Abstract:The clam Moerella iridescens is an economically important shellfish in China.However, there are few reports on the genetic relationship and germplasm resources of the clam. To explore the cytogenetic characteristics of the clam, accurate genetic and number of chromosomes and its karyotype composition of the clam were investigated. At present, due to the unknown chromosome karyotype of M. iridescens, we prepared gill tissue of M. iridescens as research materials. After treatment with colchicine, and low permeability KCl solution the cell suspension was obtained by dissociation and was fixed by methanol and acetic acid solution. The length and the arm ratio of chromosomes were measured and calculated with Nikon NIS-Elements BR 3.1 software, and the karyotype was arranged with Photoshop software. The ideal chromosome slides were obtained by using the hot drop method. The result showed that the clam had chromosome number of 2n=36, and the 18 pairs of chromosomes were divided into 3 types including 4 pairs of metacentric chromosomes(m), 8 pairs of submetacentric chromosome(sm) and 6 pairs of subtelocentric chromosome(st). On the basis of the above experiments, the well dispersed visual field of chromosome was measured by microphotography, and karyotype was analyzed. It was found that the karyotype was 2n=8m+16sm+12st, NF=72, and no heterosome and satellite chromosome were found. The finding provides a useful reference material for understanding of the genetic relationship, an effective method to research bivalve system evolution, and necessary information for further resource protection.
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