Sahnium
Sahnium Singh, Misra & Sharma, 1981 (ref. ID; 7594 original paper)
Order Amoebida Kent, 1880: Family Hartmannellidae Volkonsky, 1931 emend. Singh, 1952 (ref. ID; 7594)
[ref. ID; 7594]
Definition; The resting nucleus contains numerous very small nucleoli of uniform size attached to the nuclear membrane. During mitosis the nucleoli disappear and a spindle with chromosomes arranged as an equatorial plate is formed. Amoebae during locomotion flattened having thickened pellicle or dermal thickening. The outline may be oval, oblong, or elongated and sometimes the anterior part of the elongated forms have two or three temporary branches resembling polypodial forms. The definition of this genus is given under suggested subdivision of genus Thecamoeba. (ref. ID; 7594)
Type species; Sahnium lucknowensis (ref. ID; 7594)
- Sahnium lucknowensis Singh, Misra & Sharma, 1981 (ref. ID; 7594 original paper)
Sahnium lucknowensis Singh, Misra & Sharma, 1981 (ref. ID; 7594 original paper)
Descriptions
Amoebae on agar surface are not highly wrinkled. As the trophozoites do not properly adhere to the glass surface, their locomotive morphology was studied in wet film preparations under a coverslip. They go through their normal locomotive activity for several minutes before they gradually become rounded. During locomotion amoebae are flattened and assume various shapes. They may be oval, oblong, or elongated. Sometimes the anterior part of the elongated forms have two or three temporary branches resembling polypodial forms. A hump-like structure could be seen at the posterior end in some amoebae. Two or four irregularly spaced longitudinal dorsal folds were distinctly seen in all the individuals. Hyaloplasm region of amoebae is usually crescent-shaped. A single nucleus and a prominent contractile vacuole are present in an individual. The diameter of amoebae in rounded condition is ca. 80-120 um. (ref. ID; 7594)
- Restig nucleus: The resting nucleus in the living condition is spherical and contains numerous very small nucleoli of uniform size attached to the nuclear membrane. No chromatic granules could be clearly distinguished. In stained preparations the nucleoli and chromatic material in the form of granules and small threads, lying in the centre of the nucleus, could be clearly seen. In some nucleus the nucleoli were fused giving the appearance of bands. (ref. ID; 7594)
- Mitotic divison: The amoebae become rounded and motionless at the beginning of nuclear division.
- Prophase. The nucleoli begin to disappear and the chromosomal chromatic material, lying in the centre of the nucleus, fuses and occupies the position of the equatorial plate on the spindle which is not yet fully formed.
- Metaphase. At this stage the fully formed spindle, which does not clearly show spindle fibres, is oval in outline. The nuclear membrane is still intact, and no nucleoli could be found to be present.
- Anaphase. The oval spindle becomes somewhat elongated and the band of chromatic material divides into two equal halves. The nuclear membrane could still be seen. At a later anaphase stage the nuclear membrane disappears. The parts of the spindle which lie between the fused chromosomal plates and the poles stain more deeply and appear like caps. They become smaller and smaller as the chromosomes move to the two poles and finally disappear. When the chromosomes reach the two ends of the poles, they seem to be connected by a thread-like structure very narrow in the middle. The shape of the amoeba becomes oval.
- Telophase. The amoeba becomes elongated and a constriction appears in the middle giving rise to two daughter individuals. The nuclear membranes are formed surrounding each lump of chromatic material and the nucleoli begin to appear beneath the nuclear membrane.
It may be emphasized that there is no aster, centrosome - intra-nuclear or extra-nuclear - at any stage in the mitosis of S. lucknowensis. (ref. ID; 7594)
Remarks
In Thecamoeba proteoides Page, 1976 the resting nucleus has granular nucleoli (endosomal bodies) which are very small, 0.5 um or somewhat less. They are found in the peripheral layer which is somewhat irregular, with occasional gaps. In the interior of the nucleus sometimes threads could be seen. The nuclear division in this amoeba has not been studied by Page. Although the structure of the resting nucleus in S. lucknowensis bears some resembles to T. proteoides, the nucleoli attached to the nuclear membrane are much larger and regularly spaced. From the description of T. proteoides given by Page (1977), it is quite clear that S. lucknowensis is quite different. (ref. ID; 7594)
Type locality
This amoeba has been isolated on two different occasions from Central Drug Research Institute, Lucknow garden soil from culture plates incubated at 28 degrees C but not at 37 degrees C. It is a voracious feeder on trophozoites of Echinamoeba exundans. (ref. ID; 7594)