Oxynoemacheilus marunensis, Sayyadzadeh & Esmaeili, 2020

Sayyadzadeh, Golnaz & Esmaeili, Hamid Reza, 2020, Oxynoemacheilus marunensis, a new loach species from the Persian Gulf basin with remarks on O. frenatus (Teleostei: Nemacheilidae), Zootaxa 4885 (2), pp. 189-206: 195-200

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Oxynoemacheilus marunensis

new species

Oxynoemacheilus marunensis   , new species

( Figs. 2–7 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 )

Holotype: ZM-CBSU H2509, 43 mm SL; Iran: Khuzestan prov.: Marun / Maroon River at Kharestan , 30°39’22” N 50°12’31” E; G. Sayyadzadeh, F. Zarei, 11 Dec. 2019. GoogleMaps  

Paratypes: ZM-CBSU H2510, 36, 27–37 mm SL; same as holotype. ZM-CBSU H1998, 9, 30–41 mm SL; Iran: Khuzestan prov.: Marun River at Kharestan , 30°39’35” N 50°12’53” E; H. R. Esmaeili, G. Sayyadzadeh, M. Amini, M. Masoudi, 23 Dec 2013 GoogleMaps   .

Material used in the molecular genetic analysis: ZM-CBSU M1735; Iran: Khuzestan prov.: Maroun River at Emam Reza village , 30°40‘15“ N 50°18‘13“ E (GenBank accession numbers: MW 136427 View Materials ) GoogleMaps   .— ZM-CBSU M1736, M1737, M2812, M2813; Iran: Khuzestan prov.: Marun River at Kharestan , 30°39’35” N 50°12’53” E (GenBank accession numbers: MW 136428, MW 136429, MW 136430, MW 136431) GoogleMaps   .

Diagnosis: Oxynoemacheilus marunensis   belongs to a group of species having two bold, black, round, or comma-shaped black spots on the caudal-fin base. Other species in this group in Iran and the Persian Gulf basin are O. argyrogramma   , O. euphraticus   , O. hanae   , O. karunensis   , and O. kurdistanicus   . Oxynoemacheilus marunensis   is most similar to O. karunensis   in morphological characters except the distance between pelvic and anal-fin origins, which is longer in O. marunensis   [22.3–23.8 vs. 19.5–22.3 (% SL)]. Therefore, the distinguishing characters between O. marunensis   and other species in this group are largely common with O. karunensis   (see Freyhof 2016 and Freyhof & Abdullah 2017). Oxynoemacheilus marunensis   is also distinguished from O. karunensis   by 6% K2P COI sequence divergence.

Oxynoemacheilus marunensis   is distinguished from O. kurdistanicus   , which is widespread in the Tigris River drainage, by having a more slender caudal peduncle [caudal peduncle depth 9.8–11.3 vs. 7–8.6 (% SL)], and from O. euphraticus   by having longer distance between pelvic and anal-fin origins. [22.3–23.8 vs. 20.0–22.5 (% SL)] and shorter snout length [37.6–43.9 vs. 42.6–49.6 (% SL)]. It is also distinguished from those two species, O. kurdistanicus   and O. euphraticus   , which are widespread in the Euphrates and Tigris River drainages, by having many minute dark-brown spots on the back, the flank above the lateral midline, and the caudal peduncle, with a mottled colour pattern in the interspaces of the saddles and large blotches on the back or these interspaces with vermiculated pattern (vs. without spots, vermiculation or mottling, in some individuals with small, vertically-elongated and transversely-positioned blotches), flank usually with a mid-lateral row of short, vertically-elongated blotches usually not confluent with the saddles on the back (vs. regularly or irregularly shaped bars on the flank behind the dorsal-fin base) (see Freyhof 2016).

Oxynoemacheilus marunensis   is distinguished from O. argyrogramma   in the Euphrates and Qweik river drainages, by having a series of vertically elongated blotches or short bars along the lateral midline (vs. marbled or mottled colour pattern on the flank) and dark-brown blotches behind the dorsal-fin base being narrower than interspaces (vs. as wide or wider) (see Freyhof 2016).

It is distinguished from O. hanae   , the other species in this group from the Sirvan River drainage, a left side tributary of the Tigris River in Iraq, by the two black blotches or spots at the caudal-fin base prominent in life and preserved fishes (vs. usually being invisible in life, indistinct and overlaid by a chevron-shaped, dark-brown or black bar), the lower flank with irregularly shaped and set brown blotches forming a continuous pattern with lateral and dorsal flank pattern (vs. flank below the lateral series of blotches without colour pattern except for a longitudinal series of isolated patches of blotches or a row of small dark-brown spots) (see Freyhof & Abdullah 2017).

Among the Iranian congeners studied for molecular characters, O. marunensis   is characterised by two fixed diagnostic nucleotide substitutions in the mtDNA COI barcode region.

Description: See Figures 2–7 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 for general appearance and Table 4 View TABLE 4 for morphometric data.

Medium-sized (27–42 mm SL) and moderately-elongate (13.7–18.3 body depth % SL) species with a slightly pointed head. Head length 24.7–27.4% SL. Body deepest at dorsal-fin origin or about midline between nape and dorsal-fin origin, depth decreasing below dorsal-fin base and decreasing very slowly towards caudal-fin base. No hump at nape. Greatest body width at pectoral-fin base. Section of head roundish, flattened on the ventral surface. Caudal peduncle slender, compressed laterally, 1.4–1.9 (mean 1.7) times longer than deep. Small, usually triangular axillary lobe at base of pelvic fin, fully attached to the body. Pectoral fin equal or slightly longer than the head length and reaching approximately 89–111% of the distance from pectoral-fin origin to pelvic-fin origin. Pelvic-fin origin below first or second branched dorsal-fin ray, fin not reaching vertical of tip of last dorsal-fin ray, reaching to anus. Anal-fin origin below tip of last dorsal-fin ray. Anus about one eye diameter in front of anal-fin origin. Anal fin not reaching caudal-fin base. No dorsal or ventral adipose crest on caudal peduncle. Margin of the dorsal fin straight or slightly concave. Caudal fin deeply emarginated. Largest known specimen 43 mm SL.

