Disparella kensleyi, 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 : 189

Disparella kensleyi sp. nov.

Figures 11–14

Material examined. Holotype. Female , preparatory, 1.9 mm; NMV J18605 ; Type locality. - Australia, NSW, 74 km E of Nowra (34°56.11'S, 151°28.06'E), 3150 m, box corer, G.C.B. Poore et al, RV Franklin, 23 Oct 1988 (stn. SLOPE 64 ).

Diagnosis. Body length 3.98 times longer than width of pereonite 2. Pereonite 1 length 1.05 pereonite 2 length, 0.93 pereonite 2 width. Pereonite 5 with spine-like ventral elongation. Cephalon with 1 short anteriorly directed spine at insertion of antennae. Palp of mandible of 2 articles, article 1 with 1 small seta, article 2 terminally with 1 small seta. Incisior process with 4 teeth. Lacinia mobilis of left mandible with 4 teeth. Carpus of pereopod I length 5 times width, with ventral row of 5 long unequally bifid setae increasing in length towards the propodus and 3 setal combs inserted in a cuticular membrane, dorsally with 2 long simple setae. Pleotelson with posterolateral spines. Distal margin of operculum slightly concave, with 6 slender setae. Uropods biramous, exopod length 0.43 endopod length.

Description. Habitus: body 1.9 mm long (measured without appendages), 3.98 times longer than width of pereonite 2. Pereonite 5 with spine-like ventral elongation. Cephalon with 1 short anteriorly directed spine at insertion of antennae. Pereonite 1 slightly wider than cephalon. Pereonite 1 length 1.05 pereonite 2 length, 0.93 pereonite 2 width. Pereonite 5 anterior margin straight, lateral margins slightly concave. Coxae 1–4 produced, tipped with small stout setae. Pleotelson length 0.71 width, posterolateral spines present, lateral margins convex, posterior margin rounded.

Antennula: 0.3 mm long, length 0.16 body length, with 5 articles. Article 1 with 3 small broom setae. Article 2 length 3.83 width, 1.64 article 1 length; distally with 2 large articulated broom setae. Article 3 with 1 small slender seta, article 4 distally with 2 small broom setae, distal article terminally with 1 aesthetasc, 1 broom seta and 2 long slender setae. Antenna: About 1.1 mm long, length 0.58 body length, with about 12 articles (broken off after article 12). Article 3 with 2 small slender setae. Article 4 with 2 slender setae. Article 5 with 3 small slender setae. Article 6 marginally with 2 and distally with 3 slender setae. Flagellar articles 1–3 distally with 2 slender setae, following articles with long slender setae.

Mandible: Palp of 2 articles, article 1 with 1 small seta, article 2 terminally with 1 small seta. Incisior process with 4 teeth. Lacinia mobilis of left mandible with 4 teeth, lacinia mobilis of right mandible triangular and distally serrated (5 small teeth). Spine row containing 3 spines. Molar process with 7 setae. Maxillula: Inner lobe smaller than outer lobe (0.71 of outer lobe length), terminally with 5 setae. Outer lobe 5 times longer than wide, marginally with 3 pairs of fine setae, terminally with 9 strong spines and 4 simple setae. Maxilla: Not dissected from specimen. Maxilliped: Epipodite length 3.13 width, length similar endite length. Endite with 2 coupling hooks, terminally with 2 conate setae and 5 small setae, marginally few fine setae. Outer edge of endite and palp articles 1 and 2 with row of fine setae and 1 small seta on distal corners, inner margin of article 3 with 5 setae, outer margin with 1 seta, article 4 with 3 setae, article 5 with 2 setae. Article 1 length 0.6 width, article 2 length 0.93 width, article 3 length 1.07 width, article 4 length 2.5 width, article 5 length 3 times width.

