Fig. 1. Changes in _O2 and associated f_H (filled symbols) and f_V (open symbols) measured simultaneously for 10 min three times daily in 12 N. angustata (mean ± s.e.m., n=12, N=36 observations), subjected to the following sequential measurements. Circles, recordings made for 120 h following initial anesthesia, surgery and placement in the respirometry chamber; squares, recordings taken for the subsequent 120 h after ingestion of a 5%b.m. food ration; triangles, daily recordings made in the same fish after it had returned to pre-fed values and had then undergone anaesthesia, bilateral section of the vagal nerve and placement back in the respirometry chamber.