Ontogenetic change of body density and shape of the phyllosoma larvae of the Japanese spiny lobster Panulirus japonicus

Abstract

ABSTRACT Ontogenetic change in body density and shape of phyllosoma larvae was examined for the Japanese spiny lobster Panulirus japonicus (von Siebold, 1824) using laboratory-cultured specimens from hatching to the final phyllosoma stage before metamorphosing to the puerulus stage. Phyllosomas have a unique body form that is leaf-like and dorso-ventrally compressed with several appendages, and a long planktotrophic life in the ocean. Ontogenetic change was not found in the larval body density, and the mean density (1.097 g cm-3) was greater than the seawater density (1.024 g cm-3), indicating that they must employ strategies to control their buoyancy. The body shape of the phyllosomas changed during development into the puerulus stage where pleopods on the pleon and the pereiopods function as swimming organs and walking legs, respectively. The pleon rapidly developed after the mid-stage VI phyllosoma (10.6 mm body length (BL)). The thoracic pereiopods, including the third maxilliped, that function as swi...