Cirolana parawongat, Rodcharoen & Bruce, 2021

Rodcharoen, Eknarin & Bruce, Niel L., 2021, Two new species of the marine isopod genus Cirolana Leach, 1818 (Crustacea Isopoda: Cirolanidae) from the coast of the western Gulf of Thailand, Zootaxa 4950 (3), pp. 469-486 : 479-480

Cirolana parawongat sp. nov.

( Figs 8–11 )

Material examined. Holotype: ♂ (4.6 mm), Patiew , Chumphon province, 10°43’11” N, 99°51’23”E, 22 June 2014, trapped in 1 m of depth, seaweed associated with coral rubble, coll. E. Rodcharoen ( PSUZC-CR2088-01 ).

Paratypes: 15 ♂ (4.8, 4.9, 4.8, 4.8, 4.8, 5.1, 4.9, 5.3, 4.9, 5.0, 4.2, 4.6, 5.0, 5.3, 4.5 mm [dissected]), 6 ♀ (4.9, 5.5, 5.0, 5.4, 4.8, 4.9 mm [dissected]), same data as holotype, ( PSUZC-CR2088-02 ) ; 11 ♂ (5.1, 4.7, 4.6, 4.8, 4.4, 4.4, 4.5, 5.0, 4.7, 5.0, 4.6 mm [dissected]), 4 ♀ (4.5, 4.7, 5.0, 4.0 mm [dissected]), Samae San , Chonburi province, 12°36’21” N, 100°57’51”E, 30 July 2012, coral reef, coll. E. Rodcharoen ( PSUZC-CR2088-03 ) .

Description of male. Body 2.6 times as long as greatest width, dorsal surfaces punctuate, widest at pereonite 5, lateral margins subparallel. Rostral point absent. Eyes colour black, separated by about 58 % width of head. Pereonites 1–3 without each without transverse impressed line; pereonites 4–6 with each 2 transverse impressed lines; pereonite 7 with 3 tranverse lines with single row of nodules forming nodulose ridge. 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; posterolateral angles of pleonite 2 forming acute point, extending posteriorly to anterior of pleonite 4; pleonite 3 with row of 5–7 small tubercles, posterolateral margins acute, extending clearly beyond posterior margin of pleonite 5; pleonite 4 with median tubercle and 4 indistinct sublateral tubercules on each side, posterolateral margin of pleonite 4 rounded, clearly extending beyond posterior margin of pleonite 5; pleonite 5 with prominent elongate median tubercle and 3–4 small sublateral tubercule on each side, posterolateral angles overlapped by lateral margins of pleonite 4. Pleotelson dorsal surface with 2 tubercles and paired submedian longitudinal carina, lateral margins straight, margins smooth, posterior margin sub-truncate, with 6 robust setae.

Antennula peduncle articles 1 and 2 entirely fused; article 3 and 4 0.6 times as long as combined lengths of articles 1 and 2, article 3 1.4 times as long as wide; flagellum with 6 articles, extending to posterior margin of eye. Antenna peduncle article 4 1.8 times as long as wide, 1.7 times as long as article 3, inferodistal angel with 1 short simple seta; article 5 1 times as long as article 4, 2.1 times as long as wide, inferodistal angle with 1 pappose seta, anterodistal angle with cluster of 4 short simple setae and 2 plumose setae; flagellum with 17 articles, extending to posterior of pereonite 3.

Frontal lamina pentagonal, ventral surface entirely flat, 1.9 times as longer than greatest width, lateral margins weakly concave, anterior margin acute.

Left mandible molar process anterior margin with about 15 flat teeth; with about 5 proximal cluster of long simple setae; left mandible spine row composed of about 6 spines; palp articles 2 with about 15 distolateral setae, palp article 3 with about 16 biserrate RS. Right maxillula mesial lobe with 3 large and circumplumose RS; lateral lobe with 12 RS. Right maxilla lateral lobe with 4 long setae; middle lobe with 10 long setae; mesial lobe with 13 long setae. Right maxilliped palp article 1 mesial margin with 1 slender seta; article 2 mesial margin with 4 slender setae, lateral margin distally with 1 slender setae; article 3 mesial margin with 11 slender setae, lateral margin with 4 slender setae; article 4 mesial margin with 9 slender setae, lateral margin with 3 slender setae, article 5 distal margin 14 setae, lateral margin with 4 setae; endite with 4 long CPS, and 1 coupling setae.

