world of amoeboid organisms

From Brown, 1911

Capsellina timida Brown, 1911

I found this species sporadic in wet Sphagnum, Laegieskamp (2012).

Following description is from Brown:

The body is ovoid, with a slight narrowing towards the mouth end, and with regularly rounded posterior extremity. It is compressed, more or less, and In extreme cases to almost half its width. The body is covered with a perfectly smooth, clear, transparent membrane. So far as observed it does not undergo deformation, but it seems sufficiently flexible to allow of this. Even under high powers the test appears to be structureless. There is no second external envelope of foreign matter, as is the case with C. bryorum, Penard. The structure and characters of the mouth agree perfectly with Penard’s description of that species. In the broad view of the animal, it shows a straight line running at right angles to the end of the body, due to the tight compression of the two incurved lips. In partial side view, two curved lines crossing one another represent the edges of the lips, which in narrow view disappear; while an end view shows a straight line stretching nearly across the test. In most cases the mouth was closed tightly by compression of the lips (as may be inferred from the difficulty in getting stains to penetrate), but in one or two small individuals from High Lodore the lips were separated. Whether this is a natural state it is difficult to say.

The protoplasm fills the whole space within the test, It is colorless or grayish and contains many inclusions. Immediately within the membrane is a layer of brilliant droplets, of small size and highly refractive (oil). The general protoplasm contains many minute granules, together with larger food-bodies, including small green algae and even diatoms of considerable size. They show various stages of digestion and vary from yellowish to brownish. The size of the food-bodies observed demonstrates that the mouth is capable of considerable distention. In respect to the food-bodies this species differs very much from C. bryorum.

Several vacuoles occur. They originate in the protoplasm of the body and slowly move towards the mouth end, enlarging at the same time. Then somewhere in the neighbourhood of the mouth they disappear, but the process is not that of a sudden collapse, they seem to become lost gradually.

The nucleus is single, but not readily seen. It appears to contain a single spherical chromatin body, surrounded by a clear space. It is not of specially large size.

As is characteristic of most Rizopods from the drier mosses, the animals seem remarkably shy under observation and rarely put out their pseudopodia. This may be due in large measure to the unnatural conditions under which they are examined. In the few cases when pseudopodia were seen, a small mass of clear protoplasm was noticed on the outer side of the test in the region of the mouth (which was not observed to be dilated), and from this a single line filose pseudopodium originated, which by extension and contraction varied greatly in length. It was able to bend upon itself, and even swung round slowly as a whole. The movement of the animal is very similar to that of Euglypha, being of a somewhat jerky nature.

The animals have not been observed to divide. The process of division of C. bryorum, described by Penard, seems peculiar, in that the outer test is divided longitudinally at the same time as the inner body.

In some individuals the body protoplasm takes on a different appearance. It becomes broken up into numerous spherical bodies of about 3 µm diameter, which completely fill the test. This condition may possibly be connected with reproduction. In collections kept for some time, the protoplasm gradually retracted from the test, became more spherical in form, and the nucleus became more visible. This may have been preparatory to encystment.

The size of the animal varies slightly. Large specimens (adults) generally were about 31  µm long, 27 µm wide, and 18 µm thick, but smaller individuals were common.

It is interesting to notice that this species was discovered and examined before the author received a copy of Penard’s paper describing the only other known species of the genus.

This species was first discovered among moss growing on walls at Ecclesall, Sheffield, in November 1909. Later it also occurred among damp moss taken from the outside of a water-trough, also at Ecclesall, in which situation it has repeatedly been found since. In May, 1910, it was found among moss gathered at High Lodore, Derwentwater (Cumberland).

Ferry Siemensma, created March 2, 2019; last modified January 31, 2021
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