A review of the genus Janua, including Dexiospira (Polychaeta: Spirorbinae)

Janua (Dexiospira) brasiliensis and J. (D.) foraminosa are fully described for the first time and compared by a pictorial key with other species of Dexiospira and Pillaiospira. The former is very close to J. (D.) pseudocorrugata (=“Sptrorbis corrugatus”) and particularly to J. (D.) nipponica, whilst the latter occupies a central position in the group of five species (including J. (D.) steueri) which are characterized by having large four-lobed juvenile talons. Janua (Janua) pagenstecheri is the most widespread species of the genus, whereas J. (Leodora) knightjonesi seems to be confined to coral seas. In all, 14 species of Janua are recognized, whilst 19 names are here regarded as synonyms or varieties. Eleven other species sometimes placed in Dexiospira or Leodora should rather constitute the genera Circeis, Sinistrella and Romanchella. These are re-defined and their affinities are studied. The subgenus Dexiospira seems to be centred in the Indo-West Pacific, where it reaches maximum species-diversity and extension into cooler latitudes. J. (D.) pseudocorrugata var. mannarensis is pantropical and overlaps in the Mediterranean with the west European form and in the West Pacific with vars praeceps and fenestrata, and with subspecies ainu, which are characterized by small modifications of the tube or abdominal setae.