RESPIRATORY QUOTIENT AND CALCIFICATION OF NAUTILUS-MACROMPHALUS (CEPHALOPODA, NAUTILOIDEA)

Respiration and calcification were investigated in the ectocochleate c ephalopod Nautilus macromphalus Sowerby. Specimens were collected off New Caledonia, in October 1991, and kept at the Noumea Aquarium until December 1991. The respiratory quotient and calcification rate of 5 in dividuals were measured during 14 short term incubations (63 to 363 mi n). Oxygen uptake was recorded with a polarographic oxygen sensor. CO2 flux and calcification were calculated from changes in pH and alkalin ity (alkalinity-anomaly technique). Several methods were used to compu te the respiratory quotient (RQ); a functional regression indicated an RQ of 0.74. CaCO3 exchange rates were linearly related to respiratory quotient, calcification occurring in individuals with a low RQ. CaCO3 uptake from the surrounding water was noncontinuous. From the highest CaCO3 uptake, maximum growth rate was estimated as 7.1 mg shell wt h( -1) (= 61 g yr(-1)).