Sunday, January 27, 2019

Answer to Case 529

Answer to Parasite Case of the Week 529: Pollen grains
Congratulations to everyone who wrote in with the correct answer. Most of you recognized this as some type of artifact, with only a few suggesting that these might be helminth eggs. As Old One mentioned, "These structures superficially resemble ascarid eggs. Size, and surface texture would help with differentiation. Toxocara canis is 80-85 micrometers in greatest dimension with a golfball pitted surface texture. T. cat is 65-70 micrometers it also has the golfball pitting but smaller and less distinct then that of T. canis. Baylisascaris procyonis is 63-88 u and has a granular surface texture. I will always checkout surface texture by focusing up and down on the focal plane of an eggs surface. It is surprising the things you'll see. This is how we diagnosed a mixed infection of T. canis and B. procyonis in a dog." (!)
Here is a side-by-side comparison of the pollen in our case and a Toxocara sp. egg. Note also the pores which help to differentiate the pollen grain from a true helminth egg.

I didn't provide a size of the pollen in this case, but estimate the grains to be ~40 micrometers long.

Interestingly, Old one and SilvaB suggested that these might be pollen of the cornflower (Psephellus). I don't know much about pollen, but a quick google search revealed THIS manuscript which has some nice photos of several pollen genera that bear a resemblance to the pollen in this case. Enjoy!

1 comment:

Old One said...

The manuscript cited (THIS) also has some very interesting SEMs that demonstrates the complexity of some pollen grain morphology. Many times the pollen coat is multilayered with each layer separated with columns. There are also a variable number of pits. spikes, and slits that occur on the surface. Unlike the morphology of nematode eggs which tend to have similar characteristics within a given family, pollens are not so reliable in family form. A couple exceptions. All monocot pollen has a single pore or colpus. Dicots have more than one. Members of the pine family have pollen with 2 air floats (like Mikey Mouse ears).