Planktonic ciliates of the Baltic Sea (a review)

The data on the ciliates species composition are given for the Baltic Sea, a brackish-water semi-closed water body where a considerable part of the planktonic fauna is presented by freshwater species. During the observation period, 789 species of ciliates were found, 160 of which are typical planktonic forms. The ecological characteristics of ciliates are given, along with an assessment of their role in the productivity of the Baltic Sea pelagic communities.     

New epidemiological features on animal trypanosomiasis by molecular analysis in the pastoral zone of Sideradougou, Burkina Faso

A multidisciplinary work was undertaken in the agropastoral zone of Sidéradougou, Burkina Faso to try to elucidate the key factors determining the presence of tsetse flies. In this study the PCR was used to characterize trypanosomes infecting the vector ( Glossina tachinoides and Glossina palpalis gambiensis ) and the host, i.e. cattle. A 2-year survey involved dissecting 2211 tsetse of the two Glossina species. A total of 298 parasitologically infected tsetse were analysed by PCR. Trypanosoma vivax was the most frequently identified trypanosome followed by the savannah type of T. congolense and, to a lesser extent, the riverine forest type of T. congolense , and by T. brucei . No cases of T. simiae were found. From the 107 identified infections in cattle, the taxa were the same, but T. congolense savannah type was more frequent, whereas T. vivax and T. congolense riverine forest types were found less frequently. A correlation was found between midgut infection rates of tsetse, nonidentified infections and reptile bloodmeals. These rates were higher in G.p. gambiensis , and in the western part of the study area. T. vivax infections were related to cattle bloodmeals, and were more frequent in G. tachinoides and in the eastern study area. The PCR results combined with bloodmeal analysis helped us to establish the relationships between the vector and the host, to assess the trypanosome challenge in the two parts of the area, to elucidate the differences between the two types of T. congolense , and to suspect that most midgut infections were originating from reptilian trypanosomes.     

The unusual reproductive system of head and body lice (Pediculus humanus)

Insect reproduction is extremely variable, but the implications of alternative genetic systems are often overlooked in studies on the evolution of insecticide resistance. Both ecotypes of Pediculus humanus (Phthiraptera: Pediculidae), the human head and body lice, are human ectoparasites, the control of which is challenged by the recent spread of resistance alleles. The present study conclusively establishes for the first time that both head and body lice reproduce through paternal genome elimination (PGE), an unusual genetic system in which males transmit only their maternally derived chromosomes. Here, we investigate inheritance patterns of parental genomes using a genotyping approach across families of both ecotypes and show that heterozygous males exclusively or preferentially pass on one allele only, whereas females transmit both in a Mendelian fashion. We do however observe occasional transmission of paternal chromosomes through males, representing the first known case of PGE in which whole‐genome meiotic drive is incomplete. Finally, we discuss the potential implications of this finding for the evolution of resistance and invite the development of new theoretical models of how this knowledge might contribute to increasing the success of pediculicide‐based management schemes.     

Effects of 5-azacytidine on the development of parthenogenetic mouse embryos

This study describes the effects of 5-azacytidine (5-azaC) on the development of diploid parthenogenetic embryos (PE) of CBA, C57BL/6 and (CBA × C57BL/6)F₁ mice in vitro at the 1-cell or the blastocyst stage or in vivo after implantation. Our findings indicate that genomic imprinting is modulated by genetic background. Non-fertilized C57BL/6 eggs form diploid parthenogenetic blastocysts at a much higher frequency than CBA eggs. Eggs from F₁ hybrid females form parthenogenetic blastocysts at an approximately intermediate level between these inbred strains of mice. C57BL/6 PE do not develop to the somite stages. In contrast, CBA PE and F₁ PE develop to various somite stages. Following administration of 5–azaC at 1.0 μmol/L in vitro at the 1- -cell stage, the number of implantations of C57BL/6 PE transferred to pseudopregnant females increased. In contrast, the number of implantations and somite F₁ PE did not significantly change following exposure to 5–azaC. However, administration of 5-azaC at the 1-cell stage stimulates development of somite F₁ PE. Administration of 5-azaC at 0.2 and 1.0 μmol/L in vitro at the blastocyst stage did not change the number of implantations of C57BL/6 PE. However, the number of implantations and somite CBA PE decreased. After injection of 5azaC at 0.24mg/kg in vivo at day 8 of gestation, some F₁ PE developed to 26–35 somites compared with a maximum of 25 somites in controls. The different effects of 5-azaC on the development of PE depend upon the mouse strain used and the stage of development.     

Fruit morphology in Tragopogon L. (Compositae: Lactuceae) from the Iberian Peninsula

Achenes of all the Tragopogon species from the Iberian Peninsula were examined by means of scanning-electron microscopy and stereomicroscopy. The achenes of the eight species are described, illustrated and compared. The results are contrasted with the systematics of this genus. The isolated position of T. lamottei with regard to the other seven species is noted. A key is provided to enable the different species to be distinguished.     

First record in America of Aedes albopictus naturally infected with dengue virus during the 1995 outbreak at Reynosa, Mexico

Abstract Mosquito collections were conducted during a dengue outbreak in Reynosa, Tamaulipas, Mexico, July-December 1995. A total of 6694 adult mosquitoes (four genera and nine species) were captured, of which 2986 (78.3% females and 21.7% males) were Aedes albopictus and 2339 (39.7% females and 60.3% males) were Ae.aegypti. These two species comprised 84.2% of the total collection. Specimens were grouped into pools, nearly 50% of them processed for detection of virus by cythopathic effect in C6-36 and VERO cell cultures and by haemagglutination test. Five pools gave positive haemagglutin-ation reactions and were examined by immunofluorescence using monoclonal antibodies to flavivirus and to dengue virus. One pool of ten Ae.albopictus males was positive for dengue virus: serotypes 2 and 3 were identified by serotype-specific monoclonal antibodies arid confirmed by RT-PCR. This is the first report of Ae.albopictus naturally infected with dengue virus in America. Also, it is the very first time Ae.albopictus males have been found infected with dengue virus in the wild.