Dorsal fin with 9½–10½ branched rays. Anal fin with 5½ branched rays. Caudal fin with 8+7–8+8 branched rays. Pectoral fin with 9–10 and pelvic fin with 6–7 branched rays. Body covered by embedded scales. Lateral line complete, reaching to caudal-fin base. Anterior nostril opening at end of low, pointed, and flap-like tube. Tube of anterior nostril slightly overlapping posterior nostril when folded back. Mouth small, arched ( Fig. 6 View FIGURE 6 ). Lips thick, with poorly marked furrows. A deep median interruption in the lower lip. Median incision in upper lip very small and not visible in some individuals. Processus dentiformis narrow and pointed. No median notch in lower jaw. Inner rostral barbel reaching to base of maxillary barbel or slightly beyond; outer one reaching to vertical of anterior eye margin or slightly in front. Maxillary barbel reaching vertical through middle or posterior part of eye. Male with suborbital grove, absent in female.

Colouration: Head and body with yellowish background colour and brown pattern. Head brown on top to lower margin of eye or with spotted pattern, cheeks and ventral head surface without colour pattern. A dark-brown line between the anterior eye-margin and tip of the snout. Pre-dorsal with one to two, wide dark-brown blotches, equal or slightly wider than interspaces. Large, brown blotch at dorsal fin-origin. Two or three, wide dark-brown blotches on upper caudal peduncle, fused with blotches on flank forming saddles in few individuals. Flank below line between pectoral-fin base and anus without pattern. Flank with 7–10 dark-brown, irregularly shaped, vertically elongated blotches along lateral midline. Flank blotches narrower than interspaces, usually dissociated and often faded in front of dorsal-fin origin, more clearly set on caudal peduncle, rarely joined with saddles on the back or forming bars on the flank. Back, flank above the lateral midline and caudal peduncle with many, minute dark-brown spots, vermiculation, or even a mottled colour pattern at interspaces of saddles and large blotches. One distinct, small, roundish or comma-shaped, black spot at upper and lower posterior extremity of caudal peduncle. Dorsal fin with 2–3 and caudal fin with 3–5 brown bands of small, elongated blotches on fin-rays. Anal-, pelvic- and pectoral fins hyaline, with few dark-brown spots on rays.

Distribution and Habitat: Oxynoemacheilus marunensis   is known from the Marun, a tributary of the Jarrahi River, which flows just east of the Tigris River to the Persian Gulf.

At the sampling site, the river is about 10 m wide, with a substrate consisting of coarse gravel and small boulders, with moderate flow and semi-transparent waters ( Fig. 8 View FIGURE 8 ). Drought, water use, and pollution are the main threats to this fish.

Etymology: Oxynoemacheilus marunensis   is named for the Marun River inhabited by this species. An adjective.

Comparative remarks: Freyhof (2016) considered the oxynoemacheilid population from the Marun River as O. karunensis   along with some populations from the Karun River. He examined three specimens from the Marun River (SMF IR7, 3, 36–44 mm SL) and provided the morphological characters. In a comprehensive molecular study based on the COI barcoding region including all the Iranian and other oxynoemacheilid sequences from the Middle East available in the GenBank ( Fig. 1 View FIGURE 1 ), we found two different clades for populations from the Marun and Karun Rivers with approximately 6% K2P COI sequence divergence whereas they are similar morphologically. In addition to molecular distinguishing characters, O. marunensis   is distinguished from O. karunensis   ( Fig. 9 View FIGURE 9 ) by having a longer distance between pelvic and anal-fin origins. There are also some distingiushing (but overlapping) morphometric characters such as head length; pectoral-fin and pelvic-fin length (see Table 4 View TABLE 4 ).

Oxynoemacheilus marunensis   is distinguished from O. bergianus   , O. brandtii   , O. longipinnis   , O. parvinae   , and O. persa   , five species with forked or deeply emarginate caudal fins, by having two prominent black spots at the caudal-fin base (vs. spots absent). It is distinguished from O. tongiorgii   from the Kor River drainage of Iran by having two prominent black spots at the caudal-fin base (vs. spots absent), a deeply emarginate or forked caudal fin (vs. truncate), and a slenderer caudal peduncle (vs. deep). Oxynoemacheilus marunensis   is distinguished from O. chomanicus   , O. frenatus   , O. kiabii   and O. zagrosensis   , four additional species found in the Tigris River drainage, by having a suborbital groove in males (vs. absent) and a deeply emarginate or forked caudal fin (vs. slightly emarginate or truncate).

Among congeners studied for molecular characters, O. marunensis   is characterised by a K2P nearest neighbor distance of 2% to O. frenatus   ( Table 3 View TABLE 3 ), whereas, they are largely diverged based on morphological characters. Oxynoemacheilus marunensis   is distinguished from O. frenatus   by having a suborbital groove in males (vs. absent), a deeply emarginate or forked caudal fin (vs. slightly emarginate), complete lateral line (vs. incomplete), and having two prominent black spots at the caudal-fin base (vs. absent).


Departamento de Geologia, Universidad de Chile


Museum Wasmann