Myopiarolis koro, 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 : 41-46

Myopiarolis koro sp. n.

urn:lsid:zoobank.org:act:93A1FB2C-15CB-4F55-8172-D0EAE37D5CB1

Figs 9–12

Material. Holotype: 3 (18.4 mm), Fiji, Koro Sea , 17°22´S, 179°28´W, 5 Mar 1999, 1216– 1226 m, BORDAU 1, stn CP 1458, N/ O Alis, coll. Bouchet, Warren and Rich- er de Forges ( MNHN Is.6009) . Paratype: ♀ (ovig. 21.6 mm), same data as holotype ( MNHN Is.6010).

Description. Body 1.3 as long as wide, widest at coxae 4, dorsal surfaces punctate. Head anterolateral lobes weakly convex, anterior submarginal ‘ridge’ laterally incomplete; dorsally with pair of low sub-median tubercles anterior to eyes, posterior margin with low rounded median tubercle. Eyes present. Pereonite 1 anterolateral margin continuously convex; dorsally without tubercles. Coxae 4 extending to mid-pleonite 1; 5 extending posteriorly along 0.2 of pleotelson length; coxae 6 extending to posterior of uropods, and along 0.6 of pleotelson length. Ventral coxal plates mesially flat, mesially simple, smooth. Pleonites extending posteriorly along 0.6–0.7 pleotelson lateral margin; pleonite 1 sternal plates with acute median point, sternal plate 1 with median ridge and 2 submedian depressions. Pleotelson 0.7 times as long as anterior width, dorsal surface with median longitudinal carina, with paired sublateral carinae; lateral margins straight, posterior margin converging to angled caudomedial point, without distinct median excision.

Antennule peduncle article 2 1.8 times as long as wide; articles 3 and 4 2.2 times as long as article 2; article 3 8.5 times as long as wide; flagellum 2.4 as long as peduncle articles 3 and 4, with ̴36 articles, extending to pereonite 4. Antenna peduncle article 4 4.6 times as long as wide, 2.6 times as long as article 3; article 5 1.3 times as long as article 4, 9.1 times as long as wide; antennal flagellum 1.0 as long as peduncle article 5, with ̴18 articles, extending to posterior of pereonite 4.

Epistome with acute median point. Mandible incisor with single posterior cusp, left mandible lacinia mobilis 1.0 (0.97) as wide as incisor, right mandible lacinia mobilis distally multicuspid, mandibular spine distally serrate; palp article 2 with 22 distolateral setae, article 3 with 40 biserrate setae. Maxilla mesial lobe with 18 long, finely serrate setae;

middle lobe with 6 long simple setae (1 mesial, 5 terminal); lateral lobe with 2 distal simple setae. Maxilliped palp article 2 proximomesial margin with ̴10 setae, distomesial margin with 16 setae, lateral margin distally with 12 setae (continuous along length); article 3 lateral margin with 6 setae, distal margin with 8 setae; endite distal margin RS simple.

Pereopod 1 carpus RS distally serrate; propodus 1.9 times as long as wide, inferior margin with ̴66 RS, wide RS with finely ridged margins, narrow RS distally bifid,

