Molting and Respiration of Euphausiids

Abstract

Euphausia pacifica, Thysanoessa spinifera, T. raschii, T. longipes (unspined form), and Tessarabrachion oculatus molted at 4- to 6-day intervals at 11 to 15 C. The average dry weight of the molts of the 1st 3 species was 5.92-9.39% of the animal''s final dry weight, and the organic fraction ranged from 73 to 83% of the dry weight of the molts. The oxygen consumption of E. pacifica at 5, 10, 15, and 20 C was directly proportional to the body weight. The slopes of the regression lines were near unity at all temperatures and the difference between the regression coefficients was not significant statistically. The respiration-temperature relation of E. pacifica suggested its eurythermic character. The Q10 value was 2.21 between 5 and 10C and increased to 2.55 between 10 and 15 C. The Q10 value apparently did not increase with increase in body size. The upper limit of temperature tolerance for the observed population of E. pacifica was close to 20 C. On the day of molting, oxygen consumption of E. pacifica increased by an average of 34.2%. Feeding decreased on the day before and on the day of molting and increased after molting. At 15 C, a daily food intake of 0.022 mg carbon/mg dry body weight would be required to match the respiratory loss and the loss of integument during the molt.