Parosphromenus kishii, Shi & Guo & Haryono & Hong & Zhang, 2021

Shi, Wentian, Guo, Shujie, Haryono, Haryono, Hong, Yijiang & Zhang, Wanchang, 2021, Diagnoses of two new species of Parosphromenus (Teleostei: Osphronemidae) from Bangka Island and Kalimantan, Indonesia, Zootaxa 5060 (1), pp. 71-92 : 78-82

Parosphromenus kishii , new species

( Figures 4–7 )

urn:lsid:zoobank.org:act:03A7E23D-B1DE-4A33-9F25-38ED817B707B

Holotype MZB 25120, male, 31.4 mm SL; Indonesia, Borneo Island , Kalimantan Tengah, exact locality withheld; colls. H. Kishi, 13. Apr. 2019.

Paratypes MZB 25121, female, 1 specimen, 16.2 mm SL ; NCUMB 65135 , 8 specimens, 12.3 –15.4 mm SL; SJD KA2081, 7 specimens. 15.6–32.1 mm SL; same data as for holotype. colls. H. Kishi & W . T. Shi, 13. Apr. 2019 .

Diagnosis Parosphromenus kishii , sp. nov., is distinguished from its congeners by the following unique combination of characteristics: the unique caudal fin coloration, consisting of a uniformly reddish background; irregular faint turquoise blotches of differing sizes scattered on the central region of the caudal fin, vaguely forming a band without clear outline; caudal fin pointed rhombic shape; a long dorsal fin with XIII–XIV spines and 7–8 segmented rays (total 20–22, mode 20); anal-fin rays XII–XIII, 9–10 (total 22–23, mode 22); a broad light bluish iridescent band in dorsal- and anal-fin; pelvic fin and filament uniformly bluish.

Description Morphometric and meristic data are summarized in Table 1 . General body shape and coloration are shown in Fig. 5 A–C ; head stocky and long (27.3–39.4 % SL); body slightly stocky (16.0–43.4 % SL, mean 31.9 % SL at dorsal-fin origin). Dorsal-fin origin usually above 4 th *–5 th scale of lateral scale series. Dorsal-fin rays: XIII 7 (4), XIII 8 (1), XIV 6 * (3) or XIV 8 (1) rays, total 20 (7)* 21 (1) or 22 (1). Dorsal-fin posterior portion pointed, reaching slightly beyond caudal-fin base in male, slightly pointed but shorter in female. Caudal fin shape variable, but mainly pointed-rhombic in adults (see Remarks for details of polymorphism in caudal shape) ( Fig. 7 ); caudal fin with 3 simple, 5 + 6 branched and 2 simple rays. Anal-fin origin below 3 rd spine of dorsal-fin, posterior portion slightly pointed in male, round in female: XII, 10 (3), XIII, 9 (4)* or XIII, 10 (2), total 22 (7) * or 23 (2). Pectoral fin rounded, with 12 (2), 13 (4)* or 14 (3) rays. Pelvic fin with one spine, 1 simple and 4 branched rays, with a long filament reaching about 11 th anal-fin ray; lateral scales 29 (4), or 30* (5), and 2–3 scales on caudal-fin base; 9* scales in transverse series upward from 4 th anal-fin spine; 11* transverse scales at dorsal fin origin.

Live coloration Male ( Fig. 5. C ): Head with yellowish to grayish background. Body with grayish background color. Dark brown stripes running through flank from snout to caudal peduncle. Opercular area covered by golden sheen. Dark brown blotches on suborbital area less distinct. Dorsal and anal fins with bright bluish margin and narrow black subdistal band, followed interiorly by a broad turquoise band; interior boundary of band is less regular; anterior region of proximal part often covered by turquoise band, posterior region reddish. Caudal fin with a bright bluish margin; background uniformly reddish, irregular faint turquoise blotches scattered at center of caudal fin forming a vague crescentic pattern without clear outline. Pelvic fin iridescent turquoise bluish, with a dark bluish filament. Pectoral fin hyaline.

