A unique life history among tetrapods: An annual chameleon living mostly as an egg

Karsten, Kristopher B.; Andriamandimbiarisoa, Laza N.; Fox, Stanley F.; Raxworthy, Christopher J.

doi:10.1073/pnas.0802468105

Cited by 85 publications

(92 citation statements)

References 51 publications

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“…In many oviparous (egg-laying) organisms, the duration of incubation of the eggs may be a critical life-history variable. The duration of incubation relative to the rest of the lifespan can vary even within a single phylogenetic lineage; for example, some chameleons spend more than 50% of their total lifespan within the egg (Karsten et al, 2008) whereas in other lizards, the egg stage comprises <2% of the maximum lifespan [e.g. Varanus komodoensis (Cogger and Zweifel, 1992)].…”

Section: Introductionmentioning

confidence: 99%

Determinants of incubation period: do reptilian embryos hatch after a fixed total number of heart beats?

Radder

Sun

et al. 2009

Journal of Experimental Biology

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SUMMARYThe eggs of birds typically hatch after a fixed (but lineage-specific) cumulative number of heart beats since the initiation of incubation. Is the same true for non-avian reptiles, despite wide intraspecific variation in incubation period generated by variable nest temperatures? Non-invasive monitoring of embryo heart beat rates in one turtle species (Pelodiscus sinensis) and two lizards (Bassiana duperreyi and Takydromus septentrionalis) show that the total number of heart beats during embryogenesis is relatively constant over a wide range of warm incubation conditions. However, incubation at low temperatures increases the total number of heart beats required to complete embryogenesis, because the embryo spends much of its time at temperatures that require maintenance functions but that do not allow embryonic growth or differentiation. Thus, cool-incubated embryos allocate additional metabolic effort to maintenance costs. Under warm conditions, total number of heart beats thus predicts incubation period in non-avian reptiles as well as in birds (the total number of heart beats are also similar); however, under the colder nest conditions often experienced by non-avian reptiles, maintenance costs add significantly to total embryonic metabolic expenditure.

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Section: Introductionmentioning

confidence: 99%

Determinants of incubation period: do reptilian embryos hatch after a fixed total number of heart beats?

Radder

Sun

et al. 2009

Journal of Experimental Biology

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“…Mobile organisms can leave a deteriorating environment in search of better quality habitat patches, while those that do not have this option must survive either as dormant adults or by producing resilient embryos capable of withstanding prolonged desiccation [8,9]. The production of embryos (seeds, cysts and eggs) capable of traversing unfavourable conditions uninhabitable by the adult stage is common in plants and invertebrates but has only rarely evolved in vertebrates [10][11][12][13]. Perhaps the most prominent adaptation of such embryos is diapause-developmental arrest accompanied by a reduction in metabolic rate [14].…”

Section: Introductionmentioning

confidence: 99%

Convergent evolution of alternative developmental trajectories associated with diapause in African and South American killifish

et al. 2015

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Annual killifish adapted to life in seasonally ephemeral water-bodies exhibit desiccation resistant eggs that can undergo diapause, a period of developmental arrest, enabling them to traverse the otherwise inhospitable dry season. Environmental cues that potentially indicate the season can govern whether eggs enter a stage of diapause mid-way through development or skip this diapause and instead undergo direct development. We report, based on construction of a supermatrix phylogenetic tree of the order Cyprinodontiformes and a battery of comparative analyses, that the ability to produce diapause eggs evolved independently at least six times within African and South American killifish. We then show in species representative of these lineages that embryos entering diapause display significant reduction in development of the cranial region and circulatory system relative to directdeveloping embryos. This divergence along alternative developmental pathways begins mid-way through development, well before diapause is entered, during a period of purported maximum developmental constraint (the phylotypic period). Finally, we show that entering diapause is accompanied by a dramatic reduction in metabolic rate and concomitant increase in long-term embryo survival. Morphological divergence during the phylotypic period thus allows embryos undergoing diapause to conserve energy by shunting resources away from energetically costly organs thereby increasing survival chances in an environment that necessitates remaining dormant, buried in the soil and surrounded by an eggshell for much of the year. Our results indicate that adaptation to seasonal aquatic environments in annual killifish imposes strong selection during the embryo stage leading to marked diversification during this otherwise conserved period of vertebrate development.

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“…1) which are all sexually dimorphic, medium to large-sized, diurnal chameleons with males being larger than females (Brygoo, 1971;Karsten et al, 2008). Furcifer labordi inhabits the western and south-western regions of Madagascar, whereas F. verrucosus has a larger distribution, occurring throughout most of the west, southwest, and south.…”

Section: Methodsmentioning

confidence: 99%

“…Furcifer antimena has a much more restricted range, confined almost exclusively to the arid spiny forests near the provincial capital of Toliara (Brygoo, 1971;Glaw and Vences, 2007). All three species, like most other lizards in Madagascar, are seasonally active and reproduce during the wet season, which spans approximately November to March in this region (Karsten et al, 2008).…”

Section: Methodsmentioning

confidence: 99%

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Population densities and conservation assessments for three species of chameleons in the Toliara region of south-western Madagascar

et al. 2009

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Madagascar is a high conservation priority. Rainforests receive most of the focus, but the dry deciduous and spiny forests of south-western Madagascar house many endemics, are under high deforestation pressure, and remain largely unprotected. Charismatic vertebrates, like chameleons, face a secondary threat: harvesting for the commercial pet trade. Six chameleons inhabit the arid southwest near Toliara: Furcifer antimena, F. belalandaensis, F. labordi, F. lateralis, F. oustaleti, and F. verrucosus. We measured population densities of three of those species. Furcifer verrucosus has a large distribution, was dense (97.7 ha −1 ; 95% CI = 60.2-158.6), and inhabited forests and anthropogenic habitats. Furcifer labordi was much less dense (30.8 ha −1 ; 13.4-70.9), has a restricted range, and has a unique life history that makes it susceptible to perturbations from deforestation or illegal harvesting. Furcifer antimena was the least dense (17.0 ha −1 ; 9.3-30.9) and has an even smaller distribution range. We lack density data for F. lateralis, but this species was abundant in anthropogenic habitats. Within their respective ranges, there are currently no protected areas for F. antimena and only few for F. labordi; these two species are far less abundant than the more widely spread F. verrucosus. We recommend that high conservation priority be focused on F. antimena and the southern populations of F. labordi due to their restricted distributions, susceptibility to extirpation, lower population densities, and lack of formal protection. Establishing protected areas in the Ranobe region and north of the Fiherenana River, in the Belalanda region, would help protect important populations of these vulnerable species.

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A unique life history among tetrapods: An annual chameleon living mostly as an egg

Cited by 85 publications

References 51 publications

Determinants of incubation period: do reptilian embryos hatch after a fixed total number of heart beats?

Determinants of incubation period: do reptilian embryos hatch after a fixed total number of heart beats?

Convergent evolution of alternative developmental trajectories associated with diapause in African and South American killifish

Population densities and conservation assessments for three species of chameleons in the Toliara region of south-western Madagascar

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