Turcinoemacheilus inexpectatus, Freyhof & Jouladeh-Roudbar, 2024

Freyhof, Jörg & Jouladeh-Roudbar, Arash, 2024, Turcinoemacheilus inexpectatus, a new nemacheilid loach from the Tigris drainage (Teleostei: Nemacheilidae), Zootaxa 5399 (2), pp. 172-180 : 173-179

Turcinoemacheilus inexpectatus , new species

( Figs. 1–5 )

Holotype. ZFMK-ICH 98400 , 49.4 mm SL; Iraq: stream Kuna Massi in Sevanja , a tributary to Lesser Zab, 35.78880, 45.40298.

Paratypes. ZFMK-ICH 98401-98406 (formerly FSJF 3350 ), 6, 41–50 mm SL; same data as holotype . – FSJF 3345 , 7 , 41–51 mm SL; Iraq: stream north-west of Saburawa, a tributary of Tabin, a tributary to Lesser Zab , 35.83324, 45.10445 . – FSJF 3370 , 4 , 40–46 mm SL; Iraq: Suraw near Suraw, a tributary to Lesser Zab , 35.76244, 45.9848 . – FSJF 3358 , 3 , 30–45 mm SL; Iraq: Choman at Qubay Galala , 36.6106, 44.8381 . – FSJF 3653 , 8 , 29–51 mm SL; Iraq: Aw-e Shiler at Kewata , 35.7509, 45.4797 . – FSJF 3661 , 9 , 34–48 mm SL; Iraq: Choman at Alut , 35.9564, 45.6156 . – MZLU L021 /00002-3, 2, 48–55 mm SL; Iran: Kurdistan prov., Choman at Cherush, a tributary of Lesser Zab , 35.95400, 45.69216 . – AJRPC 1758-1759 , 2 , 40–42 mm SL; Iran: Kurdistan prov., Choman at Cherush, a tributary of Lesser Zab , 35.95400, 45.69216 . – AJRPC 1637 , 1 , 43 mm SL; Iran: Kurdistan prov., Lesser Zab at Armardeh , 35.91506, 45.72798 .

Other materials. FSJF 3358 , 1 , 52 mm SL; Iraq: Zalm at Khurmal, a tributary to Sirvan, 35.30656, 45.97081 . – FSJF 3377 , 3 , 41–46 mm SL; Iraq: Chami Rean near Ziraran, a tributary to Greater Zab, 36.94347, 44.19496 .

Additional distribution records. 35.96126, 45.64265; 35.92455, 45.70952; 35.92182, 45.72411 (AJR personal observation).

Diagnosis. Turcinoemacheilus inexpectatus belongs to the T. kosswigi species group ( T. ekmekciae , T. kosswigi , T. minimus , T. saadii ), and is distinguished from members of the T. hafezi group ( T. baheii , T. hafezi ) by the anus situated at, or in front of half-way between the pelvic-fin and anal-fin origins (vs. behind half-way).

It is distinguished from T. saadii by possessing an indistinct or prominent lateral stripe along the lateral midline often overlaid by a row of dark-brown blotches, especially on the flank behind the vertical of dorsal-fin origin (vs. no lateral stripe along lateral midline, 7–9 distinct dark saddles on back often fused with a row of isolated midlateral blotches).

The new species is distinguished from T. kosswigi by having the dark stripe broader than eye diameter along the lateral midline (vs. narrower), and a greater pre-pelvic distance (50–53% SL vs. 47–50). It is further distinguished from T. minimus by possessing 2–4 brown blotches or saddles on the back in front of dorsal-fin origin, often indistinct or absent (vs. distinct brown mottling pattern), deeper caudal peduncle (8–10% SL vs. 6–7), and 5–6 mandibular pores in mandibular canal (vs. 4–5).

Turcinoemacheilus inexpectatus is similar to T. ekmekciae and the only morphometric characters found to distinguish both species is the interorbital distance (31-37% HL in T. inexpectatus vs. 23–31 given by Kaya et al. 2023, and 28–31 in materials examined for this study). As the fish are small and this is a soft character, the standard deviation is high in our materials (2.0) as well those used in Kaya et al. (2023) (2.6). No meristic counts can be used to distinguish both species, and so is the shape and structure of the mouth, which are identical for both species.

The colour pattern in T. inexpectatus is very variable and individuals with the most intensive pattern have a series of midlateral blotches on the flank, fused into a stripe, a series of saddles or blotches on the back, and a marmorate pattern on the upper part of the flank, between the saddles and the midlateral stripe. All individuals of T. inexpectatus have a lateral stripe, only in few specimens, it is interrupted on the flank in front of dorsal-fin origin (vs. stripe absent in T. ekmekciae from Yanarsu, Kaya et al. 2023). In T. inexpectatus there are a series of saddles or blotches on the dorsal surface in front and behind the dorsal-fin origin (vs. a mottled pattern in front of dorsal-fin origin in most individuals in T. ekmekciae , saddles behind dorsal-fin base). Kaya et al. (2023) state that “there are no saddles on the back (in T. ekmekciae ). If present, they are large and brown, connected to lateral blotches along the body”.

