Description of a new species of Quadrivisio Stebbing, 1907, from Songkhla Lake, Thailand (Crustacea: Peracarida: Amphipoda: Maeridae) Author Hughes, Lauren E. Author Kaji, Tomonari text Raffles Bulletin of Zoology 2016 2016-11-21 64 351 359 journal article 10.5281/zenodo.5355546 2345-7600 5355546 43B1BFEE-71F6-4D05-813F-AA5357310547 Quadrivisio meufong new species ( Figs. 3–6 ) ? Quadrivisio bengalensis , Bussarawich, 1985: 4 , 5, fig. 3; Lowry, 2000: 319 (checklist). Type material. Holotype , male, 9.8 mm , dissected, 4 slides, PSUZC-CR 0301, Khu Khut Bird Sanctuary, Songkhla Lake, Thailand , 7°27’21.14”N , 100°24’20.21”E , in shore, on Schoenoplectus subulatus (Vahl) Lye (original label Scirpus litoralis Schrad. ), coll. J.K. Lowry & V . Lheknim, 13 December 1999 . Paratypes : male, 13.5 mm , PSUZC- CR 0302; male, 12.3 mm , PSUZC-CR 0303; female, 10.5 mm , dissected, 1 slide, PSUZC-CR 0304; 40+ juveniles and females, PSUZC-CR 0305; all from same location as holotype . Additional material examined. 10 juveniles and females, PSUZC-CR 0306 , Khu Khut Bird Sanctuary , Songkhla Lake Basin , Thailand , 7°27’N , 100°24’E , Hydrilla verticillata (L. f.) Royle , 13 December 1999 , coll. J.K. Lowry and V . Lheknim ; 3 males , 29 juveniles and females, AM P. PSUZC- CR 0307, Songkhla Lake , Thailand , 1987-1989 (several collections combined) . Type locality. Khu Khut Bird Sanctuary , Songkhla Lake , Thailand , 7°27’21.14”N , 100°24’20.21”E . Etymology. From the Thai ‘meu’ - hand and ‘fong’ – bubble, in reference to the adult male gnathopod 2 propodus palm expanded cuticle. Diagnosis. Antenna 1 accessory flagellum long, with 9-10 articles. Mandibular palp with 2 apical setae. Gnathopod 2 palm subacute, two thirds length of propodus posterior margin, subrectangular distomedial shelf with robust setae, midpalm dominated by expanded cuticle covered in fine setae, palmar margin defined by rounded corner with 2 robust setae; dactylus without posteroproximal shelf, closing along and equal to length of palm. Pereonite 7 without carina. Pleonites 1–3 bicarinate. Epimeron 1–2 posterodistal corner with 3 serrate teeth Epimeron 3 ventral margin serrate, posterodistal corner with 2 teeth. Urosomites 1–3 bicarinate. Telson each lobe with 2 long and 1–2 short apical robust setae, inner margins smooth. Description. Based on holotype male, 9.8 mm , PSUZC- CR 0301. Head. Eyes ommatidia split into two pairs on each side of head; lateral cephalic lobe broad, truncated, anteroventral margin with notch/slit. Antenna 1 longer than antenna 2; peduncular article 1 shorter than article 2, without robust setae along posterior margin; article 2 longer than article 3; flagellum articles longer than broad, with 38 articles; accessory flagellum long, with 9-10 articles. Antenna 2 peduncular article 2 cone gland not reaching to end of peduncular article 3; article 4 shorter than article 5; flagellum with 34 articles. Maxilla 1 inner plate unknown; palp 2-articulate with 6 apical robust setae. Lower lip inner and outer lobes apically setose; mandibular lobes apically subacute. Mandible accessory setal row well developed with 8 setae; molar well developed, columnar, triturative; mandibular palp well developed, 3-articulate; article 1 length 1.8 times as long as broad, 0.8 times article 2; article 2 length subequal to article 3, without setae; article 3 rectilinear, short (3.5 times as long as broad), 1.4 times article 1, with 2 apical setae. Maxilliped basal endite with 4 short apical robust setae; ischial endite medial margin lined with robust setae; palp 4-articulate, article 4 lined with slender setae, unguis preset. Fig. 2. Quadrivisio bengalensis Stebbing, 1907 , male, 11 mm, PSUZC-CR 0308, Songkhla Lake, Thailand. Scale bars = 0.1 mm. Fig. 3. Quadrivisio meufong , new species , holotype, male, 9.8 mm, PSUZC-CR 0301, Songkhla Lake, Thailand. Scale bars = 0.1 mm. Fig. 4. Quadrivisio meufong , new species , holotype, male, 9.8 mm, PSUZC-CR 0301, Songkhla Lake, Thailand. Scale bars = 0.1 mm. Pereon. Gnathopod 1 coxa anterior margin straight concave, anteroventral corner not produced, rounded, posteroventral margin with a few serration and robust seta; carpus 2.8 times as long as broad, longer than propodus; propodus medial surface with comb, palm near transverse, convex, entire, defined by posterodistal corner, with 4 robust setae. Gnathopod 2 subchelate; coxa posteroventral margin with robust seta; basis slender, anterodistal corner without lobes; ischium anterior