Patiriella mortenseni

Patiriella mortenseni is a sea star of the family Asterinidae endemic to New Zealand. Discovered as a new species in 2002, it is named after T. Mortensen, who recorded it as distinct from Patiriella regularis, the New Zealand common cushion star, in 1925.

Reciprocal transplant experiments in Fiordland have shown it is less tolerant of hyposaline conditions than close relative Patiriella regularis. This is reflected in its distribution: it lives in deeper waters (at depths of roughly 10±3 m in Milford and Doubtful Sounds), below the low salinity layer (LSL). In laboratory conditions they die after 24-hour exposure to water with salinities below 25‰.