Effect of temperature and diet (starch and fiber) on embryonic development, energy metabolism and growth of red-footed tortoise (Chelonoidis carbonaria)

Abstract

Determina el efecto de la temperatura de incubación en el desarrollo de embriones C. carbonaria que influye en el desarrollo del embrión, morfología y la tasa de crecimiento inicial. Con respecto a la dieta, determinar el efecto de una con alto contenido de fibra y otra con alto contenido de almidón, sobre el metabolismo energético, la digestibilidad de nutrientes y el crecimiento de crías de C. carbonaria. Se colectaron huevos y se incubaron a 27.5°C y 29.5°C. Las crías de 29.5°C presentaron periodos de incubación más cortos, con índice de eclosión menor. La masa de las crías y el ancho recto del plastrón fueron mayores a los 3 meses en crías incubadas a 27.5°C. 20 crías fueron divididas en dos dietas experimentales. Animales de la dieta alta en almidón mostraron una mayor ingesta de materia seca masa-específica, tiempos de tránsito y retención más cortos, mayores eficiencias digestivas, y contenido mineral y densidad ósea más bajas. La producción de calor en reposo y posprandial no fueron afectadas por la dieta. A los 13 meses, plastrones y caparazones de las crías de la dieta con alto almidón fueron más anchos, con mayores tasas de crecimiento. Ambas dietas desarrollaron un crecimiento piramidal.

There is very little information about egg incubation conditions, nutrient requirements, and captive management of the red-footed tortoise (Chelonoidis carbonaria) for conservation purposes. In the first study of this thesis, it was considered that reptile embryos respond to temperature changes with metabolic and physiological adjustments that influence hatchling success, phenotype, behaviour, and growth rate. Climate change and global warming can affect the reptile population by altering the frequencies of hatchling survival and phenotypes. Therefore, previous studies proposed artificial incubation as a potential strategy for mitigating these effects. Red-footed tortoise eggs were collected and incubated at constant temperatures of 27.5°C and 29.5°C to investigate the physiological effects of temperature on embryo development, hatchling morphology and early growth rate. The direct effects of temperature on the incubation period, lost egg mass, hatching index, hatchling size, and mass were evaluated at hatching and at three months of age. Hatchlings from 29.5°C presented shorter incubation times (141 says) than those from 27.5°C (201 days; P<0.05). Egg mass loss, hatchling mass, and size at hatching were not different between the incubation temperatures (P>0.05). However, the hatching index (survival rate) was lower (64.5% versus 100%) in eggs incubated at 29.5°C, but the hatchling mass and straight plastron width were higher at 3 months of age than those for eggs incubated at 27.5°C (P<0.05). These results clearly indicate that incubation temperature has an important influence on hatchling success and hatchling size and mass in the first months by influencing the early growth rate.