日本海産ズワイガニの幼生期

Abstract

In order to provide a detailed description of all the larval stages of Chionoecetes opilio, and determine a basis for future descriptions of all the species of the genus Chionoecetes, an ovigerous female crab was caught by the Danish seine fishery, on February 16, 1971. Hatching occurred on March 2 to 5. There are two zoeal stages and one megalopa in the larval development of Ch. opilio. The first zoea is 4.8 to 5.4 mm in length, 3.3 to 3.9 mm in width, and the second is 6.2 to 7.1 mm in length and 3.6 to 3.9 mm in width. The endo-podite of the first maxilliped has five segments with a spinal arrangement from proximal to distal of 3, 2, 1, 2, 5, and the second has three segments with a spinal arrangement 1, 1, 5. The megalopa is 2.9 to 3.3 mm in carapace length and 1.9 mm carapace width. Seven heavy processes are on the carapace: three rostral, a pair of anterior gastric lateral, and a pair of cardiac dorso-lateral. The fourth walking leg has no conspicuous hair projecting from the tip of the dactylopodite.