Effects of temperature on metabolism, growth and growth efficiency of Thysanoessa longipes (Crustacea: Euphausiacea) in the Japan Sea

Growth (assessed from intermolt period and molt increment) andmetabolism (oxygen consumption) of juvenile and adult Thysanoessalongipes from central Japan Sea were determined at eight differenttemperatures ranging from 0 to 14°C. The intermolt periodshortened progressively as temperature increased from 0 to 14°C.The molt increment was not assessed satisfactorily in the rearingexperiments, and therefore this was estimated from the naturalgrowth curve and habitat temperature, combined with laboratory-obtainedintermolt data. Oxygen consumption rates increased exponentiallyfrom 0 to 8°C and then leveled off. From these results,the growth was expressed as a function of temperature and bodysize and metabolism as a function of temperature. Because ofthe differential effects of temperature on growth and metabolism,the net growth efficiency NGE: 100 x growth/(growth + metabolism)]changed with temperature. The temperature at which T. longipesattained maximum NGE varied from 0 to 8°C, depending onthe body length of specimens of 5, 10, 15 and 20 mm. The presentresults are compared with our previous data on Euphausia pacificain relation to the body composition and habitat usage of thesetwo trophically important species in the food web of the JapanSea.