Cirolana phuketensis, Rodcharoen, Eknarin, Bruce, Niel L. & Pholpunthin, Pornsilp, 2017

Rodcharoen, Eknarin, Bruce, Niel L. & Pholpunthin, Pornsilp, 2017, Cirolanaphuketensis, a new species of marine isopod (Crustacea, Isopoda, Cirolanidae) from the Andaman Sea coast of Thailand, ZooKeys 695, pp. 1-17 : 3-9

Cirolana phuketensis sp. n.

Material examined.

Holotype: ♂ (5.0 mm), Ao Makham, Phuket Province, 07°49'51"N, 98°24'14"E, 6 August 2014, trapped in 1 m of depth, coral rubble, coll. E. Rodcharoen ( PSUZC–CR 2086-01).

Paratypes: 6 ♂ (4.6, 5.8, 5.2, 5.0, 5.3, 5.1 mm [dissected]), 3 ♀ (5.2, 4.9, 4.9 mm [dissected]), same data as holotype, ( PSUZC–CR 2086-02; MTQ W53037). 3 ♂ (5.6, 4.8, 5.3 mm [dissected]), 6 ♀ (5.2, 5.7, 5.3, 5.7, 5.6, 5.4 mm [dissected]), Laem Pakarang, Phang Nga Province, 08°44'11"N, 98°13'13"E, 15 march 2012, trapped in 2 m of depth, coral rubble, coll. E. Rodcharoen ( PSUZC–CR 2086-03; MTQ W53038). 3 ♂ (4.7, 4.9, 5.0 mm [dissected]), 7 ♀ (5.0, 4.7, 4.9, 4.9, 5.1, 4.6, 5.1 mm [dissected]), Koh Phayam, Ranong Province, 09°42'36"N, 98°23'41"E, 22 December 2012, trapped in 3 m of depth, coral rubble, coll. E. Rodcharoen ( PSUZC–CR 2086-04; MTQ W53039).

Description of male.

Body 2.8 times as long as greatest width, widest at pereonite 6, lateral margins subparallel (Figure 2A). Rostral point absent (Figure 2C). Eyes colour dark brown (Figure 2C). Pereonites 2-4 with each a single transverse impressed suture; pereonites 5-6 with each 2 transverse impressed sutures; pereonite 7 with 3 transverse sutures each with a nodulose ridge (Figure 2A). Pereonite 1 and coxae 2-3 (Figure 2B) each with posteroventral angle rounded; coxae 5-7 with entire oblique carina. Pleon (Figure 2E) with pleonite 1 largely concealed by pereonite 7; posterolateral angles of pleonite 2 forming acute point, extending posteriorly to anterior of pleonite 4; pleonite 3 with a row of 13 small tubercles, posterolateral margins not extending to posterior margin of pleonite 5, rounded; pleonite 4 with median tubercles and 5-6 sublateral tubercles on each side, posterolateral margin of pleonite 4 rounded, clearly extending beyond posterior margin of pleonite 5; pleonite 5 with prominent median tubercles and 3-4 sublateral tubercles on each side, posterolateral angles overlapped by lateral margins of pleonite 4. Pleotelson 0.7 times as long as anterior width, dorsal surface with 2 tubercles and paired submedian longitudinal carina; lateral margins weakly concave, margins serrate, posterior margin evenly rounded, without median point, with 6 robust setae interspersed among 10 slender plumose setae as figured (Figure 6C, D).

Antennula (Figure 2F) 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 1.6 times as long as wide, flagellum with 9 articles, antennula extending to anterior margin of pereonite 1. Antenna (Figure 2G) peduncle article 4 2.2 times as long as wide, 2.4 times as long as article 3, inferior margin with 1 plumose setae, inferodistal margin1 short simple setae; article 5 1.0 times as long as article 4, 2.4 times as long as wide, inferodistal angle with cluster of 3 pappose setae, anterodistal angle with cluster of 4 short simple setae and 2 plumose setae; flagellum with 16 articles, extending to middle of pereonite 4.

Frontal lamina (Figure 2D) pentagonal, lateral margins concave, anterior margin with narrowly round apex.

