[Ichthyology • 2025] Forgotten for Decades: Revalidation and Redescription of Raiamas harmandi (Sauvage, 1880) (Cypriniformes: Danionidae) from the Mekong River Basin

 Raiamas harmandi (Sauvage, 1880): (a) subadult, (c) adult;
R. guttatus (Day, 1870), (d) adult 

 in Liu, Xu, Zeng, Oo et Chen, 2025. 

DOI: doi.org/10.3390/taxonomy5030042

Abstract

The genus Raiamas currently comprises 18 valid species, only 2 of which occur in Asia; the remaining 16 are endemic to Africa. Raiamas harmandi was originally described by Sauvage in 1880 as Bola harmandi, which is distributed in the Great Lakes, Cambodia, the Mekong River Basin. It was considered a synonym of R. guttatus by later researchers. In this study, we examined 49 Raiamas individuals from the Mekong, Irrawaddy, and Salween river basins, recording both meristic counts and morphometric measurements. Based on the morphological evidence, we revised the taxonomy of Raiamas in the Mekong River Basin, confirming R. harmandi as a valid species and providing a comprehensive redescription. Raiamas harmandi can be distinguished from R. guttatus mainly by having more predorsal scales (25–28 vs. 21–23) and a different color pattern on the lateral body. Utilizing a total of 44 aligned COI and Cyt b sequences—including eight newly sequenced individuals of Raiamas from three river basins—we reconstructed its phylogenetic relationships. The analysis strongly supported four R. harmandi individuals from the Mekong River Basin forming a distinct clade, which was the sister to the clade comprising five R. guttatus individuals from the Irrawaddy and Salween river basins. Genetic distances between R. harmandi and R. guttatus ranged from 14.0 to 14.9% for COI and 16.1 to 17.0% for Cyt b. Distributionally, R. harmandi occurs throughout the Mekong River Basin, as evidenced by combined voucher specimens and molecular sequence data.

Keywords: Raiamas guttatus; taxonomy; systematics; DNA barcoding; morphology; freshwater fish; Southeast Asia

 Live individuals of (a) subadult Raiamas harmandi, 85.0 mm SL, (b) subadult R. guttatus, 95.0 mm SL, (c) adult R. harmandi, 176.5 mm SL, and (d) adult R. guttatus, 159.2 mm SL.

Raiamas harmandi stat. rev. (Sauvage, 1880)

Diagnosis. Raiamas harmandi can be distinguished from all other Asian Raiamas species by the following combination of characteristics: a distinctive color pattern of numerous small spots irregularly scattered on the lateral body; predorsal scales 25–28; lateral-line scales 45–50; total number of vertebrae 41–44; caudal vertebrae 20–22. It can be further distinguished from the most similar species, R. guttatus, by a proportionally longer upper jaw (57.9–68.6% HL vs. 56.3–61.9% HL).

Etymology. The name of this species, harmandi, is in honor of the French Navy surgeon, naturalist, and explorer François-Jules Harmand (1845–1921), who collected the holotype.

Distribution. Raiamas harmandi is widely distributed in the Mekong River Basin, with records from China (the lower Lancang River), Laos, Vietnam, Thailand, and Cambodia (Figure 1). Species of the genus Raiamas have also been recorded in the Chao Phraya River Basin, Peninsular Malaysia, and South Sumatra, and it remains to be confirmed whether they are R. harmandi.

 Cai-Xin Liu, Yi-Yang Xu, Yu-Yang Zeng, Thaung Naing Oo and Xiao-Yong Chen. 2025. Forgotten for Decades: Revalidation and Redescription of Raiamas harmandi (Sauvage, 1880) (Cypriniformes: Danionidae) from the Mekong River Basin. Taxonomy. 5(3), 42; DOI: doi.org/10.3390/taxonomy5030042 [20 August 2025]

(This article belongs to the Special Issue Taxonomy in the 21st Century: Celebrating a New Chapter—First Impact Factor Received)