Metzia bounthobi SHIBUKAWA, PHOUSAVANH, PHONGSA & IWATA, 2012

Etymology

Metzia: named for Charles William Metz, Stanford University, who helped authors identify fishes collected in Japan.

bounthobi: named “in honour of Bounthob Praxaysombath (NUOL), who was the leading researcher performing the field surveys throughout the NUOL-NEF project on 2007–2010. Eight of all 10 type series of the new species were brought from the project surveys”.

Classification

Order: Cypriniformes Family: Cyprinidae

Distribution

Known only from the Nam Ou River basin, a Mekong tributary in Phongsaly and Luang Prabang provinces, northern Laos.

Type locality is ‘Mekong basin in Sopvan, Nyoi District, Luang Prabang Province, Lao PDR (20°36.5’N, 102°39.1’E), northern Laos’.

Habitat

Collected from hill streams with clear water and slow to moderately fast-flowing water.

Maximum Standard Length

55 – 61 mm.

NotesTop ↑

This species can be distinguished from congeners by the following combination of characters: 18–20 (vs. 10-18) branched anal-fin rays; 49–55 (vs. 35-48) lateral-line scale rows; 33–36 (vs. 15-20) predorsal scale rows; 20–22 (vs. 14-18) circumpeduncular scale rows; 8–10 (vs. 12-18) gill rakers on outer side of the first gill arch.

Although it is included in the genus Metzia this grouping remains somewhat unresolved in terms of taxonomy and it may contain more than a single genetic lineage. For example, members share a number of characters with the genera Ischikauia Jordan and Snyder 1900, Hemiculterella Warpachowski 1887, and several species of Anabarilius Cockerell 1923, including a bipartite gas bladder, a non-spinous dorsal-fin ray, and a sharp ventral keel between the pelvic-fin insertion and anus.

Metzia was also recovered together with the genus Hemigrammocypris in a phylogenetic study published in 2010, thus rendering it paraphyletic. In addition,  M. formosae and M. longinasus differ from most other members of the genus in mouth position (upturned vs. terminal in putative congeners) and number of lateral line scales (43–48 vs. 35-39), and M. bounthobi differs from all congeners in number of branched anal-fin rays (18-20 vs. 10-18) and lateral line scales (49-55 vs. 35-48).

The current concept of Metzia can be diagnosed as follows: body compressed; abdomen with a sharp ventral keel between pelvic-fin insertion and anus; no barbels; no symphysal projection on the lower jaw fitting into a depression on upper jaw; lateral line complete, curved ventrally anterior to pelvic-fin insertion, running parallel with ventral profile and extending through centre of caudal peduncle above anal-fin base; gas bladder bipartite, posterior chamber with a rounded distal extremity; last simple dorsal-fin ray not spinous, origin closer to caudal-fin base than tip of snout or posterior to a vertical through pelvic-fin insertion; 10-20 branched anal-fin rays; 35-55 lateral-line scales.

References

1. Shibukawa, K., P. Phousavanh, K. Phongsa and A. Iwata, 2012 - Zootaxa 3586: 264-271
   A new species of Metzia (Cypriniformes: Cyprinidae) from northern Laos.
2. Gan, X., J.-H. Lan and E. Zhang , 2009 - Ichthyological Research 56(1): 55-61
   Metzia longinasus, a new cyprinid species (Teleostei: Cypriniformes) from the Pearl River drainage in Guangxi Province, South China.
3. Kottelat, M., 2013 - Raffles Bulletin of Zoology Supplement 27: 1-663
   The fishes of the inland waters of southeast Asia: a catalogue and core bibiography of the fishes known to occur in freshwaters, mangroves and estuaries.
4. Kottelat, M., 2001 - Environment and Social Development Unit, East Asia and Pacific Region. The World Bank: i-iii + 1-123 + 1-18
   Freshwater fishes of northern Vietnam. A preliminary check-list of the fishes known or expected to occur in northern Vietnam with comments on systematics and nomenclature.
5. Tang, K. L., M. K. Agnew, W. J. Chen., M. V. Hirt, T. Sado, L. M. Schneider, J. Freyhof, Z. Sulaiman, E. Swartz, C. Vidthayanon, M. Miya, K. Saitoh, A. M. Simons, R. M. Wood and R. L. Mayden, 2010 - Molecular Phylogenetics and Evolution 57(1): 189-214
   Systematics of the subfamily Danioninae (Teleostei: Cypriniformes: Cyprinidae).