Molecular cytogenetic analysis of a triploid population of the human broad tapeworm, Dibothriocephalus latus (Diphyllobothriidea)

Parasitology. 2021 Jun;148(7):787-797. doi: 10.1017/S0031182021000408. Epub 2021 Mar 8.

Abstract

The large-sized tapeworm Dibothriocephalus latus is known as the broad or fish-borne cestode of mammals that is capable to infect humans and cause diphyllobothriosis. Recently, molecular data on D. latus has been accumulating in the literature and a complete genome sequence has been published; however, little is known about the karyotype and chromosome architecture. In this study, an in-depth karyological analysis of 2 D. latus specimens was carried out. The plerocercoids originated from a perch caught in subalpine Lake Iseo (Italy) and the tapeworms were reared in hamsters. Both specimens contained cells with a highly variable number of chromosomes ranging from18 to 27. Nevertheless, the largest portion of mitotic figures (47%) showed a number corresponding to the triploid set, 3n = 27. Accordingly, the karyotype of the analyzed specimens consisted of 9 triplets of metacentric chromosomes. Fluorescence in situ hybridization (FISH) with the 18S rDNA probe clearly demonstrated the presence of 3 clusters of hybridization signals on the triplet of chromosome 7, thus confirming the triploid status of the specimens. FISH with a telomeric (TTAGGG)n probe confined hybridization signals exclusively to the terminal chromosomal regions, supporting the earlier findings that this repetitive motif is a conserved feature of tapeworm telomeres.

Keywords: 18S rDNA; parthenogenesis; polyploidization; telomeres; triploid.

MeSH terms

  • Animals
  • Chromosomes / genetics
  • Cytogenetic Analysis
  • Diphyllobothriasis / parasitology*
  • Diphyllobothrium / genetics*
  • Diphyllobothrium / metabolism
  • In Situ Hybridization, Fluorescence
  • Karyotype
  • RNA, Helminth / analysis
  • RNA, Ribosomal, 18S / analysis
  • Triploidy*

Substances

  • RNA, Helminth
  • RNA, Ribosomal, 18S