Description of Crenosoma vismani n. sp., parasitic in the lungs of Lynx lynx (L.) (Carnivora: Felidae), with identification key to the species of the genus Crenosoma Molin, 1861 (Nematoda: Crenosomatidae)

A new species of Crenosoma Molin, 1861 is described from the lungs of the Eurasian lynx, Lynx lynx (L.) (Carnivora: Felidae). Crenosoma vismani n. sp. differs from other species of the genus in the morphology of the male copulatory organs (two ventral rays originating from a common stem; three lateral rays with common stem; gubernaculum 79–92 μm long, well developed, spoon-shaped; spicules 232–253 μm long, slightly curved, with robust dorsal appendage) and a vulva with rounded, prominent vulvar cuticular appendage is located in middle region of body in females. An analysis of the morphology and life-cycle data for Crenosoma petrowi Morozov, 1939 from Ursus americanus Pallas indicate that this nematode should be described as a new species. The validity of Crenosoma schulzi Gagarin, 1958 is resurrected. A new identification key for the species of Crenosoma is provided. Published records of the genus Crenosoma from definitive hosts and patterns of host specificity are presented. Morphological data revealed that the genus Crenosoma should contain 15 species (14 with valid names) with different host specificity, ranging from oioxenous to euryxenous. However, a review of the current genetic data indicates that the actual number of Crenosoma spp. is greater, and the host range is still unknown, even in Europe.

     

Comparison of rDNA sequences from colchicine treated and untreated sporocysts of Phyllodistomum folium and Bucephalus polymorphus (Digenea)

The most frequently used antimitotic agent in cytogenetic studies is colchicine. We investigated whether the initial treatment of trematodes for karyological analysis with colchicine would have mutagenic or degradational effect on rDNA sequences. Dreissena polymorpha is the intermediate host of Phyllodistomum folium and Bucephalus polymorphus, and the sporocyst stage of these trematode species develop, respectively, in the gills and gonads of this mussel. Sporocysts of P. folium and B. polymorphus were obtained from D. polymorpha collected from waterbodies in Belarus and in Lithuania. 5.8S and 28S rDNA genes, ITS1 and ITS2 of P folium and B. polymorphus were sequenced and compared, and no nucleotide sequence differences between colchicine treated and untreated trematodes were found. Based on these results, we conclude that colchicine treatment for 3-5 h has no mutagenic or degradational effect on rDNA sequences. During the course of this investigation, two genetically different P. folium samples were noted in Belarus.     

Pronounced karyological divergence of the North American congeners Sphaerium rhomboideum and S. occidentale (Bivalvia: Veneroida: Sphaeriidae)

Chromosome sets of two North American sphaeriid species, Sphaeriumrhomboideum Say, 1822 and S. occidentale Lewis, 1856, were studiedusing conventional Giemsa staining and karyometric analysis.Pronounced karyological divergence of congeners was revealed.The diploid number of 2n = 44 was reported for S. rhomboideumand this is the first record of a diploid species in the highlypolychromosomic Nearctic sphaeriid fauna. The karyotype wascharacterized by medium-sized and small chromosomes, which decreasedin size gradually from 5.77 to 1.9 µm. Biarmed chromosomeswith medially and submedially located centromeres predominated,but six pairs of subtelo-telocentric elements were also observedin the karyotype. The estimated mitotic chromosome number forS. occidentale ranges from 189 to 213, but most of the cellsexamined contained about 204–209 chromosomes. A firstattempt to karyotype a polyploid sphaeriid was made. It wasrevealed that the comparatively large and middle-sized chromosomescould be grouped in four, so the karyotype presumably evolvedthrough tetraploidization. The small chromosomes formed thelarge fraction, about 137. Due to their similar and indistinctmorphologies, it was impossible to arrange them into subgroupswith confidence. Revealed karyological characteristics are discussedwith reference to the existing phylogenetic interpretationsof the evolutionary history of the Sphaeriinae. (Received 8 November 2006; accepted 25 June 2007)     

Differentiation of European freshwater bucephalids (Digenea: Bucephalidae) based on karyotypes and DNA sequences

Three species of bucephalid digeneans are known in European freshwater habitats. In this study parthenitae of Rhipidocotyle campanula (Dujardin, 1845) and R. fennica Gibson, Taskinen & Valtonen, 1992, infecting unionid bivalves, and adult Bucephalus polymorphus von Baer, 1827 from perch (Perca fluviatilis L.) were investigated using karyological analysis and DNA sequencing. Our previously published data on genetic characteristics of parthenitae of B. polymorphus from Dreissena polymorpha Pallas were used for comparative analysis. Ribosomal DNA sequences (ITS2 and 28S rDNA) were used to estimate the phylogenetic relationships of the three bucephalid species. Very close phylogenetic affinity between investigated species was revealed; the sequence difference between the two species of Rhipidocotyle Diesing, 1858 (3.78% based on 28S) was comparable with intergeneric differences observed in comparisons of B. polymorphus with R. campanula and R. fennica (3.43% and 4.49% based on 28S, respectively). A high degree of similarity was noted in karyotype structure of the two species of Rhipidocotyle. The diploid chromosome sets consist of 14 bi-armed chromosomes with the first pair of metacentric elements markedly larger than the remaining chromosomes. This chromosome set structure is also specific to B. polymorphus. One specimen of Anodonta anatina L. was infected with tetraploid R. fennica (4n = 28). On the basis of karyotype characters and molecular data, species of the genus Rhipidocotyle cannot be recognised as more closely related to each other than to B. polymorphus. Our findings of Lithuanian and Ukrainian populations of unionid mussels infected with R. fennica provide evidence that this species occurs not only in Finland but also in Central and Eastern Europe. Previous reports of B. polymorphus in unionids in these regions are equivocal because of possible confusion with R. fennica.     

Comparison of the developmental stages of some European allocreadiid trematode species and a clarification of their life-cycles based on ITS2 and 28S sequences

Genetic data were used to examine the diversity in some allocreadiid trematodes. Nuclear ribosomal DNA (ITS2 and partial sequences of 5.8S and 28S) was sampled from sexual adult and ‘larval’ stages. From these and previous reference datasets phylogenetic trees were constructed. The results uncovered genetically distinct lineages within Bunodera luciopercae (Müller, 1776), suggesting that the two Palaearctic subspecies, B. l. luciopercae and B. l. acerinae Roitman & Sokolov, 1999, and Nearctic B. luciopercae from Perca flavescens may represent distinct species with a restricted host-specificity. Identical rDNA was revealed for the sexual adult of B. l. acerinae and ‘larval’ B. luciopercae described by Wiśniewski (1958). An unexpected match between the rDNA sequences of adult B. l. luciopercae and ‘larval’ Allocreadium isoporum (sensu Wiśniewski, 1958) was also detected. The adult A. isoporum (Looss, 1894) differs significantly from the ‘larval’ A. isoporum, the level of rDNA sequence divergence between them (8.6 % for 5.8S-ITS2-28S sequences and 6.26% for 28S) being consistent with the level expected for intergeneric variation. These results revealed the possible existence of a cryptic species complex within the nominal species B. luciopercae and a clear need for reconsideration of some of the accepted, but largely untested, tenets regarding allocreadiid life-cycles.