A new deep-sea species of the genus Gracilimesus (Isopoda: Asellota: Ischnomesidae) from the Bay of Campeche, southwestern Gulf of Mexico

摘要

A new deep-sea species of isopod is described and illustrated. The material was collected in soft substratum in the Bay of Campeche, SW Gulf of Mexico, at a depth of 2,548 m aboard the research vessel “Justo Sierra” on September 4, 2009. Gracilimesus tzasnae sp. nov. can be distinguished from all other known species by its antennula with 5 articles; uropod length vs. pleotelson 0.3×; pereonite 7 not reduced; pereopod 7 absent; pleotelson dorsal surface smooth and not separated in lateral fields. The new species represents the first described Gracilimesus in the Gulf of Mexico. We present a table with the most important diagnostic characters to separate all the known species of the genus Gracilimesus .