Cobitis splendens, Erk'akan, Atalay-Ekmekçi & Nalbant, 1998

Freyhof, Jörg, Bayçelebi, Esra & Geiger, Matthias, 2018, Review of the genus Cobitis in the Middle East, with the description of eight new species (Teleostei: Cobitidae), Zootaxa 4535 (1), pp. 1-75 : 33-34

Cobitis splendens Erk'akan, Atalay-Ekmekçi & Nalbant, 1998

( Fig. 25 )

Cobitis splendens Erk'akan, Atalay-Ekmekçi & Nalbant, 1998: 11, fig. 3 (type locality: Turkey: small tributary to Black Sea, about 200 m from sea shore, 16 km east of Akçakoca [41.083, 31.116] and about 30 km south-west of Ereğli).

Material examined. FSJF 2487 , 18 , 46–86 mm SL; Turkey: Düzce prov.: stream Kovukkavla about 20 km east of Akçakoca , 41.149 31.354.—FFR 5552, 25, 52–70 mm SL; Turkey: Düzce prov.: stream Büyük Melen 17 km west of Düzce, 40.763 30.962.

Material used in molecular genetic analysis. FSJF DNA-882 ; Turkey: Düzce prov.: stream Kovukkavla about 20 km east of Akçakoca , 41.149 31.354. (GenBank accession numbers: KJ 553059 , KJ552919 , KP 050522 ) .— FSJF DNA-2911 ; Turkey: Düzce prov.: stream Büyük Melen 17 km west of Düzce, 40.763 30.962. (GenBank accession numbers: MH 795385 , MH 795386 , MH 795387 ) .

Diagnosis. Cobitis splendens is distinguished from all other Cobitis species in the Black Sea basin by a combination of characters, none of them unique. Cobitis splendens is superficially similar to C. satunini but both species are not closely related. Cobitis splendens is distinguished from C. satunini as well as from C. tanaitica , C. elongatoides and C. pontica , three related species from Europe, by the pigmentation in Z3 reduced to about head length in the male (vs. complete, reaching further behind the dorsal-fin base). While this is a very constant character state in C. splendens , in very few male C. satunini , the pigmentation in Z3 is reduced making it impossible to distinguish these individuals from C. splendens .

Cobitis splendens is distinguished from C. saniae by having the base of the single lamina circularis narrowly connected to the adjacent pectoral-fin ray (vs. widely connected). It is further distinguished from many populations of C. saniae by having roundish or irregularly squarish blotches in Z4 anterior to the dorsal-fin origin, rarely fused into one stripe (vs. horizontally elongate, often very densely set and regularly fused into short or longer stripes). Cobitis splendens is distinguished from C. puncticulata from the Marmara Sea basin by blotches in Z2 and Z4 well separated and large (vs. very small, indistinct or confluent), flank un-pigmented below Z4 (vs. pigmented) and pale yellowish or whitish body (vs. brownish). It is distinguished from C. simplicispina by having one lamina circularis in the male (vs. two).

Distribution. Cobitis splendens has been confirmed from its type locality, the stream Kovukkavla about 16 km east of Akçakoca (Black Sea) and the population from the Büyük Melen River [entering Black Sea at 41.073, 30.967] in northern Anatolia might be identified as C. splendens .

Remarks. A reduced pigmentation in Z 3 in the male is very characteristic for C. splendens and was mentioned as a diagnostic character by Erk'akan et al. (1998). This character state is not unique to C. splendens , but individual males with a very much reduced or even no pigmentation in Z3 are found in many other Cobitis species.

During this study, we found a population of Cobitis in the Büyük Melen River (Black Sea basin) which was identified as C. splendens by their COI barcoding sequence. But in this population, the pigmentation in Z3 is not reduced in the males and we found no constant character to distinguish this species from C. satunini . It is distinguished by the small focal zone in the subdorsal scales (vs. large) and the large black spot at the caudal-fin base (vs. small) from C. taenia . If this identification would be correct, C. splendens would be very difficult to identify and might represent a real cryptic species. More materials is needed to better understand its variability in colour pattern. We would not be surprised, if the population in the Büyük Melen River would not consist of pure C. splendens , but it might represent a hybrid complex of C. splendens and C. satunini (or C. taenia ). We found C. taenia geographically adjacent to the Büyük Melen River and C. taenia is well known to form hybrids with other species of the C. taenia species group ( C. elongatoides , C. tanaitica ) (see Janko et al. 2007a + b for an overview). More data are needed to test for a hybrid complex in the Büyük Melen River Cobitis .

Molecular data ( Fig. 1 ) place C. splendens in the C. taenia species group ( C. avicennae , C. elongatoides , C. emrei , C. fahireae , C. faridpaki , C. pontica , C. puncticulata , C. satunini , C. saniae , C. splendens , C. tanaitica , C. taurica and C. vardarensis ). Based on DNA barcoding it is well separated from all other included Cobitis and by a minimum K2P distance of 2.8% to C. emrei . The PTP approach delimited it as own entity.

See below for details to distinguish C. splendens from C. emrei . All species of the C. taenia group except C. puncticulata are very similar in colour pattern and other external characters and represent a cryptic species complex very difficult to distinguish from each other. Molecular data strongly support the view that at all but C. pontica represent own species. It is beyond the aim of this study to re-examine C. pontica , as we have no comparative materials. This species is very similar based on the DNA barcodes we compared to C. elongatoides , but has been distinguished from C. elongatoides by having 90 chromosome arms (vs. 96 in C. elongatoides ), a character not been studied in Anatolian Cobitis (Vasil'eva & Vasiliev 2006).

Erk'akan et al. (1998) reported C. splendens also from the lower Bakır River drainage in the northern Aegean Sea basin, from the upper Simav River drainage in the southern Marmara Sea basin and from the stream Karadere, east of Trabzon on the eastern Black Sea coast. We did not find C. splendens outside of the Kavukkavlağı River and suspect, that Erk'akan et al. (1998) misidentified these Cobitis , maybe based on single males with a reduced pigmentation in Z3. We suspect that these populations should be identified as C. fahireae (Bakır) , C. taenia (Simav) and C. satunini (Trabzon) . However, we strongly encourage dense fieldwork in the area to explore, if C. splendens might have a larger distribution range.

Figures

FIGURE 1. Maximum likelihood estimation of the phylogenetic relationships based on the mitochondrial COI barcode region (TN93 model, discrete Gamma distribution for rate differences with 3 categories +G parameter = 0.3792. Nucleotide positions with less than 95% site coverage were eliminated, resulting in 590 analysed positions. Numbers of major nodes indicate bootstrap values from 1000 pseudoreplicates from the ML, NJ and MP method. A star denotes highest possible support from all three methods. Solid bars right to the specimen labels indicate species delimitation results from PTP followed by the results of the mPTP approach as dashed bars. Except to the outgroups and the branch to the right part of the figure, the tree is drawn to scale with branch lengths depicting number of substitutions per site.

FIGURE 25. Cobitis splendens, FSJF 2487, male, about 49 mm SL; Turkey: stream Kovukkavla.