Thecochaos album (Penard, 1902) Page, 1981
Fred C. Page re-examined naked amoebae in the Penard Collection in the Natural History Museum in London, 1981. He made following remarks upon the slides of Amoeba fibrillosa:
Slide numbers. 04.5.9.17; 126.96.36.199; 188.8.131.52; 184.108.40.206; 220.127.116.11; 18.104.22.168; 22.214.171.124; 126.96.36.199 (‘avec 1 Amoeba fibrillosa’).
Total number of amoebae. 20.
Description and remarks. This is another multinucleate species of Thecamoebidae, distinct in both locomotive form and nuclear structure from the preceding.
A number of these amoebae appear to have been in locomotion when fixed, thus representing the normal locomotive form well. Only the 15 amoebae which were apparently fixed before they died of bursting or other causes than fixation were measured. Their lengths were 166 to 276 µm, with a mean of 210 µm; their length : breadth ratios were 1:1 to 2:2, with a mean of 1: 4, quite normal proportions for a Thecamoeba.
Use of an oil immersion objective and phase contrast optics permitted a closer look at the nuclei than Penard could have and resulted in a more accurate picture of their structure. However, the same problems which Penard encountered remained in counting the nuclei because, as he said, ‘la plupart ne deviennent visibles qu’après compression de l’Amibe’ (Penard, 1902), and compression was, of course, impossible. Attempts to count the nuclei in five favourable specimens yielded results of 94, 100,102, 145, and 185, in each case certainly below the actual number. In 1902 Penard thought that the number might reach several hundreds, but in 1913 he said only that it often exceeded 100.
The nuclei (Fig. 48) appeared more ovoid/ellipsoid, i.e., more elongate, in some amoebae, and more spherical to ovoid, i.e., less elongate, in others. The more elongate nuclei, 25 from each of the two amoebae, measured from 7.0 x 5.6 µm to 12.0 x 5.6 um, with a mean of 9.0 µm for the greatest diameter. The more spherical nuclei, 25 from one amoeba, had a greatest diameter of 6.5 to 7.5 µm, with a mean of 7.0 µm. The presumed nucleolar material was not scattered as spherules through the nucleus, as described by Penard (1913) (‘disséminés … dans un suc nucléaire’) and shown in Fig. 2, page 123, of Penard (1902) and Fig. 7 of Penard (1913). Rather, it was arranged parietally as variously shaped bodies, some band-shaped, which may all have been lobes of one or two parietal bands in each nucleus. These photomicrographs were made with an oil-immersion lens and phase-contrast optics, not available to Penard.
Ingested material included apparent algal filaments and a few diatoms. One slide (188.8.131.52) bears the notation ‘Parasitée par cryptogame’. This preparation (Fig. 49) contains a more or less rounded amoeba with a mass of branching, non-septate filaments coming out of an invagination. The diameter of these filaments is about 2 um or slightly more. Penard presumably examined this amoeba alive before fixing it; otherwise one might question whether the filaments were parasitizing the amoeba or the amoeba ingesting the filaments.
With his original description of A. alba, Greeff (1891) published no illustrations, an omission which led Page (1977) to doubt whether Greeffs organism was indeed a Thecamoeba and speculate whether it might not be a Leptomyxa, a fairly common genus of multinucleate amoebae in soil. However, Penard (1902) agreed with Greeff that A. alba is very rare. I have myself never seen a multinucleate Thecamoeba-like organism in many collections from nature and do not know of any reports of them by workers other than Greeff, Penard, and Cash & Wailes (1919). The figure published by Cash & Wailes is not very informative, but their text suggests that they may have had the same species as Penard. They also described A. alba as rare. A consideration of Greeffs description in the light of the Penard slides makes it quite likely that Penard’s organism is the same as Greeffs.
Page, F.C., 1981. Eugène Penard’s slides of Gymnamoebia: re-examination and taxonomic evaluation. Bull. Br. Mus. nat. Hist. (Zool.), 40,1:1-32