Printer Friendly

First report on the karyological analysis of the Churru snow trout, Schizothorax esocinus (Teleostei: Cyprinidae), from the River Jhelum, Kashmir.


Cyprinid fishes belonging to the subfamily Schizothoracinae are widely distributed in mountain streams and lakes around the Himalayan Karakorum and Hindukush Ranges, the Tibet Plateau and Central Asia (Terashima 1984). The genus Schizothorax Heckel comprises many species that inhabit the reservoirs of Central Asia from Turkamenistan and Eastern Persia in the West to the far reaches of the Mekong and Yangtzekiang in the East. Schizothorax esocinus (Fig. 1), inhabiting cold streams, rivers and lakes (Menon 1999) is distributed in the inland waters of Kashmir viz. Dal Lake, Mansbal Lake, Jhelum River, Lidder Stream etc. (Kullander et al. 1999), Nepal (Shrestha 1990) and China (Wu & Wu 1992) besides Afghanistan and Pakistan. Hill-stream fish species constitute about 3.5% of the fish fauna recorded from India and all of these could be considered as threatened species on account of the adverse effect of increasing human activity (Rishi et al. 1998). Schizothorax esocinus is edible and is an important species for commercial and sport fishing and has not been cytologically investigated previously.


Cyprinid karyotypes have not been without systematic implications (Joswiak et al. 1980) because comparative karyology has become a useful tool in fish systematic studies (e.g. Arai 1982; Buth et al. 1991). Chromosome number and morphology shows great promise for interpreting the evolution of fishes (Uyeno & Miller 1973) and permits the detection of changes that modified an ancestral karyotype as it evolved into new lines (Winkler et al. 2004) and are useful for addressing a variety of evolutionary, genetic and cytotaxonomic questions about animals (Kirpichnikov 1981; McGregor 1993). The present study was undertaken to investigate chromosomes and karyotype of S. esocinus to compare it to other members of the genus and generate information that can be utilized for management of the species.


Live fish were obtained from local fishermen in the River Jhelum and transported live to the Limnology and Fisheries Laboratory of the Centre of Research for Development, University of Kashmir and placed into 50 l fully aerated aquariums at 20[degrees] C for several days. Air-dried chromosome preparation method with some modifications was used as described by Thorgaard and Disney (1990). Fish received two doses of phytohemagglutinin (PHA) injections (4 [micro]g[g.sup.-1] body weight), in a 20-h interval at 20[degrees] C. Eight hours after the second PHA injection, colchicine was injected intraperitoneally, 0.05% at 0.1 ml/100g body weight to depress mitotic division at the metaphase stage and left for 2-3 hours before sacrificing. The fish were anesthetized by 300 ppm clove oil for 40s, their anterior kidney was removed, homogenized and hypotonised simultaneously by potassium chloride 0.56% for 35 minutes at room temperature. Suspensions were centrifuged at 1000 rpm for 10 minutes. Supernatant was removed and the cells were fixed by cold fresh Carnoy (3:1 methanol and glacial acetic acid). This process was repeated three times and the cold fresh Carnoy was replaced at 30 minute intervals. Smears were prepared on cold lamellae using splash method from 1m height and air dried for 24 h, then stained with 2% Giemsa.


A Leica DM LS2 trinocular photomicroscope with 100x 10x magnification lens oil immersion was used for taking the photographs and analysing the chromosomes. Eighty metaphase plates were counted and a proper plate was selected to obtain karyotype formulae. Microsoft Excel 2007 software was used to calculate the centromeric indices and to draw the ideogram. For each chromosome centromeric index, arm ratio and total length were calculated as described by Levan et al. (1964) and the fundamental number was also calculated. Chromosomes were classified into metacentric, sub-metacentric, sub-telocentric and telocentric following the method of Levan et al. (1964).


Relatively small and high numbers of chromosomes were observed in Schizothorax esocinus. Eighty cells from the anterior kidney tissue were analysed in total. The majority (80%) of the metaphase complements contained 98 chromosomes, though the count varied between 94-100 in a few cells (Table I). The diploid complement (Fig. 2a) comprised 15 metacentric pairs, 11 submetacentric pairs, 5 subtelocentric pairs and 18 telocentric pairs (Fig. 2b). The total length of the haploid complement equalled 228.8 [micro]m with a range in the length of shortest and longest chromosome between 2.5-8.1 [micro]m. The arm ratio and the centromeric index ranged between 1-[infinity]and 0-50 respectively. Using chromosomal indicators, an ideogram (Fig. 3) was drawn in MS Excel 2007. The chromosomal formula can be represented as: K (2n) = 98 = 30 m + 22 Sm + 10St + 36t.


