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Recently, we have managed to include in our species registry Philomelos Turdus in our laboratory. In this post, we will know a little more of this bird and the techniques used to determine its sex.
The Philomelos Turdus is a bird belonging to the Passeriformes order and the Turdidae family, commonly known as the Common Thrush. The size of this bird is rather small (between 20-22 cm) and is very common in the forests of northern Spain.
Although it can also be seen in the Mediterranean regions, it is a species that adapts quite well, as it can nest in parks and gardens of the cities. Their nests are made of mud. They are usually located in trees or shrubs.
The eggs are bluish with speckles, in a setting, the female gets to hatch between 3 and five eggs. Its diet is very varied; it feeds both different plants and insects. It is a bird able to use tools to get its food, and it uses stones to break the shell of the snail.
Like other species of Passeriformes, the male and female have a similar appearance, so it is challenging to differentiate them. Both sexes have brown backs with lower parts in a lighter tone and yellowish chest, and dark specks can be seen in the area of the neck, chest, and belly.
Is my turd philomelos male or female?
Due to this lack of external differences between the male and the female, it is better to use molecular techniques in the laboratory to differentiate them.
To do this procedure, the first thing to do is to extract the DNA from the feathers, blood or egg shells and then, in this case, the polymerase chain reaction (PCR) is used, as it is a reliable and fast method, to observe the results of the PCR is used agarose gel electrophoresis.
Sexing of Turdus philomelos by DNA
The sexing of Turdus philomelos by extraction of DNA consists of collecting genetic material for its later study. DNA is a complex molecule that is located in the nucleus of cells. Having such a small size requires a lot of cells to make these molecules visible. It is vital that the feathers treated are preferably ripped and not fallen so that there are more cells attached. Once we have
the cells, we have to break them so we can access the DNA.
PCR has to do with the DNA obtained in the previous step, a specific region of this genetic material is selected and copied it many times to get the most information from that region. That process is done when replicating the system that uses the live cell to obtain information.
Regarding birds, the area that interests us is the identification of sex which is based on the difference in size of the genes CHD. These genes are found on the sex chromosomes of all birds, although the little birds may not be sexing with these genes.
In general, the determination of sex in birds is observed by the differences in the morphology of their sex chromosomes like humans. In humans, the differential chromosome is the Y chromosome, being the males (XY) and the Women (XX).
But in birds the distinctive chromosome is the W chromosome, which is found in females, being in this way males (ZZ) and females (ZW). The gene CHD-W is located on the W chromosome, so it is unique to females. Thus, the gene CHD-Z is on the Z chromosome and therefore appears in both sexes (Griffiths et al., 1998).
To distinguish both chromosomes the size is observed. In birds, the Z chromosome is larger than the W chromosome. We have to consider that the W chromosome has less coding genetic information (we refer to data to direct and develop the organism), that makes this chromosome more susceptible to changes and mutations.
Finally, for the observation of the results of the PCR is used an agarose gel, which is subjected to electrophoresis. This technique consists in the separation of the molecules of DNA previously selected by their size and shape. In this way, the gene CHD-W and Gene CHD-Z will be in different regions of the gel. This way, you can determine the sex of the bird.