margin without lobes; merus distoventrally truncate; carpus compressed, lobate, projecting between merus and propodus with rows of dense setae; propodus massive, palm subacute, two thirds length of propodus posterior margin, subrectangular distomedial shelf with robust setae, midpalm dominated by expanded cuticle covered in fine setae, palmar margin defined by rounded corner with 2 robust setae, posterior proximal margin lined with long slender setae; dactylus without posteroproximal shelf, closing along and equal to length of palm. Pereopod 4 coxa posteroventral lobe well developed, with subrectangular posteromedial corner. Pereopods 5–6 basis weakly expanded, posterior margin straight; merus and carpus not broadened. Pereopod 7 basis expanded, posterior margin convex; merus and carpus not broadened. Pereonite 7 without carina. Pleon. Pleonites 1–3 bicarinate. Epimeron 1–2 posterodistal corner with 3 serrate teeth Epimeron 3 ventral margin serrate, posterodistal corner with 2 teeth. Urosomites 1–3 bicarinate. Uropod 1 peduncle with 1 basofacial seta, longer than rami; outer ramus subequal to inner ramus with apical and marginal robust setae. Uropod 2 peduncle longer than rami, outer ramus shorter than inner ramus with apical and marginal robust setae. Uropod 3 peduncle shorter than rami; rami foliaceous, subequal in length, lined with short robust and slender setae. Telson deeply cleft (90%), longer as broad, tapering distally, with short inner and long outer apical cusps, apical conical extension reaching less than one third along longest seta, each lobe with 2 long and 1–2 short apical robust setae, inner margins smooth. Female (sexually dimorphic characters), based on paratype female, 7.3 mm , PSUZC-CR 0304. Gnathopod 2 coxa RAFFLES BULLETIN OF ZOOLOGY 2016 Fig. 5. Quadrivisio meufong , new species , paratype, female, 10.5 mm, PSUZC-CR 0304, Songkhla Lake, Thailand. Scale bars = 0.1 mm. posterodistal corner with robust seta; carpus subtriangular, 0.9 times propodus length; propodus rectilinear, palm subacute, without distomedial shelf, palmar margin irregular, entire, lined with short robust setae, defined by posteroventral corner, with 3 spaced long robust setae; dactylus weakly recurved, closing short of palm, margins smooth. Telson lobes with 1 long and 2 short apical robust setae. Variation. Uropod 3 increases with growth stage (often regenerating or missing, broken off during sample processing). Remarks. The male gnathopod 2 propodus palm of Q. meufong , new species , has a large bubble-like expanded cuticle covered in fine setae. In the few male specimens on hand, the expanded palm cuticle may be collapsed or inflated, and it is unclear if this is related to preservation technique (with the tegument collapsing during fixation/ preservation) or growth stage (larger males have a more inflated structure) ( Figs 4 , 6 ). The palmar structure is enclosed by an outer and inner layer of cuticle ( Fig. 6B ), and there are no hemolymphal connection to propodus observed. The cuticular layers are seemingly peeled and inflated structure derived from ordinary cuticular composition, that is the inner layer might be comparable to endo and exocuticle, while the outer layer is comparable with epicuticle. Quadrivisio meufong , new species , is strikingly similar to Q. lutzi ( Shoemaker, 1933 ) from Georgetown, British Guiana on the northern coast of South America. Both species have a similarly shaped palm of the male gnathopod 2. The presence of two carinae on pleonites 1–3 and urosomite 1 separate Q . meufong from Q. lutzi , which has no carinae on the pleonites, two carinae on urosomite 1, and four carinae in urosomite 2 in female and juveniles and, notably, a smooth dorsum in males (i.e., carina formula 2-2-2-2-0 vs 0-0-0-2-4 or 0-0-0-0-0, respectively). Fig. 6. 3D reconstructed male gnathopod 2 of Quadrivisio meufong , new species , male 13.5 mm, PSUZC-CR 0302. A, overall image of carpus, propodus, and dactylus of the male gnathopod 2; B, magnified, proximal view of the expanded palm cuticle. Arrow heads indicate expanded palm structure; oc, outer layer of cuticle; ic, inner layer of cuticle. Scale bars = 0.1 mm. Material identified as Q. bengalensis by Bussarawich (1985) from Thailand do not have robust setae lining the inner margin of the telson and, therefore, may represent juveniles of Q. meufong , instead. Distribution. Thailand . Songkhla Lake (current study). Ao Yon, Ao Nam Bor, Klong Pak Pan ( Bussarawich, 1985 ).