“…The 5S rRNA genes have been primarily mapped in fish [Martins and Galetti, 1999;Martins and Wasko, 2004;Pisano and Ghigliotti, 2009], and the histone genes have been mapped in a few species, for example in mammals, amphibians, fish, mollusks, and some insects [Graves et al, 1985;Tripputi et al, 1986;Turner et al, 1988;Hankeln el al., 1993;Pendás et al, 1994;Ranz et al, 2003;Zhang et al, 2007;Cabrero et al, 2009;Cabral-de-Mello et al, 2010a, 2011a. These multigene families can be organized in separated clusters or can be associated, as has been described for example in arthropods, annelids, mollusks, and fish [Andrews et al, 1987;Drouin et al, 1987Drouin et al, , 1992Barzotti et al, 2000;Vitturi et al, 2002;Colomba et al, 2002;Eirín-López et al, 2004;Vitturi et al, 2004;Pisano and Ghigliotti, 2009;Cabral-de-Mello et al, 2010a, 2011a.…”