Genus Schizopygopsis
Steindachner, 1866

This genus contains about 8 species distributed from Iran along the Himalayas to China. There is a single species in Iran.

The osmans are characterised by an elongate and almost cylindrical body, almost scaleless, scales being restricted to the complete lateral line, the flank above the pectoral fin and as enlarged scales around the vent and anal fin base, the mouth is terminal to inferior, the lower jaw is sometimes covered by a horny sheath, lips are present but may only be developed at the mouth corners, no barbels, pharyngeal teeth in 2 rows, spatulate or cochleariform, short dorsal and anal fins, dorsal fin last unbranched ray thickened (but not strongly) and serrated or denticulate (denticles lost with age), peritoneum black, and gut very elongate.

Schizopygopsis stoliczkai
Steindachner, 1866

Common names

kopur-e barfi (= snow trout).

[lozhnyi osman or false osman in Russian; Pamir snowcarp].

Systematics

The type locality of this species is a stream near Hanle Monastery, Ladakh, India. Syntypes are in the Naturhistorisches Museum Wien under NMW 9255 (1), NMW 9256 (1), NMW 51472 (9) and NMW 51473 (2) (Eschmeyer et al., 1996; 1997 Vienna card catalogue).

The species name is spelt Stoličkai by Steindachner (1866) which becomes correctly stoliczkai since accents are not used in Latin nor capitals for the scientific species name. It is often spelt stoliczkae in the general literature.

Schizopygopsis stoliczkae infraspecies sewerzowi Herzenstein, 1890, originally described from the Bulun Kul and Karasu, Amu Darya basin in the Pamir Mountains has no taxonomic validity (it occurs together with the typical form in the upper Amu Darya) but it was used to characterise the form in the Sistan basin of Iran (Berg, 1948-1949). However, Annandale and Hora (1920) report both this and the stoliczkae form, without intermediates, in Sistan. The sewerzowi form differs from the typical form by having a larger eye (1.2-1.3 times in interorbital width as opposed to 1.5-1.7 times and 3.8-4.4 times in head length as opposed to 4.8-5.7 times), a spotted rather than monotone body, smaller size (much less than half that of the typical form), somewhat deeper body, and more oblique mouth with apex at the lower eye level. Data presented below under Food indicates that this species can be very plastic in its characters so subspecies designations would require extensive study of both characters and ecology. The Iranian fish are poorly represented by specimens and are referred here simply to the species.

Berg (1948-1949) reviews three morphae or forms of this species which indicate the great variation in this taxon. He also notes how barbel length varies independently of morpha and how the lips may be very strongly developed. The forms are as follows and the latter two were originally described as distinct species and are recognised as such by some authors: typica, eurystomus Kessler, 1872 and fedtschenkoi Kessler, 1872. Eurystomus has a transverse jaw covered by horny padding and a strong or weak dorsal fin spine. Fedtschenkoi has a lower jaw without the horny pad and the lower lip continuous or interrupted (the form with an interrupted lip is called morpha irregularis Day, 1896) and the dorsal fin spine is weak with 10-22 denticles extending to the mid-point or two-thirds along the ray. The forma typica has a crescent-shaped lower jaw without horny padding, the dorsal fin spine is well-developed with 12-32 denticles extending distally beyond the mid-point, and the lower lip is interrupted.

Syntypes of sewerzowi (dated 1891 in Eschmeyer et al. (1996)) are in the Zoological Institute, St. Petersburg under ZISP 8747 (2), ZISP 8748 (2), ZISP 8749 (2), ZISP 8780 (1), ZISP 8901 (2) (Eschmeyer et al., 1996).

Kähsbauer (1964) reports a hybrid between Schizothorax schumacheri and Schizopygopsis stoliczkae from Sistan which may in fact be Schizocypris altidorsalis.

Key characters

The anal fin base has a sheath of enlarged scales and there are a few scales in the shoulder region and along the lateral line but the body is nearly naked, the anal fin has 5 branched rays, barbels are absent, and pharyngeal teeth are in 2 rows.

Morphology

Dorsal fin branched rays 7-9, usually 8, after 3-4 unbranched rays, anal fin branched rays 5-6, usually 5, after 2-3 unbranched rays, pectoral fin branched rays 12-20, and pelvic fin branched rays 8-10. Total vertebrae 48 (Howes, 1987). The lateral line is complete, a pelvic axillary scale is present and the anus and anal fin base are sheathed in enlarged scales. Scales are also present on the anterior lateral line and between there and the anterior pectoral fin base. A double row of scales extends forward from the anal sheath to the pelvic fin bases. Lateral line scales 96-120.

