Detection of 16SrIV-A phytoplasma DNA in Colpoptera sp. (Hemiptera: Nogodinidae) insects in Yucatan Peninsula, Mexico.

Lethal yellowing (LY) is a disease that affects coconut and other palm species. It is associated to phytoplasmas of the group 16SrIV and the only reported insect vector for this pathogen so far is Haplaxius crudus. H. crudus is present in Mexico and has been associated to 16SrIV phytoplasmas, however, it was not detectable during a LY outbreak in the coast of Yucatan, Mexico, suggesting the existence of other vector species. To test this hypothesis a survey of insects was carried out and a total of 3074 insects were captured during a year of monthly sampling. Ten taxonomic orders were identified in this sample, Hemiptera being the most abundant (N=2094), and these were classified into nine families. The leafhopper Colpoptera sp. from to the Nogodinidae family was de most abundant representing 56% of the total number of insects sampled and 23% of these samples resulted positive for LY phytoplasma by PCR detection. The BLAST comparison, virtual RFLP and phylogenetic analyses of the sequenced amplicons relate the detected phytoplasma to the subgroup 16SrIV-A. The findings presented herein suggest that Colpoptera sp. could be considered as a new putative vector of the LY-causing phytoplasmas in Mexico and a candidate for further research.

Role of host plant alternation in the precocity and intensity of parasitoid activity on of cereal aphids.

Integrated pest management programs tend to reduce the chemical input by enhancing the development of biological control. Cereal aphids cause important damages to winter wheat in Europe but are currently under the pressure of several parasitoid species (Braconidae: Aphidiinae). Previous ecological studies have reported the existence of an asynchrony between aphid and parasitoid populations in early spring in cereal cultures. Here, we tested the presence of rose bushes (Rosa rugosa) as a host plant for alternative aphid-host. Aphid and parasitoid densities were recorded for two years using the plant cutting sampling method. The main results were: (i) rose bushes constitute a potential reservoir of alternative aphid hosts species for a number of parasitoid and predator species, (ii) rose aphids appear earlier in spring and were more abundant than the aphids on wheat, (iii) parasitism activity in rose bushes is synchronized with cereal fields, however (iv) rose bushes management did not induce a decrease of cereal aphid population.

Controlling the mealworm Alphitobius diaperinus (Coleoptera: Tenebrionidae) in broiler and turkey houses: field trials with a combined insecticide treatment: insect growth regulator and pyrethroid.

Trials were conducted during one year under field conditions to control the lesser mealworm, Alphitobius diaperinus (Panzer), in broiler and turkey houses. The tested combined treatment included an adulticidal compound (pyrethroid: cyfluthrin) and a larvicidal compound (insect growth regulator [IGR]: triflumuron). The combined insecticide treatment greatly reduced the adult and larval stocks throughout the different broiler growing periods, and control of A. diaperinus populations was achieved by the end of the second treatment. Control of the insect population in a turkey house was not similar. A reestablishment of the insect population was observed during the second turkey growing period in summer. Building characteristics and management practices of the breeding system (duration of the breeding period, management of the litter) interact with the combined insecticide treatment and lead to a different efficiency.

A sexually dimorphic response in supercooling temperature, enhanced by starvation, in the lesser mealworm Alphitobius diaperinus (Coleoptera: Tenebrionidae).

The effect of starvation on supercooling temperature (SCP) distribution was investigated in adults and larvae of Alphitobius diaperinus (Coleoptera: Tenebrionidae).The mean values for SCPs of adults fed at 20 degrees C were -14.5+/-2.4 degrees C (31 males) and -10.3+/-1.3 degrees C (29 females). The distribution of the SCPs of these control adults was unimodal. No significant differences were observed in either mean wet weight or mean dry weight between males and females.The mean values for SCPs of adults starved for 1 month at 20 degrees C were found to be bimodal due to sexual dimorphism. The mean SCPs for males was lower (-17+/-2.6 degrees C; 28) than that for females (-11.2+/-1.8 degrees C; 26). No significant differences were observed in either mean dry weight or wet weight between males and females.The SCPs of both fed and starved larvae, kept for 1 month at 20 degrees C were -12.3+/-2.4 degrees C (fed) and -18.0+/-2.6 degrees C (starved).

Cold resistance in the lesser mealworm Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae).

We have investigated cold resistance, measured by the supercooling point (SCP) temperature, in life stages of the lesser mealworm, Alphitobius diaperinus (Coleoptera: Tenebrionidae), collected in Brittany poultry houses. Mean SCP values drastically increased during the insect ontogeny: egg (-26.1 C), first instar larvae (-21.6 C), last instar larvae (-15.5 C), pupae (-11.6 C), teneral adults (-12.0 C) and mature adults (-13.1 C). Nymphal metamorphosis and adult maturation did not promote substantial decrease of freezing resistance. The SCP values reflect the physiological states of the developmental stages especially the absence of ice nucleating agents: (i) lower SCP values in egg and unfed newly-emerged larvae I (i.e. -25.1 C), (ii) higher SCP values in fed larvae (i.e. -14.7 C), pupae and adults most likely due to the presence of ice nucleation sites in the gut. A tropical species, A. diaperinus, seems not to use its potential cold hardiness even in winter to remain in this warm habitat in temperate regions.

Survival at low temperatures in insects: what is the ecological significance of the supercooling point?

