The Antarctic krill, Euphausia superba, has evolved seasonal rhythms of physiology and behaviour to survive under the extreme photoperiodic conditions in the Southern Ocean. However, the molecular mechanisms generating these rhythms remain far from understood. The aim of this study was to investigate seasonal differences in gene expression in three different latitudinal regions (South Georgia, South Orkneys/Bransfield Strait, Lazarev Sea) and to identify genes with potential regulatory roles in the seasonal life cycle of Antarctic krill. The RNA-seq data were analysed (a) for seasonal differences between summer and winter krill sampled from each region, and (b) for regional differences within each season. A large majority of genes showed an up-regulation in summer krill in all regions with respect to winter krill. However, seasonal differences in gene expression were less pronounced in Antarctic krill from South Georgia, most likely due to the milder seasonal conditions of the lower latitudes of this region, with a less extreme light regime and food availability between summer and winter. Our results suggest that in the South Orkneys/Bransfield Strait and Lazarev Sea region, Antarctic krill entered a state of metabolic depression and regressed development (winter quiescence) in winter. Moreover, seasonal gene expression signatures seem to be driven by a photoperiodic timing system that may adapt the flexible behaviour and physiology of Antarctic krill to the highly seasonal environment according to the latitudinal region. However, at the lower latitude South Georgia region, food availability might represent the main environmental cue influencing seasonal physiology.

南极磷虾，磷虾，已经进化出生理和行为的季节性节律，以在南大洋的极端光周期条件下生存。然而，产生这些节律的分子机制仍远未了解。本研究的目的是调查三个不同纬度地区（南乔治亚、南奥克尼/布兰斯菲尔德海峡、拉扎列夫海）基因表达的季节性差异，并确定在南极磷虾的季节性生命周期中具有潜在调节作用的基因。对 RNA-seq 数据进行了分析（a）从每个区域采样的夏季和冬季磷虾之间的季节性差异，以及（b）每个季节内的区域差异。与冬季磷虾相比，所有地区的夏季磷虾的大部分基因都显示出上调。然而，南乔治亚岛的南极磷虾基因表达的季节性差异不太明显，这很可能是由于该地区低纬度地区的季节性条件较温和，夏季和冬季之间的极端光照条件和食物供应较少。我们的研究结果表明，在南奥克尼/布兰斯菲尔德海峡和拉扎列夫海地区，南极磷虾在冬季进入代谢抑制和退化发育（冬季静止）状态。此外，季节性基因表达特征似乎是由光周期计时系统驱动的，该系统可以根据纬度区域使南极磷虾的灵活行为和生理适应高度季节性的环境。然而，在低纬度的南乔治亚地区，食物供应可能是影响季节性生理的主要环境因素。