Echinopleura cephalomagna, 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 : 194

Echinopleura cephalomagna sp. nov.

Figures 15–18

Material examined. Holotype. Female , preparatory, 1.8 mm; NMV J18600 Australia, Vic., S of Point Hicks (38°17.70'S, 149°11.30'E), 400 m depth, WHOI epibenthic sled, G.C.B. Poore et al., RV Franklin, 24 Jul 1986 (stn. SLOPE 40 ).

Paratypes. 1 female, adult, 2.2 mm; NMV J18601 ; locality. - Australia, NSW, 54 km ESE of Nowra (34°52.72'S, 151°15.04'E), 996– 990 m, WHOI epibenthic sled, G.C.B. Poore et al., RV Franklin, 22 Oct 1988 (stn. SLOPE 53 ) . 1 female, preparatory; 2.1 mm; NMV J53074 . Australia, NSW, 54 km ESE of Nowra (34°52.72'S, 151°15.04'E), 996– 990 m, WHOI epibenthic sled, G.C.B. Poore et al., RV Franklin, 22 Oct 1988 (stn. SLOPE 53 ) .

Diagnosis. Body length 3.20 times longer than width of pereonite 2. Cephalothorax highest part of body from lateral view. Pereonite 1 slightly smaller than pereonite 2. Lateral margins of pereonite 5, 6 and 7 as well as of pleotelson serrated. Incisior process with 1 rounded tooth. Lacinia mobilis of left mandible represented by 1 small bulge-like tooth.

Description. Habitus: body 2.2 mm long (measured without appendages), 3.20 times longer than width of pereonite 2. Cephalothorax highest part of body from lateral view. Pereonite 1 width 1.16 times cephalon width in dorsal view. Pereonite 1 length 0.94 pereonite 2 length, 0.91 pereonite 2 width. Pereonite 5 width 0.67 length, anterior margin straight, lateral margins serrated. Coxae 1–4 produced, tipped with small stout setae. Pleotelson length 1.06 width, lateral margins serrated, lightly convex, posterior margin smooth, rounded.

Antennula: 0.27 mm long, length 0.12 body length, with 6 articles. Article 1 with 1 small slender seta and 3 broom setae. Article 2 length 2.57 width, 0.69 article 1 length; distally with 4 articulated broom setae. Article 3 with 1 small seta, article 4 distally with 2 broom setae, distal article with 1 aesthetasc and 4 slender setae. Antenna (fig. 12): broken off.

Mandible: Article 1 of palp distally with 1 slender seta, article 2 distoventrally with 2 small setae, fringed with rows of fine setae, article 3 with 4 small and distally 1 setulate seta. Incisor process with 1 rounded tooth. Lacinia mobilis of left mandible represented by 1 small bulge-like tooth. Lacinia mobilis absent at right mandible. Spine row containing 9 spines. Molar process with 10 setae. Maxillula: Inner lobe smaller than outer lobe (0.63 of outer lobe length), distally with 7 simple setae, dorsally with 12 fine setae and ventrally with 5 pairs of fine setae. Outer lobe marginally with 21 pairs of fine setae, terminally with 11 strong spines (7 spines with setules). Maxilla (fig. 12): Medial lobe broader than other lobes, terminally with 3 slender setae, ventrolaterally with 12 setae, setae near base longest. Outer lobe dorsally with 8 pairs of fine setae, terminally with 3 long ventrally setulate setae. Maxilliped (fig. 12): Epipodite length 3.08 width, length similar endite length. Endite with 2 coupling hooks, terminally with 1 fan seta and numerous fine setae, marginally with pairs of fine setae. Edge of endite fringed with fine setae, palp article 1 with 2 setae on outer margin, article 2 with 3 setae on outer margin and 3 setae on inner margin, article 3 with 7 setae on inner margin, article 4 with 4 setae, article 5 with 3 setae. Article 1 length 0.91 width, article 2 length 0.89 width, article 3 length 1.11 width, article 4 length 1.6 width, article 5 length 2.67 width.

