Oxynoemacheilus kentritensis, Freyhof, Jörg, Kaya, Cüneyt & Turan, Davut, 2017

Freyhof, Jörg, Kaya, Cüneyt & Turan, Davut, 2017, Oxynoemacheilus kentritensis, a new species from the upper Tigris drainage in Turkey with remarks on O. frenatus (Teleostei: Nemacheilidae), Zootaxa 4258 (6), pp. 551-560 : 552-558

Oxynoemacheilus kentritensis , new species

( Figs. 1–3 )

Holotype. FFR 0 1566, 67 mm SL; Turkey: Bitlis prov.: stream Kesan about 1 km south of Güntepe , 38°21'24''N 42°37'39''E; C. Kaya & F. Kaya, 21.09.2010.

Paratypes. FFR 0 1403, 3, 57–68 mm SL; same data as holotype. — FSJF 3645, 3 , 65–79 mm SL; Turkey: Bitlis prov.: stream Horozdere east of Hizan , 38°14'41''N 42°28'45''E; C. Kaya & F. Kaya, 21.09.2010. — FSJF 3646, 2 , 68–70 mm SL; Turkey: Bitlis prov.: stream Oraniz about 1 km east of Dönertaş , 38°18'51''N 42°33'56''E; C. Kaya & F. Kaya, 21.09.2010.

Additional material (non-types). FFR 0 1412, 5, 31–56 mm SL; FSJF 3647, 4 , 39–55 mm SL: Turkey: Şırnak prov.: stream Nerduş at northwest of Toptepe , 37°28'26''N 42°22'49''E. — FSJF 3647, 9 , 47–53 mm SL; Turkey: Şirnak prov.: stream Hezil west of Bağlica , 37°26'28''N 42°44'54''E.

Diagnosis. Oxynoemacheilus kentritensis is distinguished from the other species of Oxynoemacheilus in the Tigris drainage by a combination of characters, none of them unique. Oxynoemacheilus kentritensis belongs to a group of species ( O. chomanicus , O. frenatus , O. hazarensis , O. kiabii , O. zagrosensis , O. gyndes ) which lack a suborbital groove in males (vs. present in O. bergianus , O. euphraticus , O. hanae , O. longipinnis , O. karunensis , O. kurdistanicus and O. parvinae ) and have a slightly emarginate or truncate caudal fin (vs. deeply emarginate or forked in O. bergianus , O. euphraticus , O. hanae , O. longipinnis , O. karunensis , O. kurdistanicus and O. parvinae ).

The new species occurs adjacent to O. frenatus from the upper Tigris and O. chomanicus and O. zagrosensis from the Lesser Zab. It is distinguished from O. frenatus by having distinct bars or vertically elongated blotches on the flank behind the dorsal-fin origin (vs. mottled or marbled pattern), the maxillary barbel reaching beyond the middle of the eye, usually to posterior eye margin (vs. to anterior eye margin or middle of eye), a complete lateral line (vs. incomplete) and the colour pattern on the anterior part of the flank not interrupted by an unpigmented zone along the lateral line (vs. usually interrupted on anterior part of flank).

It is distinguished from O. chomanicus and O. zagrosensis by having longer barbels, the maxillary barbel is reaching beyond the middle of the eye, usually to the posterior eye margin (vs. to anterior eye margin or middle of eye), distinct bars or vertically elongated blotches on the flank behind the dorsal-fin origin (vs. very indistinct, fuzzy bars on caudal peduncle in O. chomanicus , mottled pattern in O. zagrosensis ), a smaller interorbital distance (interorbital distance 1.6–1.9 times in snout length vs. 1.4–1.5) and a deeper caudal peduncle (caudal peduncle depth 1.2–1.3 times in caudal peduncle length vs. 1.3–1.4). Oxynoemacheilus kentritensis is further distinguished from O. zagrosensis by having the posterior process of the bony air-bladder capsule directed posteriorly (vs. directed laterally).

Oxynoemacheilus kentritensis is distinguished from O. kiabii by the presence of a central pore in the supratemporal canal (vs. absence), three pores in the supratemporal canal (vs. 4–6 pores), a shorter head (length 24% SL vs. 26–30), a larger predorsal distance (51–54% SL vs. 48–52) and a complete lateral line (vs. incomplete).

The new species is distinguished from O. hazarensis and O. gyndes by having scales on the back and flank in front of the anus (vs. absent), distinct bars or vertically elongated blotches on the flank behind the dorsal-fin origin (vs. mottled pattern or with stripes) and a complete lateral line (vs. incomplete).

