Hydroids (Cnidaria : Hydrozoa) from the Aegean Sea, mostly epiphytic on algae

The hydroid fauna of the Mediterranean Sea is one of the best known in the world, nevertheless in the Aegean Sea this fauna remains nearly unexplored. This paper reports on 31 species collected in the two Aegean islands of Ko s, in the Dodecanese, and Miles, in the Cyclades. Twenty-two species were c ollected on algae, chiefly on Cystoseira. Different hydroid species occupy specific regions of algal thalli, and different algal species harbour diffe rent hydroid assemblages. Five species were collected among the fouling com munities on oceanographic instruments, eight species on other substrata. Al l the species collected were already known from the Western Mediterranean a nd showed consistent ecology and depth distribution. The present record rai ses to 67 the total of hydroid species (or subspecific taxa) known from the Aegean Sea and nearby waters of Greece and Turkey. This figure is extremel y low by comparison with the 379 species known for the Mediterranean Sea.