Table I. Frequency of chromosomes in the counted metaphase plates

Number of chromosomes in each metaphase plate  94  96.0  98  100.0

Number of metaphase plates counted              8   6.0  64    2.0

Frequency (%)                                  10   7.5  80    2.5


The cytological analysis of Schizothorax esocinus in the present study revealed a high number of chromosomes: 2n = 98. Species with high numbers are considered to have resulted through polyploidy from an ancestral 2n = 48 or 50 (Rishi et al. 1998). Large-scale genomic expansions or whole-genome duplication events have been documented in early vertebrate evolution (Friedman & Hughes 2001; Ohno 1970; Wang & Gu 2000), near the base of the phylogenetic tree of teleost fishes (Christoffels et al. 2004; Meyer & Schartl 1999; Robinson-Rechavi et al. 2001; Wittbrodt et al. 1998), and near the basal roots of several major teleostean clades, such as salmonids (Allendorf & Thorgaard 1984), catostomids (Ferris 1984; Uyeno & Smith 1972), acipenserids (Vasil'ev 1999) and some cyprinids (Larhammer & Risinger 1994). Such genomic enlargements have been hypothesised as key factors that enable or even drive diversification in various vertebrate groups (Holland et al. 1994; Meyer & Malaga-trillo 1999; Navarro & Barton 2003a,b; Ohno 1970; Stephens 1951). Chromosome counts in nearly all cyprinid polyploids occur in multiples or combinations of the most common karyotype (48-50) and tetraploids (96, 98 or 100) and hexaploids (148-150) have arisen through hybridisation (Dowling & Secor 1997). This is well illustrated by a number of species of fish belonging to diverse orders. Buth et al. (1991) noted 52 such taxa belonging to the Cyprinidae identified through karyological analysis (Dowling and Secor 1997) and such forms are ancestral polyploids (Ohno et al. 1969). Polyploidy in fishes has been associated with traits that include large body size, fast growth rate, long life and ecological adaptability (Uyeno & Smith 1972; Schultz 1980). Since Schizothorax fishes are hill stream fishes, it may be that polyploidy may have resulted on account of the cold temperature of their habitat. The use of thermal shocks to eggs for induction of polyploidy (Chourrout 1988) provides support to the above assertion.

It is interesting that the Kashmir Valley Schizothorax esocinus showed a diploid number similar to that recorded for other species inhabiting different geographical locations eg., Schizothorax richardsonii, 2n = 98 (Sharma et al. 1992; Lakara et al. 1997), Schizothoracichthys prograstus, 2n = 98 (Rishi et al. 1983) and S. kumaonensis, 2n = 98 (Rishi et al. 1998; Lakara et al. 1997). A different fundamental arm number, which may be attributed to the intra-chromosomal changes involving pericentric and paracentric inversion, suggests an origin from the same primitive ancestor. The overall similarity in the chromosome number and morphology implies that Schizothorax species are very closely related in that they have not been isolated as evolving entities long enough for random chromosome changes to have taken place and become fixed. That a particular karyotype would be selected implies an adaptive advantage for that particular configuration. This hypothesis has been suggested for chromosome differences found in Fundulus (Chen 1971) and rivulines (Scheel 1972). The latter study followed the suggestion of Stebbins (1958) in that co-adapted gene sequences in plants have become closer linked via chromosome structural rearrangements and thus is less likely to be disrupted by normal exchange events. Similar arguments for chromosome changes paralleling species evolution in frogs and mammals can be found in Wilson et al. (1974) and for other animals in White (1978). No heteromorphic sex chromosomes were found in Schizothorax esocinus. Cells lacking normal value (2n = 94-100) were also encountered in the preparations and these probably resulted from losses during the preparation or addition from the neighbouring cells or hypotonic overtreatment (Nanda et al. 1995).

The present study is the first to describe the chromosomal characteristics of Schizothorax esocinus from the Kashmir Valley. The results of the study can be used for the genetic manipulation and management and conservation of the species.


The authors wish to thank the Director of the department for research facilities. We are also thankful to Dr. Farooz Ahmad Bhat, Assistant Professor Division of Fisheries SKAUST-K for his help in the identification of the fish and CSIR, New Delhi for providing financial assistance in the form of JRF to Farooq Ahmad.

Received: 03 January 2011 - Accepted: 09 May 2011


ALLENDORF, F. W. & THORGAARD, G. H. 1984. Tetraploidy and the evolution of salmonid fishes. In: Evolutionary Genetics of Fishes (ed. B.J. Turner): 1-53. N.Y., Plenum Press.

ARAI, R. 1982. A chromosome study on two cyprinid fishes, Acrossocheilus labiatus and Pseudorasbora pumila pumila, with notes on Eurasian cyprinids and their karyotypes. Bulletin of the National Science Museum, Tokyo (A) 8: 131-152.

