Cirolana molari, Bruce, 2017

Bruce, Niel L., 2017, Review of the species of the Cirolana ‘ parva - group’ (Cirolanidae: Isopoda: Crustacea) in Indonesian and Singaporean waters, Zootaxa 4317 (3), pp. 401-435 : 417-422

Cirolana molari sp. nov.

( Figs 9–12 )

Material examined. Holotype. ♂ (7.0 mm) St John’s Island, Singapore, 1°13.020' N, 103°51.122' E, 30 May 2013, trap, intertidal, coll. N.L. Bruce, SW119 SS4934 ( ZRC 2017.0762)

Paratypes. All Singapore. 6 ♂ (6.0 [dissected], 6.5, 6.5, 6.9, 7.0, 7.7 mm), 1 ♀ (6.0 mm), near Sudong and Semakau, 01°13'134 N, 103°44'283 E, 25 May 2013, rectangular dredge 20–22 m on sandy bottom, coll. Helen Wong and party, DR70 SS5400 ( ZRC 2017.0763 ) . 17 ♂ (4.7, 4.9, 5.0, 5.3, 5.7, 5.9, 5.9, 5.9, 5.9, 6.0, 6.0 [dissected], 6.1, 6.5, 6.7, 6.9, 6.9, 7.0 mm), 2 ♀ (4.7, 5.0 mm), 1 manca (3.1 mm), St John’s Island, 1°13.020' N, 103°51.122' E, 30 May 2013, trap, intertidal, coll. N.L. Bruce, SW119 SS4934 ( ZRC 2017.0764 ) . 1 ♂ (5.6 mm), 01°13.043'N, 103°51.319'E, between St John and Lazarus Island, 3 April 2014, trap 22.4 m, coll. Helen Wong and party, OTR356 OTC0103 (MTQ W52898).

Description. Body 2.6 times as long as greatest width, widest at pereonite 5, lateral margins subparallel. Eyes separated by about 76% width of head, eye colour black. Pereonite 1 and coxae 2–3 each with posteroventral angle rounded; coxae 5–7 with entire oblique carina; posterior margins of pereonites 5–7 smooth. Pleon with pleonite 1 largely concealed by pereonite 7; pleonites 3–5 posterior margin smooth; posterolateral angles of pleonite 2 forming acute point, extending posteriorly to anterior of pleonite 3; pleonite 3 with posterolateral margins extending clearly beyond posterior margin of pleonite 5, acute; posterolateral margin of pleonite 4 rounded, clearly extending beyond posterior margin of pleonite 5. Pleotelson 1.2 times as long as anterior width; lateral margins weakly convex, margins weakly serrate, posterior margin evenly rounded, with small distinct median point, with 8 RS.

Antennula peduncle articles 1 and 2 entirely fused; articles 3 and 4 0.8 times as long as combined lengths of articles 1 and 2, article 3 2 times as long as wide; flagellum with 11 articles, extending to anterior of pereonite 1. Antenna peduncle article 4 2 times as long as wide, 2.8 times as long as article 3, and 3 short simple setae (distal); article 5 as long as article 4, 2 times as long as wide, inferior margin without pappose setae, anterodistal angle with cluster of 4 short simple setae; anterodistal angle with cluster of 1 long simple seta; flagellum with 19 articles, extending to posterior of pereonite 4.

Frontal lamina 1.5 longer than posterior width, 1.4 longer than greatest width, lateral margins straight, diverging slightly towards anterior, anterior margin acute, forming median point.

Mandible molar process anterior margin with 23 flat teeth; with proximal cluster of long simple setae; right mandible spine row composed of 10 spines; palp article 2 with 12 distolateral setae, palp article 3 with 4 robust biserrate setae. Maxillula mesial lobe with 3 large and CPS RS; lateral lobe with 13 RS. Maxilla lateral lobe with 5 long simple setae; middle lobe with 11 long simple setae; mesial lobe with 7 distal simple setae, with 8 proximal simple and plumose setae. Maxilliped palp article 2 mesial margin with 6 slender setae, lateral margin distally with 1 slender setae; article 3 mesial margin with 12 slender setae, lateral margin with 6 slender setae; article 4 mesial margin with 14 slender setae, lateral margin with 4 slender setae; article 5 distal margin 17 setae, lateral margin with 3 setae; endite with 5 long CPS, and 2 coupling setae.

