Facultative oviparity in a viviparous skink (
            <i>Saiphos equalis</i>
            )

Laird, Melanie K.; Thompson, Michael B.; Whittington, Camilla M.

doi:10.1098/rsbl.2018.0827

Cited by 16 publications

(14 citation statements)

References 37 publications

(62 reference statements)

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“…The similarities in differentially expressed gene function between oviparous and viviparous S. equalis may provide a molecular explanation for why facultative oviparity may be possible in this species. In the first report of a mixed reproductive mode within a vertebrate clutch, one female from a viviparous population of S. equalis laid three eggs (at stage 33, close to the typical stage of oviparous lizards), and then gave birth to a live neonate from the same pregnancy (Laird, Thompson, & Whittington, 2019). This observation suggested that there may be fewer physiological barriers to transitions between parity modes than previously thought, an assertion that is supported by our gene expression data, in which oviparous and viviparous individuals expressed genes with many of the same functions during the reproductive cycle.…”

Section: Discussionmentioning

confidence: 99%

“…Nevertheless, there are genetic changes common to both viviparous and oviparous S. equalis, including uterine remodelling and the transport of respiratory gases and water, probably because oviparous members incubate developing embryos internally for an unusually long period. These similarities, including in expression of genes related to dynamic immune regulation and respiratory gas exchange, (a) suggest that there are common physiological requirements of sustaining a developing embryo in both long egg‐retention and viviparity; (b) may partially explain why it was possible for a viviparous S. equalis mother to lay eggs (Laird et al, 2019), and (c) suggest that reversals from recent origins of viviparity back to oviparity might be easier than previously thought. The large number of genes differentially expressed throughout gravidity in oviparous S. equalis are dramatically different to the gene expression profiles of typical oviparous skinks.…”

Section: Discussionmentioning

confidence: 99%

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Emergence of an evolutionary innovation: Gene expression differences associated with the transition between oviparity and viviparity

et al. 2020

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Our understanding of the evolution of complex biological traits is greatly advanced by examining taxa with intermediate phenotypes. The transition from oviparity (egg‐laying) to viviparity (live‐bearing) has occurred independently in many animal lineages, but there are few phenotypic intermediates. The lizard Saiphos equalis exhibits bimodal reproduction, with some viviparous populations, and other oviparous populations with long egg‐retention, a rare trait where most of embryonic development occurs inside the mother prior to late ovipositioning. We posit that oviparous S. equalis represent an intermediate form between “true” oviparity and viviparity. We used transcriptomics to compare uterine gene expression in these two phenotypes, and provide a molecular model for the genetic control and evolution of reproductive mode. Many genes are differentially expressed throughout the reproductive cycle of both phenotypes, which have clearly different gene expression profiles overall. The differentially expressed genes within oviparous and viviparous individuals have broadly similar biological functions putatively important for sustaining embryos, including uterine remodelling, respiratory gas and water exchange, and immune regulation. These functional similarities indicate either that long egg‐retention is an exaptation for viviparity, or might reflect parallel evolution of similar gravidity‐related changes in gene expression in long egg‐retention oviparity. In contrast, gene expression changes across the reproductive cycle of long egg‐retaining oviparous S. equalis are dramatically different from those of “true” oviparous skinks (such as Lampropholis guichenoti), supporting our assertion that oviparous S. equalis exhibit an intermediate phenotype between “true” oviparity and viviparity.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Emergence of an evolutionary innovation: Gene expression differences associated with the transition between oviparity and viviparity

et al. 2020

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“…The reason for the rarity of respective reports for reptiles may well be that such cases can easily be overlooked, or shelved away as odd flukes instead of being reported (as we first did in 1999), or that editors reject their publication in scientific journals (as happened during the late life time of the second author, with exception of a conference abstract: Hofmeyr and Kuchling, 2017). Since then facultative viviparity (capacity to deposit either eggs or developed offspring, depending on circumstances) has been reported for one more reptile, the skink Saiphos equalis, with its discovery based on a single female in a captive colony (Laird et al, 2019). Even though this reproductive lability has been rarely described in reptiles, it can be part of a viable reproductive strategy and evolutionary more significant than previously assumed.…”

Section: Discussionmentioning

confidence: 99%

Too Hot to Nest? In a Hot Summer the Tortoise Chersina angulata Can Switch From Nesting to Facultative Viviparity

Kuchling

Hofmeyr

2022

Front. Ecol. Evol.

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In a captive colony of Chersina angulata in Cape Town, South Africa, we observed in 2015/16 retention of the last egg clutch inside the female until the hatching stage was reached, conforming to the generally accepted definition of viviparity. Retrospective climatic analysis indicates egg retention until the hatching stage co-occurred with unusually hot summer weather: the average air temperatures in December 2015 and January and February 2016 were higher than during the preceding five and the following 5 years when facultative viviparity could not be observed. Late December and January appears to be the critical period for females to either deposit their last clutch of the nesting season into a nest, or to retain the last clutch for embryonic development inside the female. Over the 28 December to 24 January period the minimum, average and maximum air temperatures in 2015–16 were about 3°C higher than in the five following years. This association of facultative viviparity with unusual summer heat suggests that hot ambient temperatures at the end of the nesting season may cue females to switch from oviposition to facultative viviparity. Compared to incubation in a nest this phenotypic plasticity of the reproductive mode—to retain during hot summers the season’s last clutch inside the female—may buffer the developing embryos from excessive heat exposure: females can thermo-regulate by moving among microhabitats whereas sun exposed shallow nests cannot escape high ground temperatures. This novel reproductive strategy has the potential to enhance the resilience of species to global warming.

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“…It is unlikely that viviparity will be discovered in any lizard previously thought to be oviparous, but unexpected discoveries always have the potential to develop new avenues of research. For example, observation of both oviparity and viviparity within an individual (the first in a vertebrate) in S. equalis raises the possibility that reproductive mode may be plastic in some species (Laird et al 2019).…”

Section: Viviparity and Placentationmentioning

confidence: 99%

Australian lizards are outstanding models for reproductive biology research

et al. 2021

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Australian lizards are a diverse group distributed across the continent and inhabiting a wide range of environments. Together, they exhibit a remarkable diversity of reproductive morphologies, physiologies, and behaviours that is broadly representative of vertebrates in general. Many reproductive traits exhibited by Australian lizards have evolved independently in multiple lizard lineages, including sociality, complex signalling and mating systems, viviparity, and temperature-dependent sex determination. Australian lizards are thus outstanding model organisms for testing hypotheses about how reproductive traits function and evolve, and they provide an important basis of comparison with other animals that exhibit similar traits. We review how research on Australian lizard reproduction has contributed to answering broader evolutionary and ecological questions that apply to animals in general. We focus on reproductive traits, processes, and strategies that are important areas of current research, including behaviours and signalling involved in courtship; mechanisms involved in mating, egg production, and sperm competition; nesting and gestation; sex determination; and finally, birth in viviparous species. We use our review to identify important questions that emerge from an understanding of this body of research when considered holistically. Finally, we identify additional research questions within each topic that Australian lizards are well suited for reproductive biologists to address.

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Facultative oviparity in a viviparous skink ( Saiphos equalis )

Cited by 16 publications

References 37 publications

Emergence of an evolutionary innovation: Gene expression differences associated with the transition between oviparity and viviparity

Emergence of an evolutionary innovation: Gene expression differences associated with the transition between oviparity and viviparity

Too Hot to Nest? In a Hot Summer the Tortoise Chersina angulata Can Switch From Nesting to Facultative Viviparity

Australian lizards are outstanding models for reproductive biology research

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