Craniological Divergence of Two Genetically Closely Related Caucasian Spined Loaches: Cobitis saniae and C. derzhavini (
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raniological Divergence of Two Genetically Closely Related Caucasian Spined Loaches: Cobitis saniae and C. derzhavini (Cobitidae) E. D. Vasil’evaa, * and V. P. Vasil’evb aZoological
Museum, Moscow State University, Moscow, Russia Severtsov Institute of Ecology and Evolution RAS, Moscow, Russia *e-mail: [email protected]
b
Received February 4, 2020; revised February 6, 2020; accepted February 6, 2020
Abstract—The craniological analysis of Cobitis derzhavini from the Mingechaur Reservoir system and C. saniae from the Malyi Kyzylagach Bay drainage and the Alvady River in Azerbaijan did not reveal any fundamental differences in the general morphology of the neurocranium and cranial bones between these species, as well as from the previously studied C. taenia, C. melanoleuca and C. taurica. However, C. derzhavini showed high level of diversity from other Cobitis species in the proportions of some bones, at first, operculum. The results confirm that C. derzhavini is a separate species characterized by a predominance of opercular bone with weakly excised posterior margin, in contrast to opercular bone with deeply excised posterior margin observed in other craniologically studied species of Cobitis and Sabanejewia. Keywords: craniology, Cobitis saniae, Cobitis derzhavini, divergence DOI: 10.1134/S0032945220040207
INTRODUCTION The spined loaches from the genus Cobitis Linnaeus, 1758 are widespread in the fresh waters of Eurasia. Some of these numerous species are very similar in their appearance and differ mainly by genetic methods (Vasil’eva and Vasil’ev, 1998; Vasil’eva, 2000; Vasil’eva et al., 2016). This situation has long been observed in a group of species morphologically similar to Cobitis satunini Gladkov, 1935, which was described from the Kintrish River in Georgia, but was previously accepted as a synonym or subspecies of C. taenia Linnaeus, 1758 (Berg, 1949; Abdurakhmanov, 1962; Elanidze, 1983). C. faridpaki Mousavi-Sabet, Vasil’eva, Vatandoust et Vasil’ev, 2011 was the first newly described species (from the southeastern Caspian Sea basin) similar to C. satunini with a very specific shape of sub-dorsal scales (elongated with a small eccentric focal zone about 1/6 of the maximum scale diameter or less), the only obvious black spot on the uppermost caudal-fin base, and lamina circularis in males with wide hatchet-like plate (Mousavi-Sabet et al., 2011). The next similar species C. saniae Eagderi, JouladehRoudbar, Jalili, Sayyadzadeh et Esmaeili, 2017 was described from the Guilan province of Iran (Eagderi et al., 2017), but later it was demonstrated as the most common spined loach in Transcaucasia (Freyhof et al., 2018; Vasilyeva et al., 2019). The latter two spe-
cies are closely related in phylogenetic tries based on both mitochondrial DNA and nuclear gene markers and are well separated from C. satunini (Perdices et al., 2018; Freyhof et al., 2018; Vasil’eva et al., 2020). A new genetically distinct species from the phylogenetic lineage C. saniae—C. faridpaki was revealed in the Lower Kura River basin (Va
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