
Reticulomyxa
Fig 8: Lake Gooi, the Netherlands
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