Respiratory rate, haemolymph oxygen tension and haemocyanin level in the shrimp Palaemon adspersus: Rathke

Abstract

The marine shrimp Palaemon adspersus Rathke, frequenting Zostera meadows, shows an oxygen consumption rate (MO 2) that is independent of water oxygen tension (P wO 2) as PO 2 decreases to a critical point (P cr) near 70 mm Hg. This respiratory independence is associated with maintenance of a relatively constant “arterial” (post-branchial) haemolymph tension (P aO 2) at 70–80 mm Hg. At lower P wO 2 values, both MO 2 and P aO 2 fall, reflecting, in contrast to the above independence, a direct dependence of MO 2 on internal PO 2. Haemolymph copper measurements demonstrate relatively high haemocyanin concentrations and oxygen-carrying capacities, but MO 2 levels reflect an insignificant rôle for the pigment as an oxygen store. The data are discussed as regards adaptations for aerobic metabolism.