Heteromesus inaffectus Cunha & Wilson 2006, sp. nov.

• Main Authors: Cunha, Marina R., Wilson, George D. F.
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2006
• Subjects: Biodiversity; Taxonomy; Animalia; Arthropoda; Malacostraca; Isopoda; Ischnomesidae; Heteromesus; Heteromesus inaffectus; North Atlantic
• Online Access: https://doi.org/10.5281/zenodo.5064422; http://treatment.plazi.org/id/EB65B41CFFB4E4296A4DFA83D2BF97BF

Heteromesus inaffectus sp. nov. (Figs 19–23) Etymology Inaffectus means natural or simple. Material examined Holotype: female (4.5mm), North Atlantic, offshore of Cork, Ireland, 50º12.3’N, 13º35.8’W, 20 Aug 1972, R / V CHAIN cruise nº 106, stn. WHOI 321, epibenthic sled, 2890– 2868 m (ZMUC CRU­9876). Paratypes: male (3.1 mm), same data as holotype (ZMUC CRU­9877); 68 specimens including males, females, mancae and 1 intersex, same data as holotype (AM P 72122); adult male (4.4 mm) same data as holotype (dissected, mouthparts on slide, AM P 72121); preparatory female, same data as holotype (SEM stub AW573, AM P 72245); preparatory female, same data as holotype (SEM stub AW574, AM P 72246). Remarks on type material. Several specimens in this lot showed developmental oddities. One large specimen that had the female form and obvious pores to the spermathecal ducts, also had somewhat distorted male pleopods. Various asellote species are known to have facultative sex determination, but we suspect that this individual was only a single aberration, perhaps caused by a parasite. Three adult specimens had pereopods in the middle of the pereon that were in a rudimentary state, similar to the limbs of a manca III. Apparently, these limbs were being regenerated in subsequent molts. This species thus shows an ability to lose and regenerate limbs, perhaps as a predation escape mechanism. If the isopod needed to lose a limb, the break could occur at the thin neck between the shaft of the basis and the coxa. Diagnosis Pereonite 2 in female with no median dorsal spine or tubercle. Pereonite 5 in female length 3.1 width; in male length 6.9 width. Pleotelson posterolateral margin anterior to uropods without spines or tubercles. Antennula with 3 articles altogether. Pereopod bases proximal shoulder with bifid spines. Uropods elongate, length in female 0.50, in male 0.50–0.55 length of pleotelson. Description Body length in female 4.5 mm; granular. Head in female length 0.45 width; dorsal surface with pair of cephalic bullae; lobe on ...