Sunday, September 8, 2019

Answer to Case 559

Answer to Parasite Case of the Week 559: Hymenolepis diminuta
This was another great case by Idzi Potters. This egg had all of the characteristic features of H. diminuta: large size (80 microns), and lack of polar filaments between the striated outer membrane and the smooth inner membrane.You can also nicely see some of the hooks of the internal 6-hooked oncosphere:
Here is a side-by-side comparison of H. diminuta eggs, and the eggs of the related cestode, Hymenolepis nana. You can see that they are very similar appearing, but H. nana eggs are smaller and have polar filaments that originate from the inner membrane and extend out into the space between membranes (arrows in image below).
Some pondered why the parasite featured this week was named "diminuta" since its eggs are bigger than those of H. nana. Blaine helped us with that answer to this: "H. diminuta was described earlier (1819) then H. nana (1851). So, at the time of its description, H. diminuta may have been the smallest tapeworm known from humans. "Nana" comes from the Latin 'nanus' meaning dwarf or small." Isn't etymology fun?

A fun saying for today: People who confuse etymology and entomology bug me in a way I can't put into words 

1 comment:

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