Pathogeny of archaic mycobacteria at the emergence of urban life in Egypt (3400 BC).

In a previous study, we extracted, amplified and sequenced a DNA fragment from bone lesions similar to those of bone tuberculosis in a predynastic skeleton (Egypt, around 3400 BC). This 65 kDa gene fragment encodes the surface of the mycobacterium responsible for the lesions. In the present study, we reconstructed the phylogenetic tree of the Mycobacterium family using this fragment and 51 sequences of pathogens and environmental mycobacteria. This reconstruction enabled us to polarise the phylogenic tree and to confirm the originality of the sequence and its ancestral character. According to a recent evolutionary scenario for the Mycobacterium tuberculosis complex, these data suggest the pathogenicity of an archaic mycobacterium at the emergence of urban life. This result could lead to a better understanding of present day evolutionary processes, especially the emergence or re-emergence of non-tuberculosis mycobacteria infection and disease.

Antennal structure and oviposition behavior of the Plutella xylostella specialist parasitoid: Cotesia plutellae.

Although several species of the genus Cotesia are used in biological control programs against insect caterpillars throughout the world, little is known of their oviposition behavior. We describe here the types and distribution of antennal sensilla in Cotesia plutellae, a larval parasitoid of Plutella xylostella, and we analyze its oviposition behavior. Seven types of sensilla were found on both males and females. Only sensilla trichodea type II, with a putative contact chemoreceptive function, was significantly more abundant in females than in males, and its morphology and position on antennomeres were linked to the antennation behavior used by females during host search. We conclude that gustatory stimulus following antennal contact is probably the key stimulus inducing oviposition behavior. The sensilla type assumed to be implied in oviposition behavior was present in C. plutellae but not in two closely related species (C. glomerata and C. rubecula), which is discussed.

Molecular phylogeny of the Erebia tyndarus (Lepidoptera, Rhopalocera, Nymphalidae, Satyrinae) species group combining CoxII and ND5 mitochondrial genes: a case study of a recent radiation.

The genus Erebia is one of the more controversial groups among the Holarctic Lepidoptera. In this genus, composed of around 100 mountain species, the Erebia tyndarus complex has certainly been a major source of debate for more than a century. According to the literature, between 2 and 11 species, and at least 45 subspecies or semi-species have been recognized. For the first time, we provide a complete molecular study, based on the ND5 and CoxII mitochondrial gene sequences, including all the recognized species and 60% of the subspecies of the entire group, with European, Caucasian, Siberian and North-American taxa. Our analyses led us to recognize 11 species even though there was some poor discrimination between Western Europe species. A complete study of the events of speciation is presented in the light of glacial and interglacial cycles during the Pleistocene.

Geography and host specificity: two forces behind the genetic structure of the freshwater fish parasite Ligula intestinalis (Cestoda: Diphyllobothriidae).

Parasite species with global distributions and complex life cycles offer a rare opportunity to study alternative mechanisms of speciation and evolution in a single model. Here, genealogy and genetic structure, with respect to geography and fish host preference, have been analyzed for Ligula intestinalis, a tapeworm affecting freshwater fish. The data analyzed consisted of 109 tapeworms sampled from 13 fish host species in 18 different localities on a macrogeographic scale. Two mitochondrial genes, cytochrome oxidase subunit I and cytochrome B, and the nuclear sequence of intergenic transcribed spacer 2 (ITS2) were used for the genetic reconstruction. Different evolutionary patterns were found at the local and at the global geographic scales. On a local scale, the flat genetic structure was mainly attributed to contiguous range expansion. Migrating birds are the most likely cause of the homogenisation of the whole population, preventing the creation of significant genetic barriers. By contrast, on a global scale, genetically distant and well-separated clusters are present in different geographic areas. Reproductive isolation was found even between clades living in sympatry and infecting the same definitive host, suggesting the existence of efficient biologically determined genetic barriers, and thus possibly separate species. Although the ITS2 sequences were found to display considerable intragenomic variability, their relationships were generally in good agreement with the topology derived from mitochondrial genes.

Chemically mediated burrow recognition in the Mexican tarantula Brachypelma vagans female.

Chemically mediated communication is common in spiders but has been poorly studied in burrowing tarantulas. This study aimed to determine whether chemical cues influence the behaviour of females of Brachypelma vagans, a Mexican species of tarantula, during encounters with previously inhabited burrows or with extracts from the silk of conspecific females. In laboratory choice tests, female tarantulas entered a burrow that had previously been inhabited by a conspecific female significantly more frequently than a burrow that had never been inhabited. The identity of the previous inhabitant also affected the number of spiders that chose to enter a burrow. Spiders were quicker to choose and enter a burrow previously inhabited by themselves than a burrow previously inhabited by a conspecific or a burrow that had not been previously inhabited. Hexane, methanol and dichloromethane extracts of conspecific silk elicited different responses from female tarantulas when extracts were placed on filter paper disks at one end of an experimental arena with a control filter paper disk, on to which the corresponding solvent alone had been pipetted, placed on the other end of the arena. Spiders showed the strongest responses to hexane extracts of silk, with a significant preference to move towards the hexane extract and a significantly greater period of time spent in proximity to the hexane extract compared to the control disk. Overall and in contrast to expectations, tarantulas were most strongly attracted to the cues left by other conspecific females. As encounters between B. vagans females usually lead to aggression and mortality of one of the participants, we conclude that chemical cues are not signals that are deliberately released by burrow-inhabiting females but may inadvertently escape and cannot be easily suppressed.

Host selection by a kleptobiotic spider.

Why do kleptobiotic spiders of the genus Argyrodes seem to be associated with spiders of the genus Nephila worldwide? Observations following introduction of experimental insect prey of different sizes and weights on to host webs revealed that: (1) small prey are more effectively retained on the web of Nephila clavipes than on the web of another common host, Leucauge venusta. (2) N. clavipes did not consume small prey that accumulated on the web whereas larger, heavier prey were enveloped and stored. (3) We observed clear partitioning of prey items between N. clavipes and Argyrodes spp.; diet selection by Argyrodes did not overlap with that of N. clavipes but closely overlapped with that of L. venusta. (4) L. venusta responds very quickly to prey impact whereas N. clavipes is slower, offering a temporal window of opportunity for Argyrodes foraging. (5) The ability of L. venusta to detect and respond to small items also means that it acts aggressively to Argyrodes spp., whereas N. clavipes does not. Consequently, food-acquisition behaviours of Argyrodes were clearly less risky with N. clavipes compared with L. venusta. We conclude that when a kleptobiotic organism has a choice of various host species, it will opt for the least risky host that presents the highest rate of availability of food items. The fact that Nephila species present such characteristics explains the worldwide association with Argyrodes kleptobiotic spiders.