Sex determination and optimal development in the Moorish gecko, Tarentola mauritanica

Abstract

Under temperature sex determination (TSD), sex is determined by temperature during embryonic development. Depending on ecological and physiological traits and plasticity, TSD species may face demographic collapse due to climate change. In this context, asymmetry in bilateral organisms can be used as a proxy for developmental instability and, therefore, deviations from optimal incubation conditions. Using Tarentola mauritanica gecko as a model, this study aimed first to confirm TSD, its pattern and pivotal temperature, and second to assess the local adaptation of TSD and variation of asymmetry patterns across four populations under different thermal regimes. Eggs were incubated at different temperatures, and hatchlings were sexed and measured. The number of lamellae was counted in adults and hatchlings. Results were compatible with a TSD pattern with males generated at low and females at high incubation temperatures. Estimated pivotal temperature coincided with the temperature producing lower embryonic mortality, evidencing selection towards balanced sex ratios. The temperature of oviposition was conservatively selected by gravid females. Asymmetry patterns found were likely related to nest temperature fluctuations. Overall, the rigidity of TSD may compromise reproductive success, and demographic stability in this species in case thermal nest choice becomes constrained by climate change.

Ontogenic differences and sexual dimorphism of the locomotor performance in a nocturnal gecko, Tarentola mauritanica

“…Runs were recorded at a filming speed of 50 frames/s using a digital camera from a fixed position (Canon EOS 60D). Runs were performed at three different environmental temperatures (25°C, 27°C, and 29°C, following Marques et al, 2022; Rato & Carretero, 2015), enabled by an incubator (BINDER TM ) where animals were placed to achieve the set temperature. The incubator had an accuracy of a tenth of a degree with respect to the temperature indicated in the outside screen.…”

Pivotal temperature is not for everyone: Evidence for temperature‐dependent sex determination in three gecko species

“…The data on GSD are derived from the review (Augstenová et al, 2021) supplemented by Mezzasalma et al (2021), Pensabene et al (2023), and Pinto et al (2022). Temperature‐dependent sex determination (TSD) is well‐supported in Eublepharis macularius (Bull, 1987; Viets et al, 1993), Hemitheconyx caudicinctus (Anderson & Oldham, 1988; Viets et al, 1993), Tarentola mauritanica (Marques et al, 2023; Nettmann & Rykena, 1985), Tarentola boettgeri (Nettmann & Rykena, 1985), and Phelsuma grandis (Viets et al, 1994), newly in Pachydactylus tigrinus, Pristurus carteri , and Chondrodactylus laevigatus (this study). TSD was suspected in the genus Rhacodactylus (Seipp & Henkel, 2000), in Tarentola delalandii, T. gomerensis, T. angustimentalis, T. annularis (Nettmann & Rykena, 1985), Phelsuma dubia, Phelsuma guimbeaui, Phelsuma lineata, Phelsuma abbotti (Tytle, unpublished data in Viets et al, 1994), and Gekko japonicus (Tokunaga, 1985 but see Yoshida & Itoh, 1974).…”