Oxygen Deficient (OD) Combustion and Metabolism: Allometric Laws of Organs and Kleiber’s Law from OD Metabolism?

The biology literature presents allometric relations for the specific metabolic rate (SMRk) of an organ k of mass mk within the body of mass mB: SMR_k ∝ mBfk (body mass allometry, BMA). Wang et al. used BMA, summed-up energy from all organs and validated Kleiber’s law of the whole body: SMRM ∝ mBb’, b’ = −0.25. The issues raised in biology are: (i) why fk and b’ < 0, (ii) how do the organs adjust fk to yield b’? The current paper presents a “system” approach involving the field of oxygen deficient combustion (ODC) of a cloud of carbon particles and oxygen deficient metabolism (ODM), and provides partial answers by treating each vital organ as a cell cloud. The methodology yields the following: (i) a dimensionless “group” number GOD to indicate extent of ODM, (ii) SMRk of an organ in terms of the effectiveness factor; (iii) curve fitting of the effectiveness factor to yield the allometric exponents for the organ mass-based allometric laws (OMA); (iv) validation of the results with data from 111 biological species (BS) with mB ranging from 0.0075 to 6500 kg. The “hypoxic” condition at organ level, particularly for Covid-19 patients, and the onset of cancer and virus multiplication are interpreted in terms of ODM and glycolysis.

Why the energy transition is not enough

Efforts to accommodate the growth in global energy consumption within a fragile biosphere are primarily focused on managing the transition towards a low-carbon energy mix. We show evidence that a more fundamental problem exists through a scaling relation, akin to Kleiber’s Law, between society’s energy consumption and material stocks. Humanity’s energy consumption scales at 0.78 of its material stocks, which implies predictable environmental pressure regardless of the energy mix. If true, future global energy scenarios imply vast amounts of materials and corresponding environmental degradation, which have not been adequately acknowledged. Thus, limits to energy consumption are needed regardless of the energy mix to stabilize human intervention in the biosphere.

Why the energy transition is not enough

Efforts to accommodate the growth in global energy consumption within a fragile biosphere are primarily focused on managing the transition towards a low-carbon energy mix. We show evidence that a more fundamental problem exists through a scaling relation, akin to Kleiber’s Law, between society’s energy consumption and material stocks. Humanity’s energy consumption scales at 0.78 of its material stocks, which implies predictable environmental pressure regardless of the energy mix. If true, future global energy scenarios imply vast amounts of materials and corresponding environmental degradation, which have not been previously acknowledged. Given this reality, we also show evidence that a worldwide lifestyle limit at 2.0 kW/capita enables a dignified life for all while stabilizing human intervention in the biosphere to current levels, yet the political viability of establishing such limit is very low.

Aerial and aquatic respiration in littoral Oniscidea (Isopoda) from Southern California, USA

The large radiation of terrestrial isopods (suborder Oniscidea) includes several families that are represented primarily in marine-littoral or riparian habitats. Among these are members of Ligiidae and Tylidae as well as several basal families within the section Crinocheta. Structural and physiological evidence supports a marine-littoral ancestry of the Oniscidea. We examined aerial and aquatic respiration (measured as VCO2) in six species of marine-littoral Oniscidea representing five families, as well as one riparian and one endogean species. Complimentary data were collected for immersion tolerance and whole-animal permeability in air, and structural specialization of the respiratory pleopods was examined using SEM. Ligia occidentalis Dana, 1853 (marine, littoral) and Ligidium lapetum Mulaik & Mulaik, 1942 (riparian) showed similar VCO2 in air and water. VCO2 in air for the other species was significantly higher than in water. Compared across species, aerial VCO2 scaled with mass in accordance with Kleiber’s law (β = 0.774) while aquatic VCO2 increased in approximate proportion to mass (β = 0.957). At least some specimens of the six marine-littoral species survived over 24 h immersion. Ligidium lapetum and the endogean trichoniscid Brackenridgia heroldi (Arcangeli, 1932) also tolerated prolonged immersion in freshwater but did not survive beyond 5–6 h, probably due to limited capacity for hyper-regulation. The upper shore sand-burrowers, Tylos punctatus Holmes & Gay, 1909 and Alloniscus perconvexus Dana, 1856 had the lowest permeability among the study species and are the only representatives with elaborated pleopodal respiratory fields (Alloniscus) and lungs (Tylos). The ventral lung spiracles of T. punctatus are surrounded by an extensive cuticle meshwork and we propose that this functions as a plastron field to enhance aquatic gas exchange. Collectively, the results show that littoral species tolerate significant periods of immersion, allowing them to withstand habitat inundation during spring high tides, storm swells and, in riparian species, rainstorms and snowmelt.

