A taxonomic review of the branchial fish parasitic genus Elthusa Schioedte & Meinert, 1884 (Crustacea: Isopoda: Cymothoidae) from Indian waters, with the description of three new species

The genus Elthusa Schioedte & Meinert, 1884 from Indian waters is reviewed and three new species are described from India. A revised generic diagnosis is provided based on the type species and 13 species of Elthusa are regarded as Elthusa incertae sedis. Female stages of Elthusa fistularia sp. nov. collected from Fistularia petimba Lacepede,1803 and Elthusa pseudorhombus sp. nov. from Pseudorhombus dupliciocellatus Regan, 1905 are described based on the female. Elthusa uranoscopus sp. nov. from Uranoscopus guttatus Cuvier, 1829 described from female and male. The female and male stages of Elthusa samariscii (Shiino, 1951) are redescribed and the transitional and larval (premanca and manca) stages are described. All the species were collected from the southwest coast of India. Elthusa fistularia sp. nov. is distinguished by cephalon 1.20 times wider than long; pleotelson broadly rounded, 1.70 times as wide as long, lateral margin convex; widest pleon 0.80 width of widest pereon; uropod rami subequal; and antenna 9-segmented, antennular bases moderately wide set. Elthusa pseudorhombus sp. nov. is characterized by cephalon 1.70 times wider than long; widest pleon 0.75 width of widest pereon; pleotelson 1.50 times as wide as long, evenly rounded; antenna with 10 articles, antennal bases widely separated; and uropod endopod shorter than exopod. Elthusa uranoscopus sp. nov. can be identified by cephalon 1.60 times wider than long, moderately immersed in the pereonite 1; widest pleon 0.84 width of widest pereon; pleotelson 1.80 times as wide as long posterior margin rounded, lateral margins convex; antenna 11 articled, slightly longer than antennula, greatly wider antennal bases; and uropod rami, endopod longer than exopod.