A new crab-associated amphipod of the genus Isaeopsis Barnard, 1916 (Amphipoda: Senticaudata: Ischyroceridae) from southern Chile.

A new species of amphipod of the family Ischyroceridae is described. Isaeopsis chiloensis n. sp. was discovered in association with the cancrid species Metacarcinus edwardsii and Romaleon setosum, in the inner sea around Chiloé Island, in Southern Chile. This represents the second species of the genus Isaeopsis, a group formerly known only from South African waters.                The new species is characterized principally by the structure of the gnathopods, the propodus of pereopods 3-7 and the ornamentation of the outer ramus of uropod 3. The male gnathopod 2 has a prominent thumb in the posteroproximal margin of the propodus and the pereopods 3-7 are subchelate with the palm armed by a row of at least five strong setae. In addition, the apex of the outer ramus of uropod 3 bears a comb with more than thirty fine teeth. Isaeopsis chiloensis n. sp. is completely described and a series of illustrations is provided.