Željka Pezer: Sex determination in some Cetacean species by the polymerase chain reaction. Diploma Thesis. Faculty of Science. Zagreb, 2003.



Investigations of cetacean biology often encounter problems in gaining information from the field. It is not always possible to morphologically determine sex of an animal whose carcass was found in an advanced state of decomposition. Determining the gender of living cetaceans is also difficult or impossible, since in most species sexually dimorphic characters are poorly marked. The purpose of this study was to introduce a reliable method for molecular sexing of cetaceans that could be used on tissue samples from carcasses, as well as on skin biopsies from living animals. Total DNA was extracted from muscle tissue of 49 cetacean specimens; 27 bottlenose dolphins (Tursiops tmncatus\ 11 striped dolphins (Stenella coeruleoalba\ 7 Risso's dolphins (Grampus griseus), 2 Cuvier's beaked whales (Ziphius cavirostris) i 2 fin whales (Ba/aenoptera physalus). In one case DNA was extracted from skin. All samples were taken from corpses in different state of decomposition. The introduced method uses polymerase chain reaction (PCR) to amplify regions on ZFY and ZFX, which are the homologous genes located on Y- and X-chromosomes, respectively. Three oligonucleotide primers were employed to produce fragments specific for the ZFY and ZFX sequences. Amplification products differed in length and therefore gave distinct, sex-specific bands on 1% agarose gel after electrophoresis. The sex of 40 cetacean specimens was successfully determined. Method tailed in cases of strongly decomposed tissues, but was shown to be reliable and efficient when applied on fresh or well preserved samples.