Isocyamus Gervais and Beneden, 1859

Iwasa-Arai, Tammy, Carvalho, Vitor Luz & Serejo, Cristiana Silveira, 2017, Updates on Cyamidae (Crustacea: Amphipoda): redescriptions of Cyamus monodontis Lütken, 1870 and Cyamus nodosus Lütken, 1861, a new species of Isocyamus, and new host records for Syncyamus ilheusensis Haney, De Almeida and Reis, 2004, Journal of Natural History (J. Nat. Hist.) 51 (37 - 38), pp. 2225-2245 : 2235-2236

Genus Isocyamus Gervais and Beneden, 1859

Diagnosis

Antenna 1, with 4 articles and with a continuous band of setae on terminal article. Lower lip inner lobes fused. Maxilla 2 outer lobes fused. Maxilliped inner lobes rounded, outer lobes usually lacking, palps lacking. Gnathopod 1 palm elongate, dactylus semi-recurved. Gnathopod 2 propodus’ palm elongate. Lateral gills sausage shaped. Accessory gills present, usually sausage shaped or subtriangular; 1–2 spine-like processes present on the base of lateral gills. Oostegites plates 3 subtriangular, plates 4 oval.

Type species

Cyamus delphinii Guérin-Méneville, 1836

Remarks

Species of Isocyamus are distinguished from other genera of whale lice by their elongate, whitish appearance, reduced maxillipeds, presence of spine-like processes on the base of lateral gills (sausage-shaped gills), and large accessory gills ( Sedlak-Weinstein 1992a, 1992b). With the description of Isocyamus indopacetus sp. nov. the genus diagnosis is amended as this species shows the maxilliped with a round distal lobe, which is a unique character within the genus. Species of Isocyamus are found in different odontocete hosts, and they usually parasitise more than one host species ( Table 2) ( Leung 1970).