Heteroserolis pellucida, Bruce, 2009

Bruce, Niel, 2009, New genera and species of the marine isopod family Serolidae (Crustacea, Sphaeromatidea) from the southwestern Pacific, ZooKeys 18 (18), pp. 17-76 : 24-29

Heteroserolis pellucida sp. n.

urn:lsid:zoobank.org:act:9F6254B0-1B95-40DE-BEA4-3C17FF40A57C

Figs 1–4

Material

All material from New Caledonia.

Holotype: ♂ (10.6 mm),‘ Sud Landsdowne’, 21°05.254–04.244´S, 160°48.955– 793´E, 21 Oct 2005, EBISCO stn CP2627, 736– 711 m ( MNHN Is.6016) . Paratypes: ♂ (10.5 mm, dissected), 6♀ (4 ovig. 14.8 (drawn), 13.8, 13.5, 12.6, mm, 2 non-ovig. 12.4, 12.0 mm), ‘ Sud Landsdowne’, 21° 05.254 –04.244´S, 160°48.955–793´E, 21 Oct 2005, EBISCO stn CP2627, 736– 711 m (MNHN Is.6017) . 2♀ (ovig. 14.6, 11.8 mm, 1 very damaged), ‘ Sud Landsdowne’, 21°05.085–965´S, 160°47.425–510´E, 21 Oct 2005, EBISCO stn CP2628, 672– 678 m (MNHN Is.6018) . ♀ (ovig. 13.1 mm), ‘ Sud Landsdowne’, 20°51.216–228´S, 161°00.528– 160°59.336´E, 22 Oct 2005, EBISCO stn CP2643, 557– 565 m (MNHN Is.6019) . 6♀ (4 ovig. 13.2, 12.9, 12.6, 12.2 mm, 2 non-ovig. 11.2, 10.8 mm), ‘ Sud Landsdowne’, 20° 52.625 –54.197´S, 160°58.687– 568´E, 22 Oct 2005, EBISCO stn CP2644, 600– 625 m (MNHN Is.6020) . 2♀ (ovig. 13.5, 13.0 mm), ‘ Sud Landsdowne’, 21°31.566–330´S, 162° 32.069 –33.008´E, 23 Oct 2005, EBISCO stn CP2649, 775– 792 m (MNHN Is.6021) .

Additional material: 2♀, Iles Chesterfields, 20°07.72´S, 160°55.76´E, 21 Jul 1988, CORAIL 2, stn DE15, 590– 580 m, coll. ORSTOM, Richer de Forges ( MNHN Is.6022; dissected ovig ♀ in separate tube). 3 (pre-dissected), Iles Chesterfield, 21°00.69´S, 160°57.18´E, 21 Jul 1988, CORAIL 2, stn DE14, 650– 660 m, ORSTOM, Richer de Forges ( MNHN Is.6023) .

Description. Body 1.2 as long as wide, widest at coxae 3, dorsal surfaces smooth. Head anterolateral lobes mesially concave, anterior submarginal ‘ridge’ entire; dorsally without tubercles, posterior margin with low rounded median tubercle. Eyes medium size (between 5 and 15% head width), reniform, ommatidia distinct. Pereonite 1 anterolateral margin continuously convex; dorsal surfaces without tubercles. Coxae distal margins weakly convex; coxae 4 extending to mid-pleonite 2; coxae 5 extending posteriorly along 0.3 of pleotelson length; coxae 6 extending to mid-length of uropods, and along 0.6 of pleotelson length. Ventral coxal plates mesially flat, plates 2–4 mesially simple, smooth; plates 6 and 7 entirely separate. Sternal plate 1 with weak median ridge, with process extending to posterior of sternal plate 2. Pleotelson 1.2 times as long as anterior width, dorsal surface without median longitudinal carina, with paired sublateral carinae; lateral margins sinuate, posterior margin converging to angled caudomedial point, without distinct median excision.

Antennule peduncle article 2 3.6 times as long as wide; articles 3 and 4 2.0 times as long as article 2 (1.96); article 3 6.8 times as long as wide; flagellum 2.0 as long as pe-

duncle articles 3 and 4, with ̴34 articles, extending to pereonite 3. Antenna peduncle article 4 5.6 times as long as wide, 3.3 times as long as article 3; article 5 1.1 times as long as article 4, 6.3 times as long as wide; antennal flagellum 0.9 as long as peduncle article 5, with ̴15 articles, extending to posterior of pereonite 3.

Epistome with acute median point. Mandible incisor with two distinct posterior cusps, left mandible lacinia mobilis 0.7 as wide as incisor, right mandible lacinia mobilis distally multicuspid (with prominent process), mandibular spine simple; palp article 2 with 21 distolateral setae, article 3 with 23 biserrate setae. Maxilla mesial lobe with 7 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 4 setae, distomesial margin with 10 setae, lateral margin distally with 3 setae; article 3 lateral margin with 1 seta, distal margin with 8 setae; endite distal margin RS serrate.

