Formosania gilberti Oshima, 1919

Yeh, Ming-Fon, Li, Hsien-En, Han, Chiao-Chuan & Chen, I-Shiung, 2024, Redescription and validity of Formosania gilberti Oshima, 1919 (Cypriniformes: Balitoridae), an endemic hillstream loach from Taiwan, Zootaxa 5550 (1), pp. 287-304 : 293-302

Formosania gilberti Oshima, 1919

(吉ƃḋ口ª)

( Figs. 5A ; 6–8 ; 10A ; 11A ; 12A )

Formosania gilberti Oshima, 1919: 194 (Shintian, Taiwan).

Crossostoma lacustre (non Steindachner): Chen 1980: 103; Chen & Tang 2000: 466.

Materials Examined

NTOUP2022-05-030, 7 (45.24–83.78 mm SL); Chingshui brook, Beihuang River, Jinshan District, New Taipei City, Taiwan; coll. I-Shiung Chen et al., 30 May. 2022; NTOUP2023-05-018, 8 (67.08–100.35 mm SL); Dabao brook, Tamshui River, Sanxia District, New Taipei City, Taiwan; coll. Hsien-En Li, I-Lang, Cheng & Hue Man Tran, 18 May. 2023.

Diagnosis

Formosania gilberti can be well separated from its congeners by the following unique combination of characters (mode shown in brackets): D 3+8; A 2+5; P 1 1+14–15 (14); P 2 1+7–8 (8); LL 89–96 (89); barbels 9–13(13)+2; V 26+11=37.

Body ground color dark green, intensely mottled with cloud-like blotches, without lateral streak or vague when fresh; all fins yellowish orange, pectoral fins lined with 3 to 4 rows of large black spots; barbels orange when fresh.

Redescriptions

Body proportions as shown in Table 2, frequencies of meristic counts in Table 3 . Body slightly elongated, almost semicylindrical anteriorly and laterally compressed posteriorly behind dorsal fin base. Head depressed, bluntly triangular in dorsal view.Eye positioned dorso-laterally, with interorbital width significantly greater than eye diameter (18.13 vs. 43.56). Anterior and posterior nostrils separated with a small flap. Mouth inferior, opening curved; upper lip thick, pad like, with slightly wrinkled surface and a thin, smooth additional pad located along edge; median lower lip edge with two pairs of papillose protrusion. Total barbels 9 (3), 10 (2), 11 (3), 12 (1), or 13 (6)+2; rostral fold with specialized short, papilla-like secondary rostrum barbels located upon (sometimes indistinguishable with the rostrum folds); rostral groove narrow; maxillary barbels 2, located beside gape, a trapezoid-shaped pad present at bases of maxillary barbels, with a small, pointy papillose protrusion; all barbels no longer than half of eye diameter. Ventral side of head with numerous, tiny wart-like protrusions lined along branchiostegal region. Gill slits short, upper end not extending above eye and lower end extending forward to ventral side of head. Operculum slightly elongated, flexible, posterior tip extending beyond pectoral fin insertions. Body covered in numerous delicate, pointy tubercles along dorsal and ventral sides of head, trunk, and fin membranes, size of tubercles without significant differences between sexes. Trunk of female individuals appearing bulkier than male. Female genital papillae plumpy, blunt with wrinkled surface posteriorly and a short median notch. Vertebrates 4 (Weberian apparatus)+22 (abdominal vertebrae)+11 (caudal vertebrae)=37 total vertebrae (15).

Fins. Dorsal fin with 3 unbranched rays and 8 branched rays (15); anal fin with 2 unbranched rays and 5 branched rays (15); pectoral fins with 1 unbranched ray and 14 (12) or 15 (3) branched rays; pelvic fins with 1 unbranched ray and 7 (3) or 8 (12) branched rays. Dorsal fin triangular, with a slightly curved posterior edge; length of longest unbranched ray greater that body depth; fin origin situated before pelvic fin insertions. Posterior tip of anal fin almost reaching posterior end of caudal peduncle. Paired fins inserted horizontally; pectoral fins large, fin insertion point close to gill slit; pelvic fins separated, not fusing medially, fin ray tips extending posteriorly, covering anus when depressed; pelvic fin bases with a short, bud-like granule. Caudal fin slightly forked, with lower lobe slightly longer than upper lobe.

Squamation. Pored lateral line scales 89 (5), 90 (3), 91 (2), 92 (2), 93 (1), or 96 (3). Body completely covered in cycloid scales except naked at head and pectoral fin bases. Thoracic region loosely covered with thin circular cycloid scales, scaled region extends anteriorly until lower edge of gill slit. Body scales elliptical, slightly rounded at anterior end. Lateral line scales with a tiny tubular pore at posterior end except for those upon caudal fin base, which possess a small posterior notch.

Coloration in life. Juvenile transparent, with weakly pigmented anterior part of body and saddle like blotches on posterior end.All fins transparent, dorsal fins with a row of black median stripes and caudal fin with a black transverse band ( Fig. 6 ). For adult individuals, body with light brown background color with an orangish shade; dorsal side of body with numerous saddle-like blotches; head and lateral sides of body intensely covered in vermicular markings ( Fig. 5A ; 8 ).

Coloration when fresh. Coloration and markings similar to those in life, but gaps between vermicular markings becoming mottled and darkened in color, thus blending with markings, resulting in less-distinguishable margins of blotches; vermicular markings extending downwards but not completely covering ventral side of head and body, which is greyish white, and ventral side of body behind pelvic fin, weakly pigmented around anus and anal fin base. Rostral barbels bright orange while maxillary barbels only slightly orangish. Corners of mouth with small area pigmented. All fin ray orange, lined with rows of large black spot with dorsal fin lined with 3–4 rows, paired fins with 2–4 rows and anal fin with 2–3 rows. Upper and lower lobes of caudal fin with 5–7 rows of transverse black bands, with fin between lined with 3–4 rows of spots along fin rays ( Fig. 7 ).