Mandible molar process (Figure 3A, C) anterior margin with 12 flat teeth; without proximal cluster of long simple setae; right mandible spine row composed of 8 spines, left with 7 spines; palp articles 2 with 14 distolateral setae; palp article 3 with 17 robust biserrate setae (Figure 3B); Maxillula (Figure 3E) mesial lobe with 3 large and circumplumose RS; lateral lobe with 12 RS (plus 1 slender seta). Maxilla (Figure 3D) lateral lobe with 5 long simple setae, middle lobe with 12 long simple setae, maxilla mesial lobe with 1 distal simple seta and 12 proximal simple and plumose setae. Maxilliped palp (Figure 3F) article 2 mesial margin with 5 slender setae, lateral margin distally with 1 slender setae; article 3 mesial margin with 12 slender setae, lateral margin with 5 slender setae; article 4 mesial margin with 15 slender setae, lateral margin with 3 slender setae; article 5 distal margin 16 setae, lateral margin with 4 setae; maxilliped endite with 5 long CPS and 2 coupling setae (both left and right).

Pereopod 1 (Figure 4A, B) basis 2.0 times as long as greatest width, inferodistal angle with cluster of 2 acute setae; ischium 0.6 times as long as basis, inferior margin with 2 setae, superior distal margin with 2 RS; merus inferior margin with 6 molariform RS (set in row of 5 and 2), superior distal angle with 3 setae; carpus inferior margin with 1 RS (plus 1 slender seta); propodus 1.8 times as long as wide, inferior margin with 2 RS; dactylus (Figure 4C) 0.7 times as long as propodus; inferior margin lacking setal fringe. Pereopod 2 (Figure 4D) ischium inferior margin with 2 stout, bluntly rounded RS, superior distal margin with 2 RS; merus inferior margin with 4 stout RS (set in row 3 and 1), superior distal margin with 3 acute RS; carpus inferodistal angle with 2 RS (plus 1 slender seta); propodus 2.3 times as long as wide, with 3 cluster of acute RS; dactylus 1.3 times as long as propodus. Pereopod 3 similar to pereopod 2. Pereopod 4 (Figure 4E) intermediate in form between pereopod 3 and pereopod 5. Pereopod 6 similar to pereopod 7. Pereopod 7 (Figure 4F) basis 2.0 times as long as greatest width, superior margin convex, inferior margin with 3 palmate setae; ischium 0.6 times as long as basis, inferior margin with 7 RS (set in group 3 and 4), superior distal angle with 5 RS, inferior distal angle with 4 RS; merus 0.8 time as long as ischium, 1.5 times as long as wide, inferior margin with 3 RS, superior distal angle with 9 RS, inferior distal angle with 7 RS; carpus 0.8 time as long as ischium, 1.5 times as long as wide, inferior margin with 2 RS, superior distal angle with 17 RS, inferior distal angle with 10 RS; propodus 0.8 times as long as ischium, 2.3 times as long as wide, inferior margin with 3 clusters of RS (set in group 1 and 2), superior distal angle with 2 slender setae (plus 1 plumose seta and 3RS), inferior distal angle with 2 robust setae; dactylus 0.6 times as long as propodus.

Penes (Figure 2H) two low tubercles separated by 3% of sternal width.

Pleopod 1 (Figure 5A) exopod 1.4 times as long as wide, lateral margin straight, distally broadly rounded, mesial margin strongly convex, with 28 PMS from distal one-third; endopod 2.1 times as long as wide, distally broadly rounded, lateral margin strongly concave, with 15 PMS on distal margin only; peduncle 1.6 times as wide as long, mesial margin with 4 coupling hook. Pleopod 2 (Figure 5B) exopod with 38 PMS, endopod with 14 PMS; appendix masculina with parallel margins, 1.0 times as long as endopod, distally narrowly rounded. Pleopod 3 (Figure 5C) exopod with 39 PMS, endopod with 11 PMS. Pleopod 4 (Figure 5D) exopod with 40 PMS, endopod with 10 PMS. Pleopod 5 (Figure 5E) exopod with 38 PMS. Pleopods 2-5 peduncle distolateral margin with prominent acute RS.

Uropod peduncle (Figure 6A) ventrolateral margin with 2 RS (Figure 6B), lateral margin with medial short acute RS, posterior lobe about one-half as long as endopod; rami extending beyond pleotelson, marginal setae in single tier. Endopod apically not bifid, broadly round, lateral margin straight, without prominent excision, with 2 RS, mesial margin strongly convex, with 7 RS. Exopod extending beyond end of endopod, 2.4 times as long as greatest width, apically not bifid, notched, lateral margin straight, with 5 RS, mesial margin weakly convex, with 4 RS.

