Cirolana trulla, Sidabalok & Bruce, 2018

Sidabalok, Conni M. & Bruce, Niel L., 2018, Review of the Cirolana ‘ pleonastica-group’ (Crustacea: Isopoda: Cirolanidae) with description of four new species from the Indo- Malaysian region, Raffles Bulletin of Zoology 66, pp. 177-207 : 186-191

Cirolana trulla , new species

( Figs. 5–8 )

Material examined. All Singapore. Holotype, male (7.4 mm) ( ZRC 2018.0206 ), between St John’s Island and Lazarus

Island, 01°13.043′N, 103°51.319′E, OTC0103 OTR356, trap 22.4 m, coll. H. Wong and party, 3 April 2014.

Paratypes. 4 males (6.0 [dissected], 6.3, 6.6, 6.9 mm), 1 female (6.3 [dissected] mm) ( ZRC 2018.0207 ), same data as holotype ; 1 male (7.8 mm) ( ZRC 2018.0208 ), Pulau Ubin , Beting Bronok, 01°26.423′N, 104°02.702′E, CMBS SEA 1273 DR214, rectangular dredge 8.7 m, coll. S. Cheng and party, 7 October 2013 ; 1 male (5.2 mm) ( MTQ W34884), near Changi Naval Base , 01°18.492′N, 104°02.935′E, CMBS SEA 6139 DR361, rectangular dredge 19.2 m, coll. T. Tay and party, 8 April 2014 .

Description. Body ( Fig. 5A ) 4.3 times as long as greatest width, dorsal surfaces punctate, widest at pereonite 4, lateral margins subparallel. Rostral point absent. Eyes ( Fig. 5C ) separated by about 79% width of head, eye colour black. Pereonite 1 and coxae 2–3 ( Fig. 5B ) each with posteroventral angle rounded; coxae 5–7 with entire oblique carina; posterior margins of pereonites 6–7 with irregular submarginal nodules. Pleon ( Fig. 5F ) with pleonite 1 not visible in dorsal view; pleonites 3–5 posterior margin with row of small, regularly spaced nodules; posterolateral angles of pleonite 2 forming acute point, extending posteriorly to anterior of pleonite 3; pleonite 3 without median tubercle and 4 small sublateral tubercles on each side, posterolateral margins not extending to posterior margin of pleonite 4 or 5, acute; pleonite 4 without median tubercle and 4 sublateral tubercles on each side, posterolateral margin of pleonite 4 rounded, clearly extending beyond posterior margin of pleonite 5; pleonite 5 without median tubercle and 1 sublateral tubercle on each side and posterolateral angles overlapped by lateral margins of pleonite 4. Pleotelson ( Fig. 6F ) 0.9 times as long as anterior width; with 2 tubercles on posterior of dorsal surface; lateral margins straight, margins smooth, posterior margin sub-truncate, without median point, with 8 robust setae.

Antennula ( Fig. 5D ) peduncle articles 1 and 2 fused; articles 3 and 4 0.8 times as long as combined lengths of articles 1 and 2, article 3 1.9 times as long as wide; flagellum with 9 articles, extending to anterior of pereonite 1. Antenna ( Fig. 5G ) peduncle article 4 1.6 times as long as wide, 1.3 times as long as article 3, and 6 short simple setae (distal); article 5 1.3 as long as article 4, 2.5 times as long as wide, anterodistal angle with cluster of 1 short simple setae; flagellum with 19 articles, extending to posterior of pereonite 4.

Frontal lamina ( Fig. 5E ) pentagonal, 1.9 longer than greatest width, lateral margins straight and parallel, anterior margin straight and acute, forming median point.

Mandible ( Fig. 6D ) molar process anterior margin with 15 flat teeth; with proximal cluster of long simple setae; right mandible spine row composed of 4 spines; palp article 2 with 12 distolateral setae, palp article 3 with 4 robust biserrate and 11 plumose setae. Maxillule ( Fig. 6C ) mesial lobe with 3 large and circumplumose RS; lateral lobe with 13 RS. Maxilla ( Fig. 6B ) lateral lobe with 4 long simple setae; middle lobe with 8 long simple setae; mesial lobe with 4 distal simple setae, with 2 proximal simple and 4 plumose setae. Maxilliped ( Fig. 6A ) palp article 2 mesial margin with 9 slender setae, lateral margin distally with 1 slender setae; article 3 mesial margin with 16 slender setae, lateral margin with 10 slender setae; article 4 mesial margin with 11 slender setae, lateral margin with 5 slender setae; article 5 distal margin 12 setae, lateral margin with 6 setae; endite with 4 long CPS, and 2 coupling setae.

