Water-land Transition Research Articles

Ecological resilience in water-land transition zones: A case study of the Dongting Lake region, China

Water-land transition zones (WLTZs) are quintessential, complex human-land systems where aquatic and terrestrial environments intermingle, playing a pivotal role in bolstering global ecological resilience (ER). Human terrestrial production activities have encroached upon ecologically sensitive aquatic areas, weakening the inherent ER patterns in WLTZs. To address these issues, we developed an ER assessment process chain across the disturbance-carrying-recovery (D-C-R) dimensions. Applied it to the Dongting Lake region, this model diagnosed the spatiotemporal variations in ER from 2000 to 2020 and revealed the stress mechanisms of various driving factors. The results indicate: (1) The ER spatial pattern in the Dongting Lake region featured a radiating enhancement structure originating from a low-value core in the central plain’s lake network area, displaying distinct water-land gradient variations. Areas with declining ER levels were mainly distributed around the main body of the lake, water system runoff areas, and near governmental centers. (2) The spatiotemporal differentiation effects of ER manifested as an east–west axial development trend, tending toward polarization. The spatiotemporal aggregation effect appeared as L-L clustering and cold spots in the north, gradually expanding toward the peripheral forest areas. (3) Factors related to land use were the dominant drivers of spatiotemporal changes in ER. Simultaneously, the nonlinear interaction intensity among these driving factors showed a significant annual increase. This research framework can be extended to assess ER in similar regions, potentially offering policy recommendations for the ecological protection and sustainable management of WLTZs.

Metagenomic insights into carbon and nitrogen cycling in the water-land transition zone of inland alkaline wetlands

Inland alkaline wetlands play a crucial role in maintaining ecological functions. However, these wetlands are becoming more vulnerable to the effects of water level fluctuations caused by global climate change, especially concerning carbon (C) and nitrogen (N) cycling. Here, metagenomics sequencing was used to investigate microorganism diversity, C and N cycling gene abundance at three water level types (D (dry), MF (middle flooded), HF (high flooded)) along an inland alkaline wetland. Our findings reveal that water level was the most important factor in regulating the microbial communities. Distinct shifts in community composition were found along the water level increases, without fundamentally altering their composition. With the increase of water level, the relative abundance of pmoA decreased from 2.5 × 10−5 to 5.1 × 10−6. The C cycling processes shift from predominantly CO2-generated processes under low water levels to CO2 and CH4 co-generated processes under high water levels. The relative abundance of nosZ reached 4.9 × 10−5 in HF, while in D and MF, it is recorded at 4.5 × 10−5 and 3.4 × 10−5, respectively. Water levels accelerate N cycling and generating N2O intermediates. Furthermore, our study highlights the dynamic competition and cooperation between C and N cycling processes. This research provides a comprehensive biological understanding of the influence of varying water levels on soil C and N cycling processes in wetland.

Barystatic and steric sea level variations in the Baltic Sea and implications of water exchange with the North Sea in the satellite era

Satellite altimetry, satellite gravimetry, and in-situ subsurface salinity and temperature profiles are used to investigate the total, barystatic, and steric sea level variations in the Baltic Sea, respectively. To estimate the steric sea level, the density variations are weighted in deeper layers to prevent overestimation of their contribution. We show that the sum of barystatic and steric components exhibits excellent cross correlation (0.9) with satellite altimetry sea level variations and also explains up to 84% of total signal variability from 2002 to 2019. Considering the dominance of barystatic sea level variations in the basin and the limitation of satellite gravimetry in resolving the mass change in water-land transition zones (known as the leakage problem), the mismatch is likely attributed to the inadequate accuracy of the barystatic datasets. The total sea level and its contributors are further decomposed into seasonal, interannual, and decadal temporal components. It is shown that despite its insignificant contributions to seasonal and interannual changes, the steric sea level plays an important role in decadal variations. Additionally, we show that the interannual variations of the barystatic sea level are governed by the North Atlantic Oscillation in the basin. The sea level variation in the North Sea is also examined to deduce the water exchange patterns on different time scales. A drop in the North Sea level can be seen from 2005 to 2011 which is followed by the Baltic Sea level with a ~3-year lag, implying the outflow from the Baltic Sea to the North Sea.

