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Sexing embryos

Hampton Carson hampton at hawaii.edu
Sat Dec 12 21:19:01 EST 1998

Dear Qi Sun:

Over the years, working with larvae, my assistants and I have been able to
routinely sex 100% of larvae used for salivary gland chromosome
preparations. In the larva, the gonad can be observed under the binocular
microscope by putting the larva in a fairly large drop of saline and
placing a coverslip lightly on top.Transmit the light from the substage
mirror through the larva and use needles or a blunter instrument to slide
the coverslip gently back and forth, rolling the body and compressing it
somewhat. The gonad will be observed about two-thirds from the anterior
end, lying within the lateral fat-body. It is easy to see since the fat is
rather opaque but the gonad tissue is wholly transparent and stands out as
a bright spot. The shape of the female gonad is circular and quite small
and spherical, looking like a lower-case " o ". The male is larger and is
oval, like an upper-case " O ", with the long axis parallel with the long
axis of the body. No stain is necessary.

This operation can be done on the intact larva, after which it is quite
easy to remove the coverslip and isolate the fat body that contains the

I do not know how early in developemt these differences in size and shape
arise, but once you have mastered the technique for older larvae you could
work back to small larvae and the unhatched stages by small steps. You did
not say whether you want to be sure not to harm the embryo so that you can
incubate it to hatching. This might be quite difficult as the procedure
that I have described above (rolling and compressing the specimen) probably
would cause injury or death.

Let me know if this works for you.

With Aloha,

Hamp Carson
Department of Genetics and Molecular Biology
University of Hawaii, School of Medicine
1960 Easst-West Road
Honolulu HI 96822

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