Ontogenetic Adaptations in Growth and Respiration of Euphausia Superba in Relation to Temperature and Pressure

Abstract

The krill egg development rate is measured in relation to temperature. The duration from spawning to hatching is about 5-6 days at -0.5°C. The embryological growth is somewhat faster at 2°C. The development of krill eggs, cultured at 20 atm, showed progression through the various cleavage stages to the formation of the blastula. However, abrupt exposure of newly spawned krill eggs to 100 and 200 atm interfered with normal development and, therefore, high pressure (200 atm) inhibited embryogenesis. The pressure acclimation potential of the various ontogenetic stages of krill exhibited a definite trend in relation to the pattern of developmental ascent of krill larval and adult stages. Nauplii were successfully acclimated in the laboratory from 100-200 atm. Advanced adult stages exhibited the least level of pressure acclimation. Gravid females showed a maximum level of acclimation at 25 atm, suggesting that spawning can occur only at depths less than 250 m. The active metabolic rate of E. superba was also investigated in this study with particular emphasis on ontogenetic differences. Postspawned female krill revealed the lowest rate of oxygen consumption. Metabolic scope of Euphausia superba is discussed in relation to ontogenetic stages and in comparison with other euphausiid species in the Antarctic Ocean.