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PubMed1986

[Chromosomal study of Anopheles gambiae and Anopheles arabiensis in Ouagadougou (Burkina Faso) and various neighboring villages].

Adult females of Anopheles gambiae s.1. were collected by pyrethrum spray catch in Ouagadougou (Burkina Faso, formerly Upper Volta) and in four neighbouring villages. The collections have been carried out mostly during the 1984 rainy season. Monthly collections in some sampling sites allowed a preliminary longitudinal study. By analysis of nurse cell polytene chromosomes in adult females, An. gambiae s.str. and An. arabiensis were identified in the study area. Both species showed polymorphisms for various paracentric inversions. In all samples of An. arabiensis the frequencies of the alternative karyotypes were in Hardy-Weinberg equilibrium, suggesting panmictic conditions. Conversely, An. gambiae s.str. showed a different situation, since most of its samples had strong deficiency of certain expected heterokaryotypes. This same phenomenon was already observed in Mali, leading to the splitting of gambiae s.str. into different chromosomal forms, partially or totally reproductively isolated from each other. Each chromosomal form is characterized by different chromosomal polymorphisms. Two of these forms, Mopti and Savanna, were detected in the study area. Mopti chromosomal form is apparently associated with the presence of permanent waters (i.e. the "barrages" north of the town), while Savanna is usually found in situations where breeding places are mainly dependent from rain (e.g. in villages far from "barrages" or at the town's center).

Animals↗
PubMed1987

Morphological differentiation in Anopheles maculatus of Thailand accompanied with genetical divergence assessed by hybridization.

Anopheles maculatus of Thailand were distinguished morphologically into densely and sparsely scaled types and cross-mating experiments between these types revealed a substantial amount of genetic divergence. Progeny of wild females of An. maculatus collected throughout Thailand from north to south were examined morphologically with respect to adult tergal pale scales. Northern progeny broods could be separated into densely scaled (willmori) and sparsely scaled (maculatus) types, or W and M types, respectively. Using these two types of An. maculatus from Chiang Rai and Nakhon Phanom, cross-mating experiments were conducted, which resulted in sterile F1 male hybrids in one direction of cross and very low survival rate of F1 male hybrids in the reciprocal cross. However, southern broods could not be separated clearly because of intergradation of scaling. These results indicate that Thai An. maculatus involves at least 2 forms differentiated morphologically, as well as by incomplete reproductive isolation.

Animals↗
PubMed1986

[Variability of satellite DNA in 2 groups of field mice (Rodentia, Microtinae)].

Nuclear DNAs of three forms of Microtus juldashi--M. carruthersi (group 1) and of three subspecies of polytypic species Alticola macrotis (group 2) were compared. Intensive interpopulational karyotype differentiation was observed in both groups, particularly, for centromeric heterochromatin quantity and localization. As satellite DNAs (satDNAs) were present in C-heterochromatin of the Rodents groups studied, the latter were used as a model for comparison of the satDNAs in the species in statu nascendi. With this view, the nuclear DNAs were studied by means of the neutral CsCl equilibrium centrifugation. In both groups examined, no correlation was found between the presence, the characteristics of the satDNAs and morphological as well as cytogenetic features of the animals. These results are an indirect confirmation of the idea, according to which satDNA does not possibly play significant role in the development of the reproductive isolation and species formation.

Animals↗
PubMed1987

[The genosystematics of yeast genera Willopsis zender and Zygowillopsis kudriavzev].

The data have been compared on the yeast genomic divergence obtained in genetic molecular and biological studies of the yeast genera Williopsis and Zygowilliopsis taken as an example. The hybridization analysis, the enzyme electrophoresis and DNA reassociation comprise the noncontradictory estimation of the yeasts relation. Different methods demonstrate a convincing species discreteness among the yeast genomes. The reproductive isolation of the yeast taxons is defined more invariably by the genetic methods. A new combination Williopsis sargentensis (Wickerham et Kurtzman) Naumov comb. nov. has been formed.

Genes, Fungal↗
PubMed1967

Hybridization in the Culex pipiens complex.

Studies of crosses of different strains of C. p. molestus in widely separated countries have given very similar results: crosses between certain combinations may be fully fertile or partly sterile.In the Melbourne area of Australia, molestus x fatigans hybrids are common during summer and autumn; a similar situation occurs in Kansas, USA. In Victoria (Australia) cross-breeding between molestus and fatigans is common, but both retain their identity because of the existence of ecological barriers. It has been suggested that molestus represents a population with high gene frequencies for autogeny and stenogamy.Numerous crossing experiments have been made between fatigans and pipiens or molestus, for the most part successfully. Only in a few instances has partial or complete sterility occurred. A similar type of partial sterility has been observed when fatigans or molestus has been crossed with Culex globocoxitus.C. p. australicus is reproductively isolated from both molestus and fatigans.