with pilose flagellum. Pereopod 2 basis 4.7 times as long as greatest width; 0.8 times as long as basis, ischium 3.8 times as long as wide; merus 0.5 as long as ischium, 2.7 times as long as greatest width, inferior margin with 1 cluster of setae (2), superior distal angle with 0 setae; carpus 0.6 as long as ischium, 3.1 times as long as wide, inferior margin with 8 clusters of setae (groups indistinct; as, 1, 1, 1, 2, 1, 2, 3, 4); propodus 0.5 as long as ischium, 2.4 times as long as wide, inferior margin with indistinct heel, palm weakly concave, inferolateral margin with 6 RS, inferomesial margin with 10 RS, inferior margin RS simple, blunt, distally pilose, distal margin with ̴10 setae, dactylus 0.5 as long as propodus, unguis simple, blunt. Pereopod 6 basis 4.2 times as long as greatest width; ischium 0.9 as long as basis, 4.2 times as long as wide, inferior margin with 1 cluster setae (2), superior distal angle with 0 RS; merus 0.5 as long as ischium, 2.4 times as long as wide, inferior margin with 1 cluster of setae (1, 1 and 1), superior distal angle with 1 seta; carpus 0.8 as long as ischium, 4.7 times as long as wide, inferior margin with 10 clusters of setae (as 1, 1, 1, 2, 1, 2, 3, 3, 2, 7), superior distal angle with ̴6 setae; propodus 0.6 as long as ischium, 7.0 times as long as wide, inferior margin with 9 clusters of setae (as 1, 1, 1, 3, 3, 3, 3, 3, 3), distal margin with ̴11 setae, inferior distal angle with 1 RS; dactylus 8.7 as long as proximal width. Pereopod 7 similar to, but 0.95 as long as pereopod 6. Setae on inferior margins of pereopods 4 to 7 finely plumose. Inferior margins of pereopods 2–7 setulose fringe prominent.

Pleopod 1 peduncle 1.4 times as long as wide, mesial margin with 3 coupling setae; exopod 1.8 as long as wide, with 44 PMS; endopod 2.2 times as long as wide, 0.7 as long as exopod, with 21 PMS. Pleopod 2 peduncle 1.5 as long as wide, mesial margin with 3 coupling setae; exopod 1.5 as long as wide, with 48 PMS; endopod 3.0 as long as greatest width, lamellar part 4.2 as long as wide, with 16 PMS; appendix masculina 3.2 times as long as endopod. Pleopod 3 exopod with 52 PMS, endopod with 20 PMS. Pleopod 4 exopod with complete transverse suture, endopod with complete transverse suture. Pleopod 5 exopod with complete transverse suture, endopod with incomplete transverse suture.

Uropods (rami + peduncle) 0.2 as long as pleotelson, peduncle 0.9 as long as endopod. Endopod 2.9 as long as wide; distally broadly rounded. Exopod 0.6 as long as endopod, 2.6 times as long as wide, distally broadly rounded.

Female. As for the male.

Remarks. Myopiarolis koro sp. n., the only serolid known from Fiji, is best identified by its large size, presence of small sub-median tubercles anterior to the eyes, a relatively wide posterior margin on the pleotelson and a lack of median tubercles on the pereonites and pleonites.

Myopiarolis novaecaledoniae is similar in general appearance, but is smaller (14.6 – 18.5 mm compared to 18.4–21.6 mm), the dorsum is smooth not punctate, the palm of pereopod 2 has 3+6 robust setae (compared to 5+10), and the maxilla has the lateral and mesial lobes each with 2 long setae compared to 2 and 6 setae.

Colour. Pale brown, pale cream on coxal margins;

Distribution. Fiji, Koro Sea; depths of 1216–1226 metres.

Etymology. Taken from the region of the type locality, the Sea of Koro; noun in apposition.

Figures

Figure 9. Myopiarolis koro sp. n. Holotype, except F–H, female paratype. A dorsal view B lateral view C frons D pleon and pleotelson, ventral view E sternites and ventral pleonites F antenna G antennule H antenna article 2, ventral side.

Figure 10. Myopiarolis koro sp. n. Female paratype, except D, holotype. A right mandible B right mandible C left mandible D maxilliped palp E maxillule F maxilla G maxilliped H mandible palp, distal article 2 and article 3.

Figure 11. Myopiarolis koro sp. n. Holotype. A–D pereopods 1, 2, 6 and 7 respectively a detail of pereopod 1 propodal palm setae; E pereopod 2 propodus F pereopod 1 carpus, distal angle G pereopod 2 carpus and propodus H pereopod 7 propodus, distal margin and dactylus.

Figure 12. Myopiarolis koro sp.n. Holotype, except D, E, female paratype.A–E pleopods 1–5 respectively F pleopod 2 endopod detail G pleopod 1 peduncle H pereopod 7 propodus, distal margin and dactylus.