Many freezing-intolerant insects may die during long or even brief exposures to temperatures above their supercooling point (SCP). Consequently, the real ecological value of the SCP remains ambiguous, particularly for tropical species that never experienced cold exposures. The bimodal distribution of SCP is discussed in the light of sexual dimorphism. The importance of sex in insect cold hardiness has been regularly neglected and although we admit that in some species sex may be uneasy to determine, it should be taken into account in further studies. We suggest that supercooling ability may be, at least partially, a result of adaptations to other functions unrelated to cold, including the desiccation resistance. The potential causes of insect death at low temperatures during survival experiments have also been examined. Prolonged exposures at lethal low temperatures can produce deleterious effects (including death) even if the insect does not freeze; during long-term exposure to low temperatures the organisms may finally die from the exhaustion of energy reserves.

Are mummy characteristics reliable indicators of diapause and cold tolerance in the parasitoid wasp Aphidius rhopalosiphi (Braconidae, aphidiinae) ?

Many insect species have evolved different overwintering survival strategies such as cold tolerance or diapause. This study investigated the relationship between Aphidius rhopalosiphi mummy colour and cold tolerance and diapause. Mummy colour was insufficient to discriminate diapausing from non-diapausing individuals. This phenotypic character seems to reflect environmental conditions rather than direct developmental time and cocoon thickness (identification criteria of diapause). There is, however, a relationship between cold tolerance and mummy colour. Dark mummies exhibited significantly higher water content, survival at low temperature and lower supercooling point values than pale mummies. Mummy colour in Aphidius rhopalosiphi seems to be a phenotypic indicator of the cold tolerance.

Effects of temperature and humidity on transpiration in adults of the lesser mealworm, Alphitobius diaperinus (Coleoptera: Tenebrionidae).

Measurements of water loss were made on adults of the lesser mealworm, Alphitobius diaperinus, using a recording micro-electrobalance and a programmable heat circulator bath. This species originates in tropical regions and infests poultry houses in temperate countries. Two routes of water loss were examined: the general cuticle and via the spiracles. Temperature and relative humidity of the ambient air substantially affect the cuticular transpiration in adults (fresh body weights from 12 mg to 22 mg). At near 0% R.H., between 20 and 40 degrees C the rate of body water loss gradually increased; on the other hand, the insects gained weight in an atmosphere close to saturation. Above 40 degrees C transpiration flow abruptly increased coinciding with the start of vigorous locomotor activity. This critical point corresponds to the opening of the spiracles from which the water is expelled from the tracheal system.In dead specimens, killed by cyanide or solvent, the water vapour slowly diffused out of the spiracles and, as in atracheate insects, the transpiration curves did not show a peak as the air temperature was increased.The thermostupor point (TSP) occurred as the insects became motionless; the corresponding temperature is significantly affected by atmospheric relative humidity (TSP=47.4+/-0.6 degrees C at c. 0% R.H.; TSP=46.6+/-0.7 degrees C at c. 100% R.H.).The transpiration flow was about four times as fast in specimens treated with solvent as in the individuals (live or cyanide-killed) that had undamaged water-proof cuticle. This species has to cope with a double challenge: (i) to adapt its physiology and ecology to poultry-house conditions which constitutes an extension of its primary habitats, and (ii) to survive over winter; high drought resistance and heat tolerance may constitute a pre-adaptation to conquer anthropogenic air-conditioned sites.

Protection of mouse jejunum against lethal irradiation by Podophyllum hexandrum.

Radiation induced gastrointestinal damage occurs due to the destruction of the clonogenic crypt cells and eventual depopulation and denudation of the villi. P. hexandrum, a plant, known for its antitumour activity, has been shown to protect the mice against whole body lethal (10 Gy) irradiation. Present study was undertaken to investigate the radioprotective effect of P. hexandrum on jejunal villi cells, crypt cells, their proliferative capacity and mitigation of apoptosis. In an in vivo micro colony survival assay, pre-irradiation administration of P. hexandrum (-2 h) increased the number of surviving crypts in the jejunum by a factor of 3.0 (P < 0.05) and villi cellularity by 2.7 (P < 0.05) fold in comparison to irradiated control. Pre-irradiation administration of P. hexandrum reduced the incidence of apoptotic bodies in the crypts (P < 0.05) in a time dependent manner and depicted a mitotic arrest till the 24 h. However, after 84 h the percentage of mitosis was observed to be nearly similar to that of unirradiated control. This study suggests that arrest of cell division may help in protecting the clonogenic cells against radiation. It would be interesting to investigate further the role of P hexandrum in influencing various cell cycle regulators like bcl-2, TGF-beta, Cyclin-E etc.

Protection of jejunal crypts by RH-3 (a preparation of Hippophae rhamnoides) against lethal whole body gamma irradiation.

RH-3, an alcoholic extract of whole berries of Hippopheae rhamnoides, has been demonstrated to provide radioprotective activity in terms of survival of mice against whole body lethal irradiation (10 Gy). It was, therefore, investigated for its mode of action by monitoring crypt survival, cellularity of crypts and villi and the magnitude of apoptosis in the GI tract. Administration of RH-3 before irradiation (-30 min) increased the number of surviving crypts in the jejunum by a factor of 2.02 (p < 0.05) and villi cellularity by 2.5 fold (p < 0.05) in comparison to the irradiated control. RH-3 administration before irradiation also reduced the incidence of apoptotic bodies in the crypts (p < 0.05) in a time dependent manner and increased cellularity in the crypts and villi (84 h post irradiation) as compared to control. Caspase-3 activity was also significantly lower in the mice administered RH-3 before irradiation as compared to irradiated control. This study indicates that reduction in the radiation induced loss of cellularity of crypts and villi and also decrease in frequency of apoptosis could have contributed towards protection of mice treated with RH-3 before irradiation. The cellular and molecular mechanisms of radioprotection by Rh-3 need to be investigated further in detail.