Description of Elthusa aquabio sp. n. (Crustacea: Isopoda: Cymothoidae), a branchial fish parasitic isopod from Indian waters Author Aneesh, Panakkool Thamban Author Helna, Ameri Kottarathil Author Raj, Smrithy Author Kumar, Appukuttannair Biju text Journal of Natural History 2023 2023-08-17 57 21 - 24 1193 1205 http://dx.doi.org/10.1080/00222933.2023.2242099 journal article 10.1080/00222933.2023.2242099 1464-5262 Genus Elthusa Schioedte and Meinert, 1884 Elthusa , Schioedte and Meinert 1884: 337 . – Bruce 1990: 254 . – Trilles and Randall 2011: 453– 454 . – Hadfield et al . 2017: 125–135 . – van der Wal et al . 2019: 3 . – Aneesh et al . 2020a: 2 . Type species. Livoneca emarginata Bleeker, 1857 . Remarks. Aneesh et al . (2020a) provided a detailed generic diagnosis based on the syntype specimen of the type species examined by J.P. Trilles and the description of the same provided by Trilles and Randall (2011) . Based on the revised generic diagnosis, 13 species previously included in the genus Elthusa are currently retained in Elthusa , but as incertae sedis , as their characters do not fit the genus. The following combinations of characters distinguish the genus Elthusa : having a weakly vaulted pereion; wide pleon with all pleonites wide; antennulae shorter than or subequal in length to antennae with their bases not in contact; cephalon posterior margin that is not trilobed; coxae equal size on both sides; coxae 5–7 flat and broader than anterior coxae (2–4); coxae 6–7 equal to pereonite or extending beyond, overlapping the lateral margin of pleonites; mandible palp slender, article 3 or 2 and 3 with distolateral spines setae; pereopods with relatively short dactylus; uropods short, not reaching the posterior margin of pleotelson. For a detailed comparison of Elthusa with other branchial cymothoid genera, see Aneesh et al . (2020a) .