Pereopod 1 basis 2.8 times as long as greatest width, inferior distal angle with cluster of 2 acute setae; ischium 0.4 times as long as basis, inferior margin with 2 setae, superior distal margin with 2 RS; merus inferior margin with 5 molariform RS (set in rows of 3 and 2), superior distal angle with 2 setae (slender); carpus inferior margin with 1 RS (plus 1 slender seta); propodus 1.9 times as long as wide, inferior margin with 2 RS; dactylus 0.7 times as long as propodus. Pereopod 2 ischium inferior margin with 2 stout, bluntly rounded RS, superior distal margin with 2 RS; merus inferior margin with 7 stout RS (set as single row of 4 and 3), 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, dactylus 0.8 times as long as propodus. Pereopod 3 similar to pereopod 2. Pereopod 4 intermediate in form between pereopod 3 and pereopod 5. Pereopod 6 similar to pereopod 7. Pereopod 7 basis 2.3 times as long as greatest width, superior margin convex, inferior margin with 3 palmate setae; ischium 1.7 times as long as basis, inferior margin with 5 RS (set in groups of 2 and 3), superior distal angle with 5 RS (3 simple and 2 serrate), inferior distal angle with 2 RS; merus 0.8 times as long as ischium, 1.2 times as long as wide, inferior margin with 3 RS, superior distal angle with 8 RS, inferior distal angle with 6 RS; carpus 0.8 times as long as ischium, 2.3 times as long as wide, inferior margin with 2 RS, superior distal angle with about 11 RS (3 simple and about 8 serrate), inferior distal angle with 7 RS (5 simple and 2 serrate); propodus 0.9 times as long as ischium, 4.1 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, inferior distal angle with 2 robust setae; dactylus 0.5 times as long as propodus.

Penes two low tubercles, penial openings separated by 13% of sternal width.

Pleopod 1 exopod 1.3 times as long as wide, lateral margin straight, distally broadly rounded, mesial margin strongly convex, with 25 PMS from distal one-third; endopod 2.1 times as long as wide, distally broadly rounded, lateral margin convex, with 10 PMS on distal margin only; peduncle 1.6 times as wide as long, mesial margin with 4 coupling hooks. Pleopod 2 exopod with 31 PMS, endopod with 12 PMS; appendix masculina with parallel margins, 1.1 times as long as endopod, distally acute. Pleopod 3 exopod with 36 PMS, endopod with 9 PMS. Pleopod 4 exopod with 38 PMS, endopod with 9 PMS. Pleopod 5 exopod with 41 PMS. Pleopods 2–5 peduncle distolateral margin with prominent acute RS.

Uropod peduncle ventrolateral margin with 2 RS, lateral margin with 1 medial short acute RS, posterior lobe about one-half as long as endopod; rami extending beyond pleotelson. Endopod apically not bifid; lateral margin distally convex, with 1 RS, mesial margin strongly convex, with 5 RS. Exopod extending beyond end of endopod, 3.1 times as long as greatest width, apically shallowly and equally bifid; lateral margin weakly convex, with 5 RS; mesial margin straight, distally convex, with 4 RS, dorsal distal surface with patch of stiff setae.

Female. Of similar appearance to male but low tubercles on pleon and pleotelson and the uropodal exopod lacking the dorsal distal patch of setae.

Variation. Pleotelson (n=37 [27♂ and 10♀]) with 5–7 RS, with 6 RS (3+3) most frequent (94%), 5 (3%) and 7 (3%) occurring only once. Uropod endopod mesial margin with 5–6 RS, with 5 (97%) most frequent, 6 (3%) occurring only once, lateral margin with 1 RS (100%); exopod mesial margin with 2–4 RS, with 3 (57%), 4 (42%) and 2 (3%) occurring only once, lateral margin with 5–6, with 5 (87%) most frequent and 6 (13%).

