Carasobarbus saadatii, Jouladeh-Roudbar & Kaya & Vatandoust & Ghanavi, 2024

Carasobarbus saadatii , new species

( Figs. 15 View Fig , 16 View Fig and 17 View Fig ).

Holotype. BIAUBM 8-H , 187.6 mm SL; Iran: Khuzestan prov., Karun River at Gotvand, Persian Gulf Basin , 32.27319, 48.83521 GoogleMaps .

Paratypes. AJRPC 24-P , 4, 122.9– 179.4 mm SL; data same as holotype GoogleMaps .

New material used in molecular genetic analysis. AJRPC-DNA 1860 ( COI: PP 515189, Cyt b: PP 548217), 1861 ( COI: PP 515190, Cyt b: PP 548218), 1862 ( COI: PP 515191, Cyt b: PP 548219), 1863 ( COI: PP 515192, Cyt b: PP 548220) same data as holotype.

Diagnosis. Carasobarbus saadatii sp. n. is distinguished from C. sublimus ( Fig. 18 View Fig ), C. hajhosseini sp. n. and C. kosswigi ( Figs. 19 View Fig , 20 View Fig and 21 View Fig ) by having more scales on lateral line (38–40 vs. 27–37).

The new species can be distinguished from C. luteus ( Fig. 22 View Fig ) by having two pair of barbels (vs. one pair), well-developed median lobe on the lower lip (vs. without median lobe) ( Fig. 23 View Fig ) and more scales on the lateral line (38–40 vs. 25–30).

Description

See Figs. 15 View Fig , 16 View Fig and 17 View Fig for general appearance, Table 7 View Table 7 for morphometric data. Body moderately high, laterally compressed, without nuchal hump. The greatest body depth at point of origin of dorsal fin. Ventral head profile straight, dorsal profile has a slight to pronounced hump near the nostrils. A rounded keel on back in front of dorsal fin. Head short and narrow. Maximum body depth larger than head length. Triangular axillary scale at pelvic-fin base. Pelvic-fin origin below vertical of last unbranched dorsal fin ray. Caudal fin forked. Tip of anal fin, when pressed to body, reaching to hypural complex. Pectoral fin reaching approximately 70–80% distance from pectoral-fin origin to pelvic-fin origin. Pelvic fin not reaching anus. Eye large, but smaller than snout. Mouth inferior, lips thick and fleshy with a well-developed median lob. Two pairs of barbels, rostral reaches to eye and maxillary reaching to the posterior part of eye.

Dorsal fin with 4 (n = 5) unbranched rays and 10½ (n = 5) branched rays, outer margin deeply concave. Anal fin with 3 (n = 5) unbranched and 6½ (n =5) branched rays, outer margin straight. Pectoral fin with 14 (n = 2)–15 (n = 3) rays. Pelvic fin with 8 (5) rays. Lateral line with 38 (n = 1), 39 (n = 2), 40 (n = 2) scales. Scale rows between dorsal-fin origin and lateral line 6 (n = 4)–7 (n = 1). Scale rows between anal-fin origin and lateral line 5 (n = 6).

Coloration

In fresh: Body silverish or cream-white. The back darker than the belly. Upper lateral line scales outlined by dark pigmentation, evident in anterior and fade in posterior. Fins with scattered dark melanophores on rays and membranes. In formalin: Body cream-brown, back darker than belly. No dark pigmentation on anterior and posterior section of scales.

Distribution

The new species distributed in the lower Karun drainage as well as the Great Zab in the Tigris drainage.

Etymology

The species is named in honour of Mohamadali Saadati (Mashhad), acknowledging his significant contributions to the taxonomy of freshwater fishes in Iran. He holds the distinction of being the first Iranian Ichthyologist, conducting a systematic study on the taxonomy and distribution of freshwater fishes in Iran in 1977. To this day, his findings continue to be utilized by several Ichthyologists in Iran.