Editorial: Tetrapod water-land transition: Reconstructing soft tissue anatomy and function

Editorial: Tetrapod water-land transition: Reconstructing soft tissue anatomy and function

Terrestrial force production by the limbs of a semi-aquatic salamander provides insight into the evolution of terrestrial locomotor mechanics.

Amphibious fishes and salamanders are valuable functional analogs for vertebrates that spanned the water-land transition. However, investigations of walking mechanics have focused on terrestrial salamanders and, thus, may better reflect the capabilities of stem tetrapods that were already terrestrial. The earliest tetrapods were likely aquatic, so salamanders that are not primarily terrestrial may yield more appropriate data for modeling the incipient stages of terrestrial locomotion. In the present study, locomotor biomechanics were quantified from semi-aquatic Pleurodeles waltl, a salamander that spends most of its adult life in water, and then compared with those of a primarily terrestrial salamander (Ambystoma tigrinum) and a semi-aquatic fish (Periophthalmus barbarus) to evaluate whether terrestrial locomotion was more comparable between species with ecological versus phylogenetic similarities. Ground reaction forces (GRFs) from individual limbs or fins indicated that the pectoral appendages of each taxon had distinct patterns of force production, but GRFs from the hindlimbs were comparable between the salamander species. The rate at which force is produced can affect musculoskeletal function, so we also calculated 'yank' (first time derivative of force) to quantify the dynamics of GRF production. Yank was sometimes slower in P. waltl but there were some similarities between the three species. Finally, the semi-aquatic taxa (P. waltl and P. barbarus) had a more medial inclination of the GRF compared to terrestrial salamanders, potentially elevating bone stresses among more aquatic taxa and limiting their excursions onto land.

Eye and Skin Differences between Atelognathus patagonicus Morphotypes: Two Environments, Two Strategies (Anura; Batrachylidae)

The adults of the frog Atelognathus patagonicus display phenotypic plasticity and two morphotypes, namely, “aquatic” and “littoral”, and the transition from one to the other is a reversible way of adapting to different environments. The aquatic form lives underwater associated with vegetation and rocks and has lateral skin folds and interdigital membranes. Otherwise, the littoral form lives up to a few kilometers away from the water and does not have bagginess and the interdigital membranes are reduced. Considering that morphology and function of the visual system and skin composition are characters highly associated with habitat conditions, we performed a histological comparison of the eye and skin of both aquatic and littoral morphotypes of A. patagonicus. The aquatic morphotype A. patagonicus does not have an evident character that improves vision underwater, suggesting that clues for subaquatic life could not be only visual. However, the eyelid of the littoral morph has more mucous glands than that of the aquatic morph, which is consistent with the mucus secretion of these glands and its association with terrestrial environments. Also, the skin littoral morph is more keratinized and thicker than the aquatic one, which helps to prevent desiccation. Finally, the lateral skin of the aquatic morph is highly vascularized, suggesting an increase in cutaneous respiration. This work is a starting point for understanding, in an integrative way, the different mechanisms and systems modifications in the water–land transition of A. patagonicus.

Osteohistology of Greererpeton provides insight into the life history of an early Carboniferous tetrapod.

The vertebrate transition to land is one of the most consequential, yet poorly understood periods in tetrapod evolution. Despite the importance of the water-land transition in establishing modern ecosystems, we still know very little about the life histories of the earliest tetrapods. Bone histology provides an exceptional opportunity to study the biology of early tetrapods and has the potential to reveal new insights into their life histories. Here, we examine the femoral bone histology from an ontogenetic series of Greererpeton, an early tetrapod from the Middle-Late Mississippian (early Carboniferous) of North America. Thin-sections and micro-CT data show a moderately paced rate of bone deposition with significant cortical thickening through development. An interruption to regular bone deposition, as indicated by a zone of avascular tissue and growth marks, is notable at the same late juvenile stage of development throughout our sample. This suggests that an inherent aspect to the life history of juvenile Greererpeton resulted in a temporary reduction in bone deposition. We review several possible life history correlates for this bony signature including metamorphosis, an extended juvenile phase, environmental stress, and movement (migration/dispersal) between habitats. We argue that given the anatomy of Greererpeton, it is unlikely that events related to polymorphism (metamorphosis, extended juvenile phase) can explain the bony signature observed in our sample. Furthermore, the ubiquity of this signal in our sample indicates a taxon-level rather than a population-level trait, which is expected for an environmental stress. We conclude that movement via dispersal represents a likely correlate, as such events are a common life history strategy of aquatically bound vertebrates.

