A cytogenetic study of three parasitic wasp species (Hymenoptera, Chalcidoidea, Eulophidae, Trichogrammatidae) from Brazil using chromosome morphometrics and base-specific fluorochrome staining

Abstract

Chromosomes of three chalcid wasp species from Brazil, Palmistichus elaeisis Delvare et LaSalle, 1993, Trichospilus diatraeae Cherian et Margabandhu, 1942 (both belonging to the family Eulophidae) and Trichogramma pretiosum Riley, 1879 (Trichogrammatidae), were studied using chromosome morphometrics and base-specific fluorochrome staining. The present study confirmed that these species respectively have 2n = 12, 14 and 10. Chromomycin A₃ / 4', 6-diamidino-2-phenylindole (CMA₃/DAPI) staining revealed a single CMA₃-positive and DAPI-negative band within haploid karyotypes of both Palmistichus elaeisis and Trichogramma pretiosum. This CG-rich band clearly corresponds to the nucleolus organizing region (NOR). Moreover, analogous multiple telomeric bands found on all chromosomes of Trichospilus diatraeae may also represent NORs. Certain features of karyotype evolution of the phylogenetic lineage comprising both Eulophidae and Trichogrammatidae are discussed. The results obtained during the present study demonstrate the importance of chromosome research on tropical parasitoids that remain poorly known in this respect.

Keywords: CMA3; DAPI; NORs; Parasitoids; chromosomes; karyotypes.

Figure 1.

Diploid karyotypes of parasitoids. a Palmistichus elaeisis b Trichospilus diatraeae c Trichogramma pretiosum. Bar = 5 μm.

Figure 2.

CMA₃/DAPI-stained metaphase plates of parasitoids. a–c Palmistichus elaeisis, female d–f Trichospilus diatraeae, female g–i Trichogramma pretiosum, male a, d, g CMA₃ staining b, e, h DAPI staining c, f, i merged CMA₃/DAPI staining. Arrows and arrowheads respectively indicate CMA₃-positive and DAPI-negative bands (NORs) as well as both CMA₃- and DAPI-positive chromosome arms. Bar = 10 μm.