Chelantermedia composita, Brix, 2006

Brix, Saskia, 2006, A new genus and new species of Desmosomatidae (Crustacea: Isopoda: Asellota) from the deep sea of south-eastern Australia, Memoirs of Museum Victoria 63 (2), pp. 175-205 : 176-177

Chelantermedia composita sp. nov.

Figures 1–3

Material examined. Holotype. Female , preparatory, 2.1 mm; NMV J18612 . Australia, NSW, off Nowra (34°59.52'S, 151°5.94'E), 204.0 m, WHOI epibenthic sled, G.C.B. Poore et al., RV Franklin, 14 Jul 1986 (stn SLOPE 1 ).

Paratypes (7 specimens: 3 females, 4 males). Same data as holotype. NMV J186121 .

Description. (Holotype female). Habitus (fig. 1): body 2.1 mm long, 5.17 times longer than width of pereonite 2. Pereonite 1 width 1.16 times cephalon width in dorsal view. Pereonite 1 length 1.11 pereonite 2 length, 0.96 pereonite 2 width. Pereonite 5 width 0.60 length, anterior margin straight. Pereonite 6 and 7 fused with pleotelson, lateral margins straight. Coxae 1–4 slightly produced, without setae. Pleotelson length as long as wide, without posterolateral spines. Lateral margins straight, posterior margin slightly rounded.

Antennula: 0.23 mm long, length 0.02 body length, 5 articles. Article 1 with 2 broom setae and 1 simple seta. Article 2 length 3.67 width, 1.94 article 1 length; with 2 long articulated broom setae distally and 2 simple seta midway. Article 3 with 1 simple seta, article 4 with 2 long slender setae and article 5 distally with 1 aesthetasc and 2 long slender setae. Antenna: length about one-third of body length, with 11 articles. Article 3 with 1 small seta. Article 4 with 2 small setae. Article 5 distally with 3 simple setae, 1 simple seta located midway. Article 6 with 4 simple setae midway, distally with 2 small broom setae and 6 long slender setae. Flagellar articles with few setae.

Mandible: Without palp. Incisior process with 3 lobes. Lacinia mobilis of left mandible with 4 teeth. Spine row containing 4 spines. Molar process triangular with 7 setae. Maxilliped: Epipodite lost during dissection. Endite with 2 coupling hooks and numerous fine setae on inner margin and on distal tip. Palp of 4 articles, articles 1 and 2 clearly broader than articles 3 and 4. Article 1 length 1.14 width. Edge of palp article 2 with 4 long slender setae and inner margin with 2 long slender setae. Article 2 about 2 times width, article 3 length 5.00 width, article 4 length 3.50 width. Article 3 with 2 setae, article 4 with 3 setae.

Pereopod I: Chelate. Basis length 3.75 width, proximal to ischium ventrally 1 large seta. Ischium length 1.77 width, with 1 ventral seta. Merus length 2.38 width, ventrally with 1 strong unequally bifid seta, midway 1 slender seta, distodorsally 1 large simple seta. Carpus length 1.38 width, ventrally with claw-seta, penultimate slender seta and 1 slender seta midway. Claw-seta as long as propodus. Propodus length 2.69 width, dorsally with 2 small setae, ventral margin with cuticular membrane and 6 small slender setae. Dactylus length 3.6 width, without setae. Unguis (claw) of dactylus with 1 cuspidate and 1 conate seta, 2 slender setae medially. Pereopods II–IV: Similar. Pereopod III: Basis length 4.29 width, with 2 simple setae and 1 broom seta. Ischium length 2.15 width, with 2 simple slender setae. Merus length 1.36 width, ventrally with 2 simple setae, distodorsally 1 simple seta. Carpus length 3.90 width, ventrally 3 distally setulate setae and combs between insertion of setae, distodorsally 1 small simple seta. Propodus length 3.90 width; ventral margin with 2 setae and combs between them. Dactylus length 3.84 width, with 3 small slender seta, unguis (claw) of 1 strong spittle-like formed conate seta and 3 slender setae inserting ventrally. Pereopods V – VII: Similar. Pereopod V: Basis length 3.00 width, with 7 broom setae in irregular distances and ventrally 1 slender seta near ischium. Ischium length 2 times width, with 1 dorsal and 1 ventral simple seta. Merus length 0.89 width, distodorsally with 2 setae, ventrally 1 seta. Carpus length 2.80 width, with ventral row of 4 long slender distally unequally bifid setae, dorsally 3 slender setae and near propodus 1 small broom seta. Propodus length 5.60 width, dorsally with 3 slender distally unequally bifid setae increasing in length towards dactylus, ventrally with row of 5 slender distally unequally bifid setae increasing in length towards dactylus and 1 simple seta between 4th and 5th seta of ventral row. Dactylus length 4.67 width, (slightly damaged) with unguis (claw) of 1 small robust seta and 1 long conate seta broadened distally, 3 slender setae inserting between them.

Pleopod 2 (operculum): Length 1.15 width. Form nearly rectangular, lateral margins straight, distal margin straight. Ventral surface without setae. Distal margin with 4 slender setae. Pleopod 3: Endopod length 1.39 width, distally with 3 long plumose setae. Exopod length 1.46 of endopod length, outer margin hirsute. Pleopod 4: Endopod oval and tapering to tip, length 1.62 width. Exopod length 6.90 width, distally with 1 long plumose seta.

Uropods: Biramous. Exopod length 0.58 times endopod length. Endopod 5.14 times longer than wide, 1 small broom seta inserting medially, a bunch of 4 small broom setae and 1 slender seta inserting between the single small broom seta and the tip of the endopod, distally with 3 long broom setae and 2 small simple setae. Exopod length 4.2 width, distally with 2 long slender setae. Protopod length 1.39 width, with 1 small broom seta and 3 simple setae.

Male. Habitus similar to female, 5.43 times longer than width of pereonite 2. Antenna: 20 articles, flagellum basally swollen, with 14 articles. Pleopod 1: 4.93 times longer than distal width, tips triangular with 4 small slender setae on outer side. Pleopod 2: sympod length 2.03 times width, outer lateral margin slightly convex, distally with 4 setae. Endopod inserting about 0.50 of sympod length.

Etymology. From the latin word composita , composite. The new species is composed of character states that occur in Desmosomatidae and Nannoniscidae and are observed together in the same species for the first time.

Distribution. Off southern NSW, Australia.

Figures

Figure 1. Chelantermedia composita sp. nov. Holotype female. NMV J18612. Dorsal and lateral views (A, B). Allotype male. NMV J186121. Dorsal and lateral views (C, D).

Figure 2. Chelantermedia composita sp. nov. Paratype female, Allotype male. NMV J186121. Antennae, mouthparts, pereopod V, male pleopods.

Figure 3. Chelantermedia composita sp. nov. Paratype female. NMV J186121. Pereopods I–VII and pleopods (Op, Plp 3, 4, Urp).