The dorsal fin spine is weakly developed and lacks denticles in large fish while young have many well-developed denticles. The gut is very elongate and coiled. The lower jaw is strong, with a dark brown, horny plate. The pharyngeal teeth number 3,4-4,3 and have a rounded base becoming spatulate distally with a rounded, hooked tip. Some teeth have a weak, flat cusp with a bump posteriorly below a rounded tip.

Meristic values for Iranian specimens are:- dorsal fin branched rays 8(3); anal fin branched rays 5(3); pectoral fin branched rays 17(1), 18(1) or 19(1); pelvic fin branched rays 9(3); lateral line scales 91(1) or 92(1); total gill rakers 11(3), reaching the raker below when appressed; and total vertebrae 48(1) or 50(2).

Sexual dimorphism

Tubercles are present on the anal fin of two male specimens from Sistan in a single file on the last unbranched and first 3 branched rays. They number up to 8 and are often widely spaced. Tubercles are found low on the flank above the anal fin and anus and on the upper flank behind the dorsal fin level. They also line the posterior lateral line. There are also a very few tubercles on the top of the head, side of the snout, below the eye and on the operculum, widely scattered and small.

Colour

Dark or yellowish with small dark brown or blackish spots extending onto the fins, or olive with large grey spots, or bluish-grey. Spots can be so numerous as to give the appearance of an overall blackish colour. Tilak (1987) however states that blackish spots are absent in both old and freshly preserved material. Both spotted and non-spotted forms occur in Sistan. The belly is whitish. Fins are pink. Peritoneum dark brown to black.

Size

Reaches 75.4 cm but the Sistan form is only up to 22.0 cm and is regarded as a dwarf form by Annandale and Hora (1920).

Distribution

Found in the mountainous areas of Afghanistan, Pakistan, India and western China. In Iran, restricted to the lowland Sistan basin where reported from the Hirmand River delta and 8 miles east of Lab-e Baring (Annandale, 1921; Vijayalakshmanan, 1950).

Zoogeography

The presence of this species in Sistan is an example of a riverine highway enabling species usually found at higher altitudes to penetrate into lowlands. See also the genus Schizothorax.

Habitat

Outside Iran the adults favour the main river while young are found in shallow streams and pools.

Age and growth

Savvaitova et al. (1989) cite a life span up to 22 years. Maturity in the Sistan form is attained at 18.0 cm. Berg (1949) reports a male fish 14 cm long with fairly well-developed testes and tubercles on the anal fin which bears out the dwarf nature of the Sistan fish.

Food

Savvaitova et al. (1989) examined feeding in certain lakes of the Pamirs at altitudes over 3220 m. This is much higher than the Sistan populations and the data may not be relevant. However the false osman is a poorly studied species so such information gives a basis for comparison and future research. The false osman is a very plastic species and can adapt to a variety of conditions. The osmans of the Pamirs were divisible into four groups: herbivores, detritivores, molluscivores and predators reflected in the structure of the gut and its length, the number of gill rakers, eye diameter, length and position of fins, and the shape of the horny plate on the lower jaw. Food includes higher aquatic plants, aquatic insects, diatoms and blue-green algae, detritus, molluscs and fish. In herbivores consuming periphyton, the horny plate on the lower jaw is rasp-shaped with the pointed end aimed anteriorly. In detritivores, the plate is sharper, and in predators, it is larger with the pointed edge directed upwards to grasp prey. Predatory behaviour only develops in fish over 30 cm, until which they eat plants.

Chaudhary et al. (1991) indicate that in a Pakistani population gut length increases with age and diet changes gradually from an omnivorous to a herbivorous one.

Reproduction

Spawning in Asia occurs generally in June and July. Eggs are large at 2.0 mm diameter.

Parasites and predators

None reported from Iran.

Economic importance

None.

Conservation

This species is rarely collected in Sistan and may require conservation measures.

Further work

Detailed surveys are needed to document the occurrence of this species in Sistan and to study its biology in a lowland habitat. Comparative studies with samples of the species from other, remote localities may demonstrate some level of taxonomic distinction as is seen in other schizothoracines of Sistan.

Sources

Iranian material: BM(NH) 1905.4.7:1-2, 2, 113.0-116.5 mm standard length, Sistan (no other locality data); ZISP 25854, 1, 111.5 mm SL, Sistan (no other locality data).

Comparative material: BM(NH) 1931.10.26:2-4, 2, 85.5-138.6 mm standard length, India, Ladkah, stream into Pangong Lake (no other locality data).

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