Paralaubuca typus Bleeker, 1864

Tangjitjaroen, Weerapongse, Randall, Zachary S., Yang, Lei, Grudpan, Chaiwut & Page, Lawrence M., 2025, Taxonomic revision of Paralaubuca (Cypriniformes, Xenocyprididae), a taxon seemingly in decline, Zootaxa 5647 (4), pp. 301-330 : 316-319

Paralaubuca typus Bleeker, 1864

( Figures 1 , 2 , 5 , 6 )

Paralaubuca typus Bleeker, 1864:16 . Type locality: Thailand: Ajuthia [Ayutthaya] and Bangkok.

Lectotype: MNHN 1867 , designated by Bănărescu (1971:348, fig. 1).

Chela paralaubuca Gu ̈nther, 1868:337. Unnecessary replacement name for Paralaubuca typus

Bleeker, 1864.

Pseudolaubuca lateralis Sauvage, 1876:98 . Type locality: Cochinchine: rapids of the Mekong.

Lectotype: MNHN 3932 , designated by Bănărescu, 1971:348.

Chela stigmabrachium Fowler, 1934:109 , fig. 62. Type locality: Thailand: Chiang Rai Province:

Mekong River at Chieng Sen. Holotype: ANSP 57458

Culter riveroi Fowler, 1935:108 , fig. 34. Type locality: Thailand: Bangkok. Holotype: ANSP 60803 .

Paralaubuca typus was described by Bleeker (1864) based on four specimens, 112–120 mm TL, from the Chao Phraya River in Ajuthia [Ayutthaya] and Bangkok, Thailand. The specimens were described as having 7 branched dorsal-fin rays, 13 pectoral-fin rays, 9 pelvic-fin rays, 29–30 branched anal-fin rays, and 17 branched caudal-fin rays, and had black pigment on the pectoral fins. In his revision of Paralaubuca, Bănărescu (1971) selected a lectotype (MNHN 1867), then 92.1 mm SL, and paralectotypes (MNHN 1865 and 1866), 92–96.8 mm SL. Our count of lateral-line scales from the image of the lectotype ( Figure 6A ) is 63.

Pseudolaubuca lateralis was described by Sauvage (1876) from the Mekong River in Cochinchine—presumably in Cambodia or Laos ( Kottelat 2013). Little information on the morphology and no biometric values were provided. Sauvage (1881) relegated Pseudolaubuca lateralis to the synonymy of Paralaubuca typus Bleeker 1864 . Bănărescu (1971) examined 149 syntypes of P. lateralis , 87.0–133.0 mm SL, designated a lectotype (MNHN 3932), and agreed with Sauvage (1881) that P. lateralis is a synonym of P. typus . For the types, Bănărescu gave an average branched anal-fin ray count of 26.3 and a range of 36–37 gill rakers. Our count of lateral-line scales from the image of the lectotype ( Figure 6B ) is 60, and the estimated SL is 103 mm.

Chela stigmabrachium was described by Fowler (1934) from 7 specimens 63–160 mm in total length (TL) from the Mekong River at Chiang Sen in northern Thailand. It was described as having 7 branched dorsal-fin rays, 15 pectoral-fin rays, 9 pelvic-fin rays, 31 gill rakers, 25–27 branched anal-fin rays, and the pigment on the pectoral fin as a “variable large medial blackish or dusky area.” Bănărescu (1971) gave the SL of the holotype ( Figure 6C ) as 127.5 mm SL; we found it to be 122.4 mm SL.

Bănărescu (1971) considered Chela stigmabrachium a valid species of Paralaubuca based on black pigment on the pectoral fin but noted it otherwise to be identical to P. typus . However, P. typus often has black pigment on the pectoral fin, even noted by Bleeker (1864) in the original description of the species. After examining the holotype, we agree with Rainboth (1996) that C. stigmabrachium is a synonym of P. typus .

Culter riveroi was described by Fowler (1935) from a single specimen 153 mm TL ( Figure 6D ) collected in Bangkok, Thailand. It was described as having 53 lateral-line scales, 7 branched dorsal-fin rays, 25 branched anal-fin rays, 9 pelvic-fin rays, 14 pectoral-fin rays, and 42 gill rakers. Bănărescu (1971) examined the holotype and found it to be 125.7 mm SL; we found the holotype to be 119.3 mm SL and to have 61 lateral-line scales. Nothing in the original or subsequent published descriptions distinguishes C. riveroi from P. typus , and we consider it a synonym of P. typus .