Coloration in preservatives. Body overall greyish, all orange or dark green shades faded. All blotches and markings remained, not fading away.

Distribution

Formosania gilberti can be found in river systems of northern Taiwan, including Tamshui River, Beihuang River, and some other relatively small independent streams of northeastern Taiwan like ShuangRiver or Masu River.

Morphological comparisons

Compared with its Taiwanese relative Formosania lacustris , Formosania gilberti can be immediately distinguished from the former by meristic count differences of having lesser lateral line scale counts (89–96, x=97 vs. 82–102, x=102) and vertebral counts (22+11 vs. 22+12) ( Fig. 9 ). Formosania gilberti can be further distinguished from F. lacustris by morphometric differences of having a smaller head length (18.98% in SL vs. 20.29% in SL), shorter predorsal length (49.89% in SL vs. 51.29% in SL), and larger eye (18.19% in HL vs. 16.81% in HL). Furthermore, Formosania gilberti also has shorter barbels and rostral folds than F. lacustris . In coloration patterns, Formosania gilberti can be distinguished from F. lacustris in having mottled, vermicular markings on sides (vs. cloud-like or brownish and blotchless with a thin longitudinal lateral streak) and paired fins lined with rows of large black spots (vs. blotchless or only weakly dark-shaded) ( Fig. 10 ).

Notes on a new Formosania record from southwestern Taiwan

Our recent field collections gave a new distributional record for Formosania lacustris from the Tzengwen River basin ( Fig. 11 ) as no previous researches or documents had recorded this fish before ( Han & Fang 1997). A total of five individuals were collected, possessing 13+2 barbels, 3+8 dorsal fin elements, 2+5 anal fin elements, 1+14–15 pectoral fin elements, 1+8 pelvic fin elements, 96–99 pored lateral line scales and 22+11 total vertebrae counts. The overall coloration of the F. lacustris specimens collected from Tzengwen River showed a uniformly brownish body with a lateral streak and vague, cloud-like blotches dorsally, dorsal side of head with darkish brown markings and paired fins weakly spotted.

The habitat where the samples were collected is located in an upstream environment with rubbles and rocky substrates. However, the habitat was not very stable, as small upstream tributaries tend to dry out during dry seasons in Taiwan; the population hence has become a rather rare one and thus requires further, consistent monitoring of them.

Mitogenetic comparisons

Mitogenomic analyses of ATPase sequences, based on 24 collected and sequenced Taiwanese Formosania individuals and three selected OTUs, showed similar tree topology using NJ and ML methods ( Fig. 12 ). The 24 Taiwanese Formosania species sequenced in this study were placed in two different, well-bootstrap-supported (bootstrap values of NJ and ML both 100) clades: the first clade contained individuals from Beihuang River (BH1–4) and Tamshui River (TM1–8); these were identified as F. gilberti ; the other clade contained individuals from Jhuoshui River (JS1–3), Zhengwen River (ZW1–3), and Wu River (WU1 & WU2); these were identified as F. lacustris . Furthermore, the NCBI-downloaded OTU of AP01077 was also placed within the clade of F. gilberti .

From the genetic distances of the Formosania sequences analysed in this study, the genetic distances among F. gilberti were estimated to be 0.0000 –0.0036 (avg. 0.0013), and the genetic distances among F. lacustris were estimated to be 0.0000 –0.0024 (avg. 0.0014). The genetic distances between F. gilberti and F. lacustris were estimated to be 0.0167 –0.019 (avg. 0.0174).

Figures

FIGURE 5. A juvenile of Formosania gilberti (uncatalogued, approximately 1.5 mm SL) in its natural habitat in Yuanwangkeng creek, an upstream tributary of Shuang River, Gongliao County, Taiwan.

FIGURE 6. Formosania gilberti (uncatalogued, approximately 80 mm SL) in its natural habitat in Lujiaokeng creek, an upstream tributary of Beihuang River.

FIGURE 7. Formosania lacustris collected from Jhuoshui River basin. NTOUP2022-11-005, female, 63.20 mm SL.

FIGURE 8. Ventral side of head of the two Formosania loaches from Taiwan. A. Formosania gilberti, NTOUP2023-05-018, male, 68.80 mm SL; B. Formosania lacustris NTOUP2022-11-005, female, 75.49 mm SL.

FIGURE 9. Radiographs of the two Formosania loaches from Taiwan. A. Formosania gilberti, NTOUP2023-05-018, male, 69.99 mm SL; B. Formosania lacustris NTOUP2022-11-005, female, 75.49 mm SL. The Weberian apparatus was fused by 4 axial skeleton elements and is located anterior to the abdominal vertebrae series.

FIGURE 10. Left pectoral fin markings of the two Formosania loaches from Taiwan. A. Formosania gilberti, NTOUP2023- 05-018, male, 69.99 mm SL; B. Formosania lacustris NTOUP2022-11-005, female, 75.49 mm SL.

FIGURE 11. Formosania lacustris collected from Tzengwen River basin. NTOUP2022-11-006, female, 69.91 mm SL.

FIGURE 12. Molecular phylogenetic tree constructed by ATP8&6 sequences of 34 selected Formosania samples and 11 Cobitoidei species. Values at left and right sides of the slash at every node represents bootstrap values of neighbour-joining (NJ) and maximum likelihood (ML), respectively, and only bootstrap values that were above 75 were shown. For descriptions of every samples see Table 3.