Animals↗
PubMed1983

Cross-mating studies with Psoroptes ovis (hering) and Psoroptes cuniculi delafond (Acarina: psoroptidae).

Reciprocal cross-matings of Psoroptes ovis and P. cuniculi occurred and produced viable offspring through the F2 generation. Hybrids of these crosses were infective to both rabbits and cattle. Mean lengths of the male l4 setae of the parental species differed significantly from each other as well as from those of the hybrid males. These data show that P. ovis and P. cuniculi are not reproductively isolated. Because viable, fertile hybrids are produced, cross-matings of P. ovis and P. cuniculi are not suitable as a suppression method of cattle scabies.

Animals↗
PubMed1983

Experiments in crossing two strains of Anopheles barbirostris van der Wulp 1884 (Diptera: Culicidae) in Thailand.

Crossing experiments between two strains of Anopheles (Anopheles) barbirostris from Chumphon and Chon Buri provinces in Thailand were done by induced copulation in order to determine the genetic relationship. On comparison of the F1 hybrids and those of their parent species as the control, there was a difference in the number of eggs laid, hatchability and viability. The low viability of the F1 hybrids with high larval and pupal mortalities, producing only a few F hybrids, and the fact that F1 hybrids' salivary chromosome showed asynapsis suggest there exists reproductive isolations between both strains. The data presented suggest that these two strains exhibit possible presence of a species complex in An. barbirostris.

Animals↗
PubMed1981

Deliberations on the problems of mammomonogamus species (Nematoda, Syngamidae) in ruminants.

The taxonomy of mammomonogamids parasitic in ruminants is discussed with regard to their different rates of variability in Cuba and Mexico. Since their variability is large and the existence of biological species is not based on their morphology but on the reproduction isolation of populations, the authors came to the conclusion that the specific analysis of mammomonogamids will be convincing only in case that it is carried out using taxonomic experiments of special orientation.

Animals↗
PubMedDate not supplied

[The adaptive potentials of human head and clothes lice when parasitizing on man].

Two species of lice (Pediculus capitis and P. corporis) from various areas of Russian and adjacent republics were examined and analysed for their specific features. Each species was characterized in terms of its morphology, karyology, biology, reproductive isolation, parasitic connections, epidemiology and role as casual organisms. The two species live apart on the same host and they can live on it simultaneously. P. corporis has a higher influence on the host's metabolism than P. capitis; P. corporis seems to be a younger species and its adaptation to man has not achieved the level that is inherent in P. capitis. The head lice (P. capitis) do not affect an epidemic process in typhus and so pediculosis should be identified by the species of lice.

Adaptation, Physiological↗
PubMedDate not supplied

Chromosomal speciation and folliculogenesis in the semisterile interspecific hybrids of the varying lemmings, genus Dicrostonyx.

Karyotypes of Dicrostonyx torquatus torquatus and D. vinogradovi that are very similar phenotypically differ at least by 13-14 chromosomal rearrangements including centric and tandem fusions, fissions and paracentric inversion. In their male hybrid F1 spermatogenesis is arrested on early pre-meiotic stages, the female hybrids are semisterile. Histological investigation of ovaries has demonstrated reduced number of follicles, higher percentage of atretic follicles and an acceleration of folliculogenesis in hybrids as compared with the parental forms. As a result of the acceleration, the number of mature follicles and ovulations is not significantly diminished in the hybrid females, and their semisterility is caused, to a great extent, by high prenatal loss which most likely arises from the chromosomal imbalance in F2 hybrids. Thus, the mechanism suggested by the concept of chromosomal speciation is active, but not alone in forming reproductive isolation between twin species of the varying lemming.

Animals↗
PubMed1976

[Mice of southern France: genetic characterization of two groups of sympatric populations].

An electrophoretic survey of five proteins (lactate dehydrogenase, isocitrate dehydrogenase, esterase-1, esterase-2, albumin) shows that there are two groups of populations strongly (or completely) reproductively isolated. The first group does not differ from Mus musculus L. The second exhibits several new biochemical traits and should probably be considered a different species.

Animals↗
PubMed1997

Genetic and ecological data on the Anisakis simplex complex, with evidence for a new species (Nematoda, Ascaridoidea, Anisakidae).

