Photoperiodic control of smoltification

This experiment is intended to provide information about transcriptional changes in the gill of Atlantic salmon during smoltification, in comparison with juvenile salmon not given the appropriate photoperiodic stimuli. Also, transcriptional changes due to osmotic stress (24H salt water challenged) will be recorded. This to better understand the transformation of the gill from a fresh water-type to a salt water-type, and possibly identify novel and important genes that are dependent upon a specific photoperiodic history for their expression. Additionally the data can be used to observe the shift in salt water response as the juvenile salmon goes through smoltification. Experimental workflow: All fish started on 24H light (LL), after one week, half of the fish were moved to short photoperiod (8:16, SP). The rest remained on LL throughout. After eight weeks, half of the fish on short photoperiod were moved back onto 24H light (SPLL). Remaining fish continued under 8:16. After another eight weeks the experiment was ended. Fish were sampled on days 0, 32, 53, 68, 89 and 110. On each sampling occasion fish were sampled directly from fresh water (FW), and from a 24H salt water (SW) stay, transferred the previous day. Weight and length was noted. Gill tissue was the taken and placed in RNAlater. Additionally plasma for measuring hypoosmoregulatory capacity was taken.