birefringent pig louse

Frank · Post by **Frank** » Thu Jan 23, 2014 9:56 pm

I have two antique slides of Haematopinus suis, pig louse mounted in a media. Viewed with transmitted light both specimens are similar but when polarizers are inserted into the light path the one pictured is highly birefringent while the other remains evenly dark except for the claw's tips. Any ideas as to why the two slides are different? Could it be the mounting medium? Nikon BD 210 5x, Zerene PMax, stack and stitch.

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Cactusdave · Post by **Cactusdave** » Fri Jan 24, 2014 8:59 am

I believe that differences in the methods that the two different mounters used to prepare and clear the specimen before mounting, account for the differences. Lengthy soaking in alkali was often used to help soften and decolourise this sort of specimen. This causes loss of birefringent biological material from the inside of the louse. Specimens prepared by methods avoiding alkali are more likely to look good under polarised light, and in particular will have well preserved muscles which show clearly under polarisation.

Frank · Post by **Frank** » Sun Jan 26, 2014 7:36 pm

Hi CD
Thanks for your thoughtful reply and I suspect it is the correct answer rather than my guess if it being the mounting medium. The mounting medium on both slides is optically isotropic. The anisotropic material is mainly the chitinous exoskeleton of one specimen. Perhaps the alkali clearing method removed the layer from the inside of the exoskeleton that is producing the chitin.
Frank

carlos.uruguay · Post by **carlos.uruguay** » Sun Jan 26, 2014 9:46 pm

Excellent Frank