BUTH, D. G., DOWLING, T. E & GOLD, J. R. 1991. Molecular and cytological investigations. In: The Biology of Cyprinid Fishes (eds I. Winfield, J Nelson): 83-126. London, Chapman and Hall.

CHEN, T. R. 1971. A comparative chromosome study of twenty killifish species of the genus Fundulus (Teleostei: Cyprinodontidae). Chromosoma 32: 436-453.

CHOURROUT, D. 1988. Induction of gynogenesis, triploidy and teteraploidy in fish. In: ISI Atlas of Science: Animal and Plant Science Vol. 1 (Ed. A.M. Grimwade): 65-70.

CHRISTOFFELS, A., KOH, E. G. L., CHIA, J. M., BRENNER, S., APARICIO, S. & VENKATESH, B. 2004. Fugu genome analysis provides evidence for a whole-genome duplication early during the evolution of ray finned fishes. Molecular Biology and Evolution 21: 1146-1151.

DOWLING, T. E. & SECOR, C. L. 1997. The role of hybridisation and introgression in the diversification of Animals. Annual Review of Ecology and Systematics 28: 593-619.

FERRIS, S. D. 1984. Tetraploidy and the evolution of catostomid fishes. In: Evolutionary Genetics of Fish (Ed. B. J. Turner). N.Y, Plenum Press.

FRIEDMAN, R. & HLUGHES, A. L. 2001. Pattern and timing of gene duplication in animal genomes. Genome Research 11: 1842-1847.

HOLLAND, P. W., GARCIA-FERNANDEZ, J., WILLIAMS, J. W. & SIDOW, A. 1994. Gene duplication and the origin of vertebrate development. Development, Supplement: 125-133.

JOSWIAK, G. R., STARNES, W. C. & MOORE, W. S. 1980. Karyotypes of three species of genus Phoxinus (Pices: Cyprinidae). Copeia 4: 913-916.

KIRPICHNIKOV, V. S. 1981. Genetic Basis of Fish Selection. Springer-Verlag, Berlin. Heidelberg, New York pp. 342.

KULLANDER, S. O., FANG, F., DELLING, B. & AHLANDER, E. 1999. The fishes of Kashmir Valley. In: River Jhelum, Kashmir Valley, Impacts on the aquatic environment. (Ed. L. Nyman): 99-163.

LAKARA, W. S., JOHN, G. & BARAT, A.1997. Cytogenetic studies on endangered and threatened fishes.2. Karyotypes of two species of snow-trout, Schizothorax richardsonii (Gray) and S. kumaonensis (Menon). Proceedings of the National Academy of Sciences, India, Biological Science 67 (1): 79-81.

LARHAMMAR, D. & RISINGER, C. 1994. Molecular genetic aspects of tetraploidy in the common carp, Cyprinus carpio. Molecular Phylogenetics and Evolution 3: 59-68.

LEVAN, A., FREDGA, K. & SANDBERG, A. A.1964. A nomenclature for centromeric position on chromosomes. Heriditas 52: 201-220.

MACGREGOR, U. C. 1993. Chromosome Preparation and Analysis. Chapman & Hall Press, London.

MENON, A. G. K. 1999. Checklist-freshwater fishes of India. Records of the Zoological Survey of India. Occasional Paper 175: 366.

MEYER, A. & MALAGA-TRILLO, E. 1999. Vertebrate genomics: more fishy tales about Hox genes. Current Biology 9: 210-213.

MEYER, A. & SCHARTL, M. 1999. Gene and genome duplications in vertebrates: the one-to-four (to-eight in fish) rule and the evolution of novel gene functions. Current Opinion in Cell Biology 11: 699-704.

NANDA, L., SCHARTL, M., FEICHTINGER, W., SCHLUPP, L., PARZEFALL, J. & SCHMID, M. 1995. Chromosomal evidence for laboratory synthesis of triploid hybrid between the gynogenetic teleost Poecilia formosa and host species. Journal of Fish Biology 47: 221-227.

NAVARRO, A. & BARTON, N. H. 2003a. Accumulating post-zygotic isolation gene in parapatry: a new twist on chromosomal speciation. Evolution 57: 447-459.

NAVARRO, A. & BARTON, N. H. 2003b. Chromosomal speciation and molecular divergence-accelerated evolution in rearranged chromosomes. Science 300: 321-324.

OHNO, S., MURAMOTO, J. I., KLEIN, J. & ATKIN, N. B. 1969. Chromosomes today. Vol.2. (Eds Darlington, C. D. & Lewis, K. P.): 139-147. Oliver and Boyd, Edinburgh.

OHNO, S. 1970. Evolution By Gene Duplication. SpringerVerlag, Berlin and New York.

