Discovery of a new scale worm (Annelida: Polynoidae) with presumed deep-sea affinities from an anchialine cave in the Balearic Islands (western Mediterranean)

Abstract

A remarkable new genus and species of scale worm (Annelida: Polynoidae) was found on the bottom sediments of an anchialine cave on the island of Mallorca (Balearic Islands, western Mediterranean). Specimens reach up to 2 cm long, lack eyes and body pigmentation except for a few scattered minute speckles and show enlarged parapodia and sensorial appendages. A red brain is visible through the translucent tegument. Morphological features resemble those of Eulagiscinae, currently comprising eight species in three genera. Phylogenetic analyses of mitochondrial and nuclear DNA sequences are not conclusive on the position of the new taxon but affinity to Eulagiscinae is not ruled out, particularly when taxa with missing data or non-homologous insertion sites are excluded from the analyses. Pollentia perezi gen. & sp. nov. is characterized by a unique set of morphological features: 13 pairs of dorsal elytra; a single type of notochaetae (stout, with spinous rows and pointed tip); and two types of neurochaetae (superior flattened, spinous with tridentate tip; inferior shorter and thinner, lanceolate and pectinate). Some characteristics, such as the long parapodial appendages and swimming habits, are shared with other cave scale worms. However, the new taxon is not closely related to the other two known cave-dwelling polynoids.