Growth and respiration rates during rearing of amphipods (Pseudorchomene sp.) collected from the deep-sea floor in the Sea of Japan

Assessment of how environmental conditions influence deep-sea organisms is vital for promoting the development of deep-sea resources of the Sea of Japan; however, basic information, such as the life cycle of organisms, remains largely unclear. In the present study, a rearing experiment for deep-sea amphipods ( Pseudorchomene sp.), which participate in material circulation in the deep-sea floor environment, was conducted. Living deep-sea amphipods were collected from a depth of 600–1000 m in the Sea of Japan, and rearing experiments were conducted using of 3.2–27.7 mm individuals for approximately 4 years, over which growth and respiration rates were evaluated. Pseudorchomene sp. are considered mature when they achieve a body length of > 17 mm, which requires 12 molts at intervals of 40–122 days over approximately 3 years after hatching. Based on the relationships among number of molts, molt interval, and body length, approximately 6 years would be required to reach the maximum size of 27.7 mm in the rearing experiment. Oxygen consumption rates of individuals 9 and 24 mm in length increased with an increase in individual size andwere 0.9–9.5 μl O 2 ind. −1 h −1 . Pseudorchomene sp. is a potential model experimental organism, and the growth and respiration rates observed in the present study provide information that could facilitate quantitative assessment and minimization of the adverse impacts of deep-sea resource development on the marine environment. • Live amphipods collected from 600 to 1000 m depth successfully reared for several years. • Amphipods were identified as Pseudorchomene sp. by genetic analysis. • Growth to initial mature size (17 mm) took approximately 1000 days and 12 molts. • Pseudorchomene sp. has a lifespan of more than 6 years.