Indeterminate Growth: Could It Represent the Ancestral Condition?

Hariharan, Iswar K.; Wake, David B.; Wake, Marvalee H.

doi:10.1101/cshperspect.a019174

Cited by 39 publications

(40 citation statements)

References 59 publications

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“…Interestingly, profound growth even occurred in adult tenrecs. Indeterminate growth is considered the ancestral condition in amniotes (Hariharan et al, 2016); during indeterminate growth, increases in the length of the major body axis occur after the animal is thought to have reached a mature size. That our wild-caught adult tenrecs grew 2.5±0.37-fold suggests a degree of indeterminate growth that appears unique in the mammalian world (Hariharan et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

Extreme physiological plasticity in a hibernating basoendothermic mammal, Tenrec ecaudatus

Treat

Scholer

Barrett

et al. 2018

Journal of Experimental Biology

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Physiological plasticity allows organisms to respond to diverse conditions. However, can being too plastic actually be detrimental? Malagasy common tenrecs, , have many plesiomorphic traits and may represent a basal placental mammal. We established a laboratory population of and found extreme plasticity in thermoregulation and metabolism, a novel hibernation form, variable annual timing, and remarkable growth and reproductive biology. For instance, tenrec body temperature ( ) may approximate ambient temperature to as low as 12°C even when tenrecs are fully active. Conversely, tenrecs can hibernate with of 28°C. During the active season, oxygen consumption may vary 25-fold with little or no change in During the austral winter, tenrecs are consistently torpid but the depth of torpor may vary. A righting assay revealed that contributes to but does not dictate activity status. Homeostatic processes are not always linked, e.g. a hibernating tenrec experienced a ∼34% decrease in heart rate while maintaining constant body temperature and oxygen consumption rates. Tenrec growth rates vary but young may grow ∼40-fold in the 5 weeks until weaning and may possess indeterminate growth as adults. Despite all of this profound plasticity, tenrecs are surprisingly intolerant of extremes in ambient temperature (<8 or >34°C). We contend that while plasticity may confer numerous energetic advantages in consistently moderate environments, environmental extremes may have limited the success and distribution of plastic basal mammals.

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Section: Discussionmentioning

confidence: 99%

Extreme physiological plasticity in a hibernating basoendothermic mammal, Tenrec ecaudatus

Treat

Scholer

Barrett

et al. 2018

Journal of Experimental Biology

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“…By contrast, crustaceans that grow and molt throughout adulthood retain their ability to replace appendages (for reviews, see Khan et al, 2016;Das, 2015). Indeed, the presence and maintenance of regenerative capacity across all animal species may be linked to the continual growth of the organ or appendage (Hariharan et al, 2015). Recent studies in these various arthropod species have begun to elucidate the molecular mechanisms underlying tissue injury responses such as wound closure, regeneration and re-patterning (for reviews, see Khan et al, 2016;Das, 2015), but the wealth of genetic tools and understanding of development in Drosophila give it an experimental advantage over many of these other model systems.…”

Section: Regeneration In Juvenile and Adult Arthropodsmentioning

confidence: 99%

Model systems for regeneration: Drosophila

2020

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Drosophila melanogaster has historically been a workhorse model organism for studying developmental biology. In addition, Drosophila is an excellent model for studying how damaged tissues and organs can regenerate. Recently, new precision approaches that enable both highly targeted injury and genetic manipulation have accelerated progress in this field. Here, we highlight these techniques and review examples of recently discovered mechanisms that regulate regeneration in Drosophila larval and adult tissues. We also discuss how, by applying these powerful approaches, studies of Drosophila can continue to guide the future of regeneration research.

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“…Large amphibians have fewer predators, a lower metabolic rate, and they can more easily maintain their temperature and hydration than small amphibians. What establishes the upper limit to amphibian size is unknown, and, in some cases, amphibians increase in size throughout adulthood, a phenomenon called indeterminate growth, which is discussed in Hariharan et al (2015). Leaving environmental issues, such as food and space, aside, the maximum size for land vertebrates is limited by allometric scaling laws.…”

Section: Amphibian Body Size Limitsmentioning

confidence: 99%

Biological Scaling Problems and Solutions in Amphibians

Levy

Heald

2015

Cold Spring Harb Perspect Biol

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Size is a primary feature of biological systems that varies at many levels, from the organism to its constituent cells and subcellular structures. Amphibians populate some of the extremes in biological size and have provided insight into scaling mechanisms, upper and lower size limits, and their physiological significance. Body size variation is a widespread evolutionary tactic among amphibians, with miniaturization frequently correlating with direct development that occurs without a tadpole stage. The large genomes of salamanders lead to large cell sizes that necessitate developmental modification and morphological simplification. Amphibian extremes at the cellular level have provided insight into mechanisms that accommodate cell-size differences. Finally, how organelles scale to cell size between species and during development has been investigated at the molecular level, because subcellular scaling can be recapitulated using Xenopus in vitro systems.

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Indeterminate Growth: Could It Represent the Ancestral Condition?

Cited by 39 publications

References 59 publications

Extreme physiological plasticity in a hibernating basoendothermic mammal, Tenrec ecaudatus

Extreme physiological plasticity in a hibernating basoendothermic mammal, Tenrec ecaudatus

Model systems for regeneration: Drosophila

Biological Scaling Problems and Solutions in Amphibians

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