Ponticola bathybius

{{Short description|Species of fish}}

{{Speciesbox

| image =Ponticola bathybius.jpg

| image_caption = Neogobius bathybius from the Bandar-e Anzali Shore, Caspian Sea, Iran

| taxon = Ponticola bathybius

| authority = (Kessler, 1877)

| synonyms =

• Gobius bathybius Kessler, 1877
• Neogobius bathybius (Kessler, 1877)
• Chasar bathybius (Kessler, 1877)

}}

Neogobius bathybius is a species of goby endemic to the Caspian Sea, where it occurs in depths down to {{convert|200|m|ft}}. It is strictly confined to the brackish-water basin and does not enter fresh waters. It can grow up to a length of {{convert|25|cm|in}} TL.{{FishBase |genus= Neogobius|species= bathybius| month = June | year = 2013}}

The species was transferred to the genus Ponticola from Neogobius on the basis of relationship revealed in molecular investigations.Neilson M.E., Stepien C.A. (2009) Escape from the Ponto-Caspian: Evolution and biogeography of an endemic goby species flock (Benthophilinae: Gobiidae: Teleostei). Molecular Phylogenetics and Evolution, 52(1): 84-102.[https://dx.doi.org/10.1016/j.ympev.2008.12.023] On the other hand, recent molecular studies have proven that this species belongs entirely to the genus Neogobius.{{cite journal|url=https://link.springer.com/article/10.1007/s10750-021-04521-0|title=Mitochondrial phylogeny, diversity, and ichthyogeography of gobies (Teleostei: Gobiidae) from the oldest and deepest Caspian sub-basin and tracing source and spread pattern of an introduced Rhinogobius species at the tricontinental crossroad|year=2021|accessdate=22 February 2021|journal=Hydrobiologia|doi=10.1007/s10750-021-04521-0|last1=Zarei|first1=Fatah|last2=Esmaeili|first2=Hamid Reza|last3=Schliewen|first3=Ulrich K|last4=Abbasi|first4=Keyvan|last5=Sayyadzadeh|first5=Golnaz|volume=848|issue=6 |pages=1267–1293|s2cid=233900590}}{{cite journal|url=https://bioone.org/journals/ichthyology-and-herpetology/volume-110/issue-1/i2020015/DNA-Sequence-Support-for-Reclassification-of-the-Endemic-Southern-Caspian/10.1643/i2020015.short|title=DNA Sequence Support for Reclassification of the Endemic Southern Caspian Sea Deepwater Goby as Neogobius bathybius (Formerly Ponticola; Perciformes: Gobiidae) and Recent Population Expansion of a Continuous Population|year=2022|accessdate=20 January 2022|journal=Ichthyology & Herpetology|doi=10.1643/i2020015|last1=Tajbakhsh|first1=Fatemeh|last2=Rajabi-Maham|first2=Hassan|last3=Abdoli|first3=Asghar|last4=Stepien|first4=Carol A|last5=Kiabi|first5=Bahram H|volume=110|issue=1|pages=13–21|s2cid=245916452}}