def _read_codon_usage_orgs_file(filename):
    """Reads Codon Usage Database table of species file."""
    codon_orgs = {}
    with open(filename, 'r') as textfile:
        next(textfile)
        for line in textfile:
            tokens = line.strip().split('\t')
            codon_orgs[tokens[0]] = tokens[1]
    return codon_orgs