Pereopod 1 ( Fig. 7A ) basis 2.2 times as long as greatest width, superior distal angle without cluster of acute setae, inferior distal angle with a cluster of 4 acute setae; ischium 0.6 times as long as basis, inferior margin with 2 setae, inferior distal margin with 2 RS, superior distal margin with 4 long RS; merus inferior margin with 6 molariform RS, set as 4 and 2, with 5 simple setae, superior distal angle with 3 RS; carpus inferior margin with 1 RS and 1 simple seta; propodus 1.7 times as long as wide, inferior margin with 2 RS, inferior distal margin with 1 large RS and 1 simple seta, superior distal with 2 simple setae; dactylus 0.9 as long as propodus. Pereopod 2 ( Fig. 7B ) ischium inferior margin with 1 long acute RS, inferior distal margin with 2 RS, 1 acute RS, 1 simple seta, superior distal margin with 2 long acute setae and 3 plumose setae; merus inferior margin with 4 stout RS and 2 simple setae, set as single row, inferior distal margin with 1 stout RS, 2 acute RS and 1 simple seta, superior distal margin with 1 long acute RS and 4 simple setae; carpus inferior distal margin with 2 acute RS; propodus 2.7 as long as wide, with 2 clusters of acute RS, inferior margin with 2 RS, inferior distal margin with 1 large RS and 1 simple seta; dactylus 0.7 as long as propodus. Pereopod 3 similar to pereopod 2. Pereopod 6 ( Fig. 7C ) similar to pereopod 7. Pereopod 7 ( Fig. 7D ) basis 2.5 times as long as greatest width, superior margin straight, with 3 palmate setae; ischium 0.5 as long as basis, inferior margin with 4 long simple setae (set in group of 2 and 2), with 3 triangular processes, inferior distal angle with 2 long simple setae, superior distal angle with 5 long setae and 2 biserrate setae; merus 1.1 as long as ischium, 1.9 times as long as wide, inferior margin with 1 acute RS and 3 simple setae, superior distal angle with 11 RS (10 biserrate), inferior distal angle with 5 RS and 3 simple setae; carpus as long as ischium, 0.4 times as long as wide, inferior margin with 3 RS and 1 simple seta, superior distal angle with 8 biserrate RS, inferior distal angle with 9 RS (5 biserrate); propodus as long as ischium, 3.8 times as long as wide, inferior margin with 2 clusters of RS (set as 1 and 1), superior distal angle with 1 slender seta, 1plumose seta and 3 RS, inferior distal angle with 2 RS; dactylus 0.5 as long as propodus.

Penes ( Fig. 6E ) low tubercles, penial openings separated by 2.9% of sternal width.

Pleopod 1 ( Fig. 8A ) exopod 1.7 times as long as wide, lateral margin straight, distally narrowly rounded, medial margin weakly oblique, mesial margin strongly convex, with PMS from distal one-third, with ~38 PMS; endopod 2.4 times as long as wide, distally narrowly rounded, lateral margin straight, with PMS on distal margin only, mesial margin with PMS from distal one-third, endopod with ~13 PMS; peduncle 1.3 times as wide as long. Pleopod 2 ( Fig. 8B ) exopod with ~40 PMS, endopod with ~16 PMS; appendix masculina with parallel margins, 0.9 times as long as endopod, distally acute. Pleopod 3 ( Fig. 8C ) exopod with ~43 PMS, endopod with ~12 PMS. Pleopod 4 ( Fig. 8D ) exopod with ~37 PMS, endopod with ~9 PMS. Pleopod 5 ( Fig. 8E ) exopod with ~38 PMS. Pleopods 2–5 peduncle distolateral margin with prominent acute RS, 3–5 endopods with distomesial serrate scales.

