Sex-specific Compound Uncovered in Crabs

Males and females of many types of animals and plants are known to possess differing levels of hormones and other metabolites, but a new finding marks the first discovery in any species that a particular metabolite occurs in only one sex (PLoS One, DOI: 10.1371/journal.pone.0000780). While using ³¹P NMR spectroscopy to study the gill tissue of blue crabs, Robert A. Kleps of the University of Illinois, Chicago, and colleagues noticed a signal produced by samples from male crabs that isn't produced by samples from female crabs. The researchers identified the responsible compound as 2-aminoethylphosphonic acid (AEP, shown). It was possible that diet or habitat differences could explain why AEP is exclusive to the male crabs. But tissue from the male half of an exotic half-male, half-female blue crab contained a significant amount of AEP, while the female half contained only traces, proving that diet and habitat are irrelevant. "Unless blue crabs are unique, sex-specific metabolites are likely to be present in other animals," Kleps says. He speculates that the presence or absence of certain metabolites might contribute to human gender differences affecting disease susceptibility or anatomy.