Pereopod 1 basis 2.3 times as long as greatest width, superior distal angle without cluster of acute setae, inferior distal angle with cluster of 4 acute setae; ischium 0.4 times as long as basis, inferior margin without setae, inferior distal margin with 3 RS, superior distal margin with 1 RS; merus inferior margin with 11–13 molariform RS, set as single row, without simple setae, inferior distal margin with 1 RS, superior distal angle with 2 setae; carpus inferior margin with 2 RS, carpus inferior margin with 1 simple seta; propodus 1.7 times as long as wide, inferior margin with 3 RS, inferior margin with 1 simple seta, inferior distal margin with 1 large RS, superior distal with 2 simple setae; dactylus 0.7 as long as propodus; inferior margin with setal fringe lacking. Pereopod 2 ischium inferior margin with 1 long acute RS, inferior distal margin with 2 RS and 1 simple seta, superior distal margin with 1 long simple setae and 3 RS; merus inferior margin with 6 stout RS, set as single row, inferior distal margin with 3 stout RS, superior distal margin with 3 stout RS; carpus inferior distal margin with 2 RS; propodus 2.0 as long as wide, with 2 clusters of acute RS, inferior margin with 2 RS, inferior distal margin with 1 long RS; dactylus 0.7 as long as propodus. Pereopod 3 similar to pereopod 2. Pereopod 6 similar to pereopod 7. Pereopod 7 basis 2.0 times as long as greatest width, superior margin convex, inferior margin with 2 palmate setae; ischium 0.5 as long as basis, inferior margin with 6 RS (set in group of 1, 2 and 3), superior distal angle with 5 RS (1 biserrate), inferior distal angle with 3 RS; merus 0.9 as long as ischium, 1.5 times as long as wide, inferior margin with 3 RS, superior distal angle with 10 RS (4 biserrate), inferior distal angle with 7 RS; carpus 0.9 as long as ischium, 1.9 times as long as wide, inferior margin with 4 RS, superior distal angle with 9 RS (5 biserrate), inferior distal angle with 7 RS (3 biserrate); propodus as long as ischium, 3.5 times as long as wide, inferior margin with 2 clusters of RS, superior distal angle with 1 slender setae and 2 RS; inferior distal angle with 2 RS; dactylus 0.4 as long as propodus.

Penes low tubercles, penial openings separated by 14.3% of sternal width.

Pleopod 1 exopod 1.5 times as long as wide, lateral margin weakly convex, distally narrowly rounded, mesial margin weakly oblique, mesial margin strongly convex, with PMS from distal half, with ~25 PMS; endopod 2 times as long as wide, distally subtruncate, lateral margin weakly concave, with PMS from distal one-third, mesial margin with PMS on distal margin only, endopod with ~12 PMS; peduncle 1.6 times as wide as long, mesial margin with 4 coupling setae. Pleopod 2 exopod with ~33 PMS, endopod with ~17 PMS; appendix masculina with parallel margins, 1.8 times as long as endopod, distally acute. Pleopod 3 exopod with ~36 PMS, endopod with ~12 PMS. Pleopod 4 exopod with ~36 PMS, endopod with ~10 PMS. Pleopod 5 exopod with ~36 PMS. Pleopods 2–5 peduncle distolateral margin with prominent acute RS, 3–5 endopods with distomesial serrate scales.

Uropod peduncle ventrolateral margin with 2 RS, lateral margin with mesial short acute RS, posterior lobe about as long as endopod; rami extending beyond pleotelson, marginal setae in single tier, apices acute. Endopod apically deeply subequal bifid, lateral process prominent; lateral margin straight, proximal lateral margin with 2 RS; distal lateral margin with 1 RS, mesial margin weakly convex, with 5 RS. Exopod not extending to end of endopod, 2.8 times as long as greatest width, apically deeply subequal bifid, lateral process prominent; lateral margin weakly convex, with 6 RS; mesial margin weakly convex, with 3 RS.

Female. Similar to male.

Variation. RS number is consistent within the measured specimens (n= 26, ZRC 2017.0762–0764). Uropod exopod RS mesial margin with 3–4 (3 = 96.2%), lateral with 6–7 (6 = 92.3%); uropod endopod mesial margin with 4–5 (4 = 76.9%), lateral margin with 2–3 with 50% each.

Remarks. Cirolana molari sp. nov. can be immediately distinguished by having a continuous row of 11–13 molariform RS on the inferior margin of pereopod 1 merus (unique within the ‘ parva -group’) and antennula peduncle article 1 and 2 entirely fused.

Distribution. Known only from Singapore; intertidal to 23 metres ( Fig 1 ).

Etymology. The epithet molari comes from the Latin word molar, named after the molar shape of RS row on merus pereopod 1 which is the determining character of the species.

Figures

FIGURE 1. Distribution map of Cirolana ‘ parva group’ in Indo-Australian region (C – H, Indonesia; I, PNG; J – K, Australia). LoCation symbols: A = Thailand, B = Singapore, C = Lombok, D = Bitung, E = Pulau Pombo, Maluku, F = Raja Ampat, G = Kei Islands, H = Kaimana, I = Madang, J = Lizard Island, K = HinChinbrook Island. SpeCies symbols: Cirolana andamanensis (-), Cirolana arafurae (×), Cirolana improceros (v), Cirolana leptanga (O), Cirolana siamensis (O), Cirolana stenoura (A), Cirolana thailandica (Ł), Cirolana molari (Ɨ), Cirolana peisanae (+), Cirolana duo (Ŧ).

FIGURE 9. Cirolana molari sp. nov., holotype ♂ (7.0 mm, ZRC 2017.0762) (A, B, E – H); paratype ♂ (6.0 mm, ZRC 2017.0763) (C – D): A, dorsal view; B, lateral view; C, antennula; D, antenna pedunCle; E, head; F, frontal lamina; G, pleon; H; penial openings.

FIGURE 10. Cirolana molari sp. nov., paratype ♂ (6.0 mm, ZRC 2017.0763): A, maxilla; B, maxilliped; C, maxillula; D, right mandible; E, uropod; F, uropod apiCes.

FIGURE 11. Cirolana molari sp. nov., paratype ♂ (6.0 mm, ZRC 2017.0763) (A – D): A, pereopod 1; B, pereopod 2; C, pereopod 6; D, pereopod 7.

FIGURE 12. Cirolana molari sp. nov., paratype ♂ (6.0 mm, ZRC 2017.0763) (A – E): A, pleopod 1; B, pleopod 2; C, pleopod 3; D, pleopod 4; E, pleopod 5.