Testicular melanin pigments and the gonadal cycle in a tropical wild passerine bird, Dicrurus adsimillis (passeriformes, dicruridae).

Seasonal variation of the coloration of the testes due to the presence of melanin pigments was observed in a wild passerine bird Dicrurus adsimillis. The proportion of melanin in the testes is highest in the recrudescence period, when the lipid content is moderate and cholesterol is present in the tissue in trace amounts. In the reproductive period, when lipids are depleted, the melanin content is very low; in this stage, cholesterol is stored in the tissue in large amounts. During the post-reproductive period, melanin pigment and lipids both fall almost to zero level and only traces of cholesterol are to be found. In the recrudescence phase, the amount of all three (i.e. melanin pigment, tissue lipids and cholesterol) rapidly increases. The probable correlation between melanogenesis in testicular tissue and hormones and their lipoid precursors is discussed.