Diagnosis. Paralaubuca typus is most similar to P. barroni but distinguished by having 31–51 vs. 22–29 rakers on first gill arch, average of 58.4 vs. 54.8 lateral-line scales, and reaching much larger size, 152.5 vs 115.0 mm SL. Paralaubuca typus is distinguished from P. harmandi by having 51–68 vs. 70–87 lateral-line scales, usually 24–29 vs. usually 22–24 branched anal–fin rays, 20–28 (usually 26 or fewer) vs. 26–33 (usually 28–32) scales around caudal peduncle, 31–51 vs. 29–33 rakers on first gill arch, and 38–41 (usually 39–40, average=39.3, n=14) vs. 41–42 (usually 42, average=41.9, n=9) total vertebrae. Paralaubuca typus has longer anal fin and anal-fin base, and larger eye ( Table 9) than P. harmandi . It also has shorter lower lip than P. harmandi ( Table 9) reflecting proportionally shorter dentary ( Figure 5 ). Paralaubuca typus is further distinguished from P. harmandi osteologically as described above and shown in Figure 5 . Paralaubuca typus , reaching 152.5 mm SL, is smaller than P. harmandi , which reaches 265 mm SL.

Description. See description of genus. In three collections of P. typus from the Chao Phraya River basin in which gonads were examined to confirm the sex, females (n=17) were significantly deeper bodied than males (n=14) and reached a much larger size (152.5 vs. 116.1 mm SL) ( Figure 7 ). In addition to being more slender, males at least seasonally have a more pronounced black midlateral stripe and more black pigment on the pectoral fin and edge of the caudal fin.

Distribution. Paralaubuca typus is known from the Chao Phraya, Mae Klong, and Tachin River basins of Thailand, and the Mekong River basin of Cambodia, Laos, Thailand, and Vietnam ( Figure 8C ).

Most observations and collections of P. typus have been in flowing water in moderate to large rivers. A few specimens have also been collected in impoundments. Paralaubuca typus is widespread and common in the Chao Phraya and Mekong River basins, but in the Mae Klong it is known only from a few localities in the lower basin and has not been documented there since the 1960s. However, it occurs in the adjacent Tachin River basin, and targeted sampling may reveal its occurrence in the lower Mae Klong River basin.

Figures

FIGURE 1. Paralaubuca typus, (A) live, UF 248615, 95.6 mm SL, Ping River, Kamphaeng Phet Province, Thailand, 8 Feb 2022. (B) preserved, UF 193797, female, 123.6 mm SL, and (C) preserved male, 116.1 mm SL, Ping River, Kamphaeng Phet Province, Thailand, 10 Feb 2024. Paralaubuca barroni, (D) preserved, UF 249886, 72.9 mm SL, Mekong River, Ubon Ratchathani Province, Thailand, 16 Jul 2005. Paralaubuca harmandi, (E) live, UF 248526, 126.1 mm SL, Chao Phraya River, Ayutthaya Province, Thailand, 21 Jun 2022.

FIGURE 2. Paralaubuca typus, UF 249413, 54.4 mm SL. (A) pectoral-fin flap, (B) black dots on pores on lateral-line scales illustrating overlap in a discontinuous lateral line.

FIGURE 5. Lateral skull computed tomography (CT) scans of (A) Paralaubuca typus, UF 170312, 84.9 mm SL, Mun River, Ubon Ratchathani Province, Thailand, 16 Nov 2007, (B) P. barroni, ANSP 179934, 54.2 mm SL, Ubon Ratchathani Province, Thailand, 10 Feb 2021, and (C) P. harmandi, UMMZ 195277, 128.2 mm SL, Ratchaburi Province, Thailand, 14 Nov 1964. Dentary in blue, premaxilla in green, maxilla in pink, orbitosphenoid in yellow, parasphenoid in grey, entopterygoid in orange, supraneural 5 in red, exoccipital and supraoccipital in purple. Asterisk indicates suspensorium window of Gosline (1975).

FIGURE 6. Primary types of Paralaubuca typus and synonyms. (A) Paralaubuca typus lectotype, MNHN 1867, 92.1 mm SL, Chao Phraya River, Ayutthaya and Bangkok, Thailand. Photograph by Jonathan Pfliger. (B) Pseudolaubuca lateralis lectotype, MNHN 3932, 103 mm SL, Mekong River, Cochinchine. Photograph by Jonathan Pfliger. (C) Chela stigmabrachium holotype, ANSP 57458, 122.4 mm SL, Mekong River, Chiang Sen, Chiang Rai Province, Thailand. Photograph by Kyle R. Luckenbill. (D) Culter riveroi holotype, ANSP 60803, 119.3 mm SL, Bangkok, Thailand. Photograph by Jenna Hill.

FIGURE 7. Scatter plot and line of best fit for body depth at dorsal-fin origin divided by standard length in females (blue, n=17; y=0.2427x + 5.7235; R2=0.9534) and males (orange, n=14; y=0.2147x + 6.1889, R2=0.8667) of Paralaubuca typus.

FIGURE 8. Distributions of species of Paralaubuca. (A) Paralaubuca barroni. ★ type locality of Chela barroni, locality for P. barroni in China is an approximation. (B) Paralaubuca harmandi. · type locality of Culter siamensis, ▲ type locality of Culter wolfi, locality for P. harmandi in Cambodia is an approximation. Type localities of P. harmandi (Chao Phraya River) and Pseudolaubuca lateralis (Cochinchine) are ambiguous and not plotted. (C) Paralaubuca typus. ★ type localities of P. typus and Culter riveroi, ◆ type locality of Chela stigmabrachium.