Methodology:

An entrainment tank containing around 250 l of flowing seawater was used for studying the spatial and temporal expression of clock genes. The animals were maintained under a controlled light/environmental regime that mimicked that normally experienced by swarms at the latitude from which they were taken. After 2 days entrainment, a sample of krill (usually 10 animals) was taken at 3-hourly intervals over a period of 48 hours; these were either preserved in RNAlater (a commercially available solution for long term storage of tissues without deterioration of their RNA) or were frozen directly at -80C. During the next 24 hours samples were taken at 6-hourly intervals and fixed in PFA as above. The lights were switched off and on the 2nd, 3rd and 4th day in total darkness, the above sampling regime was repeated.

The circadian entrainment experiment was carried out twice, using animals from nets at latitudes of 60S and 52S. A total of 1,090 preserved specimens were returned to the UK for subsequent molecular genetic analysis.

A second entrainment tank was used to study the moult cycle genes. Up to 20 animals were removed each day at the same time, measured, moult staged and the heads preserved in RNAlater for subsequent use in the microarray studies to isolate the genes involved in the moult cycle. A total of 590 krill in RNAlater were returned to the UK at -20C for further analysis. The ambient water temperatures for these latitudes were taken from CTD data.

Data collection:

See the following for details:

Seear PJ, Tarling GA, Burns G, Goodall-Copestake WP, Gaten E, Ozkaya O, Rosato E (2010). Differential gene expression during the moult cycle of Antarctic krill (Euphausia superba) BMC Genomics, 11: 582.

Seear P J, Tarling GA, Teschke M, Meyer B, Thorne MAS , Clark MS, Gaten E, Rosato E (2009) Effects of simulated light regimes on gene expression in Antarctic krill (Euphausia superba Dana) Journal of Experimental Marine Biology and Ecology, 381: 57-64