Chromosomes of Acanthocephalus lucii (Muller, 1776) were observed using conventional staining techniques. The number of chromosomes in females and in their developing eggs (2n = 8) as well as the mean (La) and relative length (Lr) of the chromosomes and the localization of the centromere (Ic) were determined. Peculiarities in the behaviour of the chromosomes are also described.

Karyological studies of Trichinella spiralis, T. pseudospiralis, T. nativa and T. nelsoni were undertaken. Comparison of the karyotypes of these Trichinella species showed that the chromosome number of all four species is 2n = 6 for female specimens and 2n = 5 for males. The differences found in the relative chromosome lengths of the individual Trichinella species are not significant. Centromeric index data indicate that T. nativa and T. spiralis have similar centromere dispositions and differ from the other two species by the disposition of the centromere of the first submetacentric chromosome pair. In T. nativa and T. nelsoni the univalent sex chromosome is the second in size. It is slightly submetacentric chromosome, while in T. spiralis and T. pseudospiralis it is the third metacentric chromosome. The data from the karyological investigations may be used as additional karyosystematic characteristics when differentiating the Trichinella species studied.

The karyotypes ofVampirolepis nana, Hymenolepis diminutaandVampirolepis erinacei(Cestoda: Cyclophyllidea) have been described. The number of chromosomes in the diploid cell of the studied taxa was 2n = 12. The absolute and the relative lengths of the chromosomes ofV. nanaandH. diminutawere measured. The chromosomes had similar metric values. In the karyotypes ofV. nanaandH. diminutathere were ten one-arm chromosomes and.one two-arm chromosome (the third in length in the karyotype ofV. nanaand the first in length in the karyotype ofH. diminuta). The chromosomes in the karyotype ofV. erinaceihad one arm which was proved by the terminal localization of the constitutive heterochromatin. The examined species differed in the morphology of some chromosomes in the karyotypes.

The morphometric characteristics of the chromosomes and the variability of the C-heterochromatin blocks in the trematodes Echinoparyphium aconiatum, E. recurvatum, Echinostoma revolutum, E. echinatum, Hypoderaeum conoideum, Isthmiophora melis, Paryphostomum radiatum, Neoacanthoparyphium echinatoides, Plagiorchis maculosus and Opisthioglyphe ranae are determined. The terminal and subterminal localisation of the centromere is a characteristic of the taxa examined. Typical two-arm chromosomes are rare. The karyotype of the examined trematodes is asymmetrical, and this asymmetry is a result of differences in the lengths of the chromosome arms. It is proved that the regression of the lengths of the chromosome arms has a linear character with a similar angle of slope in the different species. Centric fusion and unreciprocal translocations are accepted as contributing significantly to chromosome changes. A hypothesis on the possible mechanism of chromosome changes in the trematode karyotype is proposed.

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