Aphanius arakensis, Teimori, Azad, Esmaeili, Hamid Reza, Gholami, Zeinab, Zarei, Neda & Reichenbacher, Bettina, 2012

Teimori, Azad, Esmaeili, Hamid Reza, Gholami, Zeinab, Zarei, Neda & Reichenbacher, Bettina, 2012, Aphanius arakensis, a new species of tooth-carp (Actinopterygii, Cyprinodontidae) from the endorheic Namak Lake basin in Iran, ZooKeys 215, pp. 55-76 : 59-62

Aphanius arakensis sp. n. Figure 2A, B

Holotype.

Male, 38.5 mm TL, 31.5 mm SL, Iran, Arak, Namak Lake Basin, 34°00'N, 49°50'E, Altitude 1786 m, 26 September 2007, A. Teimori, M. Ebrahimi, A. Gholamifard and A. Gholmhosseini (ZM-CBSU 10999).

Paratypes.

35 males (22.6-32.7 mm SL), 35 females (22.5-34.1 mm SL), same locality as holotype (ZM-CBSU 11000, 11051-11118).

Diagnosis.

The new species is distinguished by the congeners distributed in Iran by the following combination of characters: 10-12 anal fin rays, 28-32 lateral li ne scales, 10-13 caudal peduncle scales, 8-10 gill rakers, 12-19, commonly 11-13, clearly defined flank bars in males, a more prominent pigmentation along the flank added by relatively big blotches in the middle and posterior flank segments in females, a short but high antirostrum of the otolith that has a wide excisura, and a ventral rim with some small, drop-like processes and 19 molecular apomorphies (17 transitions, two transversions) in the cytochrome b gene.

Description of the holotype.

The males of the new species reach approximately 32 mm SL and have 12-19 flank bars, the females are usually larger than the males and reach approximately 34 mm SL.

The morphometric characters are summarized in Table 1. Compared to the other examined Aphanius species, Aphanius arakensis sp. n. shows higher mean values of the minimum body depth, width and length of scales, distances between the pectoral and pelvic fins and the interorbital distance, but significantly lower mean values for the eye diameter and the caudal peduncle length (differences are statistically significant, p <0.05).

The meristic characters are summarized in Table 2. The dorsal fin is characterized by a somewhat curved superior border, and has 11-14 rays; the anal fin shows a round superior border and includes 10-12 rays; the pectoral fin is rounded and consists of 14-18 rays; the pelvic fin is relatively short, positioned just anteriorly to the anal fin and comprises 6-8 rays. The caudal fin is rounded; the caudal peduncle possesses 10-13 scales. The number of lateral line series scales is 27-32. However, the ANOVA analysis reveals that only the numbers of lateral line series scales and caudal peduncle scales (in males and females), as well as the numbers of flank bars (in males), significantly differ from the values obtained for the other examined species. Moreover, there is a significant correlation between SL and numbers of flank bars (Pearson Correlation r = 0.455, p <0.05*).

The otolith is rounded-trapezoid and characterized by a very wide excisura, a medium-sized and pointed rostrum, and a quite short antirostrum. The ventral and dorsal rims are slightly curved; the ventral rim may bear small irregular processes; the dorsal rim may show a fine crenulation; the posterior rim is steep (Fig. 3W-Aa).

The flank bars in males (Fig. 2a) are narrow and the interspaces are broader than the bars. The first bar is located above the operculum, while the posteriormost bar is located at the base of the caudal fin; the interspaces are wider at the caudal peduncle than in the anterior body part. Dorsally, the head is gray and the body is dark due to a strong melanophore pigmentation. The ventral body portion does not usually sho w any dark pigmentation. The dorsal, anal and caudal fins have white margins; the first rays of the dorsal fin are dark. The pectoral fins are somewhat yellowish. The pelvic fin is yellowish. Most specimens are characterized by dark blotches at the base of the dorsal and anal fins.

