This application plans a 6 months stay for Wilson Pinto, from CCMAR and Univ. Algarve to visit Univ. Bergen and complete analysis and publication on the taurine transporter (TauT) in Senegalese sole. The project targets critical bottlenecks in the knowled ge bases for successful production of fish juveniles both in Norway and in Portugal. Taurine is present in high concentrations in animal tissues, including fish. Lacking a carboxyl group, taurine cannot be used for protein synthesis. Instead, taurine exis ts in the free form, participating in important roles such as bile salt synthesis, osmoregulation, modulation of neurotransmitters and antioxidation. Several studies have shown inter-specific and ontogenetic differences for taurine biosynthesis capacity i n fish, suggesting that during the early life stages fish can only obtain taurine from dietary sources. Hence, dietary taurine supplementation has been recommended for fish larvae. However, it is unclear if fish larvae are able to absorb dietary taurine c ontent, since TauT in digestive tract may not be functional during the early stages. Moreover, it is still unknown if TauT activity in digestive tract changes during ontogenesis, leading to differences in taurine absorption along larval development. This work aims to determine the functionality of TauT in the digestive tract of Senegalese sole larvae. For this purpose, TauT will be cloned and characterized through qPCR analysis, a very powerful in vitro technique currently used in gene expression studies. Then, a temporal and regional description of TauT expression pattern along the larval digestive tract will be done, and the aim is also to utilize in situ hybridization techniques. These methods combined will allow to visualize, locate and quantify the e xpressed mRNA of TauT genes in sole larvae digestive tract. These molecular analyses will be performed in collaboration with Prof. I.Rønnestad from the Univ. Bergen, a leading expert in fish larval digestion.