Abstract: Many parasites engaged in complex life cycles manipulate their hosts in a way that facilitates transmission between hosts. Recently, a new category of parasites (hitch-hikers) has been identified that seem to exploit the manipulating effort of other parasites with similar life cycle by preferentially infecting hosts already manipulated. Thomas et al. (Evolution 51 (1997) 1316) showed that the digenean trematodes Microphallus papillorobustus (the manipulator) and Maritrema subdolum (the hitch-hiker) were positively associated in field samples of gammarid amphipods (the intermediate host), and that the behaviour of Maritrema subdolum rendered it more likely to infect manipulated amphipods than those uninfected by M. papillorobustus. Here I provide experimental evidence demonstrating that M. subdolum is unlikely to be a hitch-hiker in the mentioned system, whereas the lucky candidate rather is the closely related but little known species, Microphallidae sp. no. 15 (Parassitologia 22 (1980) 1). As opposed to the latter species, Maritrema subdolum does not express the appropriate cercarial behaviour for hitch-hiking.

Abstract: Samples of seven of the 10 morphological species of midges of the Culicoides imicola complex were considered. The importance of this species complex is connected to its vectorial capacity for African horse sickness virus (AHSV) and bluetongue virus (BTV). Consequently, the risk of transmission may vary dramatically, depending upon the particular cryptic species present in a given area. The species complex is confined to the Old World and our samples were collected in Southern Africa, Madagascar and the Ivory Coast. Genomic DNA of 350 randomly sampled individual midges from 19 populations was amplified using four 20-mer primers by the random amplified polymorphic DNA (RAPD) technique. One hundred and ninety-six interpretable polymorphic bands were obtained. Species-specific RAPD profiles were defined and for five species diagnostic RAPD fragments were identified. A high degree of polymorphism was detected in the species complex, most of which was observed within populations (from 64 to 76%). Principal coordinate analysis (PCO) and cluster analysis provided an estimate of the degree of variation between and within populations and species. There was substantial concordance between the taxonomies derived from morphological and molecular data. The amount and the different distributions of genetic (RAPD) variation among the taxa can be associated to their life histories, i.e. the abundance and distribution of the larval breeding sites and their seasonality.

Abstract: OBJECTIVE: Feeding patterns of triatomines have contributed to elucidate its biology. Triatoma vitticeps, naturally infected with T. cruzi, has been found in domiciles. Its behavior and epidemiological patterns were investigated. METHODS: One-hundred and twenty two specimens of T. vitticeps were captured from February 1989 to April 1993 in two areas of Triunfo municipality, a subdistrict of Santa Maria Madalena municipal district, State of Rio de Janeiro, Brazil. The insects were dissected and their intestinal contents were removed and tested. It was used antisera from: man, cow, horse, dog, pig, armadillo, opossum, rodent, and bird. RESULTS: From the total analyzed, 79 were positive and 43 were negative to the nine antisera tested: armadillo (30.3%) > human and pig (13.1%) > bird and dog (11.5%) > horse (5.7%) > opossum (4.9%) > rodent (4. 1%) > cow (3.3%). Blood meals ranged from 0 to 4 and 6 in the following distribution: 0 = 25.41%; 1 = 45.08%; 2 = 10.66%; 3 = 6. 56%; 4 = 1.64%, and 6 = 0.82%. Nine of the 122 insects captured were not examined, 74 (65.54%) were positive for T. cruzi infection and 39 (34.51%) were negative. CONCLUSIONS: These results identified the T. vitticeps as being a sylvatic species and trypanosomiasis as being an enzootic disease. Epidemiological vigilance will be important to provide more information regarding the behavior of the species

Abstract: Much work on natural and sexual selection is concerned with the conspicuousness of visual patterns (textures) on animal and plant surfaces. Previous attempts by evolutionary biologists to quantify apparency of such textures have involved subjective estimates of conspicuousness or statistical analyses based on transect samples. We present a method based on wavelet analysis that avoids subjectivity and that uses more of the information in image textures than transects do. Like the human visual system for texture discrimination, and probably like that of other vertebrates, this method is based on localized analysis of orientation and frequency components of the patterns composing visual textures. As examples of the metric's utility, we present analyses of crypsis for tigers, zebras, and peppered moth morphs.

Abstract: For 20 years after the influenza A virus was discovered in the early 1930s, it was believed to be almost exclusively a human virus. But in the 1950s closely related viruses were discovered in diseases of horses, pigs and birds. Subsequently influenza A viruses were found to occur frequently in many species of birds, particularly ducks, usually without causing disease. Researchers showed that human and animal strains can hybridise thus producing new strains. Such hybrids may be the cause of pandemics in man. Most pandemics have started in China or eastern Russia where many people are in intimate association with animals. This situation provides a breeding ground for new strains of influenza A virus.