en Biology & physiology Biology & physiology پژوهشي Orginal research papers <font face="Times New Roman" size="3"> </font><p class="MsoNormal" style="margin: 0cm 0cm 0pt text-align: justify line-height: 150% unicode-bidi: embed direction: ltr text-autospace: mso-layout-grid-align: none"><font size="3"><font face="Times New Roman"><span style="mso-fareast-font-family: Calibri mso-bidi-font-family: "Times New Roman" mso-fareast-language: EN-US">The scanning electron microscope was used to investigate the ultrastructures of the egg membrane surface (unfertilized egg) of an endemic cyprinid fish, <i>Cyprinion tenuiradius</i><b> </b>Heckel, 1849. </span><span style="mso-bidi-font-family: "Times New Roman"">The eggs of this species were </span><span style="mso-fareast-font-family: Calibri mso-bidi-font-family: "Times New Roman" mso-fareast-language: EN-US">almost circular in shape</span><span style="mso-bidi-font-family: "Times New Roman"">, had a smooth surface and one type II micropyle </span><span style="mso-fareast-font-family: Calibri mso-bidi-font-family: "Times New Roman" mso-fareast-language: EN-US">consisting of the flat pit and a long canal </span><span style="mso-bidi-font-family: "Times New Roman"">in the animal polar region. </span><span style="mso-fareast-font-family: Calibri mso-bidi-font-family: "Times New Roman" mso-fareast-language: EN-US">The micropyle region was not flat, micropyle was circular or oval in shape and the micropyle canal was located in its center. Round or oval accessory pores were also observed in the pit around of the micropylar canal. The surface of zona radiata was smooth with a uniform distribution of almost round pores with lips. <o:p /></span></font></font></p><font face="Times New Roman" size="3"> </font> Morphology, Fertilization, Cyprinion tenuiradius, Micropyle, Accessory openings 657 665 http://jifro.ir/browse.php?a_code=A-10-1-187&slc_lang=en&sid=1 H. R. Esmaeili esmaeili@susc.ac.ir 10031947532846004028 10031947532846004028 Yes A. Gholamifard 10031947532846004029 10031947532846004029 No