Xenosella coxospinosa, Just, Jean, 2005

Just, Jean, 2005, Xenosellidae, a new family of Janiroidea (Asellota: Isopoda: Crustacea), for Xenosella coxospinosa gen. nov., sp. nov., from the marine bathyal of eastern Australia, Zootaxa 1085, pp. 21-32 : 25-31

Xenosella coxospinosa sp. nov.

( Figs 1–4 )

Type locality. Off Point Hicks, eastern Bass Strait, southeastern Australia.

Material examined. All material from Australia. Holotype. Preparatory Ψ, 1.4 mm, Eastern Bass Strait, south of Point Hicks, Victoria, 38°21.90’S 149°20.00’E, 1000 m, WHOI epibenthic sled, [sediment not recorded], 23 July 1986, RV Franklin, stn SLOPE 32, NMV J20161 (including three slides).

Paratypes. Same data as holotype, NMV J20162 . (♂B, 1.3 mm). Eastern Bass Strait, south of Point Hicks, Victoria, 38°16.40’S 149°27.60’E, 800 m, coarse shell, biogenic sediment, WHOI epibenthic sled, 23 July 1986, RV Franklin, stn SLOPE 34, NMV J20163 (preparatory Ψ C, 1.2 mm). North­east of Twofold Bay, New South Wales, 36°56.2'S 150°23.0'E, 1600 m, NMV dredge, 12 December 1986, RV Franklin, stn FR1086­8, AM P70422 (♂ D, plus one slide).

Description. Body broadest at pereonites 2 and 3 (coxae and lateral spines not included), male width 0.46 length, female 0.55. Head anterior margin broadly rounded, lateral margins slightly concave, dorsal surface with a number of long simple setae. Pereonites of subequal length in male, pereonites 1–3 and 5 in female of subequal length, 4 slightly longer, 6 and 7 slightly shorter; all pereonites with long simple setae; pereonite 1 with long lateral spine, lateral margin of 2–7 evenly rounded. Coxa 1 fused with pereonite, 2–4 with single long lateral spine, 5–6 with two, 7 with one lateral spine(s). Pleotelson distal to ‘neck’ ovoid, with 2 long curved spines on lateral margins and long simple setae laterally and dorsally; with subcuticular double­layered structure dorsally with numerous hollows, and small pedestals connecting the two layers ( Fig. 2 pt).

Joint insertion projection for antennula and antenna more pronounced in male. Antennula approximately 1/5 longer than antenna, composed of 6 articles; elongate article 1 slightly inflated at base, approximately as long as first 5 articles of antenna, as long as antennular articles 2 and 3 combined in male, 2–4 combined in female, article 5 distinctly elongate. Antenna articles 1–4 short, of subequal length, 3 with fan of long simple setae mediodistally, 5 and 6 slender of equal length, approximately as long as articles 1–4 combined; flagellum with 7 articles of subequal length.

Mandible incisors with 4 teeth, lacinia mobilis of left mandible as strong as incisor, with 4 teeth; setal row represented by single 2­cusped (left) and 3­cusped (right) seta; molar broadest in distal third, deeply split distally with sharply acute apices and 2 modified, club­shaped setae apically in gap.

Maxillula outer plate with 10 smooth setae apically, inner plate slender, with 2 simple setae on apex. Maxilla, all 3 plates of subequal size, with curved, mostly hemiplumose setae apically.

Maxilliped length of basis with endite approximately 1.5 width, reaching to middle of palp article 3; endite lateral and distal margins with fine setules, 2 robust setae in mediodistal corner; epipod narrow, apically rounded, reaching to basal third of palp article 2.

Pereopod 1 strong, basis width 0.33 length; ischium length 0.8 basis length; merus half length ischium, moderately expanded distally, with 1 strong robust seta on distomedial surface; carpus triangular, length subequal to merus, posterior margin projecting, with 3 strong robust setae distally; propodus ovoid, distally tapering, 1.2 times longer than basis, greatest width approximately 0.4 length, posterior margin with thin cuticular flange and 6 submarginal lateral backward pointing robust setae diminishing in length distally; dactylus with unguis reaching proximal robust seta on propodus, posterior margin with cuticular flange, notched in middle, unguis half length dactylus, secondary claw 0.3 length unguis. Pereopods 2–7 similar, slender slightly increasing in length posteriorly; carpus and propodus with 3 or 4 slender robust setae on posterior margin; unguis slender, as long as dactylus, secondary claw a tiny robust seta.

Male pleopod 1 broadest in proximal 1/5, tapering to rounded apices, lateral margins with fringe of fine setules, ventral surface of rami with single simple seta, apices with 4 simple setae; dorsal stylet guides long and sinus shaped, opening distally on apex of ramus; male pleopod 2 protopod mid­width 0.3 length, apex pointed, lateral margin with fringe of long thin setules, ventral surface with few scattered long simple setae, stylet straight, length approximately 0.75 protopod length, retracted reaching tip of protopod; female pleopod 2 (operculum) width 0.9 length, ovoid with rounded apex, lateral margins with fine setules, ventrally with 3 simple setae near lateral margins; pleopod 3 exopod longer than endopod, second article with rounded apex and 2 submarginal short simple setae, lateral margin of both articles fringed with long thin setules, endopod rectangular with 3 plumose setae on distal margin; pleopod 4 exopod article 2 with 2 simple setae, fringe of fine setules on lateral margin, endopod a simple sack approximately as long as exopod; pleopod 5 a simple sack similar to endopod of pleopod 4.

Uropods inserted in distal 1/5 of pleon; protopod approximately as long as wide; exopod half length endopod, inserted dorsally rather than laterally to endopod, with 2 apical simple setae; endopod approximately 2.5 times longer than protopod, with tuft of simple setae apically and a few similar setae on medial margin.

Size. Largest female, 1.4 mm; largest male, 1.3 mm.

Distribution. Off south­eastern Australia, 800–1600 m.

Etymology. The epithet refers to the long spines on the coxae.

Figures

FIGURE 1. Xenosella coxospinosa sp. nov. A, holotype, female; B, paratype, male B; C, paratype, female C, setae omitted. op, operculum; pt, pleotelson; vv, ventral view. Scale bar for all three habitus illustrations: 0.5 mm.

FIGURE 2. Xenosella coxospinosa sp. nov. A, holotype, female; B, paratype, male B; C, paratype, female C. cu, cuticular structure; lv, lateral view; mv, medial view; p 1, 2, 6, pereopods 1, 2, 6; pt, pleotelson; up, uropod.

FIGURE 3. Xenosella coxospinosa sp. nov. Holotype, female. l, left; md, mandible; mx 1 and 2, maxilla 1 and 2; mxp, maxilliped, r, right; vv, ventral view.

FIGURE 4. Xenosella coxospinosa sp. nov. A, holotype, female; all other illustrations, paratype, male D. dv, dorsal view; od, oviduct; oop, oopore; ov, ovary; pl 1 – 5, pleopods 1 – 5; pt, pleotelson; sd, spermathecal duct; sdo, spermathecal duct opening; sp, spermatheca; vv, ventral view; 2 – 5 in A, pereonites 2 – 5.