Description. For general appearance see Figs. 1–3 . Morphometric data are provided in Table 1. Large-sized and stout species with a blunt head. Body deepest at dorsal-fin origin or about midline between nape and dorsal-fin origin, depth decreasing below dorsal-fin base, staying almost continuously towards caudal-fin base. No hump at nape, usually a shallow hump in front of dorsal-fin origin. Greatest body width at pectoral-fin base. Section of head roundish, flattened on ventral surface. Cheeks enlarged. Caudal peduncle compressed laterally, 1.2–1.3 times longer than deep. No or a very shallow, usually roundish axillary lobe at base of pelvic fin, fully attached to body. Pelvic-fin origin below first or second branched dorsal-fin ray. Anal-fin origin slightly behind vertical of middle between dorsal and caudal-fin origins. Pectoral fin reaching approximately 60–70% of distance from pectoral-fin origin to pelvic-fin origin. Pelvic fin not reaching vertical of tip of last dorsal-fin ray, reaching to or to a short distance in front of anus. Anus about 0.9–1.4 eye diameter in front of anal-fin origin. Anal fin not reaching caudalfin base. A shallow dorsal and ventral adipose crest on caudal peduncle. Margin of dorsal fin straight or slightly convex. Caudal fin slightly emarginate. Largest known specimen 79 mm SL.

Dorsal fin with 8½ (n=8)–9½ (n=1) branched rays. Anal fin with 5½ (n=9) branched rays. Caudal fin with 10+9 (n=2), 9+9 (n=5) or 9+8 (n=1) branched rays. Pectoral fin with 12–13 and pelvic fin with 6–8 rays. Body covered by embedded scales on flank and back, usually isolated and deeply embedded on back and flank in front of dorsal-fin origin. Nape without scales. Lateral line complete, reaching to caudal-fin base. One or two lateral pore in supratemporal canal, one central pore. Anterior nostril opening at end of a low, pointed and flap-like tube. Posterior tip of anterior nostril overlapping or almost overlapping posterior nostril when folded backwards. No suborbital groove in males. Mouth large, arched ( Fig. 4 ). Lips thin with small furrows. A shallow median interruption in lower lip. Median incision in upper lip absent or a very shallow groove. Processus dentiformis narrow and pointed. A median notch in lower jaw. Barbels long, inner rostral barbel reaching to base of maxillary barbel; outer one reaching to vertical of anterior eye margin or to a point slightly in front of eye margin. Maxillary barbel reaching beyond middle of eye. Male with longer pectoral fin.

Coloration. Body yellowish with coarse, dark-brown marmorate pattern. Head and cheeks brown on top with many minute yellowish spots and vermiculation, cheeks without colour pattern ventrally. A marmorate pattern or narrow, irregularly shaped bars on flank in front of dorsal-fin origin. Flank behind dorsal-fin origin with irregularly shaped and spaced dark-brown bars, dissociated into vertically elongated blotches in most individuals, bars or blotches reaching to ventral midline. Colour pattern on flank not interrupted by lateral line. Back with 2–4, darkbrown saddles, irregularly shaped and set, wider than interspaces, not fused to lateral bars. A large, roundish, dark brown blotch at dorsal fin-origin and below posterior half or dorsal-fin base. Three to five wide dark-brown saddles on upper caudal peduncle, fused with blotches or bars on flank in few individuals. A wide, dark-brown, irregularly shaped bar at caudal-fin base. Dorsal-fin usually with many elongated, dark-brown blotches on rays, forming two bands in some individuals. Caudal-fins with many elongated, dark-brown blotches on rays, forming 2–4 wide, irregularly shaped, dark-brown bands in some individuals. Pectoral fin hyaline, with dark-brown elongated blotches on rays. Anal- and pelvic-fin with few dark-brown spots on rays or 1–2 large, dark-brown blotches.

Distribution. Oxynoemacheilus kentritensis was found in headwaters of the Botan River in Turkey. The Botan is a left side tributary to the upper Tigris joining the Tigris at the village of Çattepe in the Turkish Siirt Province. The Botan River drains the area south of Lake Van. Kaya et al. (2016) also found this species in the Hezil and Nerdus Rivers, which are small rivers entering the Tigris in the border area of Turkey, Iraq and Syria.

Etymology. Oxynoemacheilus kentritensis is named for the Kentrites, the historic name of the Botan River. The Greek historian Xenophon (ca. 431–355 BC) mentions the crossing of the Kentrites in his Anabasis . An adjective.

