Biomedical subjects

Luc Legal

Publications and source records attributed to Luc Legal.

3 recordsLinked to original sources

PubMed2006

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.

Communicable Diseases, Emerging↗

PubMed2005

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.

Animals↗

PubMed2004

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.

Animals↗