In many individuals of T. inexpectatus , the colour pattern on the back and flank is more or less faded up to being almost plain-brown, darker above than below the lateral midlines. Individuals with a wide stripe on a plain background are common in T. inexpectatus (vs. very rare in T. ekmekciae ) as well as individuals with a brown flank below the lateral stripe (vs. absent in T. ekmekciae ). Kaya et al. (2023, uppermost individual Fig. 4 ) show an individual of T. ekmekciae with almost no pattern above the lateral stripe, indistinguishable in its lateral pigmentation patterns from few such individuals of T. inexpectatus . The back of this individual is not shown by Kaya et al. (2023), but they state that T. ekmekciae lacks either saddles or blotches on the back in front of dorsal-origin (vs. present in T. inexpectatus ).

Description. For general appearance see Figures 1–5 ; morphometric data are provided in Table 1 . Small-sized and slender species. Head short, 1.3–2.0 times in body depth at dorsal-fin origin. Pre-dorsal profile slightly convex, pre-pelvic profile straight. Body deepest and widest at mid-point of pre-dorsal distance, depth decreasing towards caudal-fin base. Hump at nape absent, or very shallow. Section of head roundish, flattened on ventral surface, straight or slightly convex in interorbital space, distinctly convex on snout. Snout pointed. Caudal peduncle compressed laterally, 1.5–2.3 times longer than deep. Pelvic axillary lobe present, its tip either attached, or not attached to body. Pelvic fin origin in front of dorsal-fin origin. Pectoral fin reaching 31–46% of distance from pectoral-fin origin to pelvic-fin origin. Pelvic fin reaching beyond anus. Distance from anus to anal-fin origin 1.7–2.5 times in distance from pelvic-fin to anal-fin origins. Anal-fin origin behind vertical of tip of dorsal fin when adpressed to body. Anal fin not reaching to middle of caudal peduncle. No adipose crest on caudal peduncle. Margin of dorsal fin straight or convex. Caudal fin slightly emarginate. Largest known specimen 55 mm SL.

One central and one lateral pores on each side of supratemporal canal, 6–8 pores in anterior infraorbital canal, 3–4 pores in posterior infraorbital canal, 7–9 supraorbital canal and 5–6 pores in mandibular canal. No suborbital flap or groove in male. Dorsal fin with 6½–7½ branched rays. Anal fin with 5½ branched rays. Caudal fin with 8+8 or 8+7 branched rays. Pectoral fin with 8-9 and pelvic fin with 7 branched rays. Body without scales. Lateral line incomplete, with 15–40 pores, often interrupted in posterior part, reaching to midpoint of area between tip of pectoral fin and dorsal fin origin, to midpoint between end of dorsal-fin base and anal-fin origin. Anterior nostril opening at end of a pointed flap-like tube. Posterior nostril oval, posterior tip of anterior nostril not overlapping, or just overlapping posterior nostril when folded backwards. Mouth small, slightly arched. Lips moderately thick. Lower lip medially interrupted. Upper lip without median incision. Processus dentiformis small and blunt. No median notch on lower jaw. Barbels short, inner rostral barbel not reaching base of maxillary rostral barbel; outer one reaching base of maxillary barbel. Maxillary barbel reaching vertical of anterior part of eye. No external sexual dimorphism observed.

Coloration. Yellowish or cream background in life and formalin preserved individuals. Pattern very variable. Individuals with the most intensive pattern with a series of midlateral blotches on flank, fused into a stripe, series of saddles or blotches on back, and a marmorate pattern on upper part of the flank, between the saddles and the midlateral stripe. Lateral blotches behind dorsal and anal-fin origins reach below midlateral stripe in most individuals. In many individuals, pattern on back and flank plain-brown, darker above than below lateral midline, with a wide, indistinct midlateral stripe, darker than background.An irregularly shaped, dark brown or black bar at caudal-fin base. In front of bar, a whitish or yellowish triangle patch on upper and lower caudal peduncle. Cheeks dark olive or dark brown, ventral surface of head white or cream, head above cheeks dark brown. Pectoral-, pelvic fins yellowish, anal fin hyaline, caudal- and dorsal fins olive to dark brown. Caudal fin with small, elongated blotches on rays, forming a mottled pattern of one dark brown vertical row approximately in the middle of fin. Rays of distal and median part of dorsal fin and anterior half of pectoral fin with dark brown pigments.

