**3. Results**

#### *3.1. Molecular Characterization of NfuNT-6*

A putative NT-6 coding sequence was retrieved from the *N. furzeri* transcriptome browser [32]: the sequence is deposited under the Genebank accession number GAIB01193979.1. NfuNT-6 was aligned with the predicted NT-6/7 sequences available in some actinopterygians species (*Xiphophorus*, *Cyprinus carpio* and *Danio rerio*), as well as mammalian and *D. rerio* neurotrophins. NT-4/5 of *D. rerio* was not included in the alignment because it is not still annotated on GenBank. GDNF of *D. rerio*

was used as outgroup. The evolutionary history was inferred using the Minimum Evolution method, having selected long nucleotides sequences. The evolutionary distances were computed using the *p*-distance method and are in the units of the number of base differences per site. The analysis involved 17 nucleotides sequences (Figure 1). The ME tree was searched using the Close-Neighbor-Interchange (CNI) algorithm at a search level of 1. The Neighbor-joining algorithm was used to generate the initial tree. All positions containing gaps and missing data were eliminated. The resulting phylogram clearly shows that the *N. furzeri* sequence is nested within a clade of Actinopterygian sequences, and high percentage of conservation with fish neurotrophin-3.

**Figure 1.** Evolutionary relationships of taxa. The evolutionary history was inferred using the Minimum Evolution method. The optimal tree with the sum of branch length = 4.92138622 is shown. The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. This analysis involved 17 nucleotide sequences. Codon positions included were 1st+2nd+3rd+Noncoding. All ambiguous positions were removed for each sequence pair (pairwise deletion option). There were 3752 positions in the final dataset.