Size. Adult males (n=27) 4.2–5.3 mm (mean 4.8 mm); females (n=10) 4.0– 5.5mm (mean 4.8 mm).

Remarks: Cirolana parawongat sp. nov. is characterized by pereonites 1–3 without a transverse impressed line; pereonites 4–6 with each with two transverse impressed lines; pereonite 7 with three tranverse lines with a single row of posterior line forming nodulose ridge; antennula peduncular articles 1 and 2 fused; frontal lamina pentagonal, 1.9 times as longer than greatest width; pleotelson dorsal surface with two tubercles and paired submedian longitudinal carina, with a sub-truncate posterior margin, provided with six robust setae; the dorsal distal surface of the male uropodal exopod has patch of stiff setae; and the penes are in the form of two low tubercles, penial openings separated by 13% of sternal width.

This species can be distinguished from the sympatric C. khamensis sp. nov. by the body length, which is shorter than that of C. khamensis (average 4.8 mm both in male and female vs average 7.7 mm in male, 8.0 mm in female in C. khamensis ); pereonites 1–3 without a single transverse impressed line (vs only pereonites 1 without transverse line); antennula peduncle with articles 1 and 2 fused (vs antennula peduncle with articles 1 and 2 distinct articulated); frontal lamina pentagonal, 1.9 times as longer than greatest width (vs 2.2 times as longer than greatest width); pleotelson dorsal surface with two tubercles and paired submedian longitudinal carina, posterior margin sub-truncate, with six robust setae (vs pletelson dorsal surface with four and paired submedian logitudinal carina, posterior margin evenly rounded, with eight robust setae); dorsal distal surface of uropod exopod with patch of stiff setae (vs without patch of stiff setae on uropod exopod); penes in the form of two low tubercles, penial openings separated by 13% sternal width (vs penial openings separated by 25% sternal width)

Cirolana parawongat sp. nov. is most similar to C. wongat Bruce, 1994 ( Papua New Guinea) with the male of both species having similar pattern of setal patch on uropodal exopod dorsal distolateral surface. However, the two species can be separated the following characters: Cirolana parawongat sp. nov. has pereonites 2–3 without transverse impressed line (vs pereonites 2–3 with each a single transverse impressed line in C. wongat ); the frontal lamina is shorter than C. wongat (2.0 vs 3.0 times as long as basal width). Moreover, C. parawongat sp. nov. has pleonite 4 posterior margin not medially indented (vs pleonite 4 posterior margin medially indented) and has more tubercles on pleonite 4 and 5 than C. wongat sp. nov. (nine vs five tubercles).

Etymology. The specific name refers to the most similarity of the new species to C. wongat Bruce, 1986 , which was described from Papua New Guinea.

Figures

FIGURE 8. Cirolana parawongat sp. nov., holotype male (4.6 mm, PSUZC-CR2087-01). A–D,, paratype male (5.0 mm, PSUZC-CR2087-02); E–F, paratype male (4.8 mm, PSUZC-CR2087-02); G–H, paratype male (5.0 mm, PSUZC-CR2087-02); I, holotype; A, dorsal view; B, lateral view; C, frons; D, pleon; E, antennal peduncle;,F, antennula; G, pleotelson; H, uropod; I, penial opening, sternite 7.

FIGURE 9. Cirolana parawongat sp. nov., paratype male (5.0 mm, PSUZC-CR2087-02). A, left mandible; B, distal part of mandible; C, maxillule; D, maxilla;,E, maxilliped; F, maxilliped endite.

FIGURE 10. Cirolana parawongat sp. nov., paratype male (4.8 mm, PSUZC-CR2087-01).A, pereopod 1; B, dactylus of pereopod 1; C, mesial view of pereopod 1; D, pereopod 2; E, lateral of pereopod 7; F, mesial of pereopod 7.

FIGURE 11. Cirolana parawongat sp. nov., paratype male (4.8 mm, PSUZC-CR2087-01) A–E, pleopods 1–5 respectively.