Complex sentence: Reciprocal transplant experiments have shown it is less tolerant of hyposaline conditions than close relative "Patiriella regularis", dying after 24 hour exposure to water with salinities below 25%.
Split into simpler sentences: Reciprocal transplant experiments have shown it is less tolerant of hyposaline conditions than close relative "Patiriella regularis". In laboratory conditions they die after 24 hour exposure to water with salinities below 25%.