Variation in Articular Cartilage Thickness Among Extant Salamanders and Implications for Limb Function in Stem Tetrapods

The size and shape of articular cartilage in the limbs of extant vertebrates are highly variable, yet they are critical for understanding joint and limb function in an evolutionary context. For example, inferences about unpreserved articular cartilage in early tetrapods have implications for how limb length, joint range of motion, and muscle leverage changed over the tetrapod water-land transition. Extant salamanders, which are often used as functional models for early limbed vertebrates, have much thicker articular cartilage than most vertebrate groups, but the exact proportion of cartilage and how it varies across salamander species is unknown. I aimed to quantify this variation in a sample of 13 salamanders representing a broad range of sizes, modes of life, and genera. Using contrast-enhanced micro-CT, cartilage dimensions and bone length were measured non-destructively in the humerus, radius, ulna, femur, tibia, and fibula of each specimen. Cartilage correction factors were calculated as the combined thickness of the proximal and distal cartilages divided by the length of the bony shaft. Articular cartilage added about 30% to the length of the long bones on average. Cartilage was significantly thicker in aquatic salamanders (42 ± 14% in the humerus and 35 ± 8 in the femur) than in terrestrial salamanders (21 ± 7% in both humerus and femur). There was no consistent relationship between relative cartilage thickness and body size or phylogenetic relatedness. In addition to contributing to limb length, cartilage caps increased the width and breadth of the epiphyses by amounts that varied widely across taxa. To predict the effect of salamander-like cartilage correction factors on muscle leverage, a simplified model of the hindlimb of the Devonian stem tetrapodAcanthostegawas built. In this model, the lever arms of muscles that cross the hip at an oblique angle to the femur was increased by up to six centimeters. Future reconstructions of osteological range of motion and muscle leverage in stem tetrapods and stem amphibians can be made more rigorous by explicitly considering the possible effects of unpreserved cartilage and justifying assumptions based on available data from extant taxa, including aquatic and terrestrial salamanders.

Air-breathing and excretory nitrogen metabolism in fishes

During water-land transition, ancient fishes acquired the ability to breathe air, but air-breathing engendered problems in nitrogenous waste excretion. Nitrogen is a fundamental component of amino acids, proteins, and nucleic acids, and the degradation of these nitrogen-containing compounds releases ammonia. Ammonia is toxic and must be removed. Fishes in water excrete ammonia as the major nitrogenous waste through gills, but gills of air-breathing fishes are modified for air-breathing or largely replaced by air-breathing organs. Notably, fishes emerged from water can no longer excrete ammonia effectively because of a lack of water to flush the gills. Hence, ancient fishes that participated in water-land transition must have developed means to deal with ammonia toxicity. Extant air-breathing fishes, particularly amphibious ones, can serve as models to examine adaptations which might have facilitated the emergence of ancient fishes from water. Some of these fishes can actively emerge from water and display complex behaviors on land, while a few can burrow into mud and survive for years during drought. Many of them are equipped with mechanisms to ameliorate ammonia toxicity during emersion. In this review, the mechanisms adopted by air-breathing fishes to deal with ammonia toxicity during emersion were organized into seven disparate strategies. In addition, eight extant air-breathing fishes with distinctive terrestrial behaviors and peculiar natural habitats were selected to describe in detail how these seven strategies could be adopted in disparate combinations to ameliorate ammonia toxicity during emersion.