Female: head and body coloration similar to male. Coloration of dorsal and anal fin similar to male but less intense; caudal fin hyaline without unique pattern. Pelvic fin filament slightly bluish. Pectoral fin hyaline.

Preserved coloration Male ( Fig. 5. A, B ): head and body with whitish or light yellowish ground color; a dark brown stripe running from snout through eye along whole dorsum to caudal-fin base; a second parallel stripe present from postorbital area through flank to middle of caudal peduncle; less distinct black pigments observed on suborbital and opercular area; belly whitish without a third dark stripe. Dorsal and anal fins with hyaline margin, a narrow dark subdistal band bordered interiorly by broad hyaline band, proximal part from dark reddish to brownish. Caudal fin with a hyaline margin, remaining parts uniformly dark reddish to brownish with irregular faint hyaline blotches in middle. Pectoral fin hyaline. Pelvic fin base dark brownish with a hyaline filament.

Female: general coloration similar to male but less intense. Caudal fin light brownish without any pattern.

Distribution The species is currently only found in a small river running through a large oil-palm plantation in Kalimantan Tengah, Indonesia.

Etymology The species is named after Hiroyuki Kishi, who discovered this species and P. quindecim and who contributed much first-hand field information on this genus over the last decade.

Comparison Parosphromenus kishii sp. nov. can be easily distinguished from all other Parosphromenus by its unique reddish caudal fin with an irregular faint turquoise pattern and pointed rhombic shape; it also differs from P. deissneri and P. filamentosus by a non-filamentous branched median ray of the caudal fin (vs. simple and filamentous) and having more dorsal-fin spines (XIII–XIV* vs. XII–XIII); from P. ornaticauda and P. parvulus by more anal-fin spines (XII–XIII* vs. VII–IX) and more dorsal-fin spines (XIII–XIV* vs. IX–XI); from P. linkei and P. pahuensis by the lack of black blotches in the middle of the flank stripes (vs. presence) and presence of a subdistal band in the dorsal and anal fins (vs. absence); from P. juelinae by the reddish color of the proximal parts of the dorsal and anal fins (vs. blackish) and by the lack of reddish blotches on the body flanks (vs. presence); from P. opallios by a broad entirely turquoise band throughout the dorsal and anal fin (vs. a narrow partly or entirely reddish band); from P. quindecim by a broad turquoise band on blackish dorsal and anal fins (vs. narrow) and the light bluish pelvic fin filament (vs. black); P. kishii is distinguished from P. allani , P. barbarae and P. sumatranus by the lack of an ocellus on the dorsal fin (vs. presence); from P. anjunganensis by the turquoise band and blotches on the unpaired fins (vs. uniformly reddish); from P. bintan , P. harveyi , P. nagyi and P. gunawani by a reddish proximal part of the dorsal and anal fins (vs. black); from P. alfredi , P. phoenicurus , P. rubrimontis , and P. tweediei by a broad entirely turquoise band throughout the dorsal and anal fins (vs. a narrow partly or entirely reddish band).

Field notes The species was recorded by H. Kishi in Kalimantan Tengah as early as Nov. 1999. Currently it is only found in a single river, which is severely disturbed by human activities ( Fig. 6 ). Most of the nearby regions have been converted into oil-palm plantations. Thus, we have yet not been able to record this species outside this single river. There are still some remote locations with better potential, which have not been explored in the last survey. Further studies will be necessary to clarify the distribution of this endangered species.

All the syntopic fish species recorded from the habitats are listed as follows: Trigonopoma pauciperforatum (Danionididae) , Nandus nebulosus (Nandidae) , Betta edithae , Luciocephalus aura , Sphaerichthys selatanensis (Osphronemidae) and Hemirhamphodon tengah (Zenarchopteridae) .

