Spinoloricus neuhausi (Loricifera, Nanaloricidae), a new deep-sea species from Galápagos Spreading Center

Loricifera is a phylum of microscopic animals that live only in marine environments. To date, only 35 loriciferans species have been described. Here we describe Spinoloricus neuhausi nov. sp., the second loriciferan collected from the Galápagos Spreading Center. The postlarva of S. neuhausi nov. sp. is characterized by, among other features, a mouth cone with eight oral ridges of two different lengths and with a tiny furca, a unique double mouth cone pleat, a mouth tube telescoping inside the mouth cone; an introvert with eight rows of scalids (7th row is missing), the second row with nine leg-like spinoscalids, the third row with seven club-shaped scalids with thick hairs, the fourth row with 16 spinoscalids of two types, the eighth row with 30 very long unsegmented spinoscalids which possess a swollen base with a ventral row of minute hairs, the ninth row with 30 beak-like scalids alternating with 30 round plates each with a minute spine projecting posteriorly; a neck with eight single trichoscalids alternating with seven double trichoscalids (as in all Nanaloricidae), though the two elements in the double trichoscalids are well-separated; a lorica with eight cuticular plates and intercalary plicae, which have the anterior edge with a V- or a double arch shape; lorica with additional lateral spikes located at the corners of the 14 lorical spikes. We discuss our findings and compare the S. neuhausi nov. sp. with the other deep sea species assigned to the genus Spinoloricus, namely Spinoloricus turbatio which was also described from the Galápagos Spreading Center, and Spinoloricus cinziae that was retrieved from an anoxic hypersaline basin in the Mediterranean Sea. In addition, we compare the species described here with Culexiregiloricus trichiscalida, a species that has been suggested to be assigned to Spinoloricus.