This cool large ciliate is one of my favorite parasites. It's the largest protozoan parasite and only pathogenic ciliate to infect humans. As my predecessor, Dr. John H. Thompson, used to say, it is the aircraft carrier of the fecal flotilla.
Diagnosis is made based on the characteristic morphologic features. As Florida Fan mentioned, "At first look, the spherical object on the left of the first picture and the one of the third picture may lure us to identify them as eggs of some sort," (indeed, B. coli cysts may be easily mistaken for helminth eggs), "but the oval large object on the right side of the first picture as well as the second photo when enlarged will show us the cilia. The second picture shows also a cytostome (oral groove) on the upper end of the object."
Here is a closer look at these morphologic features of the trophozoite:
So what's up with the taxonomy? Well Blaine Mathison and I just published an update on parasite taxonomy discussing the new name, Neobalantidium, so imagine my dismay when I realized that the older (and potentially valid name) of Balantioides had already been described. As Blaine mentioned in his comment "It looks like when Neobalantidium was described in 2013, the authors overlooked a paper from 1931 that proposed the name Balantioides. If it was simply an oversight on their part, then yes the name could indeed be Balantioides. However, it is possible there was something in the description of Balantioides that rendered the name invalid (i.e., rules of nomenclature where not followed, at least for what was acceptable at the time). There is also another nomenclatural rule that states if a name is not used in the literature for a specific amount of time, it can be rendered invalid (not sure yet it that applies here)." Perhaps some of my readers can provide more insight. We are also checking with our colleagues to get more information and will report back to you, dear readers, when we have more answers.
3 comments:
In recent years it has been Balantioides coli that has become more commonly used. I can’t find any use of Balantidioides coli. Ultimately taxonomic names are about communication. I don’t really care which one is correct but it would be nice to have agreement and consistency.
Yes, sorry, Balantioides (Balantidioides was a typo on my part).
All the papers I see on 'Balantioides' are post the 2014 'ressurection', so if it has not been used since its original description it might not be valid under the prevailing usage rule.
Article 23.9.1 of the International Code of Zoological Nomenclature states:
23.9.1.1. the senior synonym or homonym has not been used as a valid name after 1899, and
23.9.1.2. the junior synonym or homonym has been used for a particular taxon, as its presumed valid name, in at least 25 works, published by at least 10 authors in the immediately preceding 50 years and encompassing a span of not less than 10 years.
So, the way I read this, because Balantioides was described in 1931 it should be the valid, accepted name.
I will ask some fellow insect taxonomists too (the concept is the same) since neither Bobbi or I have heard back from Sina yet.
I believe I have the taxonomic history figured out:
a. B. coli was described as Paramecium coli by Malmstem in 1857
b. Balandium was described in 1858 by Claparede and Lachmann with B. entozoon as the type species for the genus.
c. Balantioides was described by Alexeieff in 1931. This name apparently went unnoticed in the literature for decades.
d. Neobalantidium was described by Pomajbikova et al. in 2013.
e. Christyokova et al. (2014) brought awareness to Alexeiff's 1931 description of Balantioides.
f. Pomajbokava and Stensvold (2018) revisited Pomajbikova et al's 2013 work and acknowledged that Balantioides should indeed be the genus. [see: Pomajbikova K, Stensvold CR. 259 - Balantioides coli (formerly Balantidium coli). Principles and Practice of Pediatric Infectious Diseases (Fifth Edition). 2018. Elsevier]
So, if one was to accept B. coli is not congeneric with the type species in Balantidium, then the name would be Balantioides coli, with Neobalantidium as a synonym under Balantioides.
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