Females (Fig. 2b) are characterized by a grayish pigmentation of the back. The lateral flanks of the body are covered by dark pigmentations; series of blotches are present from the middle of the body to the caudal peduncle. The ventral part of the head and belly are light. The chin and sides of the head are speckled with melanophores. Below the eye there is a line of relatively dark melanophores. All fins are white.

Comparative remarks.

Aphanius arakensis is close to the other Iranian Aphanius species in having a similar external morphology but differs by a high number of flank bars, 12-19, commonly, 15-16 (vs. 8-13, commonly, 11-12 in Aphanius vladykovi ; 10-16, commonly, 12-13, in Aphanius farsicus ; 8-15, commonly, 11-13 in Aphanius sophiae ; 9-13, commonly, 10-11 in Aphanius isfahanensis and 11-17, commonly, 13-14 in Aphanius pluristriatus ), otolith morphology and by having 19 molecular apomorphies in the cytochrome b gene. The new species (both males and females) can be further distinguished from Aphanius vladykovi by 28-32 lateral line series scales (vs. 33-43), and by less relative width and length of scales, 3.3-4.6 and 3.3-4.5% SL, respectively (vs. 1.9-3.2 and 1.9-3.3, respectively). It differs from Aphanius sophiae in having 10-13 caudal peduncle scales (vs. 8-11), less gill rakers numbers, 8-10 (vs. 9-12), and by a greater interorbital distance, 0.9-1.2% head width (vs. 0.8-1.1). The new species differs from Aphanius farsicus in having 6-8 pelvic fin rays (vs. 6-7), and by a smaller eye diameter, 10.7-14.8% preanal distance (vs. 10.6-17.0). It can be distinguished from Aphanius isfahanensis by 8-10 gill rakers (vs. 10-13), and by a shorter caudal peduncle, 29.0-34.8% preanal distance (vs. 27.4-38.4). It differs from Aphanius pluristriatus in having 10-13 caudal peduncle scales (vs. 8-11), 28-32 lateral line series scales (vs. 24-29) and by a smaller eye diameter, 10.7-14.8% preanal distance (vs. 12.4-18.1).

Distribution and habitat.

The species has been collected from a small natural shallow pond (Fig. 4) in the Namak Lake basin, 5 km south east of the city of Arak (Fig. 1). This pond, which is about 6 x 4 m in size, is fed by the drainage of a nearby natural spring. During sampling, the water body was almost stagnant and water temperature was 23°C. There was no vegetation in the pond, but the surrounding area was covered with Juncus sp. and Typha sp. The bottom of the pond was generally muddy with small gravels. The habitat was in a bad condition due to anthropogenic pollution. Around collection time, the new Aphanius species was the only fish observed living in the pond. In addition, the new species can be found in several springs located in close proximity to the type locality (Fig. 5).

Etymology.

The species name refers to the city of Arak, which is located in close proximity to the type locality. Arak is the capital of the Markazi province in north-central Iran. A proposed common name is Arak tooth-carp. Farsi name is Kapour-e-dandandar-e-Arak.

Phylogenetic relationships

The parameters for the maximum likelihood are ln(L) = -85.11.91237, gamma shape parameter of 1.000, proportion of invariant sites of 0.097 and parsimony = 1556. The maximum parsimony phylogeny has a CI of 0.462 and RI of 0.747. The initial tree for the maximum likelihood analysis was obtained by the BIONJ algorithm. The trees of the maximum likelihood and maximum parsimony phylogenies (Fig. 6) are not significantly different in topology (Templeton test, P> 0.05). They support the hypothesis that Aphanius arakensis diverged from the clade leading to the present-day Aphanius sophiae and is sister to this species. Moreover, Aphanius farsicus is sister to Aphanius arakensis + Aphanius sophiae ; sister to these taxa is Aphanius isfahanensis , and sister to all previously mentioned species is Aphanius vladykovi . The same topology (Templeton test, P> 0.05) is observed for the tree of the Neighbor Joining (NJ) distance-based analysis. Table 4 shows the estimation of evolutionary divergence between the sequences of the new species and its relatives.