Female (non-ovigerous).

Pereonite 7 without transverse row of tubercles. Pleonites 4-5 and pleotelson with low tubercles.

Size.

Adult males (n = 13) 4.6-5.8 mm (mean 5.1 mm); females (n = 16) 4.6-5.7 mm (mean 5.1 mm).

Variation.

Pleotelson (n = 28 [12 ♂ and 16♀]) with 5-6 RS, with 6 RS (3+3) most frequent (92%). Uropod endopod mesial margin with 6-7 RS, with 6 (82%) and 8 (4%) occurring only once, lateral margin with 1 RS (96%) and 2 (4%) occurring only once; exopod mesial margin with 2-4 RS, with 4 most frequent (92%), 2 and 3 occurring only once (3%), lateral margin with 5- 6 RS, with 5 most frequent (92%).

Remarks.

Cirolana phuketensis sp. n. is characterized by pereonites 2-4 each with a single transverse suture; pereonites 5-6 each with 2 transverse sutures; pereonites 7 with 3 transverse sutures that also form a nodulose ridge; antennula peduncular articles 1 and 2 fused; pleotelson dorsal surface with 2 sub-median longitudinal carinae, each of which has one prominent anterior tubercle, lateral margin weakly convex and posterior margin narrow rounded; pereopod 1 merus inferior margin with 6 molariform RS; penes in the form of two low tubercles.

Cirolana phuketensis sp. n. belongs to a group of species within Cirolana that is characterised by dorsal is characterised by dorsal nodular ornamentation on the pereon, pleon and pleotelson ( Bruce 1986). This group of species has few widely separated robust setae on the uropodal exopod lateral margin, and the pleotelson posterior mar gin is truncate to narrowly rounded and has 6 or 8 robust seta; there is often clear sexual dimorphism in this group of species, with females more weakly ornamented that males, and dimorphic uropod shape.

In the South-East Asian region there are few similar species, although undescribed species are known. Cirolana phuketensis sp. n. differs from C. tuberculata from southern Philippines (see Delaney 1986), the only similar species in the region, by the pereon surface having tubercles on pereonite 7 (vs all pereonites lacking tubercles); coxae 4-7 with two oblique carinae (vs coxae 2-7 with single oblique carina); merus of pereopod 1 has 6 molariform robust setae (vs 4-5 molariform robust setae); pleonites 3-5 has tubercles (vs pleon smooth): uropodal exopod apex is notched (vs acute), lateral margin of exopod is straight (vs convex); lateral margin of endopod has two robust setae (vs four robust setae); dorsal surface of pleotelson with two tubercles and paired submedian longitudinal carina (vs parallel rows of four tubercles).

This species is also similar to Cirolana grumula Bruce, 1994 (Papua New Guinea) and the Australian species Cirolana oreonota Bruce, 1986. However, there are many characters that differentiate Cirolana phuketensis sp. n. from these species. Cirolana phuketensis sp. n. can be separated from C. grumula by having antennula articles 1 and 2 fused (vs unfused in C. grumula ); pleotelson dorsal surface with 2 sub-median longitudinal carinae, each of which has one prominent tubercle (vs each of which has two prominent tubercles), pleotelson lateral margin weakly convex (vs straight) and posterior margin narrow rounded (vs subtruncate); pereopod 1 merus inferior margin has 6 molariform RS (vs 5 molariform RS); penes has 2 low tubercles (vs opening flush with surface of sternite 7. Cirolana phuketensis sp. n. differs from C. oreonota by pereonites 2-4 with transverse sutures (vs without transverse sutures on pereonites 2-4); pleotelson dorsal surface with two prominent ridges each with one anterior submedian tubercle (vs ridges not prominent each with 3 of submedian tubercles), pleotelson lateral margin weakly convex (vs straight), posterior margin narrow rounded (vs sub truncate) with 6 RS (vs 8 RS); antennal flagellum extending to middle of pereonite 4 (vs extending to anterior of pereonite 3); pereopod 1 merus inferior margin having 6 molariform RS (vs 5 molariform RS); penes 2 low tubercles (vs opening flush with surface of sternite 7).

Etymology.

The epithet is taken from the type locality.