bluuebunny/crossref_metadata_2025_split huggingface dataset:
Life‐cycle stage morphology of Psoroptes mange mites
Authors: Sanders A. , Froggatt P. , Wall R. , Smith K. E. 
Published: March 2003

SummaryDetailed life‐cycle stage descriptions for the ectoparasitic mite Psoroptes ovis (Hering) (Acari: Psoroptidae) from rabbit hosts (syn. Psoroptes cuniculi) are presented. The results resolve a number of contradictions in the literature relating to the recognition of the life cycle stages of these mites. This study supports the view that there are two distinct male nymphal stages, both lacking dorsoposterior tubercles. The male tritonymph is significantly larger than the protonymph and has five pairs of metapodosomal setae rather than three. In addition, male tritonymphs have two pairs of cuticular pits on the central metapodosoma rather than the single pair of the protonymph. The results also show that the female protonymph can be distinguished from the male nymphal stages and the female tritonymph. Both female nymphal stages possess dorsoposterior tubercles, but the protonymph is significantly smaller than the tritonymph. In addition, the protonymph possesses three pairs of metapodosomal setae rather than five, one pair of cuticular pits rather than two, and a pulvillus on leg IV which is absent in the female tritonymph. The presence of dorsoposterior tubercles enables the female nymphs to be distinguished easily from the males. By contrast, distinguishing between the nymphal stages of the same sex relies on the identification of both the number of metapodosomal setae and cuticular pits. These descriptions are used to produce a key, which allows the various stages of both sexes to be distinguished.
Insecticide‐treated cattle for tsetse control: the power and the problems
Authors: Hargrove J. W. , Omolo S. , Msalilwa J. S. I. , Fox B. 
Published: March 2003

SummaryTrypanosomiasis control increasingly involves financial input from livestock owners and their active participation. If control is carried out on smaller scales than in the past, methods such as aerial and ground spraying and sterile insect techniques will have reduced application. There will be increased reliance on trypanocidal drugs, and bait methods of tsetse control – where flies are attracted to point sources and killed. If drug resistance develops, cheap and simple bait methods offer the only means of disease control that might be applied, and paid for, by stockowners themselves. The methods have been effective in some circumstances, but not in others, and it is important to understand the reasons for the successes and the failures. Analysis is presented of the results of two Tanzanian tsetse control campaigns involving the use of insecticide‐treated cattle. Between 1991, &, 1996, following the introduction of widespread dipping in the Kagera Region, trypanosomiasis declined from > 19 000 cases to < 2400 and deaths from > 1000 to 29. On four ranches in the region, tsetse have been almost eliminated and trypanosomiasis prophylaxis is no longer used. Similarly aggressive use of pyrethroids on Mkwaja Ranch in Tanga Region has not had such dramatic effects. Tsetse and trypanosomiasis are still common, despite high levels of prophylaxis and the deployment of ≈ 200 odour‐baited targets. The difference in the results is attributed to a combination of the much smaller area covered by treated animals at Mkwaja, a greater susceptibility to re‐invasion and a more suitable habitat for the flies. A better understanding of the dynamics of the use of insecticide‐treated cattle is needed before we can predict confidently the outcome of particular control operations.
Invasion of West African cattle by the tick Amblyomma variegatum
Authors: Stachurski F. 
Published: March 2003

SummaryStudies in Cameroon and Burkina Faso examined the invasion process of cattle by adult Amblyomma variegatum Fabricius (Acari: Ixodidae) ticks. Nearly all the ticks picked up in the pasture during grazing were found on the limb ends, near the hooves, where they temporarily attached. Then when the cattle lay down, the ticks moved from the feet towards the predilection sites, where they attached definitively. Many ticks disappeared during this displacement. All the female ticks and approximately 70% of the males were thus unable to attach to the predilection sites as long as the pioneer males had not attached and started to produce attraction‐aggregation‐attachment pheromones. Nevertheless, A. variegatum females and males attached to the feet in similar numbers during grazing, whether the cattle were already infested or not, indicating that stimuli originating from the hosts are powerful enough to attract both sexes. After attachment of the pioneer males, the number of ticks that successfully reached the predilection sites increased. However, even on infested animals, 40–50% of A. variegatum ticks found near the hooves after the grazing periods disappeared during the night following their capture. When moving from the temporary attachment sites towards the final ones, one‐third of the ticks changed the individual host. Considering this two‐stage infestation process, it is suggested that a targeted tick control, using a foot‐bath, might greatly reduce cattle infestation. In particular, it could be effective in traditional herds, with animals grazing permanently during the day, lying down only once back in the night pen.
Effect of carbon dioxide on the Oriental cockroach Blatta orientalis
Authors: Gannon B. , Le Patourel G. , Young R. 
Published: March 2003

