Respiration, energy balance and development during growth and starvation of Carcinus maenas L. larvae (Decapoda:Portunidae)

Abstract

In all larval stages of Carcinus maenas L. oxygen consumption was measured at three temperatures (12,18,25 °C). Values increased during development and were in the range of 0.037 ± 0.01 (zoea-1, 12°C, x ̄ ± 95% CL ) to 0.734 ± 0.047 μl O 2 · h −1 · ind −1 (megalopa, 25 °C). Growing larvae showed temperature dependent trends in weight specific respiration rates (referred to dry wt; DW), with values between ≈2.4 and 9.4 μl O 2· h −1·mg DW −1. Increase in oxygen consumption of megalops did not differ much at temperatures between 18 and 25 °C. This points to an exceptional physiological position of this stage. Fed zoea-1 of C. maenas (18 °C) revealed growth rates in terms of 40% DW, 20% carbon (C), 30% nitrogen (N) and 65% hydrogen (H). At the same time larvae gained individual energy by 13% (J · ind −1), while weight specific energy dropped by ≈ 19% (J · mg DW −1) during the first day and remained constant until the moult. Starved zoea-1 of C. maenas (18 ° C) gained ≈ 20 % in DW through the first day, probably caused by inorganic salts which enter the organism after the moult of the prezoea. DW dropped to ≈ 25 % of initial value, when starvation continued. Single components decreased by ≈50% (C), 54% (N), 57% (J · ind −1). Weight specific energy (J · mg DW −1) decreased by 40% during the first 4 days of starvation, remaining constant thereafter. Individual respiration rate ( R) dropped by 61 %, weight specific respiration rate ( QO 2) by 55 %. Individual energy loss in starved zoea-1 was 0.077 J over a period of 11 days. In this period ≈ 9.3 μl O 2·ind −1 were consumed. Thus effective oxygen capacity was lower than in growing larvae. It dropped to 5.3 J·mlO 2 −1 after 4 days and remained constant if starvation continued, i.e. 65 % of possible energy loss occurred during the first 4 days. Decrease in requirement for oxygen and its effective capacity were both recognized as independent components of survival during starvation. Partitioning of energy through individual larval development of C. maenas was investigated for all five larval stages. The cumulative budget could be calculated: consumption ( C) = 28.23 J, growth ( G) = 0.92 J, exoskeleton ( Ex) = 0.20 J, metabolism ( M) = 5.30 J, egestion and excretion ( E) = 21.82 J. Mean gross and net growth efficiency were, K 1 = 3.3% and K 2 = 14.8%, respectively.