Cirolana phangnga, Eknarin Rodcharoen, Niel L. Bruce & Pornsilp Pholpunthin, 2016

Eknarin Rodcharoen, Niel L. Bruce & Pornsilp Pholpunthin, 2016, Description of four new species of the Cirolana ‘ parva group’ (Crustacea: Isopoda: Cirolanidae) from Thailand, with supporting molecular (COI) data, Journal of Natural History 50 (31 - 32), pp. 1935-1981 : 15-23

Cirolana phangnga sp. nov.

( Figures 7 – 11 )

Material examined

Holotype, ♂ (7.9 mm), Laem Pakarang, Phangnga Province , 08°44 ’ 11"N, 98°13 ’ 13"E, 15 March 2012, trapped at a depth of 2 m, coral rubble, coll. E. Rodcharoen ( PSUZC – CR0283-01 ).

Paratypes, 10 ♂ (6.3, 6.7, 6.2, 6.0, 6.9, 6.8, 7.5, 6.2, 6.1, 6.0 mm [dissected], 10 ♀ (5.8, 6.4, 6.1, 6.3, 6.2, 5.7, 6.3, 6.6, 6.0, 5.9 mm [dissected]), 58 specimens unmeasured, same data as holotype ( PSUZC – CR0283-02; MTQ W34351). 23 ♂ (unmeasured), Laem Pakarang, Phangnga Province, 08°44 ’ 11"N, 98°13 ’ 13"E, 2 August 2014, trapped at a depth of 2 m, coral rubble, coll. E. Rodcharoen ( PSUZC – CR0283-03).

Description of male

Body 3.2 times as long as greatest width, widest at pereonite 5, lateral margins subparallel ( Figure 7 A). Eyes dark brown, separated by about 64% of width of head ( Figure 7 C). 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 ( Figure 7 B). Pleon ( Figure 7 E) with pleonite 1 largely concealed by pereonite 7; pleonites 3 – 5 posterior margins smooth; posterolateral angles of pleonite 2 forming acute point, extending posteriorly to anterior of pleonite 4; pleonite 3 with posterolateral margins extending to but not beyond posterior margin of pleonite 5, acute; posterolateral margin of pleonite 4 rounded, clearly extending beyond posterior margin of pleonite 5; pleonite 5 with posterolateral angles overlapped by lateral margins of pleonite 4. Pleotelson 0.9 times as long as anterior width, dorsal surface without longitudinal carina , lateral margins weakly convex; margins smooth, posterior margin converging to caudomedial point, with small distinct median point, with 8 RS ( Figure 11 E, F).

Antennula ( Figure 7 F) peduncle articles 1 and 2 distinct, articulated; article 2 0.8 times as long as article 1; articles 3 and 4 0.9 times as long as combined lengths of articles 1 and 2; article 3 2.2 times as long as wide, flagellum with 11 articles, extending to anterior of pereonite 1. Antenna ( Figure 7 G) peduncle article 4 1.7 times as long as wide, 2.0 times as long as article 3, inferodistal angle with 1 simple seta; article 5 1.1 times as long as article 4, 2.3 times as long as wide, inferodistal angle with cluster of 2 pappose setae and 2 simple setae, anterodistal angle with cluster of 2 pappose setae and 6 simple setae; flagellum with 21 articles, extending to middle of pereonite 4.

Frontal lamina ( Figure 7 D) pentagonal, 1.6 times as long as posterior width, 1.4 times as long as greatest width, lateral margins straight, diverging slightly towards anterior, anterior margin acute, with small median point.

Mandible molar process ( Figure 8 A, C) anterior margin with 33 flat teeth; with proximal cluster of long simple setae; right mandible spine row composed of 12 spines, left with 13 spines; palp articles 2 with 21 distolateral setae; palp article 3 lateral margin with 17 robust biserrate setae, distal margin with 3 biserrate setae ( Figure 8 B). Maxillule ( Figure 8 E) mesial lobe with 3 large and circumplumose RS; lateral lobe with 11 RS.

Maxilla ( Figure 8 D) lateral lobe with 6 long simple setae, middle lobe with 10 long simple setae, mesial lobe 15 proximal simple and plumose setae. Maxilliped palp ( Figure 8 F) article 2 mesial margin with 6 slender setae, lateral margin distally with 1 slender seta; article 3 mesial margin with 15 slender setae, lateral margin with 6 slender setae; article 4 mesial margin with 18 slender setae, lateral margin with 3 slender setae; article 5 distal margin with 19 setae, lateral margin with 4 setae; endite ( Figure 8 G) with 6 long CPS and 2 coupling setae.

