Abstract
We report on novel chromosomal characteristics of Haliotis discus hannai from a breeding population at Fujian, China. The karyotypes of H. discus hannai we obtained from an abalone farm include a common type 2n = 36 = 10M + 8SM (82%) and two rare types 2n = 36 = 11M + 7SM (14%) and 2n = 36 = 10M + 7SM + 1ST (4%). The results of silver staining showed that the NORs of H. discus hannai were usually located terminally on the long arms of chromosome pairs 14 and 17, NORs were also sometimes located terminally on the short arms of other chromosomes, either metacentric or submetacentric pairs. The number of Ag-nucleoli ranged from 2 to 8, and the mean number was 3.61 ± 0.93. Among the scored interphase cells, 41% had 3 detectable nucleoli and 37% had 4 nucleoli. The 18S rDNA FISH result is the first report of the location of 18S rDNA genes in H. discus hannai. The 18S rDNA locations were highly polymorphic in this species. Copies of the gene were observed in the terminal of long or/and short arms of submetacentric or/and metacentric chromosomes. Using FISH with probe for vertebrate-like telomeric sequences (CCCTAA)3 displayed positive green FITC signals at telomere regions of all analyzed chromosome types. We found about 7% of chromosomes had breaks in prophase. A special form of nucleolus not previously described from H. discus hannai was observed in some interphase cells. It consists of many small silver-stained nucleoli gathered together to form a larger nucleolus and may correspond to prenucleolar bodies.
Highlights
The Pacific abalone, Haliotis discus hannai, which naturally inhabits temperate waters, is one of the most commercially important marine shellfish for aquaculture in eastern Asia because of its high market value and nutrient content for human consumption
A total 50 metaphases examined from H. discus hannai showed a diploid complement of 2n = 36
It is worthwhile to note that the relative length of the fifth chromosome pair was 6.39 ± 0.42 and arm ratio was 1.45 ± 0.31, the No 17 chromosome pair relative lengths (RL) = 4.21 ± 0.45 and AR = 2.94 ± 0.24
Summary
The Pacific abalone, Haliotis discus hannai, which naturally inhabits temperate waters, is one of the most commercially important marine shellfish for aquaculture in eastern Asia because of its high market value and nutrient content for human consumption. In China, H. discus hannai is an economically important gastropod species and its large-scale cultivation started in the late 1980s [1], more than 20000 metric tons being produced annually since 2007. Cytogenetics of Abalone collection and analysis, decision to publish, or preparation of the manuscript
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