Eidinemacheilus smithi (Greenwood, 1976)

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 471-481

Eidinemacheilus smithi

Common name. Zagros blind loach.

Diagnosis. Distinguished from E. proudlovei by: ● dorsal adipose crest present / ● 7+7 branched caudal rays / ● jaws normally developed / ● head canal system reduced. Size up to 53 mm SL.

Distribution. Iran: Loven spring in Ab‐e Sirum (or Ab‐e Serum) valley near Tang‐e Haft, and springs around Tuveh in Karun drainage. Probably more widespread.

Habitat. Underground waters.

Biology. No data.

Conservation status. LC; as with all subterranean species, its distribution is difficult to understand, and threat levels may be low.

Further reading. Greenwood 1976 (description); Freyhof et al. 2014b (diagnosis).

Reductive evolution in subterranean fishes? In most habitats, the initial observation of most organisms is one of adaptation. Esox are adapted for predation, while Alburnus are adapted for fast swimming. In contrast, subterranean animals are characterised by losses rather than gains. These organisms have much-reduced eyes and pigments and often have no or few scales. This has long fascinated biologists, dating from the time of Lamarck in the late 18 th century. In no other group of biota has Lamarck’s view of use and disuse persisted so long to influence modern biology as in troglobionts. Even Darwin’s explanation of eyeless subterranean animals was a straightforward Lamarckian one and did not involve adaptation and the struggle for existence. In his 1859 work, Darwin wrote, “Their [eyes] loss may be attributed to disuse” (Darwin, 1859). Subsequently, authors proposed neutralistic explanations instead of natural selection to account for the phenomenon of “reductive evolution.” However, this view shifted in the late 20 th century, with troglomorphic features now regarded as highly adaptive to subterranean environments and selection identified as a significant driver of species adaptation to subterranean habitats. Compared to their surface-dwelling counterparts, subterranean species exhibit many constructive biological changes yet display regressive alterations, exemplified by the reduction of eyes. Indeed, the reduction of the eye is an adaptation that conserves energy. There is evidence to suggest that different changes may be connected by pleiotropy. Pleiotropy occurs when a single gene influences multiple phenotypic traits. Consequently, a mutation in a pleiotropic gene may affect some or all traits simultaneously. This contemporary perspective on the distinctive characteristics of troglomorphic species offers a novel and significant opportunity to advance our comprehension of the phenomenon of “reductive” evolution. Further reading. Darwin 1859 (origin of species); Cluver & Pipan 2009 (adaptation in cavefish).

Oxynoemacheilus Mond , where mostly loaches of the genus Paraschistura are This is the most speciose genus of freshwater fishes in the found, and from all the Arabian Peninsula.

Western Palaearctic, with 68 known species, and the largest Mature males are typically smaller than females, in West Asia, with 64 species. It is distributed throughout West with upward-curled pectorals that are longer than those Asia and one species is found in Central Asia ( O. oxianus ). of females. These rays are stiffer, wider, and covered by Three species are found in Europe in Albania and Greece ( O. numerous rows of minute tubercles. Outside the spawning bureschi, O. pindus ), and the northern Caucasus ( O. merga ). season, it can be challenging to distinguish between sexes. Oxynoemacheilus are found virtually everywhere, with one In many species, adult males have a suborbital slit or groove or more species in almost all habitats. They belong to the below the modified lachrymal bone. However, this slit or standard repertoire of nearly every river, stream, and spring. groove is absent in many other species. In some species, a However, this genus is absent in Iran from the Caspian basin, small groove may be present in the posterior outline of the east of the Sefid, and from many of the endorheic basins in lachrymal bone. In other species, the lachrymal bone may southern Iran. It is also absent from the rivers south of the be visible but completely covered by skin.

Oxynoemacheilus bergianus x Oxynoemacheilus euphraticus ; Great Zab drainage, Iraq; 70 mm SL. Individuals in this population have one or the other type of mtDNA indicating hybridisation.

Identifying Oxynoemacheilus species is often challenging, particularly for slender species with a deeply emarginate caudal and a suborbital groove in the male. Such species are usually widely distributed and may exhibit variations in colour patterns within and between populations. Unfortunately, in slender Oxynoemacheilus , several populations without morphological and only small differences in mtDNA had been recognised as separate species, indicating a need for a conceptual framework of boundaries between populations and species. Some of these are not accepted here. Many other species have a stout, massively built body, a slightly emarginate or even truncate caudal, and no suborbital groove in male. These species are often locally endemic. In sympatry, the caudal fin’s shape and the caudal peduncle’s depth can be useful to distinguish between most species. It has been demonstrated that the diversity in body shapes observed in Oxynoemacheilus does not fully correspond to the phylogeny of the different species, as slender and stout species may be closely related. However, nuclear DNA characters may lead to very different phylogenetic patterns if analysed in the future. Some stout species form monophyletic groups in Oxynoemacheilus , but slender species are a highly polyphyletic group. Notably, there are a variety of intermediate morphotypes within this large genus.