Pereopod I: Basis length 4.04 width, proximal to ischium ventrally 1 long simple seta. Ischium length 0.63 width, ventrally 1 small slender seta. Merus length 0.71 width, dorsally 2 robust simple setae, ventrally 1 seta (broken off). Carpus length 1.43 width, ventrodistally with large claw-seta and slender proximal seta, ventrally 1 small seta midway. Propodus length 3.47 width, ventrally fringed with fine setae and row of 12 small setae inserted in a cuticular membrane. Dactylus length 7.6 width, mediodistally 1 small seta. Unguis (claw) of dactylus with 1 cuspidate and 1 conate seta, 2 slender setae medially. Pereopod II: Similar to pereopod III and pereopod IV. Basis length 6.33 width, marginally with few simple setae and 1 small broom seta, proximal to ischium ventrally with 1 long simple seta. Ischium length 2.62 width, distodorsally with 1 seta, ventrally 1 seta midway. Merus length 1.45 width, distoventrally with 1 stout unequally bifid seta and 2 small slender setae, distodorsally 1 composed seta. Carpus length 5 times width, with ventral row of 5 long unequally bifid setae increasing in length towards the propodus and 3 setal combs inserted in a cuticular membrane, dorsally with 2 long simple setae. Propodus length 5.38 width, ventrally with 1 small slender seta midway, fringed with fine setae, dorsally 2 long simple setae and distally 1 small broom seta. Dactylus length 6.67 width, mediodistally 2 small setae. Unguis (claw) of dactylus with 1 conate seta, 2 slender setae ventrally. Pereopod V: Similar to pereopod VI and pereopod VII. Basis length 6.30 width, marginally with 1 small and 2 broom setae. Ischium length 4.10 width. Merus length 1.60 width, with 3 slender setae. Carpus length 4.80 width, with ventral row of 5 long slender setae and dorsally 2 long setae (broken off), distally 1 small slender seta and 1 small broom seta. Propodus length 4.13 width, ventrally with 1 small seta and 3 long slender setae, dorsally with 2 slender setae. Dactylus length 7.60 width, mediodistally 3 small setae, unguis (claw) of 1 long conate seta, 2 slender setae inserting ventrally.

Pleopod 2 (operculum):Length1.19width.Lateralmargins slightly convex, distal margin slightly concave, distal margin with 6 slender setae. Pleopod 3: Endopod length 1.44 width, distally with 3 long plumose setae. Exopod length 0.74 of endopod length, with 1 small terminal seta, outer margin hirsute. Pleopod 4: Endopod length 2.66 width. Exopod length 8 times width, distally with 1 long plumose seta.

Uropods: Biramous. Endopod length 3.5 protopod length, 4.66 times longer than wide, distally with 5 broom setae, 2 small slender setae and 2 long slender setae. Exopod length 0.43 endopod length, 4 times width, terminally with 2 slender setae. Protopod length similar width, with 1 slender seta.

Etymology. The name is in remembrance of Dr Brian Kensley.

Distribution. Off NSW, Australia.

Discussion. Disparella kensleyi sp. nov. shows affinity to species of Chelator and Prochelator Hessler, 1970 . The chela of the new species is similar to the chela as found in Chelator (ventral margin of carpus with small setae only), but Chelator species possess uniramous uropods and a lacinia mobilis with three teeth. A single midventral seta on the carpus together with the claw-seta and the penultimate slender seta is also known for the genus Prochelator but in Prochelator species the midventral seta is always of composed setal type. Due to the anteriorly directed spine at the antennular folds, which is known for all species of Disparella , and the biramous uropods, D. kensleyi fits best into Disparella . It is distinguished from the other members of the genus by the spine-like ventral elongation at pereonite 5 and the single small midventral seta on the carpus of pereopod I together with the claw-seta and the penultimate slender seta.

Figures

Figure 11. Disparella kensleyi sp. nov. Holotype female. NMV J18605. (A) Dorsal and (B) lateral views.

Figure 12. Disparella kensleyi sp. nov. Holotype female. NMV J18605. Antennae, mouthparts, pereopod I.

Figure 13. Disparella kensleyi sp.nov. Holotype female. NMV J18605. Pereopods II–V.

Figure 14. Disparella kensleyi sp. nov. Holotype female. NMV J18605. Pereopods VI and VII, pleopods (Op, Plp 3, 4) and pleotelson ventral view.