Isozyme analysis at 24 loci was carried out on anisakid nematodes of the Anisakis simplex complex, recovered from various intermediate/paratenic (squid, fish) and definitive (marine mammals) hosts from various parts of the world. A number of samples were found to belong to A. simplex sensu stricto and Anisakis pegreffii, widely extending the geographic ranges and the number of hosts of these 2 species. In addition, a new distinct gene pool was detected, showing different alleles with respect to A. simplex s. str and A. pegreffii at 5 diagnostic loci (99% level). Samples with this gene pool were assigned to a new species, provisionally labeled A. simplex C. Reproductive isolation between A. simplex C and the other 2 Anisakis species was directly assessed by the lack of hybrid and recombinant genotypes in mixed samples from sympatric areas, i.e., Pacific Canada for A. simplex C+A. simplex s. str., South Africa and New Zealand for A. simplex C+A. pegreffii, even when such samples were recovered from the same individual host. Similar levels of genetic divergence were observed among the three species (DNei from 0.36 to 0.45). At the intraspecific level, Canadian Pacific and Austral populations of A. simplex C were found to be genetically rather differentiated from one another (average DNei = 0.08), contrasting with the remarkable genetic homogeneity detected within both A. simplex s. str. and A. pegreffii (average DNei about 0.01). Accordingly, a lower amount of gene flow was estimated within A. simplex C (Nm = 1.6) than within the other 2 species (Nm = 5.4 and 17.7, respectively). Anisakis simplex C showed the highest average values of genetic variability with respect to both A. simplex s. str. and A. pegreffii, e.g., expected mean heterozygosity. Hr = 0.23, 0.16, and 0.11, respectively, in the 3 species. Data on geographic distribution and hosts of the 3 members so far detected in the A. simplex complex are given. Their ecological niche is markedly differentiated, with a low proportion of hosts shared. Intermediate and definitive hosts of A. simplex s. str. and A. pegreffii appear to belong to distinct food webs, benthodemersal, and pelagic, respectively; this would lead to different transmission pathways for the parasites.

Animals↗
PubMed1997

Anopheline species complexes & malaria control.

Species complexes comprising morphologically indistinguishable biological species that are reproductively isolated, are of common occurrence among anophelines. A list of anopheline species complexes identified so far in the world has been given. To demonstrate the importance of species complexes in malaria control, we report the Anopheles culicifacies complex as a case study. An. culicifacies is a major vector of malaria in India and neighbouring countries. This complex comprises four sibling species, A, B, C and D. Stratification of U.P. state and district Allahabad has been shown taking into consideration the biological differences among sibling species, viz., sibling species composition and vectorial potential- species B is a non-vector while others are vectors. To achieve cost effective vector control, microlevel stratification at least at the block level has been suggested. Implications of differential responses of sibling species to DDT and malathion in field operations have been discussed. To achieve selective and sustainable control, and to reduce the unnecessary selection pressure of insecticides, an insecticide spray strategy to control An. culicifacies has been provided.

Animals↗
PubMed1997

The comparison of two methods in the anthropological study of linguistic differentiation.

The paper presents the application of hidden Markov models (HMM) in the analysis of the linguistic microdifferentiation of 48 reproductively isolated populations in the Eastern Adriatic. The mathematical method is described in detail when applied for the recognition of the two main dialects (cakavian and stokavian) present in the investigated area, using two distinguished HMM. The resulting classification of villages is compared to those of the clustering methods applied previously for the same purpose.

Anthropology, Cultural↗
PubMed1998

Microsatellite analysis of the population structure of a vancouver island sockeye salmon (Oncorhynchus nerka) stock complex using nondenaturing gel electrophoresis

Variation at four microsatellite loci, Omy77, Ots100, Ots3, and Ots103, was characterized for three populations of sockeye salmon (Oncorhynchus nerka) found within 50 km of each other in the Barkley Sound region of Southwest Vancouver Island, British Columbia. We used a simple polyacrylamide gel electrophoresis technique to analyze microsatellite alleles amplified from total genomic DNA extracts of liver and archived scales. Classes from several years were examined for each population, with little significant interannual variability detected. Each microsatellite locus was highly polymorphic with 10 alleles at Omy77, 12 alleles at Ots100, 16 alleles at Ots3, and 17 alleles at Ots103; average observed heterozygosities were also high at 75%, 76%, 69%, and 85% respectively. Fst values and pairwise tests indicated that the populations had significantly different allele frequencies, suggesting that the three populations are reproductively isolated. Our results suggested that microsatellite loci can be analyzed with a simple technique to reveal population structure of sockeye salmon on a small geographic scale.