We know that the diversity of Oxynoemacheilus presented in this book sometimes not conforms to simplistic, tree-based patterns, as introgressive hybridisation between species has occurred. In several species, isolated populations differ only by small molecular differences without morphological differences, and we do not accept these as species. Of course, we observe the species diversity of Oxynoemacheilus (and other genera) to be streamlined with clusters of minimal COI differences and new species to be described with only ‘invented’ morphological differences. This process has already begun. Here, the concept of “old species” should be applied to avoid false species decriptions. Further reading. Prokofiev 2009 (genera); Freyhof et al. 2011 (diversity); Kottelat 2012 (diversity).

Variability in colour pattern of Oxynoemacheilus cilicicus left from top:lower Seyhan drainage; 50 mm SL;lower Ceyhan drainage; 55 mm SL;river connecting Lakes GÖlbaşı and Azaplı; 53 mm SL;spring ÇÖçelli,Ceyhan drainage; 50 mm SL;right from top:GÖksu delta, 55 mm SL; 55 mm SL; 55 mm SL; 52 mm SL.

Keys to species of Oxynoemacheilus in West Asia

Caspian basin, including Lake Urmia and Namak basins

Oxynoemacheilus bergi is a valid species from the Kura drainage. However, it needs to be better known to be included in the key. It may be a senior synonym of O. bergianus , but this hypothesis awaits confirmation. Oxynoemacheilus merga from the European Caspian basin in Azerbaijan, north of Baku, is excluded from the coverage of this book. Most Oxynoemacheilus species have individuals with a completely or almost complete plain brown colour pattern. The identification of species by colour pattern requires the examination of more than one or a few individuals.

1a - Suborbital groove absent in adult male; flank with 12–17 distinct, regularly shaped, and set bars; caudal slightly emarginate or truncate.

……………… O. cyri

1b - Suborbital groove present in adult male; flank without bars or bars very irregularly shaped, and set; caudal emarginate or furcate.

………………2

2a - Caudal slightly emarginate; flank mottled, with a midlateral series of indistinct blotches, often forming an irregularly shaped midlateral stripe, without distinct bars or large blotches; caudal–peduncle depth 1.3–1.6 times in its length.

……………… O. veyselorum

2b - Caudal deeply emarginate or furcate; flank pattern with distinct bars or large blotches, not forming a midlateral stripe; caudal–peduncle depth 2.0–3.2 times in its length.

………………3

3a - Flank mottled or with large, irregularly shaped, squarish, or vertically elongate blotches, usually as wide or narrower than interspaces; lateral blotches on caudal peduncle usually interrupted in size and/or shape at or above lateral midline; one central or no black, grey or brown blotch or short bar on caudal base, its colour identical to blotches on caudal peduncle.

……………… O. bergianus

3b - Flank with wide, irregularly shaped bars, much wider than interspaces; bars on caudal peduncle not interrupted in size and shape at lateral midline; an upper and a lower bold, black or dark-brown blotch on caudal base, often fused into a bar, its colour distinctly darker than bars on caudal peduncle.

………………4

4a - Caudal emarginate, with many small brown blotches on rays arranged in 3–6, narrow, pale-brown bands; flank usually with irregularly shaped and spaced, dark-brown bars, often split in middle, irregularly shaped and narrower than interspaces, or flank almost plain brown.

……………… O. elsae

4b - Caudal forked, with 1–3 wide and very bold bands; flank with brown bars or vertically elongate blotches, much wider than interspaces, usually regularly set.

……………… O. brandtii

Black and Marmara Sea basins

No external characters are known to distinguish O. banarescui (Devrekani, Filyos) , O. bergianus (Kızılırmak) , O. fatsaensis (Elekçi, Yeşilırmak) , and O. simavicus (Sursuluk, Sakarya, Büyük Melen). These four species are related and can only be distinguished by molecular characters.

1a - Suborbital groove absent in adult males.

……………… O. seyhanensis

1b - Suborbital groove present in adult males.

………………2

5a - Flank with a series of dark-brown midlateral blotches usually fused into a wide, irregularly shaped midlateral stripe, rarely a mottled pattern.

……………… O. angorae

5b - Flank with irregularly set and shaped distinct or confluent blotches and spots forming a marbled or mottled pattern, with large, roundish brown blotches in some individuals.

………………6

6a - Pre-dorsal back usually with 3–4 saddles; flank completely covered by scales.

……………… O. anatolicus

6b - Pre-dorsal back with dark-brown fine mottled pattern, without saddles; few isolated scales on flank in front of dorsal origin.

