Bacterial communities associated with invasive populations of Bactrocera dorsalis (Diptera: Tephritidae) in China

The oriental fruit fly Bactrocera dorsalis (Hendel) is a destructive insect pest of a wide range of fruits and vegetables. This pest is an invasive species and is currently distributed in some provinces of China. To recover the symbiotic bacteria of B. dorsalis from different invasion regions in China, we researched the bacterial diversity of this fruit fly among one laboratory colony (Guangdong, China) and 15 wild populations (14 sites in China and one site in Thailand) using DNA-based approaches. The construction of 16S rRNA gene libraries allowed the identification of 24 operational taxonomic units of associated bacteria at the 3% distance level, and these were affiliated with 3 phyla, 5 families, and 13 genera. The higher bacterial diversity was recovered in wild populations compared with the laboratory colony and in samples from early term invasion regions compared with samples from late term invasion regions. Moreover, Klebsiella pneumoniae and Providencia sp. were two of the most frequently recovered bacteria, present in flies collected from three different regions in China where B. dorsalis is invasive. This study for the first time provides a systemic investigation of the symbiotic bacteria of B. dorsalis from different invasion regions in China.

Rotation of male genitalia in various species of phlebotomine sandfly

Phlebotomine sandflies, vectors of Leishmania (Kinetoplastida: Trypanosomatidae) parasites that affect millions of people worldwide, breed in terrestrial biotopes. As immature stages are rarely accessible, the detection of their natural breeding sites is primarily based on findings of juvenile males with unrotated external genitalia. In males, permanent 180° rotation on the longitudinal body axis occurs soon after eclosion; however, no study has as yet addressed this aspect in detail. The present study describes the timing and duration of the rotation of male external genitalia in eight highly medically important sandfly species belonging to the genera Sergentomyia, Lutzomyia and Phlebotomus (all: Diptera: Psychodidae), kept under controlled laboratory conditions. The average duration of rotation was species-specific and varied from 12 h in Sergentomyia schwetzi to 33 h in Phlebotomus sergenti. Significant differences in rotation times were found among species, even between two closely related species of the subgenus Larroussius, Phlebotomus orientalis and Phlebotomus tobbi. The rotation of genitalia in all three studied genera was randomly oriented and similar numbers of clockwise and counter-clockwise events were observed. The study also addresses the effects of some external factors. In all species studied, rotation was not affected by the time of day of eclosion. Similarly, no differences in total rotation time were found between Phlebotomus papatasi males maintained at 25 and 20 °C, respectively. The present findings will assist in the search for natural breeding sites and in studies aimed at elucidating strategies for integrated sandfly and leishmaniasis control.

Laboratory rearing of immature Culicoides peregrinus Kieffer, a potential vector of bluetongue virus

Culicoides peregrinus (Kieffer) (Diptera: Ceratopogonidae) was reared from egg to adult using four different combinations of food and substrate (T1: absorbent cotton, mud broth with 2% yeast; T2: 1% agar, mud broth with 2% yeast; T3: absorbent cotton, nutrient broth; T4: absorbent cotton, 2% yeast). Field-collected engorged females exhibited mean fecundity of 82.45 ± 4.00. The highest rate of emergence and largest adults were obtained in T1, and the lowest rate of emergence was observed in T4. Two-way analyses of variance with post hoc Tukey tests showed significant differences in age at pupation, pupal weight and wing length among the various treatments, although the sex ratio was 1 : 1 in all food/substrate combinations. The successful rearing of immature C. peregrinus is an encouraging step towards the establishment of a laboratory colony of this prevalent species associated with livestock.