Caecoserolis bicolor, Bruce, Niel L., 2008

Bruce, Niel L., 2008, Two new deep­water species of Caecoserolis Wägele, 1994 (Isopoda, Sphaeromatidea, Serolidae) from off North Island, New Zealand *, Zootaxa 1866, pp. 453-466 : 459-465

Caecoserolis bicolor sp. nov. ( Figs 4–7 )

Material. All Hawkes Bay, eastern North Island, New Zealand.

Holotype: ď (14.1 mm), 39.4017 S – 39.3955 S, 179.9062 E – 179.9013 E, 21 Nov 2004, 2337– 2363 m, stn. TAN0413/205 ( NIWA 25903).

Paratypes: ď (14.4 mm [dissected]), 39.4408 S – 39.4373 S, 179.9508 E – 179.9442 E, 21 Nov 2004, 2255– 2220 m, stn. TAN0413/206 ( NIWA 25904). 2ď (~12.5, 14.1 [A1, A2 dissected] mm), 39.4488 S –39. 4497 S, 179.9062 E – 179.9212 E, 19 Nov 2004, 2182– 2119 m, TAN0413/192 ( NIWA 25901). 3ď (12.6 mm, 2 anterior portions only) 39.4532 S – 39.3530 S, 179.9623 E – 179.9482 E, 19 Nov 2004, 2308– 2207 m, stn. TAN0413/193 ( NIWA 25902).

Description. Body 1.1 as long as wide, widest at coxae 4, dorsal surfaces smooth. Head anterolateral lobes weakly convex, anterior submarginal 'ridge' entire; dorsally with submedian pair of tubercles joined by indistinct V­shaped ridge, posterior margin with low rounded median tubercle. Eyes absent. Pereonites 5–7 fused mid­dorsally; pereonite 1 anterolateral margin continuously convex; dorsally with median tubercles on pereonites 1–4 and 7 and pleonites 1 and 2. Coxae of pereonites 2–4 articulated, with dorsal sutures, distal margins weakly convex; coxae 4 extending to mid­pleonite 1; 5 extending posteriorly along 0.4 of pleotelson length; 6 extending to between posterior of uropods and pleotelson posterior margin, and along 0.9 of pleotelson length. Ventral coxal plate s 2–4 mesially elevated, mesially with ridges forming X­shape. Pleonites extending posteriorly along 0.4 pleotelson lateral margin; pleonite 1 sternal plates 3­cornered, with acute median point, sternal plate 1 with weak median ridge. Pleotelson 1.1 as long as anterior width, dorsal surface with median longitudinal carina, with paired sublateral carinae; lateral margins convex, posterior margin evenly rounded, without distinct median excision.

Antennule peduncle article 2 2.0 as long as wide; articles 3 and 4 1.8 as long as article 2; article 3 6.5 as long as wide; flagellum 2.4 as long as peduncle articles 3 and 4, with ~38 articles (articles 1–4 or 5 fused), extending to pereonite 4. Antenna peduncle article 4 5.2 as long as wide, 3.3 as long as article 3; article 5 1.1 as long as article 4, 10.3 as long as wide; antennal flagellum 1.1 as long as peduncle article 5, with ~13 articles, extending to middle of pereonite 3.

Epistome with obtuse median point. Mandible incisor even or minutely irregular, left mandible lacinia mobilis 0.8 as wide as incisor, right mandible lacinia mobilis distally multicuspid, mandibular spine simple; palp article 2 with 24 distolateral setae, article 3 with 36 biserrate setae. Maxilla mesial lobe with 12 long, finely serrate setae; middle lobe with 2 long simple setae; lateral lobe with 2 distal simple setae. Maxilliped palp article 2 proximomesial margin with 6 setae, distomesial margin with 16 setae, lateral margin distally with 3 setae; article 3 lateral margin with 5 setae, distal margin with 11 setae; endite distal margin RS simple.

