Spinoloricus cinziae (Phylum Loricifera), a new species from a hypersaline anoxic deep basin in the Mediterranean Sea

Loricifera is a phylum of minute animals that live exclusively in marine sediments. More than 30 species have been described so far in this group, though several more are already known from preliminary observations. Loriciferans are characterized by a complex life cycle, which involves a succession of several adult and larval stages. Here we describe Spinoloricus cinziae sp. nov., the first loriciferan living in the deep hypersaline anoxic L'Atalante Basin (Mediterranean Sea). Among other features, the adult stage of this new species is characterized by a mouth cone with 8 oral ridges of the same length, a mouth opening with 6 oral styles; an introvert with 9 rows of scalids, the third row with 7 robust feather-like scalids, the eighth row with 30 very long unsegmented spinoscalids which possess a swollen base, the ninth row with 30 short, beak-like scalids alternating with 30 small, round plates each with a minute spine projecting posteriorly; a neck with 8 single trichoscalids alternating with 7 double trichoscalids, though the two elements in the double trichoscalids are separated; lorica with 6 cuticular plates and double intercalary plicae between the plates; lorical plates with additional spikes located at the corners. These findings are discussed and compared with the deep-sea species Spinoloricus turbatio Heiner & Neuhaus, 2007 and Culexiregiloricus trichiscalida Gad, 2009, and an amended diagnosis of genus Spinoloricus is provided. The discovery and analysis of loriciferans from the deep anoxic hypersaline L'Atalante Basin opens new perspectives for understanding the evolutionary history of Loricifera, as well as for studying metazoans living in habitats lacking molecular oxygen.