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

Oxynoemacheilus marunensis , new species

( Figs. 2–7 )

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.

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 .

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 ) .— 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 ) .

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 for general appearance and 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 ). 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 ). 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 ), 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 ) 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 ).

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 ), 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).

Figures

FIGURE 1. Maximum Likelihood and Bayesian phylogeny reconstructed based on 617 bp of COI 5’ end. The values besides the branches before and after a slash are BI posterior and ML bootstrap probability values, respectively. Black bars right to the specimen labels indicates species delimitation results from PTP followed by the results of the mPTP approach as dashed bars.

FIGURE 2. Oxynoemacheilus marunensis, ZM-CBSU H2509, holotype, 43 mm SL; Iran: Marun River.

FIGURE 3. Oxynoemacheilus marunensis, paratypes; a, ZM-CBSU H2510, 36 mm SL; b, ZM-CBSU H2518, 32 mm SL; c, ZM-CBSU H2519, 27 mm SL; Iran: Marun River.

FIGURE 4. Oxynoemacheilus marunensis, paratypes; a, ZM-CBSU H2510, 36 mm SL; b, ZM-CBSU H2518, 32 mm SL; c, ZM-CBSU H2519, 27 mm SL; Iran: Marun River.

FIGURE 5. Oxynoemacheilus marunensis, paratypes; a, ZM-CBSU H2510, 36 mm SL; b, ZM-CBSU H2518, 32 mm SL; c, ZM-CBSU H2519, 27 mm SL; Iran: Marun River.

FIGURE 6. Oxynoemacheilus marunensis, ZM-CBSU H2509, holotype, 43 mm SL; ventral view of Head, Iran: Marun River.

FIGURE 7. Oxynoemacheilus marunensis, Uncatalogued, about 35 mm SL; Iran: Marun River.

FIGURE 8. Habitat of Oxynoemacheilus marunensis, Iran: Marun River at Kharestan, a tributary of Jarrahi River drainage.

FIGURE 9. Oxynoemacheilus karunensis, uncatalogued, about 50 mm SL; Iran: Dehno spring.