First record of five species of sea urchins (class echinoidea, five orders) from the Gulf of Aden

The Gulf of Aden (GA) experiences seasonal upwelling phenomena, fostering favorable conditions for diverse marine life. Despite this richness, the known sea urchin species in the Gulf of Aden has been limited to the common long-spined (Diadema paucispinum). Our study aimed to explore and document sea urchin diversity in this region. Through scuba diving and low tide collections from coral reefs and sandbanks, we obtained samples along the Hadhramout coast, spanning from the Qusayr area to the Aden Province coast, including Azizi Island opposite Ras Imran and the sub-district of the city of Aden. This survey revealed five sea urchin species, expanding the known taxa. For the first time in the Gulf of Aden, we qualitatively registered two regular and three irregular sea urchin species: Heterocentrotus mammillatus (Linnaeus, 1758), Stomopneustes variolaris (Lamarck, 1816), Echinodiscus bisperforatus (Leske, 1778), Clypeaster humilis (Leask, 1778), and Lovenia elongata (Gray, 1845). These findings contribute to our understanding of the Gulf biodiversity and emphasize the need for continued exploration in this region.