Double-Sex Crab Caught in Chesapeake Bay.

[Dros]

Actually, many crustaceans have environmental sex determination, not chromosomal like mammals and birds. For these animals, chromosomes have nothing to do with their sex, instead the environment during a critical phase of development is instead important. Examples of this are crocodilians, where if the eggs are at one temperature, they'll all be male, but raise the temp by a few degrees, and they'll be female. Some species (i.e. clownfish - like Nemo from Finding Nemo) change sex during their life as their social position changes - they are male at birth, and as they get larger and more dominant, they eventually switch to female.

For this crab, perhaps one side of the body was exposed to a condition or trigger or chemical that caused it to have a different sex than the other half. A mutation that screws up the mechanism of sex determination could also do it.

I think your second example of a mutation in the sex determination pathway is more likely. I think chromosome loss in an individual heterozygous for some aspect of the sex determination would do it. As you pointed out, it wouldn't be a sex chromosome itself that was lost, but I think instead a chromosome carrying the only functional copy of a sex determination gene.

 

[StarbucksSam]

I think your second example of a mutation in the sex determination pathway is more likely. I think chromosome loss in an individual heterozygous for some aspect of the sex determination would do it. As you pointed out, it wouldn't be a sex chromosome itself that was lost, but I think instead a chromosome carrying the only functional copy of a sex determination gene.

You sound like my bio final. LOL.

 

[applemacdude]

mmm

lets eat it

 

[Don't panic]

Actually, many crustaceans have environmental sex determination, not chromosomal like mammals and birds. For these animals, chromosomes have nothing to do with their sex, instead the environment during a critical phase of development is instead important. Examples of this are crocodilians, where if the eggs are at one temperature, they'll all be male, but raise the temp by a few degrees, and they'll be female. Some species (i.e. clownfish - like Nemo from Finding Nemo) change sex during their life as their social position changes - they are male at birth, and as they get larger and more dominant, they eventually switch to female.

For this crab, perhaps one side of the body was exposed to a condition or trigger or chemical that caused it to have a different sex than the other half. A mutation that screws up the mechanism of sex determination could also do it.

also a lot of pollutants (especially hormones and hormono-like compounds found in many plastics, for example) have caused epidemics of sex-change in many fish species in several US rivers (and i imagine elsewere). So if a pollutant would trigger the reprogramming at the embryo stage, you could have the symmettic phenotype

edit: also affects some amphibians and mollusks, so I guess crustaceans could also be affected