Syscenus Harger, 1880

Bruce, Niel L., 2005, Two new species of the mesopelagic isopod genus Syscenus Harger, 1880 (Crustacea: Isopoda: Aegidae) from the southwestern Pacific, Zootaxa 1070, pp. 31-42 : 32

Syscenus Harger, 1880

Restricted synonymy: Bruce, 1997: 113.— Bruce, Lew Ton & Poore, 2002: 163. Type species: Syscenus infelix Harger, 1880 , by monotypy.

Remarks. Recent publications on species of Syscenus include Kensley (2004), Kensley & Cartes (2003), and Ross et al. (2001) on the parasitic habits of Syscenus infelix Harger, 1880 . Bruce (1997) provided a revised generic diagnosis. The genus can be recognized by the pleon being abruptly narrower than the pereon, lamellar uropods and maxilliped palp with three articles; all but two species entirely lack eyes. The monotypic genus Xenuraega Tattersall, 1909 , also with a narrow pleon, is immediately distinguished by the uropodal rami, with a short and stub­like endopod and an exceptionally elongate, filamentous exopod with numerous plumose setae ( Bruce 1993, figs 1 and 2).

Most species of the genus lack any trace of eyes or ommatidia. Syscenus peruanus Menzies & George, 1972 , the only previously described species known to have eyes, is known from a single juvenile specimen, atypically deep for the genus at 4526–4609 m, from off Peru. Syscenus karu sp. nov. has distinct eyes, and the lack of eyes can no longer be considered a generic character state for the genus.