Conservation Status Parosphromenus kishii sp. nov. is confined to a single river, which now functions as a natural irrigation canal for a large oil-palm plantation. The habitat is extremely impacted. Any further works at the plantation may lead to dredging and expansion of this river, which may eradicate the only known population of this species. Thus, following the IUCN Red List Categories and Criteria (ver. 3.1), we propose that this species be listed as Critically Endangered B2ab (iii, v), based on its very restricted distribution within a single river running through an oil-palm plantation (<50 km 2) with only a single known location and the extremely high likelihood of becoming extinct due to the potential works of surrounding oil-palm plantations. Immediate in-situ or ex-situ conservation is highly recommended for this species.

Molecular analysis. The consensus phylogenetic tree based on the mitochondrial cytb gene suggests that Parosphromenus kishii sp. nov. is a monophyletic group distinct from its sister group P. filamentosus by an uncorrected p-distance of 8.65% ( Fig. 4 ; Table S2). Furthermore, P. kishii sp. nov. is substantially distinct from other congeners too, with cytb genetic distances ranging from 13.84–17.28%. These results suggest that genetic differences among the new species and its congeners is indicative of divergence at a species-level. Morphologically, P. kishii sp. nov. also differs from all known Parosphromenus species in its unique caudal fin coloration. Thus, based on both molecular and morphological data, this fish from Kalimantan Tengah is formally recognized as a distinct species.

Remarks Different forms of the caudal fin shape can be found within Parosphromenus kishii : a pointed rhombic shape in most specimens (44 out of the 50 collected adult specimens), rhombic with a convex in the middle in specific specimens (2 out of 50) and lanceolate with a projected short filamentous tip in certain older adults (the median ray branched instead of simple, 4 out of 50) ( Fig. 7 A–C, G ). Except the convex morph ( Fig. 7 G ), which might be an aberrant one, other phenotypes have been preserved in the next generation. We observed again in the same batch of F1 from a single pair, three different morphs of caudal fin shapes: round, pointed rhombic and lanceolate with a projected short filamentous tip ( Fig. 7 D–F ). The rays of the fin are not damaged in the examined specimens, and these shapes are not aberrant due to regrowth following injury. Thus, these distinct caudal fin shapes are most likely a potential polymorphism in this species.

Figures

FIGURE 4. Phylogenetic tree of Parosphromenus species based on cytb gene sequences and ML approaches. The two new species in the phylogenetic tree are highlighted in red (Photograph of Parsophromenus parvulus: Jianhui Dai, 2019; Photograph of Parsophromenus harveyi; Parosphromenus sp. Tangkit: Ji, Yuhan Ji, 2017; Photograph of Parsophromenus cf. gunawani: Weilin Zhong, 20. Apr, 2020).

FIGURE 5. (A) Parosphromenus kishii sp. nov., MZB 25120, 31.4 mm SL male holotype, freshly preserved (laterally inverted); (B) P. kishii, CKH–P102, 27.5 mm SL, male paratype (photograph: H. Kishi, Jan. 2021); (C) P. kishii, about 35 mm SL, male, from the type locality, live coloration, not preserved.

FIGURE 6. Photograph of type locality of Parosphromenus kishii in Kalimantan Tengah, a clear water river running through an oil-palm plantation, Apr. 2019.

FIGURE 7. (A) The rounded caudal fin of juveniles: posterior edge of the fin smoothy rounded, not pointed; not preserved; (B). The most common rhombic caudal-fin shape in adults, posterior edge of the fin projected outwards into a pointed rhombic shape, SJD KA2081, from type locality; (C). The third variant of the caudal-fin shape, the median ray branched and elongated into a short filament in some adults, SJD KA2081, from type locality; (D) The rounded caudal-fin shape in F1 adults (offspring of the male in Fig. 5 C); (E) The pointed rhombic caudal-fin shape in F1 adults (offspring of the same clutch of the male in Fig. 5 C); (F) The spade-shaded caudal-fin shape with a short filament (median ray branched) in F1 adults (offspring of the same clutch of the male in Fig. 5 C); (G) Another variant of the caudal-fin shape in adults, the middle part of the posterior edge of the caudal fin aberrantly elongated outwardly into a center convex rhombic shape, but without filament; same fish with Fig. 5 C, not preserved. (laterally inverted).