Vertical migration in Antarctic krill
Gene function in Antarctic krill: determining the role of clock-genes in synchronized behavioural patterns (NERC grant: NE/D008719/1 - E.Rosato, E.Gaten, C.P.Kyriakou)
Antarctic krill is a strategically-important species in the Southern Ocean ecosystem, being the principal food item of many higher predators such as whales, seals and sea-birds, and a major consumer of phytoplankton. Its success in the Antarctic is reflected in the large biomass levels, unparalleled anywhere else in the World’s oceans. It has been commercially harvested since the 1960s and today is the subject of an active fishery by several nations. The aim of this project is to describe for the first time how the daily migration behaviour and the long-term moulting behaviour of krill are controlled by clock genes. This will involve a series of behavioural observations to show how krill migrate under controlled conditions and molecular investigations to identify the circadian genes associated with this behaviour. We also aim to identify the genes that control the reproductive and moulting rhythms and show how their actions vary with time.
This work is being carried out in association with Ben Hunt (NERC-funded PhD student), Dr Ezio Rosato & Prof C.P. Kyriacou (Department of Genetics, University of Leicester) and Dr Geraint Tarling (British Antarctic Survey) funded by NERC (Antarctic Funding Initiative, round 7, 2007-2011).
Field work in the Southern Ocean, 2008
During January and February 2008, I carried out fieldwork on vertical migration of Antarctic krill (Euphausia superba) as part of cruise JR177 aboard the RRV James Clark Ross.
Krill from two areas were used, one from around 60 degrees South from the vicinity of Signy Island (South Orkneys), and the second from North-West of South Georgia at around 52 degrees South.
Vertical migration behaviour was investigated using an activity monitor that recorded the spatial movements of individual krill over a 10 day period, both under a light/dark cycle and in continuous darkness.
Entrainment tanks were used to obtain krill for molecular analysis of circadian rhythms and the moult cycle in addition to krill taken directly from the nets.
Analysis of the activity monitor experiment revealed the influence of both 24 h and 12 h endogenous rhythms on the activity of krill, although it is clear that social interactions and food availability have a profound effect on both entrainment to light and behaviour (Gaten et al., 2008). Analysis of gene expression in dark-incubated krill (corresponding to winter light conditions) have provided the first molecular validation of a photoperiodic response in krill (Seear et al., 2009). The molecular analysis of entrained animals has resulted in the identification of many genes that are differentially expressed across the krill moult cycle. Using cDNA microarray techology combined with detailed moult staging, we have obtained one of the most highly resolved molecular descriptions of the crustacean moult cycle achieved to date (Seear et al., 2010).