Jonah crab

The maximum reported carapace width for males is 8.7 in (222 mm), while females rarely exceed 5.9 in (150 mm). It is the closest relative to the European brown crab in the Western Atlantic. Males and females grow at about the same rate before reaching a carapace width of 1.2–1.6 in (30–40 mm), which is about the size of gonadal sexual maturity. After this point, females grow more slowly than males. Males tend to mature at a smaller size than females, but only reach functional sexual maturity at around 5.02 in (127.6 mm), when they are capable of engaging in the copulatory embrace. Size at gonadal maturity is greater for populations at higher latitudes. A study in Rhode Island Sound found a discrete molting season in June for smaller (carapace width less than 4.7 in (120 mm)) male Jonah crabs. With each successive molt, post-molt width increments decreased for female crabs and increased for male crabs.