Effects of temperature on pigmentation and duration of the puerulus stage in Panulirus japonicus metamorphosed from cultured phyllosomas, with reference to wild pueruli

Abstract

The effects of temperature on the development of Panulirus japonicus pueruli metamorphosed from laboratory-cultured phyllosomas were investigated. Fifty pueruli were cultured individually in a still-water system at nine temperatures from 16˚C to 28˚C until moulting to the first-instar juvenile. The puerulus stage was divided into five developmental phases based on changes in pigmentation. The duration of each puerulus phase depended on the temperature; Bêlehrádek’s equation, D = a(T–α)^b,appropriately expressed the relationship between the duration (D) and temperature (T), where a, b, and α are constants. From the equation, the times taken at 16, 20, 24, and 28˚C to reach the first-instar juvenile after metamorphosis were estimated at 40.0, 24.1, 16.3, and 11.9 days, respectively. Field study using collectors at one coastal site in Japan showed that P. japonicus pueruli settled from May to November and that the duration of the natural puerulus stage appears to have a rather wide range depending on the seasonal variation in temperature. Most wild pueruli of this study were beyond the second phase of development when collected, so wild pueruli may spend several days offshore before settling in coastal areas.