lorica flask-shaped, with broadly rounded base, stalk absent
base of lorica often thickened and irregular
length of lorica about 10 µm
cell spherical, diameter about 5 µm, attached to bottom of lorica
one chloroplast
one flagellum of body length
one contractile vacuole located apically
spherical nucleus near posterior end
aperture of lorica with a distinct cloud of spherical granules
Lepochromulina bursa is a very small Chrysophyceae, which I rarely find in the Simmelried. I usually find the specimens growing on detritus flakes. So far I have not been able to find any specimens on algal filaments.
The cells are at most 5 µm in size, spherical and with one chloroplast. They build an approximately 10 µm long, flask-shaped case, which always has a cloud of spherical granules around its opening. If these granules are absent, then it is the similar species Lepochromulina calyx, which also has a stalk.
It was assumed by Fott (1963) that the grains around the aperture of the lorica were possibly symbiotic bacteria, as they are always present in Lepochromulina bursa. However, it was later shown by Hibbert (1983) that these granules are formed intracellularly and then excreted. Similar bodies are also found in Spongomonas spec. or Rhipidodendron huxleyi. At high magnification I could see that these approximately 1 µm large granules are obviously hollow (s. fig. 2 b). Why they are deposited around the aperture of the lorica opening is not known. Since they are all held in position, there is probably also a gelatinous sheath, but this cannot be seen in the DIC.
Fig. 1 a-b:Lepochromulina bursa. L = 8.6–9.1 µm (of lorica). Slightly different focal planes of two specimens. Note the cloud of spherical granules around the apertures of the loricae. Nu = nucleus. Obj. 100 X.
Fig. 2 a-b:Lepochromulina bursa. L = 9.5 µm (of lorica). Two focal planes of a specimen. The spherical granules (SG) seems to be hollow globules with a diamter of about 1 µm. Nu = nucleus. Obj. 100 X.
Fig. 3 a-c:Lepochromulina bursa. L = 9.2 µm (of lorica). A third specimen attached to a detritus flake. CV ?= probably the contractile vacuole. Obj. 100 X.