SummaryExposure to high concentrations of carbon dioxide (CO2) killed adult and nymphal stages of the oriental cockroach Blatta orientalis L. (Dictyoptera: Blattidae) with LT50 values of 11.5–16.2 h for 60% CO2 in air and 5.7–7.1 h for 100% CO2 at 20°C; corresponding LT50s at 28°C were 2.8–4.6 h for 60% CO2 in air and 2.3–3.6 h for 100% CO2. Complete kill of mobile stages was obtained within 24 h using 60% CO2 at 20°C. Survivors of treatments with 100% CO2 at 28°C remained completely paralysed for up to 3 days post‐treatment and took up to 5 days to regain normal movement, but adult females then resumed production of oothecae with no significant loss in fecundity. Oothecae 5 or 30 days after deposition required 60–84 h exposure to 60% CO2 at 20°C to prevent emergence of nymphs but less time using 100% CO2 at 28°C. At 28°C, when adult females were treated with 100% CO2 and 52% r.h. for 6 h (giving 100% mortality) loss of weight was significantly greater than that following treatment with air at 52% r.h. for 6 h (giving no mortality). However, significantly greater weight loss also occurred when they were treated with dried air (< 10% r.h.) for 6 h, also with no mortality. The toxicity of CO2 to mobile stages of the oriental cockroach appeared to result from irreversible effects on the nervous system, rather than from water loss during exposure.
Evidence for p‐glycoprotein modification of insecticide toxicity in mosquitoes of the Culex pipiens complex
Authors: Buss D. S. , Mccaffery A. R. , Callaghan A. 
Published: March 2003

Abstract Pesticide resistance has parallels with multi‐drug resistance syndrome of tumours in clinical medicine, which has been linked to an ATP‐dependent pump, p‐glycoprotein (P‐gp). P‐gps pump drugs out of the cell, thereby reducing cellular concentrations of the chemical. P‐gps have been found in several invertebrate species and have been shown to provide a defence against environmental xenobiotics, including pesticides.This study used a model cell culture system to investigate the interaction of pesticides with P‐gp. Ivermectin and endosulfan were shown to be strong inhibitors of dye transport out of cells, which is a standard measure of P‐gp modulation. We then investigated the action of a P‐gp inhibitor, verapamil (calcium channel blocker), on insecticide toxicity to fourth‐instar mosquito larvae of the Culex pipiens L. complex (Diptera: Culicidae). Verapamil increased toxicity to examples of three insecticide classes (cypermethrin, endosulfan, ivermectin), but not to chlorpyrifos (organophosphate).The discovery of a novel protective mechanism in mosquitoes, with a wide substrate range, has implications for the control of important pest and vector species.
Motivation for medical school: the relationship to gender and specialty preferences in a nationwide sample
Authors: Vaglum  , Wiers‐Jenssen  , Ekeberg  
Published: March 2003

