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Notes on Heteromita (Protozoa, Flagellata)

Published online by Cambridge University Press:  06 April 2009

Muriel Robertson
Muriel Robertson
Affiliation:
Protozoologist at the Lister Institute.
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Extract

1. A Heteromita species, probably Heteromita globosa, is described and the methods of culture and observation are detailed.

Heteromita globosa is a flagellate with a karyosome nucleus. The karyosome body is an achromatic structure. The chromatin lies on or around the periphery of the karyosome as a narrow diffuse layer and is also distributed upon the inner side of the nuclear membrane. There are two unequal flagella which arise from two blepharoplasts which are situated close together at the anterior end of the body. The blepharoplasts are connected with the nuclear membrane by fine rhizoplasts.

2. The division, encystation and excystation of the flagellates are described from living and stained material. The nuclear division is characterised by a well-developed spindle and the chromatin is arranged in an equatorial plate at the metaphase. The blepharoplasts play the part of centrosomes in the division of the nucleus.

3. The normal division in the living state takes 7 to 15 minutes. The blepharoplasts can be seen to separate, the nuclear space becomes hyaline and ceases to refract in the characteristic way, the space elongates, the blepharoplasts each with the flagellum attached come to lie at opposite poles of the elongating organism and a second flagellar rudiment can be seen to arise at each end alongside of the original one. The nuclei can be observed to reconstruct and the protoplasmic body draws apart rapidly, leaving a narrow protoplasmic junction which breaks through and the two daughter individuals separate.

4. A process of delayed division was observed. If after the division of the nucleus and the drawing apart of the main bulk of the protoplasm the actual breaking of the narrow junction between the two daughters fails to take place immediately, there seems to be no means of effecting this actual separation until the occurrence of a new nuclear division.

In the course of a few hours, usually 3 to 6, a second division occurs and each nucleus undergoes mitosis and the creature splits into four daughters.

The double individuals may encyst and when they emerge they do so as a single binucleate protozoan equipped with a double flagellar apparatus.

5. Syngamy has not been observed.

Type
Research Article
Information
Parasitology , Volume 20 , Issue 1 , April 1928 , pp. 10 - 24
Copyright
Copyright © Cambridge University Press 1928

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