The evolution of the tetrapod humerus: morphometrics, disparity, and evolutionary rates

ABSTRACTThe present study explores the macroevolutionary dynamics of shape changes in the humeri of all major grades and clades of early tetrapods and their fish-like forerunners. Coordinate point eigenshape analysis applied to humeral outlines in extensor view reveals that fish humeri are more disparate than those of most early tetrapod groups and significantly separate from the latter. Our findings indicate sustained changes in humeral shape in the deepest portions of the tetrapod stem group and certain portions of the crown. In the first half of sampled tetrapod history, subclades show larger than expected humeral disparity, suggesting rapid diffusion into morphospace. Later in tetrapod evolution, subclades occupy smaller and non-overlapping morphospace regions. This pattern may reflect in part increasing specialisations in later tetrapod lineages. Bayesian shifts in rates of evolutionary change are distributed discontinuously across the phylogeny, and most of them occur within rather than between major groups. Most shifts with the highest Bayesian posterior probabilities are observed in lepospondyls. Similarly, maximum likelihood analyses of shifts support marked rate accelerations in lepospondyls and in various subclades within that group. In other tetrapod groups, rates either tend to slow down or experience only small increases. Somewhat surprisingly, no shifts are concurrent with structural, functional, or ecological innovations in tetrapod evolution, including the origin of digits, the water–land transition and increasing terrestrialisation. Although counterintuitive, these results are consistent with a model of continual phenotypic innovation that, although decoupled from key evolutionary changes, is possibly triggered by niche segregation in divergent clades and grades of early tetrapods.

The Molecular Apgar Score: A Key to Unlocking Evolutionary Principles

One of the first “tools” used for systematically evaluating successful newborn transitional physiology at birth was the Apgar Score, devised by Virginia Apgar in 1953. This objective assessment tool allowed clinicians to immediately gauge the relative success of a newborn infant making the transition from the in utero liquid immersive environment to the ex utero gas environment in the delivery room during the first minutes after birth. The scoring system, although eponymous, is generally summarized as an acronym based on Appearance, Pulse, Grimace, Activity, and Respiration, criteria evaluated and scored at 1 and 5 min after birth. This common clinical appraisal is a guide for determining the elements of integrated physiology involved as the infant makes the transition from a “sea water” environment of 3% oxygen to a “land” environment in 21% oxygen. Appearance determines the perfusion of the skin with oxygenated blood—turning it pink; Pulse is the rate of heart beat, reflecting successful oxygen delivery to organs; Grimace, or irritability, is a functional marker for nervous system integration; Activity represents locomotor capacity; and, of course, Respiration represents pulmonary function as well as the successful neuro-feedback-mediated drive to breathe, supplying oxygen by inspiring atmospheric gas. Respiration, locomotion, and metabolism are fundamental processes adapted for vertebrate evolution from a water-based to an atmosphere-based life and are reflected by the Apgar Score. These physiologic processes last underwent major phylogenetic changes during the water–land transition some 300–400 million years ago, during which specific gene duplications occurred that facilitated terrestrial adaptation, in particular the parathyroid hormone-related protein receptor, the β-adrenergic receptor, and the glucocorticoid receptor. All these genetic traits and the gene regulatory networks they comprise represent the foundational substructure of the Apgar Score. As such, these molecular elements can be examined using a Molecular Apgar evaluation of keystone evolutionary events that predict successful evolutionary adaptation of physiologic functions necessary for neonatal transition and survival.

OBSERVAÇÕES E MODELAGEM DA CAMADA LIMITE INTERNA NO ENTORNO DE EXTENSOS SISTEMAS AQUÁTICOS

The determination of the spatial extent of the internal boundary layer (IBL) across a step change in surface roughness and surface heat flux and temperature is an important environmental aspect to the operation of industries, fossil-fuel, nuclear and wind power plants. The IBL of the land-water transition zone, such as in coastal regions, lakes and reservoirs, is strongly influenced by surface properties, as the roughness and stability change considerably within this zone. An observational study was conducted to measure meteorological properties near a large tropical reservoir and investigate the IBL at the water-land transition. A 42 m height meteorological mast was instrumented with sonic wind anemometers, air temperature and relative humidity sensors at 3, 10, 20 and 40 m height. Comparisons of the log profile model with the Monin-Obukhov similarity theory (MOS) and the observed wind profiles, shown that the MOS estimated the wind profile more accurately, especially if winds were from water to land.

On the Evolution of the Mammalian Brain.