ObjectivesMotivation for going to medical school and career plans of a 1 year cohort of students entering medical school in Norway (n = 420 response rate: 90%, 54% women, mean age: 22 years) were surveyed by a postal questionnaire the first month after they had started.DesignMotives for choosing medicine were categorized into three indexes: `people orientated', `status/security orientated' and `natural science orientated' motives.SettingUniversity of Oslo.SubjectsMedical students.ResultsStudents picked out which they preferred among 53 specialties. The highest motivational scores were on the `person orientated' index, female students scoring higher than men. Female students were, however, nearly as highly motivated by status/security and interests in natural science as were men. `Person orientated' and `natural science orientated' motives exerted the strongest influence on specialty preferences. Those who preferred family medicine were more person orientated and less natural science orientated, while those who preferred internal medicine were more natural science orientated. Father being a physician did not influence the motivational pattern, but increased the preference for laboratory and internal medicine. Frequently repeated upper secondary school exams for acceptance into medical school were negatively related to natural science motivation, and to increased preference for becoming a surgeon.ConclusionsIn this first month of the curriculum students regarded person oriented motives as the most important for becoming a doctor.
Microevolution, low clonal diversity and genetic affinities of parthenogeneticSitobionaphids in New Zealand
Authors: Wilson A. C. C. , Sunnucks P. , Hales D. F. 
Published: March 2003

AbstractIn sharp contrast to their southeast Asian and European counterparts, Sitobion miscanthi andS.nearfragariaeaphids in Australia exhibit a complete absence of sexual reproduction. This demands an explanation within the context of the evolution and maintenance of sex and parthenogenesis. Accordingly, we executed a genetic analysis of the two species in neighbouring New Zealand. Microsatellites and single‐stranded conformation polymorphism/sequence analysis of the nuclear gene elongation factor 1α were used to identify aphid clones and confirm species identification, respectively. Karyotypic variation was also investigated. The New Zealand fauna showed few (nonrecombining) genotypes and appears to have received migrants from both Australia and Asia. Other genotypes have apparently arisenin situin New Zealand, exhibiting stepwise mutation of microsatellite alleles and also karyotypic change. Thus, these data represent rare evidence of evolution within wild‐living parthenogenetic lineages. Karyotypic changes appear to occur at a rate even greater than that of microsatellite evolution. Strong geographical partitioning of genotypes/karyotypes was found, with certain ones predominating over large areas. These data suggest that clonal selection could be important in the distribution and patterning of genetic variation. We present a model to explain the genetic patterns, with particular reference to the absence of sexual reproduction inSitobionaphids in New Zealand and Australia.
Influence of glaciation on divergence patterns of the endemic minnow, Zacco pachycephalus, in Taiwan
Authors: Wang Hurng‐Yi , Tsai Mung‐Pei , Yu Ming‐Jenn , Lee Sin‐Che 
Published: March 2003

AbstractThe genetic subdivision of the endemic minnow, Zacco pachycephalus, in 12 rivers of Taiwan was studied by allozyme electrophoresis. Among 26 loci surveyed, six were significantly differentiated among sites. Allozyme genotype frequencies within samples accord with Hardy–Weinberg expectations. A highly divergent genetic structure among sites (FST = 0.497) with low genetic variability within samples (H = 0.006–0.062, mean = 0.03) suggests that local populations originated from a small number of founders. upgma and Fitch trees derived from Nei’s genetic distance and hierarchical analysis of FST values reveal that samples of Z. pachycephalus can be divided into northern, middle, and southern subgroups and that most genetic variation (87%) is distributed among rather than within groups. It is proposed that there were two isolated refugia during the most recent glacial period, and that populations of the southern group (Group I) originated from a southern refugium in Taiwan below the boundary of the Kaoping River, and other groups (Group II), including northern and middle subgroups, originated from a refugium located on the extinct landbridge between Taiwan and mainland China. The postglacial division between northern and middle subgroups may be due to hydrological differences between these two regions.
Genetic variation within a fragmented population ofSwietenia humilisZucc.
Authors: White G. M. , Boshier D. H. , Powell W. 
Published: March 2003