………………7

7a - Dorsal and ventral adipose crests not elevated from dorsal profile, straight, rarely convex, caudal peduncle highest at end of hypural complex; dorsal adipose crest reaching behind vertical of posterior anal base, absent in some individuals; caudal–peduncle depth 1.5–1.9 times in its length; shortest middle caudal ray is 83–91 % of longest ray of upper caudal lobe; usually flank with irregularly set and shaped, distinct, large blotches forming a marbled pattern.

……………… O. eregliensis

7b - Dorsal and ventral adipose crests elevated from dorsal profile, usually with convex margin, caudal peduncle shallower at end of hypural complex and at maximum height of dorsal adipose crest; dorsal adipose crest reaching to or exceeding vertical of anal base; caudal–peduncle depth 1.2–1.6 times in its length; shortest middle caudal ray is 88–98 % of longest ray of upper caudal lobe; usually flank with irregularly set and shaped confluent small blotches and spots forming a mottled pattern, rarely with larger blotches forming a marbled pattern.

……………… O. axylos

Göksu, Seyhan, Ceyhan, and Orontes rivers, plus coastal drainages within their bounds

1a - Suborbital groove absent in male.

…………………2

1b - Suborbital groove present in male.

…………………6

2a - Caudal slightly emarginate, almost truncate.

………………… O. seyhanensis

2b - Caudal deeply emarginate or forked.

…………………3

3a - Lateral line terminating above anal base or on hypural complex; many isolated and embedded scales on back and flank in front of dorsal origin.

………………… O. ceyhanensis

3b - Lateral line terminating anterior to or below dorsal base, rarely above anus or anal base; no or very few ( O. namiri ) isolated and embedded scales on back and flank in front of dorsal origin.

…………………4

4a - Flank pattern, usually with 6–17, very distinct and regularly shaped and set bars, usually all or most flank-bars, at least behind dorsal base, extending to middorsal saddles and usually meeting contralateral.

………………… O. namiri

4b - Flank pattern mottled or with many, very narrow, irregularly shaped and set, pale-brown bars, usually flank-bars separated from middorsal saddles and not meeting contralaterals.

…………………5

2a - Lateral line incomplete, terminating in front of or above anal base.

………………3

2b - Lateral line complete, terminating behind vertical of anal base or at caudal base.

………………5

3a - Scales present on back and flank in front of anus; central pore in supratemporal canal present.

……………… O. frenatus

3b - Scales absent on back and flank in front of anus; central pore in supratemporal canal absent.

………………4

4a - Lateral line very short, terminating slightly behind pectoral base, not reaching vertical through dorsal origin; a midlateral series of small, horizontally elongated, dark-brown blotches often fused into an irregularly shaped midlateral stripe, one additional stripe above and below midlateral stripe in many individuals.

……………… O. gyndes

4b - Lateral line long, terminating under dorsal base or above anal base; flank with vertically elongated, irregularly shaped blotches or narrow bars.

……………… O. kiabii

5a - Posterior process of bony air-bladder capsule directed posteriorly.

……………… O. zagrosensis

5b - Posterior process of bony air-bladder capsule directed laterally.

………………6

6a - 8+8 branched caudal rays; caudal–peduncle depth 1.0–1.2 times in caudal–peduncle length; interorbital distance 1.1–1.4 times in snout length; colour pattern on flank behind dorsal base mottled or marmorated.

……………… O. zarzianus

6b - 10+9, 9+9, or 9+8 branched caudal rays; caudal–peduncle depth 1.3–1.8 times in caudal–peduncle length; interorbital distance 1.4–1.9 times in snout length; colour pattern on flank behind dorsal base with bars or vertically elongated blotches.

………………7

7a - Very indistinct, fuzzy bars or vertically elongated blotches on caudal peduncle; maxillary barbel reaching to anterior eye margin or middle of eye; interorbital distance 1.4–1.5 times in snout length; caudal–peduncle depth 1.3–1.4 times in caudal–peduncle length.

……………… O. chomanicus

7b - Distinct bars or vertically elongated blotches on flank behind dorsal origin; maxillary barbel reaching beyond middle of eye, usually to posterior eye margin; interorbital distance 1.6–1.9 times in snout length; caudal–peduncle depth 1.2–1.3 times in caudal–peduncle length.

……………… O. kentritensis

8a - Flank naked, only caudal peduncle behind anus with scales; lateral line incomplete; caudal slightly emarginate. ……………… O. hazarensis

8b - Flank completely covered by scales; lateral line complete; caudal deeply emarginate or forked.

………………9

9a - Flank with a distinct series of midlateral blotches, fused to each other or fused into a stripe, isolated patches of blotches, or a row of small dark-brown spots below lateral series of blotches.

……………… O. hanae

9b - Flank mottled or marmorated, lower flank without colour pattern or colour pattern of midlateral flank reaching down to lower flank.

………………10