Volume 58, Nº 1 (2024)

Variability and phenotypic diversity of Diplostomum petromyzifluviatilis metacercariae from two lamprey species, the river lamprey Lampetra fluviatilis (Baltic Sea basin) and the Pacific lamprey Lethenteron camtschaticum (Arctic Ocean basin), were studied. It was found that metacercariae from both hosts are similar as in the number of variations in body shape, oral and ventral suckers, and pharynx, so in the frequency of occurrence. Differences in population diversity by variations in the shape of the Holdfast organ were found. It was shown that gostal forms possess the similar range of variability of plastic characters, but has different distribution of frequency classes of the variation curve. We hypothesized that the change in the distribution and character of variation in the size of metacercariae from the Arctic lamprey is one of the population mechanisms of species adaptation to the northern limit of its range.

In the littoral zone of the oxbow of the Lyutoga River (Southern Sakhalin), which remains connected to the main channel, a high population density of parasitic copepods was found (103 ind./m²). Ergasilus briani Markewitsch, 1933, widely distributed in Eurasia, but not previously recorded in South Sakhalin and noted only for one water body in northwestern Sakhalin (Lake Sladkoe), demonstrated the highest population density (98 ind./m²). The abundance of the second species, Thersitina gasterostei (Pagenstecher, 1861) was significantly lower (5 ind./m²). T. gasterostei has previously been noted in South Sakhalin, but the present finding is the first for the Lyutoga River. The high abundance of free-living stages of ergasilids is presumably related to the reproductive peak and the hydrological nature of the collection site (littoral area with a slow current and strong overgrowing with macrophytes).

Polymorphidae is a family of acanthocephalans, obligatory parasites with a complex life cycle involving arthropods as intermediate hosts and vertebrates of different taxa as definitive hosts. The current taxonomy of Polymorphidae seems to be equivocal. Its type genus Polymorphus has been shown to be polyphyletic based on molecular data. We obtained partial sequences of 28S rDNA gene and cox1 mitochondrial gene of two species of this genus, Polymorphus phippsi and P. magnus, and used them in a reconstruction of the polymorphid phylogeny. As a result, P. magnus was included into the same clade as the type species of the genus, P. minutus, while P. phippsi appeared to be close to Profilicollis spp. The position of P. phippsi agrees with the polyphyly of Polymorphus but does not correspond to its taxonomic status based on described phenotypic characters.

In the outbreak of the pine moth Dendrolimus pini (Linnaeus, 1758) (Lepidoptera, Lasiocampidae) in Voronezh Oblast, mass infection of its pupae with the pupal parasitoid wasp, Aprostocetus xanthopus Nees, 1834 (Hymenoptera, Eulophidae), was revealed. It had destroyed from 7 to 25% of all phytophage pupae, which indicates its significant impact on the cocoon moth abundance. Previously, this parasitoid was frequently noted as an entomophage of the pine moth, but it has always been low in number. The biology of A. xanthopus has not been studied enough completely and this hampers its use as an agent of biological protection of pine forests from the pine moth.