AbstractWith large tracts of once continuous forest now modified by human use to leave reduced and highly fragmented stands of trees, the determination of the genetic consequences of forest fragmentation is a priority for ascertaining the conservation value of resultant stands, and in formulating sustainable management strategies. The levels and distribution of genetic diversity over 10 microsatellite loci were investigated within a fragmented population of the neotropical treeSwietenia humilisZucc. High levels of genetic variation, typical of a highly outcrossing species, were found in all fragments at all loci (meanHE = 0.548). The majority of the variation was within rather than between fragments (RST = 0.032), giving high indirect estimates of gene flow (Nm = 8.9), probably reflecting the genetic structure of the trees present under more continuous forest. A high proportion of loci also showed significant departures from Hardy–Weinberg equilibrium with associated significant levels ofFIS. The initial effects of fragmentation were, however, seen in the fragments through the loss of low‐frequency alleles present in the continuous ‘control’ stand. The percentage of this allelic loss increased with a decrease in fragment size.
Patterns of microsatellite polymorphism in the range‐restricted bonobo (Pan paniscus): considerations for interspecific comparison with chimpanzees (P. troglodytes)
Authors: Reinartz G. E. , Karron J. D. , Phillips R. B. , Weber J. L. 
Published: March 2003

AbstractThe endangered great ape,Pan paniscus(bonobo) has the smallest range of the African apes. Virtually nothing is known about the genetic diversity or genetic structure of this species, while substantial amounts of polymorphism have been reported for the bonobo’s widespread congener, the chimpanzee (P. troglodytes). Given its restricted range, what is the extent of genetic variation in the bonobo relative to the chimpanzee, and is the bonobo genetically depauperate? To investigate patterns of genetic polymorphism, bonobos of wild origin were genotyped for 28 microsatellite loci. The mean number of alleles per locus (5.2) and the mean observed heterozygosity (0.52) in bonobos were similar to variation observed in a wild chimpanzee community (P. t. schweinfurthii). The rarer bonobo is not genetically depauperate and may have genetic diversity comparable to the eastern chimpanzee subspecies. Bonobos have approximately 55% of the allelic diversity and 66% of the observed heterozygosity exhibited by all three chimpanzee subspecies sampled across equatorial Africa. Resampling techniques were used to quantify the effects of sample size differences and number and choice of loci between bonobos and chimpanzees. The examination of these variables underscores their importance in accurately interpreting interspecific comparisons of diversity estimates.
Multiple paternity increases effective size of southern Atlantic salmon populations
Authors: Martinez J. L. , Moran P. , Perez J. , De Gaudemar B. , Beall E. , Garcia‐Vazquez E. 
Published: March 2003

AbstractGenetic analyses were performed on the progeny of Atlantic salmon (Salmo salar L.) sampled in natural redds of three rivers flowing into the Bay of Biscay, the Nivelle, the Mandeo and the Sella. These rivers are at the southern limit of the European distribution of the species and their populations are small and endangered by human activities. Nine variable number of tandem repeat (VNTR) loci (five minisatellites and four microsatellites) were used for parentage analysis. Multiple male participation was recognized in the fertilization of eggs. A large proportion was fertilized by precociously mature parr. We demonstrate that multiple paternity derived from mature parr is crucial for the conservation of genetic variability in small populations of Atlantic salmon.
Higher impact of female than male migration on population structure in large mammals
Authors: Tiedemann Ralph , Hardy Olivier , Vekemans Xavier , Milinkovitch Michel C. 
Published: March 2003

AbstractWe simulated large mammal populations using an individual‐based stochastic model under various sex‐specific migration schemes and life history parameters from the blue whale and the Asian elephant. Our model predicts that genetic structure at nuclear loci is significantly more influenced by female than by male migration. We identified requisite comigration of mother and offspring during gravidity and lactation as the primary cause of this phenomenon. In addition, our model predicts that the common assumption that geographical patterns of mitochondrial DNA (mtDNA) could be translated into female migration rates (Nmf) will cause biased estimates of maternal gene flow when extensive male migration occurs and male mtDNA haplotypes are included in the analysis.
The molecular population genetics of regulatory genes
Authors: Purugganan Michael D. 
Published: March 2003

