Psilorhynchus rahmani
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| Conway & Mayden , 2008 |
Psilorhynchus rahmani is a spindle loach ( Psilorhynchus ) from the suborder carp fish-like (Cyprinoidei), which is only known from a mountain stream near the University of Chittagong and from a tributary of the Sangu in the Bandarban district in southeast Bangladesh .
description
Psilorhynchus rahmani is a small species of the genus Psilorhynchus with a standard length of up to 37.4 millimeters for adults . The body is elongated with a strongly flattened belly and a large head, which are typical for bottom-dwelling fish. The eyes are strikingly large, the mouth small, underneath and the tip of the snout is rounded. There are two fontanelles on the skull, the front one of which is smaller. The basic color of specimens preserved in ethanol is a light creamy white. On the flanks there is a longitudinal row of large dark brown spots that can merge into an irregular longitudinal stripe. The lively color is a creamy white basic color with a series of round or nearly square dark spots or an irregular dark vertical stripe on the flanks.
In the lateral row there are 29 to 32 large scales, in the transverse row 6½ and around the caudal stalk 10 scales. The high dorsal fin ends in a point, its rear edge is straight to slightly concave. The anal fin is short and does not extend to the base of the caudal fin, it has a straight or slightly convex rear edge. The caudal fin is divided into two lobes, the upper one being slightly longer than the lower one.
- Fin formula
Dorsal III / 9, anal III / 5–6, ventral II / 6–7, pectoral V – VI / 9–10.
Psilorhynchus rahmani can be distinguished from the very similar species Psilorhynchus amphicephalus , Psilorhynchus balitora and Psilorhynchus nepalensis by their pattern , namely the lack of two to three dark, irregular vertical stripes on the caudal fin and the dark spot at the distal end of the dorsal fin. Compared to Psilorhynchus amphicephalus , P. rahmani has a shorter head relative to the standard length, a flat body and a smaller number of side-line scales. Compared to Psilorhynchus balitora and Psilorhynchus nepalensis , the head is larger and there are more fin rays in the lower lobe of the caudal fin. Psilorhynchus sucatio has fewer split rays in the dorsal fin and in all other species the posterior fontanelles on the skull are significantly larger.
Distribution and habitats
 
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Localities of Psilorhynchus rahmani in Bangladesh |
The type locality is a small mountain stream ( 22 ° 28 '25.8 " N , 91 ° 46' 59.3" O ) west of the University of Chittagong to the north of the city of Chittagong , Chittagong District , Division Chittagong , in southeastern Bangladesh . It is a rapidly flowing brook about 25 meters above sea level, at the foot of a small waterfall, two to five meters wide and with an irregular bottom made up of rocks, pebbles, sand and mud. Meanwhile, another location has become known. It is located in the Bandarban district in the Sangu River ( 22 ° 10 ′ 58 ″ N , 92 ° 13 ′ 54 ″ E ) at an altitude of about 18 meters above sea level.
The habitats of Psilorhynchus rahmani are rapidly flowing, turbulent rivers with oxygen-rich water over sandy, loamy and stony ground. There the species feeds on zooplankton and phytoplankton . Psilorhynchus rahmani lives sympathetically with zebrafish ( Danio rerio ), Esomus danricus , Garra sp. , Pracht barbs ( pethia conchonius ) Acanthocobitis botia , Schistura sp. , Panchax ( Aplocheilus panchax ), half- beak ( Dermogenys sp. ), Badis chittagongis and giant spiny eel ( Mastacembelus armatus ).
Hazard and protection
Psilorhynchus rahmani was added to the Bangladesh Red List of Endangered Species in 2015 . Although only one locality was known, it was assumed that the species has a wide distribution, at least in Bangladesh. Therefore, a classification was dispensed with and reference was made to the insufficient data basis (category DD - Data Deficient ). The species was also listed in the IUCN's global red list in 2010 in the Data Deficient category.
Systematics and taxonomy
Psilorhynchus rahmani is one of about thirty species of the genus spindle loach (Psilorhynchus) McClelland , 1839 in the monotypic family Psilorhynchidae. This forms with about a dozen other families with more than 2300 species the suborder carp fish-like (Cyprinoidei) in the order carp-like (Cypriniformes).
After a phylogenetic examination, the spindle loaches were divided into three groups in 2011 , with Psilorhynchus rahmani belonging to the Psilorhynchus balitora group. The assignments were based primarily on osteological examinations. On the basis of molecular genetic analyzes, three groups were again confirmed in 2014, but they have a different composition. The Psilorhynchus balitora group comprises about half of the species, including Psilorhynchus rahmani .
The first description of Psilorhynchus rahmani was made in 2008 by the American ichthyologists Kevin W. Conway and Richard L. Mayden from Saint Louis University in Missouri . The holotype is an adult specimen of 37.4 millimeters standard length captured in December 2007. It is in the collection of the Florida Museum of Natural History in Gainesville , Florida with two paratypes . Three other paratypes are kept in the Zoological Reference Collection at the National Museum of Singapore . The species name rahmani honors the Bangladeshi ichthyologist AT Ataur Rahman in recognition of his contributions to the knowledge of the ichthyofauna of Bangladesh.
Web links
- Psilorhynchus rahmani on Fishbase.org (English)
- Psilorhynchus rahmani onthe IUCN Red List of Threatened Species .
Individual evidence
- ↑ a b c d e f g Kevin W. Conway and Richard L. Mayden: Description of two new species of Psilorhynchus (Ostariophysi: Psilorhynchidae) and redescription of P. balitora . In: Ichthyological Exploration of Freshwaters 2008, Volume 19, No. 3, pp. 215-232, ISSN 0936-9902 .
- ↑ a b Abu Tweb Abu Ahmed, Md. Mizanur Rahman and Suman Mandal: Biodiversity of hillstream fishes in Bangladesh . In: Zootaxa 2013, Volume 3007, No. 2, pp. 282-293, doi: 10.11646 / zootaxa.3700.2.6 .
- ↑ a b Md. Mizanur Rahman: Psilorhynchus rahmani . In: IUCN Bangladesh (ed.): Red List of Bangladesh. Volume 5. Freshwater Fishes . International Union for Conservation of Nature (IUCN), Bangladesh Country Office, Dhaka 2015, ISBN 978-984-34-0738-2 , p. 296.
- ↑ Psilorhynchus rahmani in the endangered Red List species the IUCN 2010. Posted by: LK Singh, 2010. Retrieved on 1 June of 2019.
- ↑ Kevin W. Conway: Osteology of the South Asian Genus Psilorhynchus McClelland, 1839 (Teleostei: Ostariophysi: Psilorhynchidae), with investigation of its phylogenetic relationships within the order Cypriniformes . In: Zoological Journal of the Linnean Society 2011, Volume 163, No. 1, pp. 50-154, doi: 10.1111 / j.1096-3642.2011.00698.x .
- ↑ Kevin W. Conway: Erratum. Osteology of the South Asian Genus Psilorhynchus McClelland, 1839 (Teleostei: Ostariophysi: Psilorhynchidae), with investigation of its phylogenetic relationships within the order Cypriniformes . In: Zoological Journal of the Linnean Society 2012, Volume 164, No. 1, p. 243, doi: 10.1111 / j.1096-3642.2011.00698.x .
- ↑ Kevin W. Conway et al .: Molecular systematics of the Asian torrent minnows (Ostariophysi: Psilorhynchidae) inferred from nuclear and mitochondrial DNA sequence data . In: Journal of Zoological Systematics and Evolutionary Research 2015, Volume 53, No. 1, pp. 33-44, doi: 10.1111 / jzs.12090 .