Marine Biology

, Volume 150, Issue 6, pp 1183–1189 | Cite as

Chromosomal mapping of major ribosomal rRNA genes in the hard clam (Mercenaria mercenaria) using fluorescence in situ hybridization

  • Yongping Wang
  • Ximing GuoEmail author
Research Article


Karyotype and chromosomal location of the major ribosomal RNA genes were studied in the hard clam (Mercenaria mercenaria Linnaeus) using fluorescence in situ hybridization (FISH). Metaphase chromosomes were obtained from early embryos. Internal transcribed spacers (ITS) between major RNA genes were amplified and used as FISH probes. The probes were labeled with digoxigenin-11-dUTP by polymerase chain reaction and detected with fluorescein-labeled anti-digoxigenin antibodies. FISH with the ITS probes produced two to four signals per nucleus or metaphase. M. mercenaria had a haploid number of 19 chromosomes with a karyotype of seven metacentric, four metacentric or submetacentric, seven submetacentric, and one submetacentric or subtelocentric chromosomes (7M + 4M/SM + 7SM + 1SM/ST). Two ITS loci were observed: one located near the centromere on the long arm of Chromosome 10 and the other at the telomere of the short arm of Chromosome 12. FISH signals on Chromosome 10 are strong and consistent, while signals on Chromosome 12 are variable. This study provides the first karyotype and chromosomal assignment of the major RNA genes in M. mercenaria. Similar studies in a wide range of species are needed to understand the role of chromosomal changes in bivalve evolution.


Internal Transcribe Spacer Bivalve Hard Clam Haploid Number Mercenaria Mercenaria 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



This study was supported by grants from the U.S. Sea Grant (B/T-9801; R/OD-2003-1), U.S. Department of Agriculture (96-35205-3854) and New Jersey Commission on Science and Technology (02-2042-007-11), and from China’s Natural Science Foundation (39825121) and China’s High-tech 863 program (2001AA628150). This is publication IMCS-2006-13 and NJSG-06-641.


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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  1. 1.Haskin Shellfish Research Laboratory, Institute of Marine and Coastal SciencesRutgers UniversityPort NorrisUSA
  2. 2.Experimental Marine Biology Laboratory, Institute of OceanologyChinese Academy of SciencesShandongPeople’s Republic of China

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