Incubation of alligator snapping turtle (Macrochelys temminckii) eggs in natural and agricultural soils

Physicochemical properties of incubation substrates may affect embryonic growth, development, and sexual differentiation in oviparous species with temperature-dependent sex determination. Thus, the physicochemical modification of incubation substrates associated with anthropogenic activities may pose a risk to normal embryonic and hatchling development in the alligator snapping turtle (Macrochelys temminckii), an oviparous species with temperature-dependent sex determination. The present study evaluated the development of alligator snapping turtle embryos and hatchlings incubated in vermiculite, and in Tunica Soils Series from a natural nesting area and from a cotton farm. Differences between agricultural and natural soils included particle size composition, concentrations of phosphorus, nitrates (NO3), magnesium, manganese, potassium, calcium, sodium, and copper concentrations, salinity, and cation exchange capacity (CEC). Soil pH, and iron, boron and sulfate (SO4) concentrations were similar. Agricultural soils received applications of herbicides (glyphosate, fluometuron, pyrithiobac sodium, 2,4-D, trifluralin) and insecticides (methyl parathion, dicrotophos), and natural soils did not. No significant differences were detected in incubation period, clutch success, hatchling mass, sex ratio, or frequency of abnormalities in offspring from the different incubation substrates. Increases over a four-month period in mass and tail length of hatchlings incubated in natural soils were, however, significantly greater than in hatchlings incubated in other substrates. We therefore suggest that future studies should examine how physicochemical factors of incubation substrate affect hatchling growth.