Numerical and biomass growth study of Bulimulus bonariensis (Rafinesque, 1833) (Gastropoda: Bulimulidae) under laboratory conditions.

Bulimulus bonariensis is considered a species of relevance to agribusiness, having been declared a pest with indirect damage because of its negative effects on several crops such as soybeans, chickpeas, and corn in central and northern Argentina. The objective of this work was to analyze the growth pattern of a population born under laboratory conditions, to explore population aspects such as survival and mortality, to estimate the age and size at gonadal maturity and first reproduction, and to contribute to the knowledge of the reproductive biology of this gastropod. From the clutches obtained, the basic biologic parameters were calculated and the individuals hatched under laboratory conditions counted and measured every two weeks. The clutches contained an average of 44 eggs, which took about 13.7 days to hatch at a birth rate of 41.82%. The growth pattern in the five clutches was analyzed individually, and the logistic model used was the one with the highest degree of fit to that observed growth pattern, followed by the Gompertz model, and finally the von Bertalanffy model. In addition, the models were applied to the 102 specimens analyzed together as a cohort, where the best fitting model was also proved to be the logistic growth model. A concave type III survival curve was obtained from the horizontal life table. The cohort was reduced by 48% during the first 50 days after birth. Beyond one month of hatching, life expectancy gradually increased and remained high between 65-302 days of life. After day 330, life expectancy decreased and only 13.72% exceeded one year of birth, with an average length of 16.68 mm. The last specimen died after 23 months at a total length of 20.24 mm, and the life expectancy was estimated at almost three years. In addition, it was inferred that gonadal maturity, when these gastropods reach 12 mm of total shell length, is reached after 200 days of life. Therefore, the individuals that are born are able to reproduce for the first time a year after birth, when they have the approximate size of 16.68 mm.

Gametic cycle and gonadal maturity of Bulimulus bonariensis (Rafinesque, 1833) (Gastropoda: Bulimulidae), in a rural area of Buenos Aires, Argentina.

Bulimulus bonariensis, a snail distributed over a large part of Argentina, has generated negative effects on the agribusiness. We accordingly conducted a seasonal sampling during 2018-2019 in order to characterize the gametic cycle and establish the size of this gastropod at gonadal maturity. Three reproductive stages were identified: the mature in autumn; the spawn, which begins in winter but occurs mainly in the spring, followed by the post-spawn in summer, where an absence of gonadal rest was evidenced. In the fall, in maturity resorption was observed in addition to abundant primary spermatocytes, secondary spermatocytes, and growing vitellogenic oocytes. At the same time, could correlate the degree of spermioviduct development with the stage of gonadal development. Moreover, we used a logistic regression to calculate the size at gonadal maturity, which was established at the total shell length of 12 mm. In addition, we found that at the beginning of reproductive development those gastropods are protogynous hermaphrodites, but after reaching gonadal maturity became simultaneous hermaphrodites. Finally, B. bonariensis also proved to be an iteroparous species. The information provided here will be essential for delineating and establishing population control strategies.

How many patients with rheumatic diseases and TNF inhibitors treatment have latent tuberculosis?

OBJECTIVES: Spanish clinical guidelines recommend screening patients for tuberculosis (TB) before TNF inhibitors (TNFi) treatment. Our objective was to estimate the prevalence of TST seroconversion as an estimation of the prevalence of latent TB in patients with rheumatic diseases and TNFi treatment that have already been screened for tuberculosis. METHODS: TST, booster and chest x-ray were performed to patients with rheumatic diseases, TNFi treatment, negative tuberculin skin tests before treatment and that were attending the rheumatology Department of three different hospitals in Barcelona. According to the Spanish Society Rheumatology guidelines, these patients had not received TB prophylaxis treatment. RESULTS: One hundred and forty patients were included in the study. The tuberculin skin test was positive in 4.28% (n=6) of the patients. 50% of the patients were undergoing TNFi ≤ 2 years, being two of the patients only one year on the TNFi when a positive TST was detected. This shows that a conversion of the TST can occur even few months or years after the TNFi is started. CONCLUSIONS: The present study observed that 4.28% of patients with rheumatic diseases on TNFi who did not have performed a pre-treatment TB prophylaxis, had a conversion of the TST. Moreover, the conversion of the TST had been within the first two years of treatment in half of the patients of our cohort. In spite of these results, false TST positives in the diagnosis of latent TB cannot be excluded as an explanation for our results.