Hobson and Friston have hypothesized that the brain must actively dissipate heat in order to process information (Hobson et al., 2014). This physiologic trait is functionally homologous with the first instantation of life formed by lipids suspended in water forming micelles- allowing the reduction in entropy (heat dissipation). This circumvents the Second Law of Thermodynamics permitting the transfer of information between living entities, enabling them to perpetually glean information from the environment, that is felt by many to correspond to evolution per se. The next evolutionary milestone was the advent of cholesterol, embedded in the cell membranes of primordial eukaryotes, facilitating metabolism, oxygenation and locomotion, the triadic basis for vertebrate evolution. Lipids were key to homeostatic regulation of calcium, forming calcium channels. Cell membrane cholesterol also fostered metazoan evolution by forming lipid rafts for receptor-mediated cell-cell signaling, the origin of the endocrine system. The eukaryotic cell membrane exapted to all complex physiologic traits, including the lung and brain, which are molecularly homologous through the function of neuregulin, mediating both lung development and myelinization of neurons. That cooption later exapted as endothermy during the water-land transition (Torday, 2015a), perhaps being the functional homolog for brain heat dissipation and conscious/mindful information processing. The skin and brain similarly share molecular homologies through the “skin-brain” hypothesis, giving insight to the cellular-molecular “arc” of consciousness from its unicellular origins to integrated physiology. This perspective on the evolution of the central nervous system clarifies self-organization, reconciling thermodynamic and informational definitions of the underlying biophysical mechanisms, thereby elucidating relations between the predictive capabilities of the brain and self-organizational processes.

Port cities and urban waterfronts: how localized planning ignores water as a connector

People have redesigned coastlines, creating ports, shaping waterfronts, and building cities to connect water and land. Specialists from many disciplines have explored the function and design of the water–land transition over many centuries. Among them is planning, a discipline that engages both with the functionality of working ports and the design of the waterfront for the urban public. In order to explore the development of working ports and the revitalization of abandoned inner‐city waterfronts since the 1960s, this paper reviews planning and planning history literature in regard to the specific appreciation of water. It first examines the planning of ports and its focus on improving the speed, safety, and logistics, assigning water an industrial role. Second, it reflects on the design of post‐industrial waterfront spaces, which ascribes a more aesthetic and symbolic as well as leisure‐related role to water. Third, it points to the recent reconnection of cruise shipping with inner‐city waterfront redevelopment and the coastline in general. In conclusion, the paper underscores localized perceptions of water in planning literature and the need to recognize how interconnected water systems connect otherwise separated areas along the same coastline. It argues for the integrated planning of port, waterfront, and city in conjunction with a comprehensive study of the environmental and ecological role of water in each of those places, both as a resource they share and, with climate change, a risk to which they must collectively respond. WIREs Water 2016, 3:419–438. doi: 10.1002/wat2.1141This article is categorized under: Engineering Water > Planning Water Human Water > Water as Imagined and Represented

Heterochrony as Diachronically Modified Cell-Cell Interactions.

Heterochrony is an enabling concept in evolution theory that metaphorically captures the mechanism of biologic change due to mechanisms of growth and development. The spatio-temporal patterns of morphogenesis are determined by cell-to-cell signaling mediated by specific soluble growth factors and their cognate receptors on nearby cells of different germline origins. Subsequently, down-stream production of second messengers generates patterns of form and function. Environmental upheavals such as Romer’s hypothesized drying up of bodies of water globally caused the vertebrate water-land transition. That transition caused physiologic stress, modifying cell-cell signaling to generate terrestrial adaptations of the skeleton, lung, skin, kidney and brain. These tissue-specific remodeling events occurred as a result of the duplication of the Parathyroid Hormone-related Protein Receptor (PTHrPR) gene, expressed in mesodermal fibroblasts in close proximity to ubiquitously expressed endodermal PTHrP, amplifying this signaling pathway. Examples of how and why PTHrPR amplification affected the ontogeny, phylogeny, physiology and pathophysiology of the lung are used to substantiate and further our understanding through insights to the heterochronic mechanisms of evolution, such as the fish swim bladder evolving into the vertebrate lung, interrelated by such functional homologies as surfactant and mechanotransduction. Instead of the conventional description of this phenomenon, lung evolution can now be understood as adaptive changes in the cellular-molecular signaling mechanisms underlying its ontogeny and phylogeny.