Pereopod 1 ( Figure 9 A, B) basis 2.3 times as long as greatest width, inferior distal angle with cluster of 2 acute setae; ischium 0.6 times as long as basis, inferior margin with 1 acute seta, inferior distal angle with 3 RS, superior distal margin with 2 RS; merus inferior margin with 5 molariform RS (set in rows of 3 and 2), superior distal angle with 3 setae; carpu s inferior distal margin with 1 RS; propodus 1.8 times as long as wide, inferior margin with 3 RS; dactylus ( Figure 9 C) 0.6 times as long as propodus, inferior margin with setal fringe on propodus and carpus. Pereopod 2 ( Figure 9 D) ischium inferior margin with 3 stout, bluntly rounded RS, superior distal margin with 2 RS; merus inferior margin with 8 stout RS (set as single row of 5 and 3), superior distal margin with 7 acute RS; carpus inferodistal angle with 3 RS (plus 1 long slender seta); propodus 2.6 times as long as wide; dactylus 0.6 times as long as propodus. Pereopod 4 ( Figure 9 E) intermediate in form between pereopod 3 and pereopod 5. Pereopod 6 similar to pereopod 7. Pereopod 7 ( Figure 9 F) longer than pereopod 6; basis 2.2 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 6 RS (set in groups of 2, 3 and 1), superior distal angle with 7 RS inferior distal angle with four RS; merus 0.7 times as long as ischium; 1.7 times as long as wide, inferior margin with 3 RS, superior distal angle with 9 RS (5 biserrate), inferior distal angle with 8 RS; carpus 0.9 times as long as ischium, 2.3 times as long as wide, inferior margin with 4 RS, superior distal angle with 10 RS (6 biserrate), inferior distal angle with 12 RS (6 biserrate); propodus 1.0 time as long as ischium, 4.1 times as long as wide, superior distal angle with 3 slender setae (plus 1 plumose seta and 2 RS), inferior distal angle with 2 RS; dactylus 0.4 times as long as propodus.

Penes ( Figure 7 H) 2 low tubercles, penial openings separated by 12% of sternal width.

Pleopod 1 ( Figure 10 A) exopod 1.6 times as long as wide, lateral margin weakly convex, distally broadly rounded, mesial margin strongly convex with 26 PMS from distal one-third; endopod 2.1 times as long as wide, distally broadly rounded, lateral margin weakly concave, with 11 PMS on distal margin only; peduncle 1.7 times as wide as long, mesial margin with 5 coupling hooks. Pleopod 2 ( Figure 10 B) exopod with 31 PMS, endopod with 17 PMS; appendix masculina with parallel margins. 1.4 times as long as endopod, distally acute. Pleopod 3 ( Figure 10 C) exopod with 34 PMS, endopod with 11 PMS. Pleopod 4 ( Figure 10 D) exopod with 34 PMS, endopod with 8 PMS. Pleopod 5 ( Figure 10 E) exopod with 32 PMS. Pleopods 2 – 5 peduncle distolateral margin with prominent acute RS. Pleopods, endopods 3 – 5 with distomesial serrate scales.

Uropod ( Figure 11 A, B) peduncle ventrolateral margin with 2 RS (plus 3 long setae), lateral margin with 1 medial short acute RS, posterior lobe about one-half as long as endopod; rami extending beyond pleotelson, marginal setae in single tier, apices acute. Endopod ( Figure 11 A, D) apically deeply bifid, lateral process prominent, lateral margin weakly convex, without prominent excision, with 3 RS, mesial margin strongly convex, with 4 RS. Exopod ( Figure 11 A, C) not extending to end of endopod, 0.9 times as long as endopod, 2.6 times as long as greatest width, apically deeply bifid, lateral process prominent, lateral margin weakly convex, with 7 RS, mesial margin convex, with 3 RS.

Sub-adult male

Pereopod 1 has a less-developed setal fringe than on the adult male.

Female

Of similar appearance to male but lacks a setose fringe on pereopod 1.

Variation

Pleotelson (n = 21 [11 ♂ and 10 ♀]) with 6 – 8 RS, with 8 RS (4 + 4) most frequent (71%), 7 (24%) and 6 (5%) occurring only once. Uropod endopod mesial margin with 4 – 6 RS, with 5 (76%) most frequent, 4 (14%) and 6 (10%), lateral margin with 2 – 3 RS, with 3 (86%) most frequent and 2 (14%); exopod mesial margin with 3 RS 100%), lateral margin with 7 – 8, with 7 (57%) most frequent and 8 (43%).