Toward universal laws of technology evolution: modeling multi-century advances in mobile direct-fire systems

This paper explores the question of whether a single regularity of technological growth might apply to a broad range of technologies, over a period of multiple centuries. To this end, the paper investigates a collection of diverse weapon systems called here the mobile direct-fire systems. These include widely different families of technologies that span the period of 1300–2015 CE: foot soldiers armed with weapons from bows to assault rifles; horse-mounted soldiers with a variety of weapons; foot artillery and horse artillery; towed antitank guns; self-propelled antitank and assault guns; and tanks. The main contribution of this paper is that, indeed, a single, parsimonious regularity describes the historical growth of this extremely broad collection of systems. Multiple, widely different families of weapon systems—from a bowman to a tank—fall closely on the same curve, a simple function of time. This suggests a general model that unites allometric relations (such as Kleiber’s Law) and exponential growth relations (such as Moore’s Law). To this author’s knowledge, no prior research describes a regularity in the temporal growth of technology that covers such widely different technologies and over such a long period of history. This regularity is suitable for technology forecasting, as this paper illustrates with explorations of two systems that might appear 30 years in the future from this writing: a heavy infantryman and a tank. In both cases, the regularity helped lead to nonobvious conclusions, particularly regarding the power of the weapons of such future systems. Furthermore, this result suggests a possibility—and related research questions—that even broader collections of technology families might evolve historically in accordance with what might be called universal laws of technological evolution.

Generalized size scaling of metabolic rates based on single-cell measurements with freshwater phytoplankton

Kleiber’s law describes the scaling of metabolic rate with body size across several orders of magnitude in size and across taxa and is widely regarded as a fundamental law in biology. The physiological origins of Kleiber’s law are still debated and generalizations of the law accounting for deviations from the scaling behavior have been proposed. Most theoretical and experimental studies of Kleiber’s law, however, have focused on the relationship between the average body size of a species and its mean metabolic rate, neglecting intraspecific variation of these 2 traits. Here, we propose a theoretical characterization of such variation and report on proof-of-concept experiments with freshwater phytoplankton supporting such framework. We performed joint measurements at the single-cell level of cell volume and nitrogen/carbon uptake rates, as proxies of metabolic rates, of 3 phytoplankton species using nanoscale secondary ion mass spectrometry (NanoSIMS) and stable isotope labeling. Common scaling features of the distribution of nutrient uptake rates and cell volume are found to hold across 3 orders of magnitude in cell size. Once individual measurements of cell volume and nutrient uptake rate within a species are appropriately rescaled by a function of the average cell volume within each species, we find that intraspecific distributions of cell volume and metabolic rates collapse onto a universal curve. Based on the experimental results, this work provides the building blocks for a generalized form of Kleiber’s law incorporating intraspecific, correlated variations of nutrient-uptake rates and body sizes.

Evidence for hormonal control of heart regenerative capacity during endothermy acquisition

Tissue regenerative potential displays striking divergence across phylogeny and ontogeny, but the underlying mechanisms remain enigmatic. Loss of mammalian cardiac regenerative potential correlates with cardiomyocyte cell-cycle arrest and polyploidization, as well as the development of postnatal endothermy. We reveal that diploid cardiomyocyte abundance across 41 species conforms to Kleiber’s law−the ¾-power law scaling of metabolism with bodyweight−and inversely correlates with standard metabolic rate, body temperature, and serum thyroxine level. Inactivation of thyroid hormone signaling reduces mouse cardiomyocyte polyploidization, delays cell-cycle exit, and retains cardiac regenerative potential in adults. Conversely, exogenous thyroid hormones inhibit zebrafish heart regeneration. Thus, our findings suggest that loss of heart regenerative capacity in adult mammals is triggered by increasing thyroid hormones and may be a tradeoff for the acquisition of endothermy.

Body size-dependent energy storage causes Kleiber’s law scaling of the metabolic rate in planarians

Kleiber’s law, or the 3/4 -power law scaling of the metabolic rate with body mass, is considered one of the few quantitative laws in biology, yet its physiological basis remains unknown. Here, we report Kleiber’s law scaling in the planarian Schmidtea mediterranea. Its reversible and life history-independent changes in adult body mass over 3 orders of magnitude reveal that Kleiber’s law does not emerge from the size-dependent decrease in cellular metabolic rate, but from a size-dependent increase in mass per cell. Through a combination of experiment and theoretical analysis of the organismal energy balance, we further show that the mass allometry is caused by body size dependent energy storage. Our results reveal the physiological origins of Kleiber’s law in planarians and have general implications for understanding a fundamental scaling law in biology.