AbstractRegulatory loci, which may encode both trans acting proteins as well as cis acting promoter regions, are crucial components of an organism’s genetic architecture. Although evolution of these regulatory loci is believed to underlie the evolution of numerous adaptive traits, there is little information on natural variation of these genes. Recent molecular population genetic studies, however, have provided insights into the extent of natural variation at regulatory genes, the evolutionary forces that shape them and the phenotypic effects of molecular regulatory variants. These recent analyses suggest that it may be possible to study the molecular evolutionary ecology of regulatory diversification by examining both the extent and patterning of regulatory gene diversity, the phenotypic effects of molecular variation at these loci and their ecological consequences.
Genetic variability among endangered Chinese giant salamanders, Andrias davidianus
Authors: Murphy Robert W. , Fu Jinzhong , Upton Darlene E. , De Lema Thales , Zhao Er‐Mi 
Published: March 2003

AbstractThe endangered Chinese giant salamander (Andrias davidianus) is endemic to mainland China. Genetic divergence among six populations of the species was investigated by means of isozyme electrophoresis and mitochondrial DNA (mtDNA) sequences. Forty allozyme loci were resolved for all populations; the amount of genetic divergence among populations was comparable to that in other amphibians. mtDNA sequences showed a similar level of divergence. The population from Huangshan is distinct from other populations, indicating the existence of localized divergence. Both allozyme and mtDNA data failed to associate the populations into a pattern corresponding to the three Chinese river systems, which may be the consequence of human relocation. Conservation policies should emphasize the protection of localized populations and cessation of human‐facilitated introductions. Future studies should focus on investigating the divergence among localized populations from isolated mountain regions, particularly using more fine‐grained techniques such as microsatellite DNA.
Maternal control of sex ratio in Rana rugosa: evidence from DNA sexing
Authors: Sakisaka Y. , Yahara T. , Miura I. , Kasuya E. 
Published: March 2003

AbstractParental control of primary sex ratio has been reported in a mammal (red deer), some birds, and a snake. However, it remains uncertain whether other vertebrates including Amphibia can control sex ratio. In this paper, we examined the possibility in a wild population of the Japanese frog Rana rugosa which has female heterogamety. Sex ratios of their eggs were determined using DNA markers. The eggs were sampled in the field from May to August in 1998. Each egg was then sexed by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) using a sex‐specific DNA marker. The result showed a male bias early in the season which changed to a female bias later, suggesting that females of R. rugosa can control the primary sex ratio.
Genetic lineages and postglacial colonization of grayling (Thymallus thymallus, Salmonidae) in Europe, as revealed by mitochondrial DNA analyses
Authors: Koskinen M. T. , Ranta E. , Piironen J. , Veselov A. , Titov S. , Haugen T. O. , Nilsson J. , Carlstein M. , Primmer C. R. 
Published: March 2003

AbstractIn stark contrast to other species within the Salmonidae family, phylogeographic information on European grayling, Thymallus thymallus, is virtually nonexistent. In this paper, we utilized mitochondrial DNA polymerase chain reaction–restriction fragment length polymorphism (mtDNA PCR–RFLP) and sequence variation to infer the postglacial dispersal routes of T. thymallus into and within northern Europe, and to locate geographically, potential evolutionarily distinct populations. Mitochondrial analyses revealed a total of 27 T. thymallus haplotypes which clustered into three distinct lineages. Average pairwise interlineage divergence was four and nine times higher than average intralineage divergence for RFLP and sequence data, respectively. Two European grayling individuals from the easternmost sample in Russia exhibited haplotypes more genetically diverged from any T. thymallus haplotype than T. arcticus haplotype, and suggested that hybridization/introgression zone of these two sister species may extend much further west than previously thought. Geographic division of the lineages was generally very clear with northern Europe comprising of two genetically differentiated areas: (i) Finland, Estonia and north‐western Russia; and (ii) central Germany, Poland and western Fennoscandia. Average interpopulation divergence in North European T. thymallus was 10 times higher than that observed in a recent mtDNA study of North American T. arcticus. We conclude that (i) North European T. thymallus populations have survived dramatic Pleistocene temperature oscillations and originate from ancient eastern and central European refugia; (ii) genetic divergence of population groups within northern Europe is substantial and geographically distinct; and (iii) the remainder of Europe harbours additional differentiated assemblages that likely descend from a Danubian refugium. These findings should provide useful information for developing appropriate conservation strategies for European grayling and exemplify a case with a clear need for multinational co‐operation for managing and conserving biodiversity.