RISHI, K. K., SHASHIKALA & RIHI, S. 1998. Karyotype study on six Indian hill-stream fishes. Chromosome Science 2: 9-13.

RISHI, K. K., SINGH, J. & KAUL, M. M. 1983. Chromosome analysis of Schizothoracichthys progastus (McCll) (Cypriniformes). Chromosme Information Service 34: 12-13.

ROBINSON-RECHAVI, M., MARCHAND, O., SCHRIVA, H., BARDET, P. L., ZELUS, D., HUGHES, S. & LAUDET, V. 2001. Euteleost fish genomes are characterized by expansions of gene families. Genome Research 11: 781-788.

SCHEEL, J. J. 1972. Rivuline karyotypes and their evolution (Rivulinae, Cyprinodontidae, Pisces). Journal of Zoological Systematics and Evolutionary Research 10: 180-209.

SCHULTZ, R. J. 1980. The role of polyploidy in the evolution of fishes. In: Polyploidy: Biological Relevance. (ed. Lewis, E. W. H.): 313-339. New York: Plenum Press.

SHARMA, O. P., GUPTA, S. C., TRIPATHI, N. K & KUMAR, R. 1992. On the chromosomes of two species of fishes from Jammu. Perspectives in Cytology and Genetics 7: 1211-1215.

SHRESTHA, T. K. 1990. Resource ecology of the Himalayan waters. Curriculum Development Centre, Tribhuvan University, Kathmandu, Nepal. p. 645.

STEBBINS, G. L. 1958. Longevity, habitat and release of genetic variability in higher plants. Cold Spring Harbour Symposia on Quantitative Biology 23: 365-378.

STEPHENS, S. G. 1951. Possible significance of duplications in evolution. Advances in Genetics 4: 247-265.

TERASHIMA, A. 1984. Three new species of the Cyprinid genus Schizothorax from Lake Rara, Northwestern Nepal. Japanese Journal of Ichthyology 31 (2): 122-134.

THORGAARD, G. H & DISNEY, J. E. 1990. Chromosome preparation and analysis. In: Methods for Fish Biology (eds Schreck C. B, Moyle P. B): 171-190. Bethesda, M. D: American Fisheries Society.

UYENO, T. & MILLER, R. R. 1973. Chromosomes and the evolution of plagopterin fishes (cyprinidae) of the Colorado River System. Copeia 4: 776-782.

UYENO, T. & SMITH, G. R. 1972. Tetraploid origin of the karyotype of catostomid fishes. Science 175: 644-646 VASIL'EV, V. P. 1999. Polyploidization by reticular speciation in acipenseriform evolution: a working hypothesis. Journal of Applied Ichthyology 15: 29-31.

WANG, Y & GU, X. 2000. Evolution of gene families generated in the early stages of vertebrates. Journal of Molecular Evolution 51: 88-96.

WHITE, M. J. D. 1978. Modes of Speciation. W. H. Freeman and Co., San Francisco.

WILSON, A. C., SARICH, V. M. & MAXSON, L. R. 1974. The importance of gene rearrangement in the evolution evidence from studies on rates of chromosomal, protein and anatomical evolution. Proceedings of the National Academy of Science 71: 3028-3030.

WINKLER, F. M., GARCIA-MELYS, D. & PALMA-ROJAS, C. 2004. Karyotypes of three South East Pacific Flounder species of the family Paralichthyidae. Aquaculture Research 35: 1295-1298.

WITTBRODT, J., MEYER, A. & SCHARTL, M. 1998. More genes in fish? Bioessays 20: 511-512.

WU, Y. & WU, Y. 1992. The fishes of the Qinghai-Xizang Plateau. Sichuan Publishing House of Science and Technology, Chengdu, China.

Farooq A Ganai (1) *, A. R. Yousuf (1), N. K. Tripathi (2)

(1.) Limnology and Fisheries Laboratory, Centre of Research for Development, University of Kashmir 190006, India.

(2.) Animal Cytogenetics Laboratory, P. G. Department of Zoology, University of Jammu, Jammu, India.

* Corresponding author:
COPYRIGHT 2011 Aquapress Publisher
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2011 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Ganai, Farooq A.; Yousuf, A. R.; Tripathi, N. K.
Publication:aqua: International Journal of Ichthyology
Article Type:Report
Geographic Code:90ASI
Date:Oct 15, 2011
Previous Article:Diet of the Pacific sierra Scomberomorus sierra (Perciformes: Scombridae) in two areas of north-west Mexico coast.
Next Article:Description of a unique catshark egg capsule (Chondrichthyes: Scyliorhinidae) from the North West Shelf, Western Australia.

Terms of use | Privacy policy | Copyright © 2022 Farlex, Inc. | Feedback | For webmasters |