Abstract
Reproductive cycle, mating behavior and early growth of the stone crab Hapalogaster dentata were studied from September 1989 to November 1994 at Kattoshi, Hakodate Bay, Japan. Histological examination and appearance of ovigerous females revealed that the spawning season is from October to November, females oviposit once a year, and eggs are incubated for about 110 days. Size at female sexual maturity is 8 mm carapace length when they are two or more years old. During the mating season, a male guards a ripe female just prior to oviposition by grasping her or covering her with his body. Although such guarding behavior is commonly observed for the Lithodinae, this is the first description for Hapalogastrinae which belongs to the same family, Lithodidae. The guarded female undergoes molting, and immediate spawning after copulation, during the two or three days of guarding, which suggests that mate guarding might deprive other competitive males of access to ripe females. Although H. dentata shows some differences to lithodine crabs, such as smaller body size, fewer eggs, and no seasonal or size dependent migration, these reproductive behaviors strongly resemble those of the Lithodinae, which suggests the behavioral relatedness of both subfamilies.
