Costasiella usagi is known in the Marshalls from two specimens found by Marissa and Peter Brown in the lagoon off Kwajalein Island on 6 February 2015. They were 8 to 10mm in length and crawling on the sea grass Halophila minor at a depth of about 13m. Specimens were previously known from Guam and Japan through Australia, and the Marshalls represents a range extension eastward.
Created 6 February 2015