Influence of host preference, mating, and release density on the parasitism of Telenomus remus (Nixon) (Hymenoptera, Platygastridae)

ABSTRACT We evaluated the influence of host preference, mating, and release density on Telenomus remus (Nixon, 1937) (Hymenoptera: Platygastridae) parasitizing eggs of Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae). First, we tested host preference of T. remus (free choice test) offered a choice between eggs of Corcyra cephalonica (Stainton, 1865) (Lepidoptera: Pyralidae) and S. frugiperda. Parasitism capacity and host preference (S. frugiperda) of T. remus reared on either of the two hosts did not differ. Secondly, we evaluated the influence of mating behavior of T. remus females on its parasitism. Only the offspring sex ratio differed between treatments, indicating that the species reproduces by parthenogenesis of the arrhenotoky type. Finally, we evaluated the influence of release density on T. remus parasitism. This was tested by releasing different numbers of the parasitoid per S. frugiperda egg using T. remus reared for different numbers of generations on C. cephalonica eggs. The regression analysis between percentage of parasitism and density of released T. remus females showed a quadratic effect for all tested parasitoid generations (F35, F40, and F45) with maximum parasitism from 65.07% to 71.69%. Our results allow the conclusion that (a) T. remus prefers S. frugiperda eggs, regardless of the host on which this parasitoid was reared, showing no preimaginal conditioning; (b) Mating does not affect the number of eggs parasitized by T. remus or the development of its offspring; and (c) The optimal T. remus release density when reared on C. cephalonica is between 0.133 and 0.150 females/S. frugiperda.

Número óptimo de ovocitos: modelo de predicción para fertilización in vitro / Optimal number of oocytes: In vitro fertilization predictive model

Resumen OBJETIVO: desarrollar un modelo de predicción para conseguir un recién nacido vivo con el menor número de ovocitos capturados. MATERIALES Y MÉTODOS: estudio observacional, longitudinal y retrolectivo, efectuado en el Instituto Nacional de Perinatología entre 2011 y 2016 en ciclos de FIV en fresco. Criterios de inclusión: pacientes mayores de 18 años de edad, con diagnóstico de infertilidad, a quienes se realizó fertilización in vitro con transferencia de embriones en fresco (FIV-TE). Las variables de estudio fueron: edad, IMC, concentración basal de FSH, tipo de infertilidad, tiempo de infertilidad y número de ovocitos capturados. Se elaboró un árbol de decisión tipo CHAID y un modelo binario de regresión logística. Para el análisis estadístico se utilizó el programa Statistic Package for Social Sciences (SPSS). Se consideró significativa la probabilidad de error alfa < 5%. RESULTADOS: se registraron 673 ciclos, de los que se obtuvieron 5,910 óvulos. El número óptimo de ovocitos recuperados fue mayor de 12 (independientemente de la edad), con RM = 4.666, IC95%: 2.676-8.137, p = <0.01. Las mujeres menores de 37 años de edad, con concentración basal de FSH <4.2 mUI/mL y recuperación de hasta 5 ovocitos tuvieron mayor posibilidad (28%) de obtener un recién nacido vivo (χ2 = 7.797; gl = 1, p = <0.047); por su parte, las pacientes entre 38 y 40 años de edad (RM = 0.338, IC95%: 0.147-0.776, p = <0.011) y tiempo de infertilidad de 10 a 12 años de evolución (RM = 0.394, IC95%: 0.181-0.858, p = 0.019) tuvieron menor posibilidad de obtener un recién nacido vivo. CONCLUSION: el número óptimo de ovocitos a recuperar es mayor de 12 (independientemente de la edad). Las mujeres menores de 37 años de edad, con concentración basal de FSH <4.2 mUI/mL y captura de hasta 5 ovocitos tienen mayor posibilidad de tener un recién nacido vivo.

Abstract OBJECTIVE: Develop a model to optimize the reproductive outcome (live birth rate). Identify the minimal number of oocytes to capture. MAERIALS AND METHODS: Observational, longitudinal, and retrolective study was made. In fresh IVF cycles, performed at INPer between 2011-2016. A logistic regression model was fitted with a CHAID, and performed a decision tree to predict live birth (LBR). Inclusion criteria: patients over 18 years of age, diagnosed with infertility, who underwent in vitro fertilization with fresh embryo transfer (FIV-TE). The study variables were: age, BMI, basal FSH concentration, type of infertility, time of infertility and number of oocytes captured. A decision tree type CHAID and a binary logistic regression model were performed. Statistical Package for Social Sciences (SPSS) was used for the statistical analysis. The probability of error alpha <5% was considered significant. RESULTS: A total of 673 cycles were studied. The optimal number was >12 oocytes (OR = 4.666, 95% CI: 2.676-8.137, p=<0.01). The highest chance to have LB (28%), was in women <37 years old, with FSH <4.2 mIU / mL and <5 oocytes; χ2 = 7.797 (df = 1, p = <0.047). The lowest chance was in 38-40 years (OR = 0.338, 95% CI: 0.147-0.776, p = <0.011) with a longer lapse of infertility; 10-12 years (OR = 0.394, 95% CI: 0.181-0.858, p = 0.019). CONCLUSION: Our data suggest that in the >12 oocytes may be the optimal number to obtain, independent of the age. On the other hand the best chance to have a live birth is with an age <37, FSH <4.2 mIU/mL and <5 oocytes. Fewer oocytes than previously deemed optimal, because the probability of having a euploid embryo in this group of people is much bigger.