Oxynoemacheilus axylos, Yoğurtçuoğlu & Kaya & Freyhof, 2022

Yoğurtçuoğlu, Baran, Kaya, Cüneyt & Freyhof, Jörg, 2022, Revision of the Oxynoemacheilus angorae group with the description of two new species (Teleostei: Nemacheilidae), Zootaxa 5133 (4), pp. 451-485 : 472-477

Oxynoemacheilus axylos , new species

( Figs. 14–16 )

Holotype. FFR 15616, 66 mm SL; Turkey: Konya prov.: spring at Baltalı in 30 km east of Haymana , 39.2393 32.7501.

Paratypes. FFR 15602, 30, 39–73 mm SL ; FFR 15620, 3, 62–67 mm SL; same data as holotype .

Additional material. FFR 15601, 3, 51–79 mm SL; Turkey: Aksaray prov.: Melendiz River under the bridge on the road from Gülağaç to Kızılkaya, 38.3549 34.2296. —FFR 15603, 2 , 58–66 mm SL; Turkey: Aksaray prov.: a tributary of Melendiz River at Gülağaç, 38.3910 34.3527. —FFR 15604, 12 , 28–64 mm SL; Turkey: Konya prov.: spring Pınarbaşı at İnsuyu, 38.7375 32.7041. — FSJF 1861 , 10 , 41–52 mm SL; Turkey: Konya prov.: İnsuyu stream about 1 km downstream of Pınarbaşı, 38.7206 32.7249. — FSJF 2530 , 24 , 54–80 mm SL; Turkey: Konya prov.: stream north of Sarı Yayla, draining to former Lake Samsam , 39.1189 32.7592. — FSJF 2609 , 6 , 43–67 mm SL; Turkey: Aksaray prov.: stream at Gölyazı, at road from Eskil to Cihanbeyli, 38.5526 33.2009. — FSJF 3208 , 29 , 49–83 mm SL; Turkey: Aksaray prov.: Melendiz River at Ihlara, 38.2359 34.3119 .

New material used in molecular genetic analysis. FSJF-DNA 1078 ; Turkey: Konya prov.: stream north of Sarı Yayla, draining to former Lake Samsam , 39.1189 32.7592 (GenBank accession numbers: ON123706 , ON123707 , ON123708 ) .

Additional distribution records. Kelleci et al. 2021: 38.1041 34.2746, 38.1156 34.1239, 38.1217 34.2310, 38.1502 34.1841, 38.1601 34.1718, 38.1716 34.0306, 38.1934 34.1426, 38.2152 34.1309, 38.4924 34.0729; unpublished records: 38.3263 34.2408, 38.4775 34.3569, 38.4800 34.3600, 38.6725 32.8481.

Diagnosis. Oxynoemacheilus axylos is distinguished from other species of O. angorae group by a combination of characters, none unique. It is distinguished from O. eregliensis by possessing of an elevated and prominent dorsal and ventral adipose crest (vs. crests absent or very shallow), with a convex margin in most individuals (vs. margin of adipose crest straight), the dorsal crest reaching or exceeding the vertical of the anal-fin base (vs. dorsal adipose crest reaching behind vertical of posterior anal-fin base). Oxynoemacheilus axylos is further distinguished from O. eregliensis by possessing an almost truncate or very slightly emarginate caudal-fin (shortest middle caudal-fin ray 88–98% of the longest ray of the upper caudal-fin lobe vs. 83–91%), a deep caudal peduncle (caudal peduncle depth 1.2–1.6 times in its length vs. 1.5–1.9), and the flank usually with irregularly set and shaped, confluent, small blotches and spots forming a mottled pattern; rarely with larger blotches forming a marbled pattern (vs. flank usually with irregularly set and shaped, distinct, large blotches forming a marbled pattern).

The new species is distinguished from O. angorae by having a mottled flank or a pattern of irregularly shaped large roundish, irregular blotches (vs. a series of dark-brown midlateral blotches usually fused into a wide, irregularly shaped midlateral stripe, rarely a mottled pattern), no depigmented stripe along the anterior part of the lateral line (vs. usually present), a shorter caudal peduncle (caudal peduncle length 14–18% SL vs. 17–21%), and the dorsal part of the head and the upper part of the cheek with a vermiculate or marbled pattern (vs. mottled). Oxynoemacheilus axylos is distinguished from O. anatolicus by lacking saddles on the pre-dorsal back, usually having a dark-brown, fine mottled pattern (vs. usually 3–4 saddles), and few isolated scales on the flank in front of the dorsal-fin origin (vs. flank completely covered by densely set scales).