Pereopod 1 carpus RS distally pilose; propodus 2.2 as long as wide, inferior margin with ~58 robust setae; wide RS with finely ridged margins, narrow RS distally bifid, with pilose flagellum; dactylus with acute unguis. Pereopod 2 basis 3.3 as long as greatest width; ischium 0.6 as long as basis, 3.8 as long as wide; merus 0.5 as long as ischium, 1.8 as long as greatest width, inferior margin with 1 cluster of setae (of 2), superior distal angle with 3 setae; carpus 0.5 as long as ischium, 2.0 as long as wide, inferior margin with 9 clusters of setae (as 1, 1, 2, 1, 1, 1, 2, 1, 1); propodus 0.6 as long as ischium, 2 as long as wide, inferior margin with indistinct heel, palm weakly concave, inferolateral margin with 6 RS (2 acute), inferomesial margin with 4 RS, inferior margin RS simple, blunt, smooth, distal margin with ~14 setae; dactylus 0.9 as long as propodus, unguis simple, slender. Pereopod 6 basis 5.3 as long as greatest width; ischium 0.7 as long as basis, 3.6 as long as wide, inferior margin with 1 cluster of setae (1 distal), superior distal angle with 0 robust setae; merus 0.6 as long as ischium, 2.3 as long as wide, inferior margin with 5 clusters of setae (as 1, 2, 1, 2, 3), superior distal angle with 2 RS; carpus 0.9 as long as ischium, 3.7 as long as wide, inferior margin with 8 clusters of setae (as 1, 2, 4, 3, 2, 3, 3 and 5), superior distal angle with ~10 setae; propodus 0.8 as long as ischium, 5.8 as long as wide, inferior margin with 8 clusters of setae (1, 1, 2, 2, 3, 3, 3 and 1), distal margin with ~12 setae, inferior distal angle with 1 RS; dactylus 9.5 as long as proximal width. Pereopod 7 similar to, but 0.7 as long as pereopod 6. Setae on inferior margins of pereopods 4–7 distally rough and distally flexible. Inferior margins of pereopods 2–7 setulose fringe weakly developed.

Penial openings fused, penes opening flush with surface of sternite 7.

Pleopod 1 peduncle 1.9 as long as wide, mesial margin with 3 coupling setae; exopod 2.0 as long as wide, with 36 PMS; endopod 1.8 as long as wide, 0.7 as long as exopod, with 19 PMS. Pleopod 2 peduncle 2.1 as long as wide, mesial margin with 2 coupling setae; exopod 1.9 as long as wide, with 41 PMS; endopod 2.9 as long as greatest width, lamellar part 3.6 as long as wide, with 20 PMS; appendix masculina 3.3 as long as endopod. Pleopod 3 exopod with 42 PMS, endopod with 26 PMS. Pleopod 4 exopod with complete transverse suture, endopod with complete transverse suture. Pleopod 5 exopod with complete transverse suture, endopod with complete transverse suture.

Uropods (rami + peduncle) 0.2 as long as pleotelson, peduncle 0.7 as long as endopod. Endopod 2.2 as long as wide; distally broadly rounded. Exopod 0.6 as long as endopod, 1.9 as long as wide, distally broadly rounded.

Size: Males 12.5–14.4 mm (mean 13.5 mm); females not known.

Colour: Anteriorly (head to pereonites 1–4) dark slate grey, posteriorly white.

Remarks. Caecoserolis bicolor sp. nov. is a distinctive member of the genus bearing no close resemblance to other species of the genus. It is entirely without eyes or traces of ocular lobes, and is further readily identified by the irregular nodules on the head (appearing like a shallow ‘V’); wide body shape (only just longer than wide) widest at pereonites 3 and 4, colour pattern (anteriorly dark, posteriorly pale); fused penial processes; relatively short antennule peduncle; pereopods 5–7 with a somewhat curved dactylus; small median nodules on pereonites 1–4, 7 and the pleonites; and the cuticle being moderately pitted rather than polished.

Distribution: Off Hawkes Bay, North Island, eastern New Zealand; 2119–2337 m.

Figures

FIGURE 4. Caecoserolis bicolor sp. nov. A – E holotype; G, H, ♂ 14.1 mm, NIWA 25901. A, dorsal view; B, lateral view; C, pereonal and pleonal sternites; D, ventral view, coxae 2 – 4; E, detail of coxal join, coxae 1 and 2; F, frons; G, antenna; H, antennule.

FIGURE 5. Caecoserolis bicolor sp. nov. A – G, paratype ɗ 14.4 mm, NIWA 25904; H – I holotype. A, maxilliped; B, maxilliped palp; C, maxilla; D, maxillule (endite lost); E, mandible palp and seta from article 2; F, left mandible apex; G, right mandible apex; H, pereopod 6, distal articles; J, distal setal cluster, pereopod 6 carpus; I, distal setal cluster, pereopod 6 propodus.

FIGURE 6. Caecoserolis bicolor sp. nov. Paratype ɗ 14.4 mm, NIWA 25904. A, pereopod 1; B, pereopod 1, propodal setae; C, pereopod 1, carpal setae; D, pereopod 2; E, pereopod 2, carpus and propodus; F, pereopod 6; G, pereopod 7.

FIGURE 7. Caecoserolis bicolor sp. nov. Paratype ɗ 14.4 mm, NIWA 25904. A – E, pleopods 1 – 5; F, uropods, ventral view.