Karyomorphology of Three Indian Major Carps From Haryana, India

Abstract

The purpose of the present study was to investigate and compare the karyotypes of three Indian major carps, Catla catla (Hamilton, 1822), Labeo rohita (Hamilton, 1822), Cirrhinus mrigla (Hamilton, 1822) in terms of chromosomal architechture, karyotype formula and number of chromosomes from aquatic ecosystems of Haryana, India. Karyotypes of these carps were investigated by examining metaphase chromosomes. The results indicated that the diploid (2n) chromosome number of all the three major carps was 50. Catla catla consisted of 22 acrocentric, 2 subtelocentric, 20 submetacentric and 6 metacentric chromosomes. Labeo rohita consisted of 32 acrocentric, 4 subtelocentric, 6 submetacentric, 8 metacentric while Cirrhinus mrigla consisted of 30 acrocentric, 8 subtelocentric, 6 submetacentric, 6 metacentric chromosomes. Centromeric Index, arm ratio and fundamental number was also determined. No heteromorphic sex chromosomes were cytologically detected. The variability in size, shape and arm number (NF) of chromosomes among these three species suggest that diversification in these fish species of same family is related to structural changes in chromosomes. Variations in karyotype formulae are also observed with respect to earlier studies which may be due to variations in habitat conditions as a result of anthropogenic activities.

A study of constitutive heterochromatin and NOR banding in three species of Indian major carps from the State of Haryana, India

“…The most commonly occuring diploid number in family Cyprinidae is 50, considered to be the modal number in case of this family (Manna, 1984;Rishi, 1989). Karyotype studies of Indian major carps have been worked out by numerous scientists (Gui et al, 1986;Zhang et al, 1991;John et al, 1992;John et al, 1993, Jana, 1993Nagpure et al, 2001) who reported similar results, i.e., 2n=50 which are in accordance with the present results and earlier publication of our laboratory (Bhatnagar et al, 2014) Positive C-bands identify regions of constitutive heterochromatin, which contains transcriptionally inactive highly repetitive DNA sequences (Gold et al, 1990). Most species invariably possess Cbands at or around the centromeres (pericentromeric) and, frequently, at the chromosome end (telomeric).…”

A high-quality chromosome-level genome assembly of rohu carp, Labeo rohita, and its utilization in SNP-based exploration of gene flow and sex determination

“…Despite its importance to aquaculture, the mechanisms governing sex-determination in rohu are currently unknown. Karyotypic analyses suggest that if rohu has sex chromosomes, they are likely homomorphic (Bhatnagar et al 2014), similar to many other fish (Heule et al 2014), and are indistinguishable from the remaining chromosomes. We screened the rohu genome for regions linked to sex by evaluating read mapping in each ddRAD region from female versus male fish.…”

“…Together, these results suggest that rohu has a male-heterogametic (XX/XY) system of sex determination. Furthermore, since the sex chromosomes are indistinguisable by karyotype (Bhatnagar et al 2014) and the uniquely male regions comprise only a small region of the chromosome, rohu may only have a Y-specific region (or “young Y”), similar to Oryias latipes (medaka) (Kondo et al 2006); however, sequences similar to the medaka homolog for male-determination (i.e., dmY (Matsuda et al 2002; Hornung et al 2007)) were not found in the rohu assembly, indicating that further study is needed.…”