Plasticity and limitations of extended egg retention in oviparous Zootoca vivipara (Reptilia: Lacertidae)

Abstract

The transition between oviparity and viviparity in reptiles is generally accepted to be a gradual process, the result of selection for increasingly prolonged egg retention within the oviduct. We examined egg retention plasticity in an oviparous strain of the lacertid lizard Zootoca vivipara, a species having both oviparous and viviparous populations. We forced a group of female Z. vivipara to retain their clutch in utero by keeping them in dry substrata, and assessed the effect on embryonic development and hatching success, along with offspring phenotype and locomotor performance. Forced egg retention for one additional week affected the developmental stage of embryos at oviposition, as well as hatchling robustness and locomotor performance. However, embryos from forced clutch retention treatment reached one stage unit more than control embryos at oviposition time. Embryos from control eggs were more developed than embryos from experimental eggs after approximately the same period of external incubation, showing that embryonic development is retarded during the period of extended egg retention, despite the high temperature inside the mother's body. Significant differences in external incubation time were only found in one of the two years of study. Hatching success was much lower in the experimental group with forced egg retention (21.1%) than in the control group (95.4%). Therefore, we conclude that there are limitations that hinder the advance of intrauterine embryonic development beyond the normal time of oviposition, and that extended egg retention does not represent clear advantages in this population of Z. vivipara. Nevertheless, the fact that some eggs are successful after forced egg retention could be advantageous for the females that are able to retain their clutch under unfavourable climatic conditions.

The role of climate and maternal manipulation in determining and maintaining reproductive mode in Liolaemus lizards

“…Most experimental studies on embryological development have relied on constant temperature experimental treatments with limited understanding on the effect of time available for maternal thermoregulation on embryo development that may have a strong impact on viviparity (Foucart et al., 2018). Our approach on the species of the L. darwinii group provided strong support for the maternal manipulation hypothesis as viviparous pregnant females showed a significantly lower CV than ovigerous females of oviparous species, as observed in other studies (Ji et al., 2007; Rodríguez‐Diaz & Braña, 2011; Schwarzkopf & Andrews, 2012; Wang et al., 2017). Preferred temperature (Hare et al., 2009; Qualls & Andrews, 1999) showed no significant differences between these reproductive modes in Liolaemus , providing little support for the cold climate hypothesis in this experiment.…”

Extreme plasticity in reproductive biology of an oviparous lizard

“…Subsequent research rejected that view, but recent experimental studies have confirmed that exposure to dry conditions or low temperatures can induce females to retain their eggs in utero for longer than usual (Stamps, 1976;Telemeco, Radder, Baird, & Shine, 2010;Warner & Andrews, 2003). Nonetheless, such prolongation typically has little effect on subsequent incubation periods (Mathies & Andrews, 1999;Rodriguez-Diaz & Brana, 2010;Shanbhag, Saidapur, & Radder, 2003;Telemeco et al, 2010;Warner & Andrews, 2003). In Sceloporus aeneus and S. scalaris, however, oviductally retained embryos continue to develop in utero, reducing the subsequent incubation period (Andrews & Mathies, 2000).…”

Short‐term and long‐term consequences of regeneration on the reproductive investment of a multivoltine lizard

“…Moreover, our results indicate that although the energetic demands of regeneration seem to constrain reproductive investment in P. muralis , they do not affect the incubation time. This probably indicates that there were no differences between intact and regenerating females in the retention time and the level of development reached by the embryos at the time of egg laying, although this trait may have a certain plasticity in lacertid lizards (Braña et al., 1991; Rodríguez‐Díaz & Braña, 2011). Previous studies showed that oviposition in female wall lizards occurs when embryos reached stages 25–29, according to the Dufaure and Hubert (1961) development table (Braña et al., 1991), and that the incubation time at 29°C ranges from 33 to 35 days and is not affected by egg mass (Ji & Braña, 1999), which is in accordance with our results.…”