Journal Article↗
PubMedDate not supplied

[Immunological and biological characteristics of viral isolates of porcine reproductive and respiratory syndrome].

Described in the paper are study results of some immunobiological properties of 5 field isolates of the porcine reproductive and respiratory syndrome virus (PRRSV), obtained in Russia and Byelorussia in 1998-2001. According to the research work, the PRRSV isolates with different immunobiological properties have been circulating in the territories of Russia and Byelorussia. Three of the 4 examined virus isolates were found to be pathogenic and 1 avirulent to pigs.

Animals↗
PubMed1998

Experimental inoculation of swine at various stages of gestation with a Danish isolate of porcine reproductive and respiratory syndrome virus (PRRSV).

Following intranasal inoculation of three groups of pregnant swine (in total 11 dams) with a Danish isolate of porcine reproductive and respiratory syndrome virus (PRRSV) on or about day 85, 70 and 45 of gestation, respectively, reproductive disturbances were observed in the first two groups. Transplacental transmission of PRRSV occurred in four out of five litters from dams inoculated around day 85 of gestation and in two out of three litters from dams inoculated on day 72 of gestation. In the third group, inoculated around day 45 of gestation, transplacental infection could not be demonstrated. Thirty-two (56%) piglets from dams inoculated on day 85 of gestation and 14 (33%) piglets from dams inoculated on day 72 of gestation, were transplacentally infected. Sixteen (28%) and six (14%) piglets, respectively, in these groups became infected in the perinatal period. Thirty-two (56%) piglets from dams inoculated on day 85 of gestation were stillborn or died within a 6-8 weeks observation period, 29 being stillborn or dying within the first two weeks of observation. Thirteen (30%) piglets from dams inoculated on day 72 of gestation died within the two weeks observation period. The duration of the viraemic phase varied considerably, from one day to four weeks, for both dams and their offspring. Most frequently, PRRSV was isolated from lung and/or tonsil tissues from dead and euthanized piglets younger than 14 days of age. Histopathological investigations of piglets typically revealed focal nonsuppurative inflammatory conditions, especially in the lung and heart. In conclusion, the present results support the hypothesis, that PRRSV infection of dams late in pregnancy has the greatest likelihood of transplacental infection of fetuses.

Animals↗
PubMed1995

Antigenic differences between European and American isolates of porcine reproductive and respiratory syndrome virus (PRRSV) are encoded by the carboxyterminal portion of viral open reading frame 3.

Antigenic differences between European and American isolates of porcine reproductive and respiratory syndrome virus (PRRSV) were revealed by serologic analysis of a recombinant protein derived from PRRSV open reading frame 3 (ORF 3). The hydrophilic carboxyterminal 199 amino acids encoded by the ORF 3 of a European (Lelystad) isolate of PRRSV were expressed as a recombinant fusion protein (BP03-P) in a baculovirus gene expression system. Sera from gnotobiotic swine exposed to prototypic reference European and American isolates of PRRSV and sera from conventionally reared European and American swine convalescing from naturally acquired PRRSV infections were used to characterize the BP03-P protein. Sera from gnotobiotic and conventionally reared swine exposed to European isolates of PRRSV were significantly more reactive (P < 0.01) with BP03-P than were the corresponding American PRRSV antisera using the indirect immunoperoxidase monolayer assay (IPMA). Prototypic European, but not American, PRRSV antisera also recognized BP03-P using western immunoblotting and radioimmunoprecipitation assay (RIPA) procedures. However, gnotobiotically derived antiserum to an atypical American-origin PRRSV was reactive with BP03-P by both IPMA and western immunoblot. Despite a predicted potential for N-linked glycosylation, studies with tunicamycin and peptide-N-glycosidase F (PNGase F) indicated that BP03-P was not N-glycosylated in either insect cell cultures or Trichoplusia ni larvae infected with the recombinant baculovirus. Sera from rabbits inoculated with BP03-P failed to neutralize both the European (Lelystad) and American (ATCC VR-2332) reference isolates of PRRSV and did not react by IPMA with PRRSV-infected cell cultures. Taken together, the data suggest that the carboxyterminal portion of PRRSV ORF 3 encodes a non-neutralizing viral peptide that is partially responsible for the serologic differences noted between European and most American isolates of PRRSV.

Animals↗