Remarks. Oxynoemacheilus kentritensis is described from within the distribution area of O. frenatus . Oxynoemacheilus frenatus was described from Mosul in Iraq, an area that can actually not be accessed for safety reasons. As there are only small tributaries flowing to the Tigris in the area of Mosul, the syntypes of O. frenatus must have been collected from these tributaries or from the Tigris itself. We exclude the possibility that all six syntypes might have been washed downriver by a flood. Freyhof et al. (2011) as well as Freyhof & Özuluğ (2017) identified fishes from the upper Tigris in Turkey as O. frenatus and treat O. afrenatus as a synonym. Oxynoemacheilus afrenatus was described from small tributaries to the Tigris around the Turkish city of Diyarbakır . Mosul is about 400 km downstream from Diyarbakır . Diyarbakır is the lowermost point in the Tigris River itself, where we found loaches identified as O. frenatus . But this species is also known from headwaters of the Batman River, which enters the Tigris 80 km downstream of Diyarbakır ( Kaya et al. 2016). Despite its quite ubiquitous habitat choice in the uppermost Tigris, it has not been found in the tributaries of the Tigris downstream of the Batman River as the Botan, the Khabur, the Greater Zab or any of the more southern tributaries of the Tigris. JF did find this species in the Tigris in Diyarbakır and above but failed to find it in the Tigris in Hasankeyf. Kaya et al. (2016) did not find it in the main stream of the Tigris in Turkey and K. Borkenhagen (pers. comm.), who visited the Tigris at the border between Syria and Turkey, did not record this species or any other Oxynoemacheilus .

The question is, had O. frenatus bee continuously distributed in the Tigris downriver from Diyarbakır at least until Mosul, maybe still in the middle of the 19th century? If so, it might have vanished from the Tigris below Diyarbakır, maybe due to pollution, which is considerable in that area. Between Diyarbakır and Mosul, the Botan River and the small rivers Hezil and Nerdus enter the Tigris and are inhabited by O. kentritensis , a species described above. Oxynoemacheilus frenatus might also occur in these rivers, but has not yet been recorded. This is the most likely explanation, as O. frenatus is found in all kinds of streams in the upper Tigris and should therefore inhabit also streams, and not only the main river, downstream. But we can also not exclude that O. frenatus might correspond to a yet undiscovered additional species in the Tigris. The syntypes of O. frenatus cannot be distinguished from the fishes from the upper Tigris by the characters examined in this study (body shape, position of fins, colour pattern, length of lateral line, pattern of scale cover). All syntypes of O. frenatus are diagnosed by having an incomplete lateral line, reaching to a vertical between the pectoral-fin tip and the anal-fin origin and a mottled flank pattern without bars or large, vertically elongated blotches on the caudal peduncle. Even the prominent dark-brown stripe between the snout and the eye ( Fig. 5 ), which inspired Heckel (1843) to apply the name “ frenatus ”, is well visible in the fishes from the upper Tigris. The only difference between the fishes from the upper Tigris and the syntypes might be the colour pattern on the anterior part of the flank, which is interrupted by an unpigmented zone along the lateral line in fishes from Turkey. This unpigmented zone is not visible in the figure of Cobitis frenata by Heckel (1843) ( Fig. 5 ) but visible in the syntypes ( Fig. 6 ). The syntype on the figure by Heckel (1843) ( Fig. 5 ) has a deeper emarginate caudal fin than the fishes from the upper Tigris, in which the caudal fin is almost truncate. Sadly, the caudal fin is damaged in all syntypes of O. frenatus . Therefore, we have no case to treat the fishes from the upper Tigris as a distinct species ( O. afrenatus ). If it might be possible to visit Mosul in the future, it might turn out that there are additional characters which might distinguish O. afrenatus from O. frenatus but until then we keep O. afrenatus as a synonym of O. frenatus .

Gozianpour et al. (2011) as well as Jouladeh-Roudbar et al. (2016) reported O. frenatus from Iran. Following the results of this study, it is possible that O. frenatus occurs in Iranian rivers. The species reported by Gozianpour et al. (2011) and Jouladeh-Roudbar et al. (2016) should be carefully re-examined.

Figures

FIGURE 1. Oxynoemacheilus kentritensis, FFR 0 1566, holotype, 67 mm SL; Turkey: stream Kesan south of Güntepe.

FIGURE 2. Oxynoemacheilus kentritensis, FSJF 3645, paratypes, 79 mm SL, 77 mm SL, 65 mm SL; Turkey: stream Horozdere east of Hizan.

FIGURE 3. Oxynoemacheilus kentritensis, FSJF 3645, paratypes, 79 mm SL, 77 mm SL, 65 mm SL; Turkey: stream Horozdere east of Hizan.

FIGURE 4. Oxynoemacheilus kentritensis, FSJF 3645, paratype, 79 mm SL; Turkey: stream Horozdere east of Hizan. Left maxillary barbel lost in this individual.

FIGURE 5. Oxynoemacheilus frenatus, syntype; Iraq: Tigris River at Mosul. Modified from Heckel (1843).

FIGURE 6. Oxynoemacheilus frenatus, NMW 48552, syntypes, 70 mm SL, 43 mm SL; Iraq: Tigris River at Mosul.