Although its essential role has not yet been demonstrated in all animals, FUT8 aa sequence and FUT8 enzymatic activity are well conserved throughout the animal kingdom as testified by several molecular cloning and functional studies in vertebrates and invertebrates. In the present study, we report the molecular cloning and functional characterization of a cDNA AZD3839 encoding fut8 from the Sf9 lepidopteran insect cell line. As in most animal genomes, fut8 is a single-copy gene organized in several exons. These properties and the high conservation of amino acids in FUT8 catalytic domain were used to retrieve Tenovin-6 unique fut8 orthologs from a large variety of metazoan genomes and to study their exon-intron structure evolution in several insect orders. The results of this analysis allow us to propose a model of fut8 evolution throughout the animal kingdom. Furthermore, fut8 evolutionary history could be used to measure the divergences among insect genomes highlighting the frequent intron losses and gains in arthropods. We took advantage of the growing list of sequenced metazoan genomes to identify in silico several potential orthologs of the previously described FUT8 protein sequences. BLAST searches using the human FUT8 sequence and the previously described fucosyl motifs I, II and III, as hallmarks for ortholog identification, allowed the identification of 96 highly conserved FUT8-related sequences from early metazoan genomes to protostome and deuterostome genomes. In most of these genomes, one single-copy fut8 gene was identified with the notable exception of Danio rerio, Xenopus laevis and Saccoglossus kowalevskii in which two fut8 paralogs were found. Multiple sequence alignments using ClustalW highlighted the presence of the three conserved motifs and of a new ����Cys-rich���� peptide motif that is highly specific to FUT8 proteins. We then assessed the evolutionary relationships of these animal sequences as described in the Materials and Methods section. To understand the orthology relationships of arthropods FUT8 sequences, we performed Maximum Likelihood and Neighbor Joining reconstructions.