Sexing Cleaner Shrimps?

[fiskkeeperpro]

Does anybody know how to determine the gender of cleaner shrimps?
I have 2 one is quite large and the other smaller but, one has a dark yellowy white underside where the othr 1 hasnt. Also, one has a large black spot and the other a small black spot- could these be male and female?

thx.
will

 

[Lynden]

Back when I kept cleaner shrimps, both of them were constantly tending eggs; but when one was killed, the survivor never spawned again. This to me suggests incomplete hermaphroditism.