Uropod ( Fig. 5H–5I ) peduncle ventrolateral margin with 1 RS, lateral margin with medial short acute RS, posterior lobe about 0.9 as long as endopod; rami extending beyond pleotelson, marginal setae dense, in two tiers, apices not bifid. Endopod lateral margin proximally convex, without prominent excision, proximal lateral margin with 1 RS, distal lateral margin with 1 RS; mesial margin strongly convex, with 9 RS. Exopod not extending to end of endopod, 1.8 times as long as greatest width; lateral margin weakly convex with setal fringe on the posterior, with 3 visible widely separated RS; mesial margin straight, proximally convex, with 4 RS.

Female. The uropodal exopod lacks the dense setal fringe on the posterior lateral margin.

Size. Males 5.2–7.8 mm, mean 6.6 mm (n=7); non-ovigerous female 6.3 mm (n=1); all from type series.

Variation. RS count was measured from all type series (n = 8). Uropod exopod lateral: 3 = 75%, 4 = 25%; mesial: 3 = 50%, 4 = 50%. Uropod endopod lateral: 2 = 87.5%, 3 = 12.5%; mesial: 7 = 12.5%, 8 = 62.5%, 9 = 25%. Pleotelson: 8 = 100%.

Remarks. Cirolana trulla , new species, is characterised by having a more elongate body than most Cirolana (4.3 vs. ~3.0 times as long as wide), a triangular rostrum in dorsal view, the presence of three triangular processes (= broadbased spines) on the inferior margin of ischium of pereopods 6–7, low tubercle-like penial openings (not processes) and the presence of two small posteriorly positioned nodules on of pleotelson. The male uropodal rami are distinctive in shape, but especially distinctive in terms of their setation, with a two-tier and dense setal fringe on the posterior of lateral and mesial margins of exopod.

Cirolana trulla , new species, is most similar to C. bruscai Bruce & Olesen, 2002 , both species having a relatively elongate body, the head anteriorly produced and overriding the antennular bases, a few sublateral tubercles on pereonites 3–5, scattered nodules on posterior of pleotelson, long simple setae on superior distal angle of the ischium– merus of pereopods 1–2 and on the inferior margin of the ischium–merus of pereopods 6–7, the triangular processes on the ischium of pereopods 6–7, the two tiered-setae that form dense mass of setae on the posterior lateral margin of uropod exopod and endopod. Despite these similarities there are numerous differences between the two species: Cirolana trulla is 4.3 times as long as greatest width (vs. 3.1 in C. bruscai ), has 8 robust setae on the pleotelson (vs. 6), the anterior of the head is strongly produced (vs. weakly produced), pleopod 1 endopod and exopod lateral margins are straight (vs. convex); uropodal exopod not extending to end of endopod (vs. beyond) with a narrow apex (vs. semi-truncate), the mesial margin is distinctly angled midlength (vs. evenly convex) and the second submarginal tier of setae (distal one-third vs. distal three-quarters), and two small submedian tubercles on pleotelson (vs. absent). The body length-to-width ratio (2.5) of Cirolana bruscai in the original description is inaccurate owing to the curved state of the holotype; we recalculated the ratio, which is 3.1.

Distribution. Singapore; 8 to 24 metres.

Etymology. The epithet is the Latin word for shovel, alluding to the shovel-shaped rostrum.

Figures

Fig. 5. Cirolana trulla n. sp. A–C, E–F, holotype male (7.4 mm) (ZRC 2018.0206), Singapore. D, G, H, paratype male (6.0 mm) (ZRC 2018.0207), Singapore. I, paratype female (6.3 mm) (ZRC 2018.0207), Singapore. A, dorsal view; B, lateral view; C, head; D, antennula; E, frons; F, pleon; G, antenna peduncle; H, uropod male; I, uropod female.

Fig. 6. Cirolana trulla n. sp. E, holotype male (7.4 mm) (ZRC 2018.0206), Singapore. A–D, F, paratype male (6.0 mm) (ZRC 2018.0207), Singapore. A, maxilliped; B, maxilla; C, maxillule; D, right mandible; E, penial process; F, pleotelson.

Fig. 7. Cirolana trulla n. sp. A–D, paratype male (6.0 mm) (ZRC 2018.0207), Singapore. A, pereopod 1; B, pereopod 2; C, pereopod 6; D, pereopod 7.

Fig. 8. Cirolana trulla n. sp. A–E, paratype male (6.0 mm) (ZRC 2018.0207), Singapore. A, pleopod 1; B, pleopod 2; C, pleopod 3; D, pleopod 4; E, pleopod 5.