Oxynoemacheilus axylos is distinguished from O. germencicus , O. isauricus , O. mediterraneus , O. nasreddini , and O. theophilii by having a very slightly emarginate or almost truncate caudal fin (middle caudal-fin ray 88–98% of length of the longest caudal-fin ray vs. emarginate or deeply emarginate, 72–82 in O. germencicus , 71–85 in O. isauricus , 65–76 in O. mediterraneus , 76–91 in O. nasreddini , 71–80 in O. theophilii ). The new species is further differentiated from O. germencicus and O. isauricus by having an elevated dorsal adipose crest (vs. shallow or absent), often with a convex margin (vs. margin straight), reaching or exceeding the vertical of the anal-fin base (vs. reaching behind vertical of the posterior anal-fin base), a stouter caudal peduncle (caudal peduncle depth 1.2–1.6 times in its length vs. 1.5–1.8 in O. germencicus ; 2.2–2.6 in O. isauricus ), and no scales on the belly (vs. few scales between pelvic fins in O. germencicus ). Oxynoemacheilus axylos is further distinguished by having a mottled flank, marbled or with large roundish irregular blotches in some individuals (vs. usually a series of vertically elongated blotches along the lateral midline in O. mediterraneus ), a stouter caudal peduncle (caudal peduncle depth 1.2–1.6 times in its length vs. 1.5–2.1 in O. nasreddini ), no scales on the belly (vs. with few scales between pelvic fins in O. nasreddini and O. theophilii ). A slowly decreasing body depth between the dorsal-fin base and the anterior end of the adipose crest (vs. not decreasing, i.e. the ratio of body depth at dorsal fin base to the body depth at caudal fin base is equal or almost equal to 1 in O. theophilii ).

Description. See Figures 14–16 for general appearance and Table 3 for morphometric data. Medium sized and moderately slender species. Head long, body depth at dorsal-fin origin 1.1–1.4 times in head length. Body deepest at dorsal-fin origin and widest at pectoral fin base. A prominent hump at nape in many individuals. Body depth slowly decreasing between anterior dorsal-fin bases, until anterior anal-fin base. Section of head roundish, flattened on ventral surface, slightly convex or straight in interorbital space and on snout. Snout roundish. Caudal peduncle compressed, 1.2–1.6 (mean 1.4) times longer than deep. A rudimentary pelvic axillary lobe, attached to flank, absent in some individuals. Pelvic-fin origin below first or second branched dorsal-fin ray. Anal-fin origin posterior to vertical of midline between dorsal and caudal-fin origins. Pectoral fin reaching to approximately 60–70% of distance from pectoral-fin origin to pelvic-fin origin in female and 65–80% in male. Pelvic fin usually reaching anus, not reaching to genital papillae; reaching vertical of tip of last dorsal-fin ray. Anus about 20–50% of an eye diameter anterior to anal-fin origin. Anal fin not reaching caudal-fin base. An elevated and prominent dorsal and ventral adipose crest on caudal peduncle, with a convex margin in most individuals, dorsal crest reaching or exceeding vertical of anal-fin base. Largest known individual 83 mm SL.

Dorsal fin with 7½ (15) branched rays, outer margin straight or slightly convex. Anal fin with 5½ (15) branched rays, outer margin straight or slightly convex. Pectoral fin with 9 (9) and 10 (6) branched rays, outer margin convex. Pelvic fin with 5 (13) and 6 (2) branched rays, outer margin straight or slightly convex. Caudal fin slightly emarginate, almost truncate in some individuals, shortest middle caudal-fin ray 88–98% of longest ray of upper caudal-fin lobe. Caudal fin with 9+8 branched rays. Flank and back covered by few embedded scales, scales fewer and isolated on predorsal flank than on postdorsal. Belly and chest without scales. Lateral line usually incomplete, with 48–82 pores, terminating on vertical to anal-fin base or on anterior hypural complex, complete in some individuals reaching posterior hypural complex. Anterior nostril opening at end of a low, ovoid, flap-like tube. Posterior tip of anterior nostril overlapping or slightly exceeding posterior nostril when folded backwards. One central pore and one or two lateral pores on each side of supratemporal head canal, 8–10 pores in infraorbital canal, 7–8 pores in supraorbital canal, and 10–12 pores in preoperculo-mandibular canal. One out of 20 individuals with two central pores. A deep suborbital flap in male, in which a needle can be inserted below lachrymal bone. Nuptial tubercles on flap in spring. Mouth small, arched. Lips with furrows. Lower lip thicker than upper lip. A median interruption in lower lip. Upper lip with shallow median incision. Processus dentiformis narrow and rounded. Lower jaw rounded, without median notch. Barbels moderately long; inner rostral barbel reaching or slightly exceeding base of maxillary barbel, outer rostral barbel reaching to or slightly behind the anterior eye margin. Maxillary barbel reaching to, or slightly exceeding vertical through posterior eye-margin.

