Gymnochanda ploegi, Hui & Taxonomy & species & Gymnochanda & dimorphism & Asia, 2014

Hui, Tan Heok, Taxonomy, Kelvin Lim Kok Peng, species, new, Gymnochanda, dimorphism, sexual & Asia, Southeast, 2014, Gymnochanda ploegi, a new species of ambassid glassperch from West Kalimantan, Indonesia, Raffles Bulletin of Zoology 62, pp. 688-695 : 689-691

Gymnochanda ploegi , new species

( Figs. 1A, B , 2B, C , 3 , 4A, B )

Gymnochanda cf. flamea – Kottelat & Widjarnati, 2005: 164.

Material examined. Holotype: MZB 17220, (male) 25.9 mm SL; West Kalimantan: Sanggau area ; local collector, 12 August 2014 . Paratypes: MZB 17221, 1 ex. (female), 26.0 mm SL; same locality as holotype . — ZRC 54552, 24 ex. (8 males, 16 females), CMK 25256, 6 ex. (3 males, 3 females), 21.3–27.5 mm SL; same locality as holotype ; local collector, 12 August 2014. — CMK 10234, 1 ex.; West Kalimantan: Kapuas Lakes area: Nanga Semunak , dry season location (0°56ʹ37ʺN 112°05ʹ31ʺE); M Kottelat, 8 September 1993. Diagnosis. Gymnochanda ploegi can be differentiated from its congeners by the following characters: mature males with pinkish body with the dorsal half suffused with reddish pigments, expanded anal and second dorsal fins, the soft rays of both fins expanded to reach 2 / 3 of caudal fin forming a crescentic profile, without any individual fin ray free from the interradial fin membrane; anterior part to whole of both anal and second dorsal fins maroon red in life, with posterior portion of distal rays black forming a crescentic pattern (hyaline when preserved); whole caudal fin lightly suffused with red in life (hyaline when preserved); female with yellowish body suffused with reddish pigments without any fin elongation (hyaline when preserved), both dorsal fins suffused with reddish pigments (hyaline when preserved) .

Description. See Table 1 for morphometric data for holotype and nine paratype specimens. Body compressed, relatively deep, roughly elongate ovoid with a pointed head, deepest at second dorsal-fin origin. Dorsum of head to pre-dorsal-fin with a slanted slope, forming a slight hump at region before first dorsal-fin origin. The first dorsal-fin base with a slight concave profile, then a convex profile at second dorsal-fin origin and base. Ventrum with a convex profile peaking at anal-fin origin. Body tapering to its narrowest at the caudal peduncle. No scales present. Lateral line indistinct.

Terminally positioned mouth small and slighty upturned, lower jaw included when closed. Teeth in upper jaw in a single row laterally and in 2 rows near symphysis, in a narrow band in lower jaw. Gill rakers long and slender, 12 on lower branch of first branchial arch.

Preorbital ridge with 4 strong, backward oriented serrae. Preorbital margin with up to 6 strong serrae. Preoperculum with 8 serrae along its lower edge and up to 9 blunt serrae along its posterior vertical margin. Supraorbital ridge with up to 12 low serrae. Interorbital, suborbital, operculum, suboperculum and interoperculum entire. See Fig. 3 for more details on serration distribution on the head.

First dorsal-fin origin just posterior to pelvic-fin origin, which is about halfway of pectoral-fin base. First dorsal fin relatively tall, adpressed fin touching branched ray 3 or 4 of second dorsal-fin. Second dorsal-fin origin just posterior to anal-fin origin, which is at about position of first dorsal-fin spine 6. Pelvic fin with 1 spine and 5 branched rays; pelvic fin short, adpressed fin not touching anal-fin origin. Pectoral fin with 12 rays. Caudal fin with 9+9 principal rays.

Male: First dorsal fin with 7 spines, second spine longest (more than twice length of first spine), third spine about ¾ of second spine, spines 6 and 7 much reduced. Second dorsal fin with 1 spine and 11 branched rays, continuous with first dorsal fin by a very low membrane, spine about same length as third spine of first dorsal fin; branched ray 4 to 6 longest, adpressed fin reaching middle of caudal fin. Anal fin with 3 spines and 11 branched rays, branched ray 4 to 6 longest, adpressed fin reaching middle of caudal fin. Extended dorsal and anal fin lateral profile having a crescentic shape. The shape of air bladder is different from female, deeper posterior section, reaching base (see Fig. 4A for a schematic representation).

Female: First dorsal fin with 7 spines, second spine longest (more than twice of first spine), third spine about ¾ of second spine, spines 6 and 7 much reduced. Second dorsal fin with 1 spine and 11 branched rays, continuous with first dorsal fin by a very low membrane, spine about same length as anterior half of branched rays. Anal fin with 3 spines and 11 branched rays, spines about same length as anterior half of branched rays. The shape of air bladder is different from male, less deep posterior section, not reaching base (see Fig. 4B for a schematic representation).

