According to these considerations, a 201 bp fragment(primers included) of the mitochondrial cytochrome b gene was selected for PCR amplification and SSCP analysis. The primers used—cytb4m13 and cytb2—successfully amplified the targeted fragment in all species analyzed (Figure 1). The degenerate primer cytb4m13 includes a –21 M13 universal sequencing site into its chain because it was designed in a previous work to facilitate sequencing of PCR products (22). The
sequencing tag was not removed in this study because, as also shown by other authors (51), it enhances the specificity while retaining the efficiency of the PCR amplification (data not
shown). The big difference in length between the cytb2 and cytb4m13 primers does not arise in any problem in PCR amplification because tagged primers, usually having melting temperature (Tm) > 72ºC, yield good results at annealing temperatures from 50º to 65ºC (51).