Pereopod 1 propodus 2.1 times as long as wide, inferior margin with ̴38 RS; wide RS with deeply serrate margins and ridged surface, narrow RS simple, deeply bifid; dactylus with acute unguis. Pereopod 2 basis 5.1 times as long as greatest width; 0.7 times as long as basis, ischium 3.8 times as long as wide; merus 0.4 as long as ischium, 1.5 times as long as greatest width, inferior margin with 1 cluster of setae (of 1), superior distal angle with 1 seta; carpus 0.5 as long as ischium, 2.7

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times as long as wide, inferior margin with 2 clusters of setae (as 2 and 2); propodus 0.5 as long as ischium, 2.0 times as long as wide, inferior margin with indistinct heel, palm straight, inferolateral margin with 6 RS, inferomesial margin with 5 RS, inferior margin RS both blunt and acute, distally pilose, distal margin with 5 setae; dactylus 0.8 as long as propodus, unguis simple, blunt. Pereopod 6 basis 4.5 times as long as greatest width; ischium 0.8 as long as basis, 4.9 times as long as wide, inferi- or margin with 0 clusters of setae, superior distal angle with 0 RS; merus 0.6 as long as ischium, 3.1 times as long as wide, inferior margin with 2 clusters of setae (as 1 and 2), superior distal angle with 1 setae; carpus as long as ischium, 5.1 times as long as wide, inferior margin with 5 clusters of setae (as 2, 2, 2, 2 and 3; setae stiff), superior distal angle with 2 setae; propodus 0.5 as long as ischium, 5.7 times as long as wide, inferior margin with 4 clusters of setae (as 1, 1, 1, 1; RS), distal margin with 6 setae, inferior distal angle with 1 RS; dactylus 5.4 as long as proximal width. Pereopod 7 similar to, but 0.6 as long as pereopod 6. Setae on inferior margins of pereopods 4–7 distally rough or finely plumose. Inferior margins of pereopods 2–7 setulose fringe absent.

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

Pleopod 1 peduncle 2.1 times as long as wide, mesial margin with 2 plumose slen- der setae; exopod 1.6 as long as wide, with 22 PMS; endopod 2.1 times as long as wide, 0.5 as long as exopod, with 12 PMS. Pleopod 2 peduncle 2.5 as long as wide, mesial margin with 2 plumose slender setae; exopod 1.7 as long as wide, with 26 PMS; endopod 4.0 as long as greatest width, lamellar part 3.0 as long as wide, with 9 PMS; appendix masculina 3.5 times as long as endopod. Pleopod 3 exopod with 28 PMS, endopod with 16 PMS. Pleopod 4 exopod with complete transverse suture (lateral margin with conspicuously thickened rim), endopod without transverse suture. Pleopod 5 exopod with complete transverse suture (lateral margin distal part with thickened rim), endopod with incomplete transverse suture.

Uropods (rami + peduncle) 0.6 as long as pleotelson, peduncle 0.2 as long as endopod. Endopod 3.6 as long as wide; distally with apical point. Exopod 0.6 as long as endopod, 3.5 times as long as wide, distally broadly rounded.

Female. As for male, but pleonites 1–3 each have a weak sub-carinate nodules on pereonite 1, and the median nodule on the posterior margin if the head is more developed.

Size. Two males measured 10.5 and 10. 6 mm; ovigerous females 11.8–14.8 mm (mean = 13.2 mm); non-ovigerous females 10.8–12.4 mm (mean = 11.6 mm).

Remarks. Heteroserolis pellucida sp. n. is characterised by the semi-transparent cuticle, lack of obvious dorsal nodules, the narrow and acute pleonite margins, a relatively short rostral point and the posterior margin of the pleotelson forming an angled medial point. In addition it is the only species of the genus with a wide lacinia mobilis on the left mandible. Most species of Heteroserolis show some degree of dorsal ornamentation, the exceptions being the East Pacific species H. tropica and two eastern Australian species, H. longicaudata and Heteroserolis sp. ( Harrison and Poore 1984). H. longicaudata (southeastern Australia) has a nodular pleotelson and the pleotelson apex is excised, while Heteroserolis sp., known from two immature specimens from shallow water off Townsville, northern Queensland has a truncate pleotelson apex and obscure median nodules on pereonites 2 and 3.

Heteroserolis pellucida has a very distinctly thickened rim to the lateral margin of pleopod 4 exopod, and a slightly less prominent rim on the distal part of the exopod of pleopod 5. Pleopods 4 and 5, where illustrated for other species, have not appeared to show this character state, at present I regard this as a unique species character.

Distribution. New Caledonia; at depths of 557–792 metres.

Etymology. From the Latin adjective pellucidus ‘admitting light’ or semi-transparent.

Figures

Figure 1. Heteroserolis pellucida sp. n. Holotype, except where indicated. A dorsal view B lateral view C lateral view (♀ 14.8 mm, Is.6017) D pleon and pleotelson, dorsal view (♀ 14.8 mm, Is.6017) E pleonites F head, anterior margin G sternites and ventral pleonites H ventral coxae 2–4 I ventral join pereonites 2 and 3 Į frons; 3 10.5 mm, Is.6017 K antennule L antenna.

Figure 2. Heteroserolis pellucida sp. n. Paratype 3 10.5 mm, Is.6017. A maxilliped B right mandible C left mandible D mandible palp E maxillule F maxilla.

Figure 3. Heteroserolis pellucida sp. n. Paratype 3 10.5 mm, Is.6017. A–D pereopods 1, 2, 6 and 7 respectively; a, detail of pereopod 1 propodal palm setae E pereopod 2 distal articles F pereopod 6, distal articles.

Figure 4. Heteroserolis pellucida sp. n. Paratype 3 10.5 mm, Is.6017. A–E pleopods 1–5 respectively F uropods G lateral margin, pleopod 1 exopod.