Abstract:
Irrawaddy dolphin (Orcaella brevirostris) is one of the marine mammals species in Thailand. Since the continuing decline of Irrawaddy population, they have been classified by the IUCN as critically endangered species. There are many reproductive studies of several dolphin species. However, only limited studies on Irrawaddy species have been investigated. The objectives of this study were to determine the characteristics and morphology of Irrawaddy dolphins sperm and to find the staining properties for semen quality evaluation. Three male Irrawaddy dolphins were used for semen collection by self-ejaculated technique. The semen samples were stained with Papanicolaou, Shorrs stain, Diff Quick, Eosin, 0.1% Toluidine blue, Williams stain, Hematoxylin & Eosin and Eosin-nigrosin stain. All specimens were evaluated under light microscope and electron microscope. The result showed that the color of Irrawaddy dolphins semen was milky white. The average semen volume was 3.42±0.49 ml., The average sperm density was 1.44±0.586x109 sperm/ml. The dorsal view of sperm heads was elongated and ellipsoidal. The anterior region of sperm head was thin, flat and slightly concave. The ridges running parallel were long axis of the posterior region of these sperm heads. The neck was thick and long. The sperm length and width were 4.37±0.18 μm and 1.61±0.14 μm, respectively. The results indicated that sperm with DNA damage could be evaluated by Touidine blue staining. In addition, Diff Quick, William's staining, Hematoxylin & Eosin, Papanicolaou and Shorrs staining were applicable for assessing sperm morphology.