Coloration. Background colour pale brown, beige, golden or yellowish in live, pale brown or yellowish in preserved individuals.Flank pattern dark brown, often only slightly darker than background, absent in few individuals. Pattern highly variable. Many individuals with coarse or fine mottled, marbled or vermiculated pattern formed by irregularly shaped and set, partly confluent blotches. Some individuals with irregularly set, large, roundish blotches on flank. Blotches usually smaller on upper part of flank and at predorsal back, darker and more often confluent along mid-lateral flank, more isolated from each other on lower part of flank in many individuals. Belly without pattern, or rarely with few small dots, ventral caudal peduncle usually covered with small dots. Back usually with a dark-brown, fine mottled pattern, or without pattern. In some individuals, post-dorsal back with 4 or 5 saddles. An irregularly shaped, dark-brown bar at caudal-fin base present, absent or dissociated into two dark-brown blotches in some individuals. Cheeks and head above cheeks with small brown spots sometimes fused into a mottled or vermiculated pattern, rarely without pattern. Ventral surface of head and belly pale yellow. All fins with many elongated blotches on rays, forming 2–4 dark vertical rows in dorsal fin, and 3–7 vertical rows in caudal fins, 1–2 in anal and pelvic fins. Blotches not forming rows in pectoral fins. Anal and pelvic fins usually with blotches.

Distribution. Oxynoemacheilus axylos is known from springs, rivers and streams in the endorheic Lake Tuz basin including Cihanbeyli, Gölyazı, Melendiz, and Samsam drainages in Central Anatolia.

Etymology. The species is named for the ancient name Axylos, a region in Lycaonia, south of Lake Tatta (ancient Lake Tuz), covering the species present day distribution range. A noun in apposition.

Remarks. Several studies have demonstrated that two large paleolakes, namely Paleo-Tuz and Paleo-Konya, have expanded and shrunk many times in the northern and southern subbasins after their formation during the late Pleistocene and early Holocene ( Erol 1986; Kuzucuoglu 2004). Today, Ereğli and Lake Tuz drainages represent two separate sub-basins, being the remnants of these two ancestor paleo-lakes, which almost disappeared about 6,000 – 20,000 years BP ( Bayari et al. 2009). We speculate that O. eregliensis and O. axylos might had been isolated within these sub-basins and evolved into two allopatric species. Lake Paleo-Konya might have had contact to Lake Beyşehir as there are several species that are shared between Lake Beyşehir and Paleo-Konya Lake (today Karaman / Ereğli) basins but absent from the Paleo-Tuz basin, namely Garra kemali , Squalius anatolicus , Pseudophoxinus anatolicus , P. battalgilae , Cobitis bilseli , and Seminemacheilus tubae . These are replaced by relatives Squalius cappadocicus , Pseudophoxinus crassus , P. iconii , Cobitis turcica , and Seminemacheilus ekmekciae in Lake Paleo-Tuz basin. Alternatively, these species might have moved between Karaman /Ereğli and Lake Beyşehir basin within the last century through an irrigation canal (Çarşamba) between Lake Beyşehir/Suğla and Karaman, which was constructed in the early 1900s ( Fig. 17 ). The comparatively low molecular distance between O. eregliensis and O. axylos should be a repeated pattern between some congeneric species in Lake Beyşehir/Ereğli and in Lake Tuz basin. The best-known examples with such a low molecular distance and clear morphological differences from this range are between Pseudophoxinus crassus (Lake Tuz/Melendiz) and P. anatolicus (Lake Beyşehir/Ereğli); P. iconii (Lake Tuz) and P. battalgilae (Lake Beyşehir/Ereğli); Squalius cappadocicus (Melendiz) and Squalius anatolicus (Lake Beyşehir/Ereğli); Cobitis turcica (Lake Tuz/Melendiz) and C. battalgilae (Lake Beyşehir/Ereğli); Gobio insuyanus (Insuyu) , G. gymnostethus (Melendiz) and G. microlepidotus (Lake Beyşehir/Ereğli). It is a widespread phenomenon that young species would have been closely related with no or low COI distance between them. However, as formulated by Yeates et al. (2011), and followed and properly applied by several recent studies ( Yoğurtçuoğlu & Freyhof 2018; Fagundes et al. 2020; Malabarba et al. 2021; Yoğurtçuoğlu et al. 2021a), if consistent morphological differences also imply a distinct evolutionary path, then the entities are treated as separate species. This is well in agreement with the approach proposed by Freyhof et al. (2022) discussing thresholds in COI sequence distance in Oxynoemacheilus . Here, we follow this approach in recognising O. axylos as a distinct species, which is likely mirrored also by the other freshwater fish species in Central Anatolia, as exemplified above.

Figures

FIGURE 14. Oxynoemacheilus axylos, FFR 15616, holotype, 66 mm SL; spring at Baltalı.

FIGURE 15. Oxynoemacheilus axylos, FFR 15602, paratypes, from top, 64 mm SL; 65 mm SL; 61 mm SL; spring at Baltalı.

FIGURE 16. Oxynoemacheilus axylos, from top: FSJF Melendiz River; 77 mm SL; not preserved, about 70 mm SL; Melendiz River, 38.3263 34.2408; FSJF 3208, 83 mm SL; Melendiz River; FSJF 2609, 60 mm SL; stream Gölyazi; FSJF 2530, 73 mm SL; stream north of Sarı Yayla.

FIGURE 17. The Lake District in south-central Anatolia with maximum limits of pluvial lakes in Pleistocene. Modified from Erol (1984).