The role of the antennal gland in ion and acid-base regulation during hyposaline exposure of the Dungeness crab Cancer magister (Dana)

A cannulation technique was developed for the collection of intermittently voided urine from the antennal glands of Cancer magister both in control (100% sea water) and following 72 h in 60% sea water. Urine flow rates determined by inulin clearance (Table 1) agreed well with volumes collected directly (Fig. 1). Ion and acid-base balance of the urine were assessed relative to haemolymph levels. In 60% SW C. magister tolerated some internal dilution but maintained levels of electrolytes above ambient except for Mg²⁺ which was hyporegulated as in control (Fig. 2). The initial acid-base response was a hypercapnic acidosis (Fig. 3) which gave way progressively to a nonrespiratory alkalosis which could be correlated with an increase in the strong ion difference. In 100% SW the urine constituted an avenue for considerable electrolyte (Fig. 4) and bicarbonate loss (Fig. 7). Urinary effluxes were elevated during the initial 12 h following transfer to low salinity but subsequently accommodated (Figs. 4, 5), and reflected, in the main, changes in tubular postfiltrational processing. In 100% SW, the antennal gland strongly reabsorbed all electrolytes except Mg²⁺, which was secreted (Fig. 6). Following external dilution, Mg²⁺ secretion stopped and Ca²⁺ reabsorption declined. Initially, increased HCO₃^- efflux (Fig. 7) accounted for the alkalinization of the urine (Fig. 5), but reabsorption increased with time. The present investigation has demonstrated that the antennal gland plays a role in acid-base balance in addition to volume and divalent cation control.