Distribution. Turcinoemacheilus inexpectatus is known from the Greater Zab in Iraq, the Lesser Zab and the Sirvan in both Iran and Iraq. A detailed distribution map was published by Kaya et al. (2023).

Etymology. The new species is named in - for “not” and expectatus, Latin for “expected” because for 10 years, we had been confident that these populations were T. kosswigi , so their identification by Kaya et al. (2023) came as a great surprise. An adjective.

Habitat. This species is typically found in fast-flowing, clear, and cold-water parts of rivers and streams, often in rapids and riffles containing coarse gravel or rocks. They usually inhabit interspaces in bottom substrate.

Remarks. Finding Turcinoemacheilus kosswigi to be restricted to the upper Greater Zab drainage, and the occurrence of two distinct species of this genus in this tributary of the Tigris ( Kaya et al. 2023), calls for the re-assessment of the conservation status of T. kosswigi i.e., Least Concern (LC) ( Freyhof 2014). As the species assessed as T. kosswigi is here described as T. inexpectatus , the conservation status LC might be correct for this species. Turcinoemacheilus kosswigi , on the other hand, might have a much smaller range and potentially qualify for a threatened category (Vulnerable, Endangered, or Critically Endangered). Detailed collection of data and information on distribution and threats is therefore much encouraged, and could contribute to our understanding of the conservation status of the species.

Naturally, it cannot be fully excluded that T. kosswigi and T. inexpectatus might co-occur or that both have a contact zone with potential for hybridisation. The loach fauna of the Greater Zab continues to be poorly studied, and more details on the distribution of both species is required.

Four species of the T.kosswigi group ( T. kosswigi , T.minimus , T.ekmekciae , T. inexpectatus ) are indistinguishable by meristic counts and poorly distinguished by morphometric characters and colour pattern. Especially T. ekmekciae and T. inexpectatus demonstrate high morphological variability which creates substantial overlap in many characters. This variability can only be detected, if fish from several populations are examined, as there is a considerable variation between populations. A similar case was recently published by Freyhof et al. (2022) on the loaches of the Oxynoemacheilus bergianus group, in which a high variability in colour patterns and morphometric characters was found between different populations within the same monophyletic clade, making it impossible to distinguish different molecular groups. A wide range of K2P distance values was detected for 10 molecular groups in the O. bergianus group, all indistinguishable by external characters. The distances between these molecular clades ranged from 0.6–5.9%. Following a large analysis of K2P distances in morphologically diagnosable species in Oxynoemacheilus , a threshold of 2.9% was applied to delineate populations, distinguishable by molecular characters, from morphologically indistinguishable species.

In the T. kosswigi group, all species ( T. kosswigi , T. minimus , T. ekmekciae , T. inexpectatus ) can be distinguished by morphological characters, even if these differences are small, and all species are separated by a K2P distances of more than 3.0% in their COI barcoding gene.

For the O. bergianus group, it is worth noting that Turan et al. (2023) described two new synonyms of O. simavicus ( O. melenicus and O. sakaryaensis ) to assign names to poorly differentiated molecular groups, disregarding the data presented by Freyhof et al. (2022). Freyhof et al. (2022) already show that characters used later by Turan et al. (2023) to distinguish O. simavicus , O. melenicus , and O. sakaryaensis are very variable, and that they do not allow to distinguish these species.

Figures

FIGURE 1. Turcinoemacheilus inexpectatus, ZFMK-ICH 98400, holotype, 49 mm SL; Iraq: Kuna Massi in Sevanja.

FIGURE 2. Turcinoemacheilus inexpectatus, from top: ZFMK-ICH 98401-98404, paratypes, 49 mm SL, 45 mm SL, 43 mm SL, 43; Iraq: Kuna Massi in Sevanja.

FIGURE 3. Turcinoemacheilus inexpectatus, paratypes; from top: MZLU L021/00003, 48 mm SL; AJRPC 1637, 43 mm SL; AJRPC 1758, 42 mm SL; AJRPC 1759, 40 mm SL; Iran: Choman River.

FIGURE 4. Turcinoemacheilus inexpectatus, from top, Iraq: FSJF 3370, 45 mm SL; Suraw near Suraw; not preserved, about 40 mm SL; Choman at Rashakal; FSJF 3653, 51 mm SL; Aw-e Shiler; FSJF 3345, 47 mm SL; Saburawa; ZFMK-ICH 98401, 49 mm SL; Kuna Massi.

FIGURE 5. Turcinoemacheilus inexpectatus; MZLU L021/00002, 55 mm SL (above); MZLU L021/00003, 48 mm SL (below); Iran: Choman River and Lesser Zab.