Habitat

The new species is usually found in the deeper parts of rivers and dam reservoirs, where water flows are slower and there is ample vegetation and cover ( Fig. 24 View Fig ). During the summer months, it disperses into faster-flowing waters as well, likely due to warming water temperatures in their typical habitat. It prefers areas along the banks and around islands where tree roots and aquatic plants are accessible. This allows it to forage while remaining hidden among the vegetation to avoid predators. The species appears to be most abundant in the middle and lower Karun. Luciobarbus barbulus (Heckel, 1847) , Capoeta aculeate (Valenciennes, 1844) , Garra rufa , Chondrostoma regium , Alburnus sellal , Squalius lepidus , Squalius berak and Glyptothorax cous , were found coexisting with the new species.

Discussion

In general, fishes of the genus Carasobarbus are bottom feeders, with morphological characters specialised for such behaviour. This is especially visible in the differences in the development of their mouth structure and lips. Similar developments have been observed in other species of barbs 26, 27. The lips development in Carasobarbus fishes, seems to be a suitable character to separate species 28. In the newly described species, the C. hajhosseini species present the smaller lips (less developed). On the other hand, C. doadrioi species, appear to show the most developed lips among them. Check the ventral head view figure ( Fig. 23 View Fig ) to compare these differences and observe that both latter mentioned species show both ends of the spectrum. Carasobarbus saadatii species also present intermediate lips development similar to C. sublimus for example, but we do not have an acceptable picture to show in this work.

Borkenhagen and Krupp 2 questioned the locality data of the C. sublimus specimen ( CMNFI 1979-0277), as the morphometric and meristic characters (scales in the lateral line, above the lateral line, and around the least circumference of the caudal peduncle; length of the dorsal, pectoral, ventral, and anal fins) of this specimen are within the range of C. sublimus and outside the range of C. kosswigi . This discrepancy is unsurprising because the Karkheh population belongs to C. hajhosseini , and the range of these characters matches the locality mentioned for this voucher specimen. However, they considered C. hajhosseini populations as C. sublimus , and C. doadrioi and C. saadati as C. kosswigi , which caused the range of morphometric characters to expand and positioned C. kosswigi and C. sublimus as paraphyletic in the phylogenetic trees.

In general, nearly all the internal nodes are well resolved in all three datasets ( COI, Cyt b and concatenated datasets) used in molecular phylogenetic analyses. But as expected, the concatenated dataset resulted in the best resolved tree. Both genetic markers used in the concatenated dataset are mitochondrial markers, i.e. they sare the same evolutionary history. This point out that the improvement in the phylogenetic resolution is most probably due to the increment in the phylogenetic signal coded in a longer sequence fragment. This point underlines the importance of including multiple markers to be able to resolve remaining obscure relationships within the genus. On the other hand, being hexaploid, complicates the inclusion of any nuclear marker in any genetic study in near future 29. This point is important as some species of the genus (for example C. luteus ) is widespread in a variety of habitats and therefore will not be surprising to find that different populations does not share the same evolutionary history. This will not be visible without analysing both mitochondrial and nuclear genomic markers.

In the obtained mitochondrial phylogenetic results in the actual study, the only unresolved relationship, is the one between C. doadrioi , C. hajhosseini and C. saadatii . The very short internal branch at this level, when present, shows a potential rapid speciation event, resulting in small number of conserved changes to resolve this relationship. In our results, based on the partial COI gene, two clearly separate clades are formed with both containing sequences identified as C. harterti and C. fritschii . This is most probably the result of misidentification, or also it can be due to introgression events. As we do not have access ourselves to the material used in this case (genetic material was retrieved from GenBank), we cannot further develop on this and corroborate the identity of each of the clades. On the other hand, using other individuals identified as these two species, they do separate well in the results of the cyt b gene dataset, with no further issues. Another possible issue which will need further investigation is the inclusion of samples identified as C. apoensis within the C. luteus clade, with practically no genetic difference with them. This point was also mentioned in Borkenhagen 28. Based on this observation we recommend a systematic revision of both C. apoensis and C. luteus in further studies.