A new species of Olavius (Tubificidae) from the Algarve coast in Portugal,the first East Atlantic gutless oligochaete with symbiotic bacteria

The gutless oligochaete Olavius algarvensis sp.n. is the first representati ve of the speciose genus of bacteria-symbiotic tubificids from the East Atl antic shore. In diagnostic features of the genital organs it deviates from its Caribbean congeners while ir conforms with them in ultrastructural deta ils of the bacterial symbiosis. Moreover. the ecological situation of the w orms is similar in both localities, although the sediment in the Algarve co ast is siliceous and not calcareous. Phylogenetic relationships of the symb iotic bacteria with those of Caribbean gutless tubificids remain to be clar ified.