Ischnomesus

Kavanagh, Fiona A., Frutos, Inmaculada & Sorbe, Jean Claude, 2015, Ischnomesus harrietae sp. nov., a new benthic asellote (Crustacea: Isopoda: Ischnomesidae) from bathyal bottoms of the southern Bay of Biscay, Zootaxa 3911 (2), pp. 201-217 : 210

Ischnomesus sp.1

( Fig. 7 )

Material examined. One preparatory female (MNHN-IU-2014-4007; BL = 2.8 mm), co-occurring with holotype of I. harrietae in sample TS11-R-N1. Sampling characteristics and environmental data as for this holotype.

Diagnosis. Pereonite 1 with anterolateral pedestal setae. Pereonite 5 and pleotelson with dorsal pedestal setae. Pereopod I carpus wide (length/width ratio = 1.7). Distal margin of pleopod II with simple setae in adult females.

Description. Head length 0.5 width. Pereonite 1 width 0.16 BL. Pereonite 4 length 1.1 width. Pereonite 5 length 2.5 width, 0.3 BL. Pleotelson length 1.3 width. Pereonite 1 with 1 small pair of anterolateral pedestal setae. Pereonite 5 with 10 pairs of dorsal pedestal setae. Pleotelson with 6 pairs of dorsal pedestal setae.

Maxilliped with 2 receptaculi on basal endite. Palp narrower and shorter than basal endite, articles 1–3 expanded, wider than long, with numerous simple setae, article 2 wider than article 1 and 3, articles 4 and 5 longer than wide. Epipod without spines.

Pereopod I weakly carposubchelate. Ischium with 1 posterior robust seta. Merus with 1 posterior robust seta. Carpus with short fringe of fine setae interspersed with 2 posterior robust seta and 11 robust flagellate setae. Carpus with 2 anterior simple setae. Propodus with 4 posterior simple setae and 5 anterior simple setae. Dactylus with 4 simple setae.

Pleopod II (operculum) with narrow proximal neck, laterally convex, broadening posteriorly to rounded corners, posterior margin concave, with 4 simple distal setae (no plumose setae).

Remarks. This preparatory female is the sole representative of this species collected from the surveys listed. Although it has distinctive pedestal setae present on pereonites 1 and 5, it lacks the dorsal and lateral pedestal setae on the other pereonites as observed in I. harrietae . Further material is required for a full description.

Figures

FIGURE 7. Ischnomesus sp. 1. (preparatory female MNHN-IU- 2014 - 4007). A: habitus, dorsal view; B: habitus, lateral view; C: left pereopod I; D: left maxilliped, ventral view; E: pleotelson ventral view. Scale bars: A, B: 1.0 mm; C, D: 0.2 mm; E: 0.5 mm.