Taxonomy and geographic distribution of the ischnomesidae family (crustacea, isopoda) from brazilian deep sea

Abstract

The family Ischnomesidae belongs to the order Isopoda; they are marine benthic animals, essentially from the deep sea, and distributed all around the world. They are included in the suborder Asellota, and presents distinctive features diagnostic such as pereonite V elongated in relation to the others and the completely immobile head, fused to the pereonite I. The main objective of this study was to make a taxonomic and geographic distribution of the family Ischnomesidae from the Brazilian deep sea, through the identification and description of the species found in this region. The material examined was collected during oceanographic campaigns coordinated by Petrobrás in three Brazilian's sedimentary Basins: Alagoas-Sergipe Basin, Espírito Santo and Campos Basin. The specimens are deposited in the crustacean collections of the "Universidade Federal de Pernambuco" (UFPE), "Universidade Federal de Sergipe" (UFS) and "Museu Nacional do Rio de Janeiro" (MNRJ). The specimens were dissected and drawn using a microscope with a slide. The specimens were stained in Clorazol Black and their parts were mounted on semi-permanent slides with gelatin-glycerinated. The digital drawings were made in CorelDRAW® X7 graphics program. As result, five new species were found for science and a new genus: Ischnomesus sp. nov. 1, Ischnomesus sp. nov. 2, Ischnomesus sp. nov. 3, Gracilimesus sp. nov. and Ischnomesidae gen. nov. et sp. nov. In addition, the discovery of these species permitted to register new occurences for the genera: Ischnomesus and Gracilimesus for South Atlentic. The discovery of the new genus brought a new diagnosis to the family, with the addition of biramaous uropods, never before described for the group. The new genus also presents the body surface covered with small setae; antennula with 6 articles; pereonites V-VII, pleonite 1 and pleotelson freely articulated. The species with the widest geographic distribution was Gracilimesus sp. nov. found in all Basins studied. The species with restrict geographic distribution were Ischnomesus sp. nov. 1 (Espírito Santo Basin and Campos) and Ischnomesus sp. nov. 2 (Espírito Santo Basin and Alagoas-Sergipe).