Total vertebral count 9 + 16 = 25 (n=12). Largest specimen recorded 27.5 mm SL (male).

Life colouration. See Figs. 2B, C . Male: Head with red and black pigments concentrated around lips and snout. Eye with black pigments on dorsal margin. Region above and posterior to eye with gold colour. Opercular region suffused with red, partly due to translucent opercle cover showing the gills. Body translucent pink suffused with tiny yellow and red chromatophores, posterior half of body with up to 14 thin complete or interrupted black bars; with dorsal and anal-fin processes visible, main vertebral column discernible, hypural plate also visible; large translucent air bladder visible directly above abdominal cavity, which is covered with a silvery peritoneum lining. First dorsal fin mainly hyaline, with distinct red and black pigments. Second dorsal fin with basal interradial fin membranes suffused with red pigment, posterior half of branched fin-rays and interradial fin membrane maroon red, distal part of posterior rays with thick (up to half of ray length) black margin. Anal fin anterior with black pigments, basal interradial fin membranes suffused with red pigment, posterior half of branched fin-rays and interradial fin membrane maroon red, distal part of posterior rays with black margin. Caudal fin suffused with faint red pigments. Pelvic and pectoral fins hyaline.

Female: colouration as above, except dorsal, caudal and anal fins are suffused with faint red pigments, with hyaline pelvic and pectoral fins.

Preserved colouration. See Fig. 1 . Both male and female: no strong colours retained, region above and posterior to eye with black blotch, body an opaque white, with scattered black pigments, very faint black bars visible on body, and slight orange on body dorsum, and slight orange on both dorsal fins, anal and caudal fin bases.

Distribution. Gymnochanda ploegi is currently known from the Sanggau and Kapuas Lakes regions in West Kalimantan ( Fig. 5 ).

Habitat notes. As its congeners, this species inhabits still water pools near swamp forest and riverine systems. Apparently, this is the first import for the ornamental fish trade (August 2014) and it took the collectors more than three hours to trek to the site (A Meng pers. comm.). In the Kapuas Lakes region, G. ploegi could be sympatric with G. filamentosa ; but they were not collected in the same sample from fish traps in a swampy area with brown water (M. Kottelat pers. comm.).

Etymology. This species is named in memory of Alex Ploeg, a good friend, fellow taxonomist, advisor and fellow conservationist against alien aquatic species; for his services to the ornamental fish trade in this region and abroad in his role as the Secretary General of the Ornamental Fish International; who unfortunately perished in a terrible tragedy over Ukraine on 17 July 2014.

Remarks. From its congeners, the adult male Gymnochanda ploegi is easily distinguished in having long and broad anal and second dorsal fins without individual fin-ray extensions beyond the fin membrane; a character shared with G. verae (see Fig. 2 ). In comparison, the males of both G. filamentosa and G. flamea have highly elongated (up to three times body length) free fin-ray extensions on the anal and second dorsal fins. Gymnochanda limi , however, has short fins without elongated rays, but a very long second anal-fin spine, which is unique to this species.

Gymnochanda ploegi can be further distinguished from G verae (see Fig. 2 ) in having a more slender body profile (body depth at anus 30.1–33.8, vs. 35.3–40.0% SL), with reddish opercle cover (vs. absence), lack of intense red pigments on caudal fin (vs. marked red areas on both upper and lower caudal fin lobes); deeper air bladder with posterior end reaching base (vs. less deep air bladder with posterior section not reaching base; see Fig. 4C for schematic diagram); shorter

Figures

Fig. 1. Gymnochanda ploegi: A, MZB 17220, 25.9 mm SL male holotype (note: anal fin is damaged); B, MZB 17221, 26.0 mm SL female paratype.

Fig. 2. A, Gymnochanda verae – ZRC 53122, 22.3 mm SL male paratype, freshly dead specimen; B, Gymnochanda ploegi – MZB 17220, 25.9 mm SL male holotype, freshly dead specimen (note: anal fin is damaged); C, Gymnochanda ploegi – MZB 17221, 26.0 mm SL female paratype, freshly dead specimen.

Fig. 3. Gymnochanda ploegi – line drawing of head, MZB 17220, 25.9 mm SL male holotype, showing serrations (scale bar = 1 mm) (Artwork by Kelvin Lim).

Fig. 4. Schematic diagram showing air bladder shapes of: A, Gymnochanda ploegi male; B, G. ploegi female; C, G. verae male (based on specimens depicted in Fig. 2).

Fig. 5. Map of Sundaland showing distribution of Gymnochanda: round = G. filamentosa; triangle = G. flamea; square = G. limi; inverted triangle = G. verae; and diamond = G. ploegi.