Black-faced blenny 2007) and "T. tripteronotum" (Risso, 1810). Besides "T. delaisi", all species are endemic to the Mediterranean Sea. The species "T. delaisi" is subdivided in two subspecies: "T. delaisi delaisi" in the Mediterranean Sea and "T. delaisi xanthosoma" in the Atlantic Ocean. The subspecies can be distinguished by their courtship behaviour: "T. delaisi delaisi" court in free water and "T. delaisi xanthosoma" stay on the ground for courtship behaviour. The speciation process is still under discussion and several hypotheses have been proposed. Black-faced blenny The black-faced blenny ("Tripterygion delaisi") is a small benthic fish from the family Tripterygiidae (triplefin-blennies). It occurs
Sand goby rounded. In males, there is a conspicuous dark spot on the anterior dorsal fin and in both sexes there is a black patch on the caudal peduncle. The general colour is sandy brown with indistinct dark blotches and reticulations on the dorsal surface and dark striations on the pale fins. The colour of the male darkens during the breeding season and his fins become more coloured. The average size is about . The sand goby normally lives at greater depths than the common goby. It feeds on small invertebrates living on the seabed especially amphipods. It is well camouflaged and