Influência da temperatura de incubação e da motilidade embrionária sobre o crescimento dos membros de Caiman yacare (Daudin, 1802)

Abstract

Temperature and pharmacological embryo action can result in modifications to the size and proportion of the limb bones. This study aimed to evaluate whether temperature and controlled increases in embryo motility can similarly influence the skeletal development of the Pantanal alligator (Caiman yacare). The collection of the eggs, identification, transportation, and incubation were performed with the required care; all eggs were incubated with 90% humidity at 29°C for the first 45 days. Thereafter, the incubation temperature was either maintained at 29°C and embryos simultaneously treated with 4-aminopyridine on days 46, 47, 48, and 49 (4AP, n = 15), maintained at 29°C (n = 14) or increased to 33°C (n = 14). Embryo movement was measured using an Egg Buddy® digital monitor on days 30, 35, 42, 49, 56, and 60, at which point embryos were sacrificed and samples collected for analysis of both axial and appendicular skeletal elements. Analyses showed that there were no differences observed between embryo motility following incubation at the lower (29°C) or higher (33°C) temperatures, with equivalent whole embryo and limb proportions as well as identical length of individual segments. In contrast, the motility was greater in embryos treated with 4-AP at 29°C (P < 0.001) on day 49 and this was associated with higher proportions of snout-vent and hands. These data have demonstrated for the first time that pharmacologically-induced increases in embryo motility result in phenotypic divergence with proportion of elements during prenatal ontogeny, effectively altering the adaptation of the animals in specific environments.