Synthesis towards a global-bathymetric model of metabolism and chemical composition of mysid crustaceans

• Respiration of 32 mysids was a function of body mass, temperature and habitat depth.
• Ammonia excretion of 13 mysids was a function of body mass and temperature.
• Body N and C decreased and increased, respectively, with increasing habitat depth.
• Judging from C:N ratios, protein was the major organic component of most mysids.
• As exceptions, lipids predominated in the body of some deep-sea mysids.

Respiration and ammonia excretion data and chemical composition data [water content, ash, carbon (C), nitrogen (N) and C:N ratios] of 13–32 mysids from freshwater, coastal littoral, epipelagic and abyssopelagic zones of the world's oceans were compiled. The independent variables including body mass, habitat temperature and sampling depth were all significant predictors of respiration, accounting for 74–85% of the variance in the data, while body mass and habitat temperature were significant predictors of ammonia excretion, accounting for 85–86% of the variance. Atomic O:N ratios (respiration: ammonia excretion) ranged from 7.9 to 44.8 (median: 18.7), indicating protein-oriented metabolism. Body water content and ash were not correlated with body mass, habitat temperature and sampling depth, but C composition and N composition increased and decreased, respectively, with the increase of sampling depth. As judged by C:N ratios, protein was considered to be the major organic component of most mysids. However, some deep-sea mysids exhibited high C:N ratios (8.6–10.6), suggesting a predominance of lipids in the body.