Metrical and Non-metrical Skull Variations in Norwegian Wild Mink (Mustela vison Schreber)

Variations in fifteen metrical measurements and six non-metrical traits in 131 mink skulls were investigated. The skulls were subdivided geographically into three samples: Eastern Norway, Western Norway and Trøndelag. Separation into juveniles and adults was in accordance with the criterion that all sutures are closed in adults. This seemed to work well. No age or sex variations were found in the non-metrical traits. Relatively little geographic variation found in either the metrical measurements or the non-metrical traits indicated little genetic variation. Gene-flow is regarded as one of the reasons for this.     

Invasion and Early Development of Sarcocystis muris (Apicomplexa,Sarcocystidae) in Tissue Cultures1

Ultrastructural observations on the invasion and early development of merozoites (bradyzoites) of Sarcocystis muris in Madin-Darby canine kidney (MDCK) cells are presented. Invading merozoites cause the host cell plasmalemma to invaginate; they form a membrane junction (moving junction) and move into the host cell where they are enclosed in a primary parasitophorous vacuole (PV). Within 30–45 min after becoming intracellular, merozoites begin to vacate the newly established primary PV and move, forming a new membrane junction, into a secondary PV. Simultaneously with the movement of the parasite, the contents of dense granules in the apical part of the merozoites are shed by exocytosis into the lumen of the developing secondary PV. A lamella of the endoplasmic reticulum of the host cell becomes attached to the PV membrane, forming a PV limited by three host cell membranes.     

Tick infection rates with Borrelia Ixodes ricinus versus Haemaphysalis concinna and Dermacentor reticulatus in two locations in eastern Germany

Unfed nymphal Ixodes ricinus, Haemaphysalis concinna, and adult Dermacentor reticulatus were collected in two locations of Saxony in July and September 1991 by flagging. In July, the abundance of nymphal I. ricinus was about 2-3 times higher than that of nymphal H. concinna, a time of the year when nymphs of both species are reported to have a seasonal peak of activity. No D. reticulatus were flagged concurrently. In September, host-seeking activity of nymphal I. ricinus was again quite high as was that of adult D. reticulatus but only low numbers of nymphal H. concinna were collected. The flagged ticks were individually examined for Borrelia by an indirect immunofluorescence assay (I. ricinus: n = 414; H. concinna: n = 96; D. reticulatus: n = 116). The prevalence of Borrelia (probably B. burgdorferi) in I. ricinus varied from 12.1% to 21.0%. No borreliae were found in H. concinna. Of the examined D. reticulatus from one site (n = 97) 11.3% contained either B. burgdorferi or a related Borrelia. This may be the first finding of Borrelia in an Eurasian Dermacentor species.     

Intraspecific VariabiIity in Acrobeloides nanus (de Man) Anderson (Nematoda, Cephalobidae) and a Note on External Morphology

Uniparental free-living nematodes, Acrobeloides nanus (de Man, 1880) Anderson, 1968, were isolated from the raw humus layer at two coniferous forest sites in central Sweden. Intraspecific variability in progeny from single females cultured both on agar and in soil was studied. Females from field populations were much shorter than those from laboratory cultures and significant differences in length between cultured specimens from the two sites were found. No significant difference in length of animals from comparable cultures on agar and in soil was obtained. The substrate had some effect on the tail shape, but not on the labial probolae shape. No significant differences in taxonomic characters between populations from the two localities were observed. Enzyme analyses by horizontal starch gel electrophoresis showed qualitative differences in isozyme patterns of malate dehydrogenase (MDH) and superoxide dismutase (SOD) in populations from the two sites, while the esterase patterns were unstable with time and less suitable for population analysis.