Study

Effects of incubation temperature on sex determination in the endangered Magdalena river turtle, Podocnemis lewyana

  • Published source details Gómez-Saldarriaga C., Valenzuela N. & Ceballos C.P. (2016) Effects of incubation temperature on sex determination in the endangered Magdalena river turtle, Podocnemis lewyana. Chelonian Conservation and Biology, 15, 43-53.

Actions

This study is summarised as evidence for the following.

Action Category

Alter incubation temperatures to achieve optimal/desired sex ratio: Tortoises, terrapins, side-necked & softshell turtles

Action Link
Reptile Conservation
  1. Alter incubation temperatures to achieve optimal/desired sex ratio: Tortoises, terrapins, side-necked & softshell turtles

    A replicated, randomized study in 2012 in laboratory conditions in Columbia (Gómez-Saldarriaga et al. 2016) found that incubating Magdalena River turtle Podocnemis lewyana eggs at lower temperatures produced more male hatchlings, and higher temperatures produced more females. Hatching success ranged from 57–100%. Lower incubation temperatures resulted in fewer female hatchlings (29°C: 8% female; 31°C: 18%; 34.7°C: 86%). When incubating at 29°C, a 10-day high temperature pulse resulted in more female hatchlings compared to the constant temperature if it came during day 21–30 (37% female), but a similar number if it came at day 31–50 (4–20% female). At 31°C, a pulse during day 21–50 resulted in more females than the constant temperature (32–67% female). In 2012, a total of 227 eggs were collected from 10 nests (14 beaches searched). Eggs were incubated at either a constant temperature (29, 31 or 34.7°C; 30–31 eggs/temperature), or at 29 or 31°C with a 10-day period at a high temperature (35.1–35.5°C) during day 21–30, 31–40 or 41–50 (19–25 eggs/treatment). Sex of 20 individuals was determined by assessing gonadal histology. Detailed morphology of these 20 individuals was used to estimate the sex of all hatchlings (see paper for details).

    (Summarised by: William Morgan)

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