Preliminary studies on habitat and diversity of some sea urchin species (Echinodermata: Echinoidea) on the southern Levantine basin of Egypt

Abstract For many years the sea urchin (Echinodermata: Echinoidea) diversity and habitat in the Mediterranean Levantine basin lacked complementary data despite the critical role they have as keystone species to any marine ecosystem. As the first step of the present study two stations were selected along the Alexandria coast for investigation. These two stations are the Miami area and the Abou Qir Bay. Around 200 individuals were collected monthly from each station from April 2012 till April 2013 using Scuba diving. A comparison between the two stations was done that included a comparison between the inhabiting sea urchin community and the present associated macrobenthic fauna and flora. The results showed a great similarity between the two stations in relation to the sea urchin species present in these two areas as well as the surrounding habitat. This study aims to combine the morphology tool and the molecular tool along with data gathered from the habitat of the sea urchin present in these two stations to clear uncertainties in species identification of the sea urchin community found off the coast of Alexandria. The results showed four apparent morphologically different sea urchin specimens. To ensure our findings DNA extraction and Polymerase Chain Reaction (PCR) methods were used where the amplified 16S mitochondrial DNA products from all four sea urchin groups showed four sets of bands with different sizes which suggest that these four groups of sea urchins might be of four different species. Furthermore, the morphological characters along with the resulting DNA bands cleared uncertainties about two species the Paracentrotus lividus (Lamarck, 1816) and the Arbacia lixula (Linnaeus, 1758). The other two sea urchins that were thought to be Psammechinus microtuberculatus (Blainville, 1825) and Sphaerechinus granularis (Lamarck, 1816), remained unclear in identification and this requires further biological and genetic studies.