Size

Adult males (n = 11) 6.0 – 7.9 mm (mean 6.6 mm); females (n = 10) 5.7 – 6.6 (mean 6.1 mm).

Remarks

Cirolana phangnga sp. nov. is characterised by antennula peduncle articles 1 and 2 distinct, articulated; antenna flagellum extending to middle of pereonite 4; pereopod 1 on male with setal fringe on carpus and propodus; pleonite 3 with posterolateral margins extending to but not beyond posterior margin of pleonite 5; penes two low tubercles, penial openings separated by 12% of sternal width; pleopod 1 endopod lateral margin weakly concave; appendix masculina distally acute, with parallel margins, 1.4 times as long as endopod; uropod peduncle ventrolateral margin with two robust setae (plus three long setae), rami extending beyond pleotelson; endopod apically deeply bifid, lateral process prominent, lateral margin with three robust setae, mesial margin with four robust setae; exopod apically deeply bifid, lateral process prominent, lateral margin with seven robust setae, mesial margin with three robust setae; pleotelson with eight robust setae.

There are two species that are similar to Cirolana phangnga sp. nov., namely the Australian species Cirolana erodiae Bruce, 1986 (Great Barrier Reef) and Cirolana hesperia Bruce, 1986 (Western Australia). Cirolana phangnga sp. nov. can be readily separated from C. hesperia by the antenna flagellum extending to pereonite 4 (vs pereonite 3); with the setal fringe on carpus and propodus (vs with setal fringe on merus, carpus and propodus); apex of uropodal rami deeply bifid, lateral process prominent in both endopod and exopod (apex of uropodal rami deeply bifid, but only exopod with lateral process prominent, endopod with equally bifid). Cirolana phangnga sp. nov. differs from C. erodiae by having pleopod 1 with the endopod lateral margin concave and a straight appendix masculina (vs endopod lateral margin straight and appendix masculina bent laterally).

Cirolana phangnga sp. nov. is very similar to the allopatric Cirolana siamensis sp. nov. and Cirolana thailandica sp. nov. in having a setal fringe on the male pereopod 1, antennula peduncle with four articles, uropod peduncle ventrolateral margin with three sensory setae and penial processes two low tubercles separated by 12 – 13% of sternal width. Cirolana phangnga sp. nov. can be separated from C. siamensis sp. nov. and C. thailandica sp. nov. by the appendix masculina of C. phangnga sp. nov. being consistently shorter than that of both C. siamensis sp. nov. and C. thailandica sp. nov. (1.4 times as long as endopod vs 1.6 and 1.9 times as long, respectively); pleonite 3 with posterolateral margins extending to but not beyond posterior margin of pleonite 5 (vs pleonite 3 with posterolateral margins extending clearly beyond posterior margins of pleonites 4 and 5). Moreover, the pleopod 1 endopod has the lateral margin concave in C. phangnga sp. nov., whereas C. thailandica sp. nov. and C. siamensis sp. nov. pleopod 1 endopod has a straight lateral margin.

Etymology

Cirolana phangnga sp. nov. is named for the type locality.

Figures

Figure 7. Cirolana phangnga sp. nov., male holotype PSUZC – CR 0283 - 01 (7.9 mm). (A – E, H), male paratype PSUZC – CR 0283 - 02 (6.9 mm) (F, G). (A) dorsal view; (B) lateral view; (C) head; (D) frons; (E) pleon; (F) antennula; (G) antenna peduncle; (H) penial opening, sternite 7.

Figure 8. Cirolana phangnga sp. nov., male paratype PSUZC – CR 0283 - 02 (6.9 mm). (A) right mandible; (B) dorsal view of article 3 of right mandible palp; (C) distal part of left mandible; (D) right maxilla; (E) left maxillule; (F) right maxilliped; (G) endite.

Figure 9. Cirolana phangnga sp. nov., male paratype PSUZC – CR 0283 - 02 (6.9 mm). (A) pereopod 1; (B) mesial view of pereopod 1; (C) mesial view of dactylus of pereopod 1; (D) pereopod 2; (E) pereopod 4; (F) pereopod 7.

Figure 10. Cirolana phangnga sp. nov., male paratype PSUZC – CR 0283 - 02 (6.9 mm). (A – E) pleopods 1 – 5, respectively.

Figure 11. Cirolana phangnga sp. nov., male paratype PSUZC – CR 0283 - 02 (6.9 mm). (A) uropod; (B) ventral view of uropod peduncle and exopod; (C) uropod exopod apex; (D) uropod endopod apex; (E) pleotelson; (F) pleotelson apex.