Taxonomy & naming
Proterorhinus scythicus was described in 2026 by Ekaterina Vasil'eva, Maria Levina, Sergei Podolyako, Ilya Turbanov and Boris Levin in the Journal of Ichthyology, as part of a broader paper addressing species diversity, diagnostic characters and distribution across the genus Proterorhinus (family Gobiidae, subfamily Gobiinae) — a group commonly known as the tubenose gobies for the small tube-like extension of the anterior nostril shared across the genus. The Catalog of Fishes notes that the new species first appeared online without ZooBank registration, so its formal nomenclatural date is tied to the printed edition rather than the earlier online-first posting — a procedural detail rather than anything affecting the species' validity.
No copy of the full description text was available for this article, so its content is limited to what the Catalog of Fishes record itself preserves — the type locality, distribution and habitat given below — plus genus-level background. The specific epithet scythicus most plausibly derives from Scythia, the classical name for the Pontic-Caspian steppe region that encompasses the species' Kalmykia type locality, though this derivation could not be confirmed against the paper's own etymology section, which was not available in the source material captured for this article. Proterorhinus itself is generally understood to combine the Greek proteros ('before, in front') with rhinos ('nose'), a reference to the genus's tube-nostril character — again a genus-level generality rather than a statement confirmed against this specific paper.
Morphology
No morphological description of Proterorhinus scythicus was captured in the source material available for this article. As a member of Proterorhinus, it can generally be expected to share the genus's tubenose-goby build — a small, elongate gobiid body typically under 3.9 in, with the characteristic tube-like extension of the anterior nostril — but this is stated only as a genus-level generality, not a confirmed description of this species.
Habitat
The type locality is the Vostochniy Manych River at the Chograiskiy discharge channel, which connects it with the Kuma River, in the Republic of Kalmykia, Russia (45°19′34.0″ N, 45°18′16.2″ E). The Catalog of Fishes records the species' broader distribution as the Vostochniy Manych River drainage, the Sostinskiye Lakes, the Chernozemel'skiy channel and the estuary of the Volga River, all within the northwestern Caspian Sea basin — a Ponto-Caspian steppe-lake-and-river system. Habitat is recorded as both freshwater and brackish, consistent with the broad salinity tolerance documented across Proterorhinus generally, several of whose species move between fresh, brackish and estuarine water.
Feeding
No dietary information has been documented for this species. Gobies of the genus Proterorhinus and related Ponto-Caspian gobiids are generally benthic micropredators, taking small invertebrates from the substrate; this is offered here only as a genus-level generality, not a confirmed observation for P. scythicus.
Mating
No courtship or spawning behaviour has been documented for this species.
Breeding
No breeding record exists for this species, in the wild or in captivity. Gobiid fishes generally, including Ponto-Caspian tubenose and sand gobies, are cave or crevice spawners in which the male guards an adhesive egg clutch until hatching; this is stated here only as a widespread family-level pattern, not a confirmed observation for P. scythicus.
In the aquarium
Proterorhinus scythicus has no aquarium trade history and there is no evidence it has entered the hobby. It was described in 2026 from a steppe-lake-and-river drainage system in Kalmykia, southern Russia, a region with no established ornamental collection or export trade for this genus. No care information can be offered responsibly given the complete absence of husbandry data for this species.
Conservation
Proterorhinus scythicus has not been assessed on the IUCN Red List and is recorded here as Not Evaluated. Its documented range spans several connected water bodies within the northwestern Caspian Sea basin — the Vostochniy Manych River drainage, the Sostinskiye Lakes, the Chernozemel'skiy channel and the Volga estuary — rather than a single isolated locality, though no population-level data are available. Unlike some of its congeners, which have become invasive outside their native Ponto-Caspian range, there is no evidence that P. scythicus occurs, or is of conservation concern, outside the Caspian basin drainage system in which it was described.