Why do I have males?


I thawed my N2 stock from the -80 C, allowed them to grow to gravid adults, and then performed an egg prep to get eggs (I’m trying to synchronize the worms).
This was all done at 20 C.

I saw several males hatch from the eggs (from the egg prep)!
Why does this happen? I thought you need a 30 C heat shock to induce males.
Did I just accidentally invent a new way to get males?

And a related question:
If a plate of worms has some males, will the males disappear eventually (with multiple chunkings to new plates)?
Theorectically, if a male mates with a hermaphrodite, then 50% of the progeny is male, right?
So how do I get rid of the males?


Various stresses (heat shock, ethanol exposure) will induce X nondisjunction and generate males. I’ve not heard of a report that thawing from a frozen stock does this (especially since the thawed animals are L1s), but it’s conceivable.

Males will eventually go away with chunking; I’ve never really looked into the math to figure out why this is so.

If you want to get rid of males without waiting for chance to take care of it for you, pick larval hermaphrodites to a new plate and self them. If you still get males, your strain is a bit Him (or your incubator or benchtop is heatshocking your worms for you) and you should replace your N2 stock (or store your worms more carefully).

Also, do the hermaphrodites end up with a bit of bodily material protruding out of their vulva after mating?

I think what you are describing is a copulatory plug. As far as I know, N2 strain males should not show this trait, but other natural isolates of C. elegans do, for instance Hawaii. Hawaii strain also has a higher incidence of males (compared to N2), so I wonder if that’s your problem. You could identify if your worms are N2 or Hawaii by looking at a behavioral trait. N2 worms spread all over the bacterial lawn, but Hawaii worms tend to stay in the borders of the lawn. IF that’s the case, get a new N2 stock.


In addition to what Alejandro said, it is possible you’re seeing vulval bursting. I’m not aware of vulval bursting being caused by mating, although I suppose it’s conceivable. In any case, it’s not something you should see in N2, whether it’s bursting or it’s plug formation. I would recommend that you get new stocks of N2 and OP50.