Classification of Opalina
Phylum :- Protozoa (Unicellular)
Sub-phylum :- Plasmodroma (Cilia absent, locomotion by pseudopodia.)
Class :- Opalinata (Cilia-like organelles in oblique rows)
Genus :- Opalina
General Study of Opalina
Opalinids are entocommensals in intestine and rectum of tadpoles and adult anuran amphibians (frogs and toads) and occasionally other cold blooded vertebrates. It has cosmopolitan distribution.
Opalina is a parasite in the rectum of frogs and toads. Body is oval and flax with longitudinal rows of many equal – sized cilia- like organelles of locomotion.
It is multinucleate; each nucleus has both trophochromatin and idiochromatin. There is no cytostome or contractile vacuole. The parasite absorbs digested food of the host. Reproduction is by longitudinal binary fission most of the year, in fission kinetia are not cut but shared equally between two daughter cells; this is an interkinetal division of kinetia.
In spring reproduction is by binary plasmotomy in which cell division is repeated again and again without division of the nuclei, so that many daughter cells are produced, each having only a few nuclei, generally three to six. The daughter cells become encysted and pass out of the host into water from where they are swallowed by tadpoles.
The cysts dissolve in the intestine of tadpoles and the cells divide to form uninucleate minucleate microgametes or macrogametes. These gametes of tadpoles and the male and female anisogametes fuse to form a zygote. The zygote encysts, then by growth and nuclear division it becomes an adult which emerges from the cyst into the alimentary canal.
Previously Opalina was placed in Ciliophore, then it was placed in Flagellata, but now it is placed in a separate super class Opalinata since it is neither a ciliate nor a flagellate because of the following reasons:
- Its many nuclei are similar or monomorphic, they are micro-nucleus and macronucleus.
- In binary fission the cleavage is longitudinal and parallel to kinetia which is shared by the daughter cells and new kinetia are supplied by the primary ones to generally transverse, the cleavage cells receive half of each kinetia which, thus, have genetic continuity.
- In Opalina there is no conjugation which is common in ciliates.
- In Opalina anisogametes are formed and sexual reproduction is by syngamy. While in cilates sexual reproduction is by conjugation or autogamy, and no gametes are formed. 5. It has no chromatophores, contractile vacuole, and gullet as seen in flagellates.
Identifying features
Since the animal has oval flattened body, uniform small cilia At the time of egg laying of their hosts, the Opalina divide into small forms, the encysted form pass out in the faeces and when ingested by tadpoles, encysted and then divide into anisogamous gametes. The zygote either encysts again or passes out to infect other tadpoles or all once develops into the adult and all above features hence it is Opalina.