Supervisors:

PI: Bettina Meyer, Co-PIs: Mathias Teschke, Gabriele Gerlach

Projects and Research: 

Background

Antarctic krill, Euphausia superba, a key species in the Southern Ocean, is able to adapt to extreme seasonal fluctuations in light availability, primary productivity and sea ice extent, synchronizing its seasonal life cycle to the local light regime and food supply. This includes the growth and reproductive cycle as well as seasonal physiological patterns in metabolic activity and lipid turnover. It has been proposed that these adaptational seasonal rhythms are controlled by an endogenous timing system in krill and that photoperiod seems to act as a main Zeitgeber, synchronizing the internal clock with the natural year. However, the signaling cascade that links the photoperiod cue to the target response is unknown yet and molecular mechanisms of the seasonal timing system remain far from being understood. Moreover, the circumpolar distribution of Antarctic krill extends a remarkably broad latitudinal range from ~51°S to ~70°S meaning that the seasonal photoperiodic regime as well as the accompanied seasonal food pattern experienced by krill may differ significantly with latitude.

Aim of the study

This PhD project aims to study latitude dependent gene expression patterns during the phenology of krill focussing on physiological functions such as lipid dynamics, metabolic activity and maturation. In addition, the project aims to investigate the putative role of the krill’s circadian clock in photoperiodic time measurement. The project is divided into three sub-projects: (1) the analysis of seasonal gene expression patterns from different latitudinal regions, (2) studying differential gene expression during long-term photoperiodic controlled lab experiments of simulated latitudinal regions and (3) determining transcript levels of canonical clock genes in correlation with key physiological target genes around the diurnal cycle under different photoperiodic conditions throughout the season.

Analytical approach

An RNAseq approach will be used to examine the transcriptomic profile of summer and winter field samples of three different latitudinal regions: South Georgia (54°S), Bransfield Strait (63°S) and Lazarev Sea (66°-70°S). Based on these results selected genes will be used to develop a TaqMan low density array card representing up to 300 seasonally important target genes. Subsequently, these cards will be used to test the impact of photoperiod on physiological functions of Antarctic krill within lab experiments under controlled light conditions (54°S, 63°S and 66°S) and maximum food supply over a period of 1 year. The role of the endogenous clock of Antarctic krill in seasonal time keeping will be analysed in field samples of 24-h sampling periods in different seasons. Single gene assays and a clock orientated TaqMan card will be used to look for rhythmic gene expression patterns of internal clock genes in correlation to oscillations of metabolic key enzymes.