Growth and respiration during the larval development of Hyas coarctatus (Decapoda: Majidae)

Abstract

The spider crab Hyas coarctatus Leach was reared in the laboratory from hatching to metamorphosis, and growth and respiration were measured in all larval stages at regular intervals of time. Growth, measured as dry weight (W), carbon (C), nitrogen (N), hydrogen (H), and energy (E; calculated from C), can be described in the zoeal stages by a power function, and as a non-linear (quadratic) regression equation of time (t; days) in the megalopa. C, H, and E showed higher growth rates than W or N during the zoeal stages, suggesting accumulation mainly of lipids rather than protein. Respiration (R; expressed as μg O₂h^-1 individual^-1) increased as a linear function of t in the zoeal stages. From this simple relationship and the above power function for increase in W, equations describing the relationships between R and W and between QO ₂ (μg O₂h^-1 mg^-1), t, and W were derived for zoeal development. Both R and QO ₂ first decreased during megalopa postmoult, then increased for a short period, before decreasing again toward metamorphosis. No descriptive models were proposed for these changes in the ultimate larval stage. The total amount of energy lost by zoeal respiration was less than their net gain by body growth, whereas the megalopa respired almost 14 times the amount of energy eventually gained. This means that net growth efficiency is far lower in the megalopa than in the zoeal stages of H. coarctatus.