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Differences Between Opalinata & Ciliates

Ciliates are single-celled microorganisms whose bodies are surrounded by short hairlike structures called cilia, which they use for locomotion and feeding. Opalinata posses certain superficial characteristics which make them similar to ciliates, and were once even thought to be ancestors of ciliates. Most notably, some opalinata have short flagella or microtubules which resemble the cilia from which ciliates get their name. Despite this similarity, several notable differences exist between ciliates and the various divisions of opalinata which distinguish them from each other.

Differences Between Ciliates and All Opalinata
- While different divisions of opalinata posses distinct traits, certain attributes among all opalinata set them uniformly apart from the ciliates. For example, ciliates posses an opening similar to a mouth, which they use to feed on bacteria, while opalinata do not. ciliates may have two types of nuclei which bear their genetic information. Opalinata have only one type of nucleus. Opalinata have complex reproduction cycles, whereas ciliates multiply by simple cell division, or fission. The three main divisions of opalinata are opalinea, proteromonadea and blastocystis. Each of these shares the aforementioned common traits, and other distinct properties of its own.
Opalinea
- This division of opalinata lives in the intestines of amphibians, such as frogs and toads, and also lives in the intestines of some reptiles and fish. Opalinea are capable of both sexual and asexual reproduction, as determined by the needs of their environments and their host's life cycle. While opalinata only posses one type of nucleus, a single specimen may contain more than one actual nucleus of that type. Opalinea are known for possessing two or more nuclei, and may even have hundreds.
Protomonadea
- Proteromonadea reside in the intestines of amphibians, reptiles and mammals but are not found in fish or other animal organisms. They have one or two pairs of flagella, and each pair is a different size, as well as tripartite hairs. The presence of these tripartite hairs is what links them to the stramenopiles, and they are sometimes classified as heterokontophyta due to their use of flagella.
Blastocysts
- Blastocystis are gut parasites. One species, Blastocystis hominus, is a human-specific parasite. They have no observable flagella and their appearance is relatively simple compared to opalinea and proteromonadea. Blastocystis are spherical and oxygen-intolerant. They tend to contain unusual and highly-specialized mitochondria as well as multiple nuclei of the same type. Although some of their physical characteristics may raise questions as to their status as opalinata, they are genetically more similar to the other opalinata than to other microorganisms.

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