Reproductive ecology of phorid parasitoids in relation to the head size of leaf-cutting ants Atta sexdens Forel.

The leaf-cutting ant Atta sexdens Forel (Hymenoptera: Formicidae) is one of the most damaging agricultural pests in the Neotropics. Management strategies predominantly rely on the use of general insecticides. What is needed are more species-specific and environmentally friendly options. Parasitioids such as phorid flies (Diptera: Phoridae) may be one such option, but a greater understanding of the ecology of the flies and their ant hosts is essential to devise biological control strategies. Here we report parasitism rates, ant host size, parasitoid abundance per host and resultant sex ratios of two phorid species Apocephalus attophilus Borgmeier and Eibesfeldtphora tonhascai Brown parasitizing A.sexdens. The two species achieved parasitism rates of 1.48 and 1.46%, respectively and the pupal period was 14.7 ± 1.1 days and 22.1 ± 2.8 days, respectively. There was no significant difference between the head capsule width of ants parasitized by either A. attophilus or E. tonhascai. Likewise, there was no significant effect between the head capsule width of parasitized and unparasitized ants for both species. A significant positive correlation was found between the head capsule width of the parasitized ants and the number of adult parasitoids A. attophilus emerged. Ants parasitized by E. tonhascai survived significantly longer than those parasitized by A. attophilus. There was no significant effect of ant head width on the sex ratio of the offspring of either parasitoid species and no significant difference in the sex ratio (male: female) of their offspring. In summary, these data addressed here are important steps when considering natural enemies for biological control. Studying survival of the parasitized ants, parasitoid offspring sex ratio and host size preference allows for a better understanding of ant natural biological control in the field and can help in rearing of A. attophilus and E. tonhascai in laboratory.

Gallbladder hypokinesia in Crohn's disease.

For the purpose of shedding some light upon the possible mechanisms involved in gallstone formation in patients with Crohn's disease, we have investigated gallbladder emptying by means of ultrasonography in two groups of subjects: controls (n = 40) and Crohn's disease (n = 30). Diminished gallbladder emptying after a liquid fatty-meal stimulus was observed in patients with Crohn's disease when compared with controls (p < 0.001). Also, the values for the residual gallbladder volume (RGV) and maximal decrease in gallbladder volume (MDGV), both in milliliters and percentage were, respectively, increased (RGV = 9.6 ml) and diminished (MDGV = 14.8 ml; MDGV = 60.9%) in patients with Crohn's disease when compared with controls (RGV = 5.9 ml, p < 0.001; MDGV = 19.9 ml, p = 0.003; MDGV = 77.8%, p < 0.001). Hence, reduced gallbladder emptying with consequent stasis might be a contributory factor to the increased prevalence of gallstones in Crohn's disease.

Reproducibility of the ultrasound method for measurement of gallbladder volume.

Gallbladder motility has largely been studied in recent years. Since the ultrasonographic method can be used in gallbladder emptying studies, we investigated the reproducibility of the ultrasound method for measurement of gallbladder volume. The ultrasonographic method was highly reproducible (r = 0.97) and, due to its safeness and lack of use of radioactive agents, it is attractive option for gallbladder motility studies in conditions associated with increased frequency of cholelithiasis.

Measurement of gastric emptying time by real-time ultrasonography in patients with Crohn's disease.

In order to gain some insight into the possible influence of gastric emptying on gallbladder hypomotility in patients with Crohn's disease, the gastric emptying time (GET) was measured by means of ultrasonography in 10 healthy controls and 10 patients with Crohn's disease. No significant difference was observed between both mean values for GET studies (GET: controls, 165.0 min +/- 12.8; Crohn, 142.0 min +/- 11.5; p = 0.208) after ingestion of a liquid meal. Thus, the gallbladder hypomotility described in patients with Crohn's disease, after a liquid fatty-meal stimulus, can not be explained by prolonged gastric emptying time.