Phenological and Physiological Changes in Adult Piezodorus guildinii (Hemiptera: Pentatomidae) Due to Variation in Photoperiod and Temperature

Abstract

The effect of photoperiod and temperature on Piezodorus guildinii (Westwood) adult body morphometry, color, lipid content, development of reproductive organs, and feeding activity at different ages was studied in the laboratory. Three different conditions were tested, each at 80 ± 10% RH: 14:10 h L:D at 25°C, 10:14 h L:D at 25°C, and 10:14 h L:D at 20°C. Adults at 25°C under 14 h photophase were larger and exhibited lower lipid content than those held at 20°C under 10 h photophase. Highest percentages of females with clear pronotum band and connexivum were recorded at 10 h photophase regardless of the temperature. Development of the ovary was affected by both photoperiod and temperature. At 15, 30 and 45 days of age under 14 h photophase at 25°C, the percentage of females with immature ovaries remained constant at 0%; in contrast, at 10 h (20°C) this percentage declined from 60 to 33%. Testes size was affected by photoperiod and temperature; males at 14 h (25°C) and at 10 h (20°C) showed the largest and the smallest testes, respectively. The ectodermal sac condition was affected starting with males 15 days of age; the percentage of males with an expanded ectodermal sac was greater under the 14 h (25°C) treatment than under the 10 h (20°C) treatment. Feeding activity of adults under short photophase conditions (10 h) decreased. These laboratory results indicate that adults of P. guildinii maintained under a short (10 h) photophase at 20°C enter into reproductive diapause, accumulate energetic reserves (lipids), show undeveloped reproductive structures and smaller size, clear coloration of the pronotum band and connexivum, and less feeding activity.

El objetivo de este estudio de laboratorio fue evaluar el efecto del fotoperiodo y la temperatura en: la morfometria, el color del cuerpo, contenido de lipidos, desarrollo de los organos reproductivos y la actividad alimentaria de Piezodorus guildinii (Westwood). Fueron evaluadas tres condiciones diferentes (14:10 y 10:14 h L:O a 25°C, y 10:14 h L:O a 20°C), a 80 ± 10% HR. Los adultos en 14 h de fotofase (25°C), fueron mas grandes y tuvieron menor contenido de lipidos que en 10 h (20°C). La mayor proporcion de hembras con banda del pronoto y conectivo claro fue registrada en 10 h de fotofase (20 y 25°C). La condicion del ovario fue afectada por el fotoperiodo y la temperatura. A los 15, 30 y 45 dias de edad, en 14 h de fotofase (25°C), 0% de las hembras exhibio el ovario inmaduro; por el contrario en 10 h (20°C), durante ese periodo el porcentaje de hembras con ovario inmaduro disminuyo de 60 a 33%. El fotoperiodo y la temperatura afectaron el tamano de los testiculos; siendo mayor y menor a 14 h (25°C) y a 10 h (20°C), respectivamente. La condicion del saco ectodermico fue afectada a partir de los 15 dias de edad; la proporcion de machos con saco ectodermico expandido fue mayor a 14 h (25°C) que a 10 h (20°C). La actividad alimentaria de los adultos disminuyo en condiciones de fotofase corta (10 h). Los resultados obtenidos indican que los adultos de P. guildinii en condiciones de 10 h de fotofase y 20°C ingresan en diapausa reproductiva, acumulan reservas energeticas (lipidos), tienen estructuras reproductivas inmaduras, cuerpo mas pequeno, banda del pronoto y conectivo de coloracion clara, y actividad alimentaria menor.

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