Pseudoscaphirhynchus

Pseudoscaphirhynchus is a genus of relatively small, highly threatened sturgeons that are restricted to the Aral Sea system (although extirpated from the Aral Sea itself), including the Amu Darya and Syr Darya river basins, in Central Asia.^[3][4]

Pseudoscaphirhynchus
Pseudoscaphirhynchus fedtschenkoi
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Acipenseriformes
Family:	Acipenseridae
Genus:	Pseudoscaphirhynchus A. M. Nikolskii, 1900
Species
Pseudoscaphirhynchus fedtschenkoi Pseudoscaphirhynchus hermanni Pseudoscaphirhynchus kaufmanni
Synonyms[1][2]
Kessleria Boghdanov 1882 non Nowicki 1864 non Lichtenstein 1886 Pseudoscaphirhynchus (Hemiscaphirhynchus) Berg 1911 Hemiscaphirhynchus (Berg 1911)

P. fedtschenkoi is restricted to Syr Darya, but has not been seen in decades and it is possibly extinct.^[5][6] The two other species in the genus are restricted to Amu Darya: P. hermanni survives in very low numbers and P. kaufmanni in low numbers, with both being rated as Critically Endangered by the IUCN.^{[7][8][9][10]}

Compared to other sturgeons, Pseudoscaphirhynchus are small. The largest species, P. kaufmanni, reaches up to 75 cm (30 in) in total length (excluding tail filament), while the smallest, P. hermanni, only reaches 27.5 cm (10.8 in), making it the smallest member of the sturgeon family.^[4][9] P. kaufmanni has a long thin tail filament, P. hermanni lacks it, and it can be long or short in P. fedtschenkoi.^[9] They have a relatively long, broad and flattened snout, somewhat like Scaphirhynchus of North America. Little is known about the behavior of Pseudoscaphirhynchus, but they mainly feed on the bottom on small fish and aquatic insect larvae.^[11]

Taxonomy and species

Three different P. hermanni seen from above

There are currently three recognized species in this genus:^[4]

• Pseudoscaphirhynchus fedtschenkoi (Kessler, 1872) (Syr Darya sturgeon)
• Pseudoscaphirhynchus hermanni (Kessler, 1877) (dwarf sturgeon, small Amu Darya sturgeon)
• Pseudoscaphirhynchus kaufmanni (Kessler, 1877) (Amu Darya sturgeon)

Historically, the two species in the Amu Darya River were known to hybridize.^[11] Unusually, P. fedtschenkoi occurs (or occurred) in three morphs that can be separated by the length of their snout and tail filament, and P. kaufmanni occurs in two morphs that can be separated by their total size and colour.^[9][10][11]

Although Pseudoscaphirhynchus and Scaphirhynchus traditionally are placed together in the subfamily Scaphirhynchinae based on their similar morphology, several genetic and karyotypic studies have shown that this grouping is polyphyletic.^[10][11][12]

References

• fish portal

1. Froese, R.; Pauly, D. (2017). "Acipenseridae". FishBase version (02/2017). Retrieved 18 May 2017.
2. "Acipenseridae" (PDF). Deeplyfish- fishes of the world. Retrieved 18 May 2017.
3. "ITIS - Report: Pseudoscaphirhynchus".
4. Froese, Rainer; Pauly, Daniel (eds.). "Species in genus Pseudoscaphirhynchus". FishBase. May 2019 version.
5. Mugue, N. (2010). "Pseudoscaphirhynchus fedtschenkoi". IUCN Red List of Threatened Species. 2010: e.T18599A8496937. doi:10.2305/IUCN.UK.2010-1.RLTS.T18599A8496937.en. Retrieved 23 May 2019.
6. Mitrofanov, I.V.; and N.Sh. Mamilov (2015). Fish diversity and fisheries in the Caspian Sea and Aral–Syr Darya basin in the Republic of Kazakhstan at the beginning of the 21st Century. Aquatic Ecosystem Health & Management 18(2): 160–170. doi:10.1080/14634988.2015.1028870
7. Mugue, N. (2010). "Pseudoscaphirhynchus hermanni". IUCN Red List of Threatened Species. 2010: e.T18600A8497165. doi:10.2305/IUCN.UK.2010-1.RLTS.T18600A8497165.en. Retrieved 23 May 2019.
8. Mugue, N. (2010). "Pseudoscaphirhynchus kaufmanni". IUCN Red List of Threatened Species. 2010: e.T18601A8498207. doi:10.2305/IUCN.UK.2010-1.RLTS.T18601A8498207.en. Retrieved 23 May 2019.
9. Salnikov, V.B.; V.J. Birstein; and R.L. Mayden (1996). The contemporary status of the two Amu Darya River shovelnose sturgeons, Pseudoscaphirhynchus kaufmanni and P. hermanni. The Sturgeon Quarterly 4(3): 10–14.
10. Kovalev, K.V.; D.A. Balashov; A.L. Cherniak; E. B. Lebedeva; E.D. Vasil'eva; and V.P. Vasil'ev (2016). The karyotype of the Amu Darya sturgeon, Pseudoscaphirhynchus kaufmanni (Actinopterygii: Acipenseriformes: Acipenseridae). Acta Ichthyologica Et Piscatoria 44(2): 111-116.
11. Birstein, V.J.; J.R. Waldman; and W.E. Bemis, editors (1997). Sturgeon biodiversity and conservation, pp. 146, 381–382. Kluwer Academic Publishing. ISBN 0-792-34517-7
12. Sheraliev, Bakhtiyor; Peng, Zuogang (2020). "Complete mitochondrial genome sequence and phylogenetic position of the Amu Darya sturgeon, Pseudoscaphirhynchus kaufmanni (Acipenseriformes: Acipenseridae)". Journal of Applied Ichthyology. 36 (4): 389–392. doi:10.1111/jai.14043. S2CID 219007942.