Resource partitioning in two carcinophagous confamiliars: distribution and feeding habits of psychrolutid fish on the southern Patagonian shelf

Psychrolutes marmoratus and Cottunculus granulosus, two psychrolutids, inhabit the shelf and continental slope of the southern South America between 45 and 1,250 m. Over this range, the P. marmoratus is found in depths of less than 400 m, whilst C. granulosus inhabits waters of >200 m. There is a trend of increasing total length with increasing water depth for P. marmoratus and the converse for C. granulosus. The total lengths of the species are different in the depth zone that they overlap in (200–400 m), and we hypothesise that this may reduce interspecific competition. Both are specialised carcinophagous feeding on crabs, large isopods and sea spiders, but they also prey upon polychaets and gastropods. There was no difference in the feeding spectra of similar-sized fish sampled at the same depth, indicating a similar foraging strategy. In contrast to this, the feeding spectra are quite different between the species over different depths as well as at different adult sizes. The feeding niche breadth in these species is similar to other slope dwelling fish in the area.     

N.m.r. studies of metabolism in perfused organs

Several metabolites and intracellular pH in intact organs can be studied in a non-destructive manner by phorphorus nuclear magnetic resonance (31P n.m.r.). This possibility was demonstrated by us nearly five years ago. Since then we have developed the appropriate physiological techniques and improved the n.m.r. method for the study of animal hearts and kidneys. Here we described measurements aimed at clarifying three problesm. (1) Having measured the enzyme-catalysed fluxes between phosphocreatine and ATP by the method of saturation transfer n.m.r., we examine the relations between energy supply and heart rate in the isolated perfused rat heart. (2) We describe experiments to establish the validity of the perfusion model. For the first time, we report 31P n.m.r. measurements of an in vivo rat heart and compare the results with those obtained for the perfused rat heart. (3) Ischaemia and metabolism in rabbit kidneys is investigated to establish the relation between functional and metabolic recovery after a renal transplant operation.