en Biology & physiology Biology & physiology پژوهشي Orginal research papers <span class="longtext1"><span style="line-height: 115% font-family: "Times New Roman","serif" font-size: 12pt mso-bidi-language: AR-SA mso-fareast-font-family: Calibri mso-ansi-language: EN-US mso-fareast-language: EN-US mso-ascii-theme-font: major-bidi mso-hansi-theme-font: major-bidi mso-bidi-theme-font: major-bidi">Sea Urchin is one of the most useful tools in developmental biology studies because this organism has the simplest kind of developmental stages. We aimed to determine developmental stages and timetable of <i>Echinometra</i> <i>mathaei</i> embryo (the species of Persian Gulf). The spawning of <i>E.</i> <i>mathaei</i> was induced by</span></span><span style="line-height: 115% font-family: "Times New Roman","serif" font-size: 12pt mso-bidi-language: AR-SA mso-fareast-font-family: Calibri mso-ansi-language: EN-US mso-fareast-language: EN-US mso-ascii-theme-font: major-bidi mso-hansi-theme-font: major-bidi mso-bidi-theme-font: major-bidi"> <font face="Times New Roman"><font size="3"><span class="longtext1"><span style="line-height: 115% mso-ansi-font-size: 12.0pt mso-bidi-font-size: 12.0pt">0.5M KCl injection (1ml) into the coelomic cavity. After fertilization, embryos were placed in beakers and were incubated at </span></span>29</font>^◦C <span class="longtext1"><span style="line-height: 115% mso-ansi-font-size: 12.0pt mso-bidi-font-size: 12.0pt"><font size="3">and</font></span></span></font></span><span style="line-height: 115% font-family: "Times New Roman","serif" font-size: 12pt mso-bidi-language: AR-SA mso-fareast-font-family: "Times New Roman" mso-ansi-language: EN-US mso-fareast-language: EN-US mso-ascii-theme-font: major-bidi mso-hansi-theme-font: major-bidi mso-bidi-theme-font: major-bidi"> a salinity of</span><span class="longtext1"><span style="line-height: 115% font-family: "Times New Roman","serif" font-size: 12pt mso-bidi-language: AR-SA mso-fareast-font-family: Calibri mso-ansi-language: EN-US mso-fareast-language: EN-US mso-ascii-theme-font: major-bidi mso-hansi-theme-font: major-bidi mso-bidi-theme-font: major-bidi"> 39 ppt </span></span><span style="background: white line-height: 115% font-family: "Times New Roman","serif" font-size: 12pt mso-bidi-language: AR-SA mso-fareast-font-family: Calibri mso-ansi-language: EN-US mso-fareast-language: EN-US mso-ascii-theme-font: major-bidi mso-hansi-theme-font: major-bidi mso-bidi-theme-font: major-bidi">until embryos reached the pluteus</span><span class="mediumtext"><span style="line-height: 115% font-family: "Times New Roman","serif" font-size: 12pt mso-bidi-language: AR-SA mso-fareast-font-family: Calibri mso-ansi-language: EN-US mso-fareast-language: EN-US mso-ascii-theme-font: major-bidi mso-hansi-theme-font: major-bidi mso-bidi-theme-font: major-bidi"> </span></span><span class="longtext1"><span style="line-height: 115% font-family: "Times New Roman","serif" font-size: 12pt mso-bidi-language: AR-SA mso-fareast-font-family: Calibri mso-ansi-language: EN-US mso-fareast-language: EN-US mso-ascii-theme-font: major-bidi mso-hansi-theme-font: major-bidi mso-bidi-theme-font: major-bidi">stage. The developmental stages of embryos and the timing of each stage including cleavage, morulae, blastula, gastrula, prism and pluteus larvae were studied under the microscope. Our results showed that after 30 hours from fertilization time, the embryos developed to pluteus larvae. <i>E.</i> <i>mathaei</i> had the shorter development time in comparison to the other Sea Urchin species. </span></span><span style="line-height: 115% font-family: "Times New Roman","serif" font-size: 12pt mso-bidi-language: AR-SA mso-fareast-font-family: "Times New Roman" mso-ansi-language: EN-US mso-fareast-language: EN-US mso-ascii-theme-font: major-bidi mso-hansi-theme-font: major-bidi mso-bidi-theme-font: major-bidi">Therefore, it may be appropriate as </span><span class="longtext1"><span style="line-height: 115% font-family: "Times New Roman","serif" font-size: 12pt mso-bidi-language: AR-SA mso-fareast-font-family: Calibri mso-ansi-language: EN-US mso-fareast-language: EN-US mso-ascii-theme-font: major-bidi mso-hansi-theme-font: major-bidi mso-bidi-theme-font: major-bidi">a model organism in biological researches</span></span><span style="line-height: 115% font-family: "Times New Roman","serif" font-size: 12pt mso-bidi-language: AR-SA mso-fareast-font-family: "Times New Roman" mso-ansi-language: EN-US mso-fareast-language: EN-US mso-ascii-theme-font: major-bidi mso-hansi-theme-font: major-bidi mso-bidi-theme-font: major-bidi">.</span><span style="line-height: 115% font-family: "Times New Roman","serif" font-size: 12pt mso-bidi-language: AR-SA mso-fareast-font-family: Calibri mso-ansi-language: EN-US mso-fareast-language: EN-US mso-ascii-theme-font: major-bidi mso-hansi-theme-font: major-bidi mso-bidi-theme-font: major-bidi"> </span> Sea Urchin, Echinometra mathaei, Biological Model, Development, Timetable, Persian Gulf 294 304 http://jifro.ir/browse.php?a_code=A-10-1-156&slc_lang=en&sid=1 V. Ghorani 10031947532846003192 10031947532846003192 No M. S. Mortazavi mseddiq1@yahoo.com 10031947532846003193 10031947532846003193 Yes E. Mohammadi 10031947532846003194 10031947532846003194 No E. Sadripour 10031947532846003195 10031947532846003195 No M. Soltani 10031947532846003196 10031947532846003196 No N. Mahdavi Shahri 10031947532846003197 10031947532846003197 No F. Ghassemzadeh 10031947532846003198 10031947532846003198 No