Gobio insuyanus, Ladiges, 1960

Gobio insuyanus View in CoL View Figure

Common name. Cihanbeyli gudgeon.

Diagnosis. Distinguished from other species of Gobio in Anatolia by: ○ 39–45 total lateral-line scales / ○ head length 25–30 % SL / ○ chest completely scaled, scales extending forward to or almost to isthmus / ○ 8–10 scales between posterior extremity of pelvic base and anus / ○ scales on belly approximately equal to pupil diameter / ○ 8–9 scale rows between dorsal origin and lateral line / ○ predorsal length 48–52 % SL. Size up to 135 mm SL.

Distribution View Figure . Türkiye: Insuyu (Cihanbeyli) drainage in western Lake Tuz basin.

Habitat. Springs and spring-associated streams with slow to moderately fast-flowing waters on sandy and gravelly bottoms, often among very dense aquatic vegetation.

Biology. Lives up to 7 years. Omnivorous, feeding mainly on detritus and macroinvertebrates such as gammarids and dipteran larvae.

Conservation status CR; restricted to one site and in serious decline due to desiccations of its habitat.

Further reading. Ladiges 1960 (description); Naseka et al. 2006 (identification); Johnson et al. 2025 (biology) Gudgeons and the history of Lake Tuz basin. The present-day Lake Tuz ( Türkiye) is an inhospitable environment for freshwater species. It is the second-largest lake in Türkiye, with a surface area of 1,665 km ². It is also one of the largest hypersaline lakes in the world. During the last glacial pluvial period, Central Anatolia received significantly more rainfall than it does today, and Lake Tuz was a vast freshwater lake. Two high lake-level stages have been identified, dated approximately 20,000 –17,000 years ago during the glacial maximum and again 13,000 years ago, during the Younger Dryas period. At the high lake stages, the water level rose by more than 15 m above the present lake level. This resulted in the lake area spreading widely to the southern edge of the basin, encompassing the cities of Ereğli and Karaman. In the Holocene, the lake level fell, and extensive lake terraces were formed in the southeast part of the basin. In the wetter periods, Lake Tuz was most likely inhabited by freshwater fishes. It can be speculated that these were the species surviving today within its former catchment area, including Cobitis turcica , Oxynoemacheilus eregliensis , O. axylos , Seminemacheilus ekmekciae , Anatolichthys anatoliae , Garra kemali , Pseudophoxinus , and Gobio species. The large Lake Tuz basin has dried out since and become so hypersaline that even exceptional floods cannot

support freshwater fish’s survival in its waters. Fishes survived this postglacial desiccation event in the streams and springs that once flowed to Lake Tuz. There, they became isolated, and some evolved into the currently recognised species. Furthermore, the system has been employed as a model for the evolution of new species in allopatry in populations that are small, isolated, and exhibit stream-specific characters. This is particularly evident in the genus Gobio . It is obvious that low-resolution molecular markers, such as COI or Cytochrome b, are not suitable for differentiating the recently separated species within the Lake Tuz gudgeon complex, which includes G. gymnostethus , G. hettitorum , G. insuyanus , and G. microlepidotus . Further reading. Kashima 2010 (Lake levels of Lake Tuz).