Pereopod I: Basis length 5.94 width, marginally with 14 setae. Ischium length 3.17 width, ventrally with 7 small slender setae, dorsally with 2 simple slender setae. Merus length 1.18 width, ventrally with a row of 4 simple setae, distodorsally with 1 seta (broken off). Carpus length 3.20 width, ventrally with dorsal row of 7 setae, distal and penultimate seta longest, distally setulate, dorsally with 3 small slender setae. Propodus length 8.00 times width, with few setae distally. Dactylus length 4.20 width, mediodistally 3 small setae. Unguis (claw) of dactylus with 1 cuspidate and 1 conate seta, 2 slender setae medially. Pereopod II: Similar to pereopod III. Basis length 4.00 times width, marginally with 27 small setae, proximal to ischium ventrally 1 long simple seta. Ischium length 3.13 width, ventrally 16 simple seta, dorsally 4 simple setae. Merus length 1.38 width, ventrally with row of 6 setae, distodorsally 2 simple setae. Carpus length 3.57 width, with ventral row 11 long unequally bifid setae increasing in length towards the propodus, dorsolaterally with row of 11 long simple setae, dorsally with 6 small slender setae. Propodus length 2.70 times width, ventrally with 1 small slender seta, 2 small stout unequally bifid setae and 2 setal combs inserted in a cuticular membrane, dorsally with row of 8 long simple setae. Dactylus length 2.50 width, mediodistally 3 small setae. Unguis (claw) of dactylus with 1 cuspidate and 1 conate seta, 2 slender setae medially. Pereopod VI: Similar to pereopod VII, pereopod V missing from specimen. Basis length 4.19 width, with 2 large broom setae, marginally with 13 small setae. Ischium length 3.39 width, laterally with 9 small setae, dorsally with 6 slender setae. Merus length 1.38 width, ventrally with 3 small slender setae. Dorsally with 1 small seta and 1 long simple seta. Carpus length 4.11 width, ventrally with row of 12 long slender setae, dorsally with row of 9 slender setae and 4 small setae. Propodus length 3.79 width, ventrally with row of 5 long slender setae, dorsally with row of 6 setae. Dactylus length 8.50 width, distally with 1 slender seta, unguis (claw) of 1 long conate seta, 2 slender setae inserting ventrally.

Pleopod 2 (operculum): Length 1.37 width. Lateral margins straight, operculum tapering towards distal tip, setose (ventral surface with about 34 setae), marginally with 58 setae. Pleopod 3: Endopod length 1.8 width, distally with 3 long plumose setae. Exopod length 0.44 of endopod length, margins hirsute, distally with 1 simple seta. Pleopod 4: Endopod oval-shaped, length 2 times width. Exopod length 7.80 width, distally 1 long plumose seta.

Uropods: Uniramous. Endopod length 2.04 protopod length, 8.17 times longer than wide, marginally with 6 slender setae, distally with 5 long slender setae, 2 small setae and 5 broom setae. Protopod length 1.85 width, with 12 setae.

Etymology. The name refers to the extremely large cephalothorax of the new species.

Distribution. South-eastern Australia, off Vic.

Discussion. Echinopleura cephalomagna sp. nov. is the second species of the genus Echinopleura Sars, 1897 . It belongs to this genus because of the slender pereopod I and the features of the mandible and the serrated body margins from pereonite 5 to the pleotelson. The simplified mandible is unique to Echinopleura . The new species is easy to distinguish from the only other species, E. aculeata Sars, 1897 , by the presence of a well developed mandibular palp. In E. aculeata the whole body is serrated, even the cephalon and the coxae. E. aculeata possesses a dorsal hook on the ischium of pereopod II, E. cephalomagna lacks this hook. While the antennula of E. aculeata consists of five articles, the antennula of E. cephalomagna consists of six articles.

Figures

Figure 15. Echinopleura cephalomagna sp. nov. Holotype female. NMV J18600. (A) Dorsal and (B) lateral views.

Figure 16. Echinopleura cephalomagna sp. nov. Paratype female. NMV J18601. Antennula, mouthparts.

Figure 17. Echinopleura chephalomagna sp. nov. Paratype female. NMV J18601. Anterior pereopods.

Figure 18. Echinopleura cephalomagna sp. nov. Paratype female. NMV J18601. Posterior pereopods, pleopods (Op, Plp 3, Plp 4, Plp 5, Urp).