Macroevolution of genome size in sarcopterygians during the water–land transition

Genome size spans over a 300-fold range among vertebrates (132pg for Protopterus aethiopicus, the marbled lungfish, and 0.35pg for Tetraodon nigroviridis, the green spotted pufferfish). While phylogenetic analysis of genome size has helped clarify how this variation evolved in multiple tetrapod groups, the ancestral tetrapod condition still remains poorly characterized, and this obscures our understanding of character state polarity and macroevolutionary trends in genome size. To address this problem, we used phylogenetic comparative methods to analyze paleohistological data from eight taxa of the Middle and Late Paleozoic to the Early Mesozoic: Eusthenopteron, Ichthyostega, Acheloma, Eryops, Trimerorhachis, Wetlugasaurus, an unidentified dissorophoid, and Chroniosaurus. Five other extinct taxa were included from previous studies to better frame our results, including Marmorerpeton, Cardiocephalus, Diplocaulus, an unidentified basal sauropsid, and Mycterosaurus. We augmented a previously reported histological and genome size data set (including data from 14 lissamphibians, three testudines, Sphenodon, five squamates, two crocodilians, 11 birds, and 22 mammals) with genome size and histological data from extant Latimeria and three extant actinopterygians. Our results suggest that all eight of the newly analyzed extinct taxa had genome sizes ranging between 3.2 and 3.9pg. These results imply that basal tetrapods had genome sizes (and underlying genomic architectures) similar to extant mammals and lepidosaurs. We find no major shifts in genome size during the tetrapod water-to-land transition. Our analysis suggests that Eusthenopteron and Ichthyostega had genome sizes well within the range of extant actinopterygians and Latimeria, despite several whole-genome duplications in actinopterygians.

The Evolution of Bony Vertebrate Enhancers at Odds with Their Coding Sequence Landscape.

Enhancers lie at the heart of transcriptional and developmental gene regulation. Therefore, changes in enhancer sequences usually disrupt the target gene expression and result in disease phenotypes. Despite the well-established role of enhancers in development and disease, evolutionary sequence studies are lacking. The current study attempts to unravel the puzzle of bony vertebrates’ conserved noncoding elements (CNE) enhancer evolution. Bayesian phylogenetics of enhancer sequences spotlights promising interordinal relationships among placental mammals, proposing a closer relationship between humans and laurasiatherians while placing rodents at the basal position. Clock-based estimates of enhancer evolution provided a dynamic picture of interspecific rate changes across the bony vertebrate lineage. Moreover, coelacanth in the study augmented our appreciation of the vertebrate cis-regulatory evolution during water–land transition. Intriguingly, we observed a pronounced upsurge in enhancer evolution in land-dwelling vertebrates. These novel findings triggered us to further investigate the evolutionary trend of coding as well as CNE nonenhancer repertoires, to highlight the relative evolutionary dynamics of diverse genomic landscapes. Surprisingly, the evolutionary rates of enhancer sequences were clearly at odds with those of the coding and the CNE nonenhancer sequences during vertebrate adaptation to land, with land vertebrates exhibiting significantly reduced rates of coding sequence evolution in comparison to their fast evolving regulatory landscape. The observed variation in tetrapod cis-regulatory elements caused the fine-tuning of associated gene regulatory networks. Therefore, the increased evolutionary rate of tetrapods’ enhancer sequences might be responsible for the variation in developmental regulatory circuits during the process of vertebrate adaptation to land.

The cell as the mechanistic basis for evolution.

The First Principles for Physiology originated in and emanate from the unicellular state of life. Viewing physiology as a continuum from unicellular to multicellular organisms provides fundamental insight to ontogeny and phylogeny as a functionally integral whole. Such mechanisms are most evident under conditions of physiologic stress; all of the molecular pathways that evolved in service to the vertebrate water-land transition aided and abetted the evolution of the vertebrate lung, for example. Reduction of evolution to cell biology has an important scientific feature—it is predictive. One implication of this perspective on evolution is the likelihood that it is the unicellular state that is actually the object of selection. By looking at the process of evolution from its unicellular origins, the causal relationships between genotype and phenotype are revealed, as are many other aspects of physiology and medicine that have remained anecdotal and counter-intuitive. Evolutionary development can best be considered as a cyclical, epigenetic, reiterative environmental assessment process, originating from the unicellular state, both forward and backward, to sustain and perpetuate unicellular homeostasis.

On the Cellular Evolution of the Lung

The water‐land transition (WLT) marked the evolution of human physiology (Torday, Evolutionary Biology Redux. Pers Biol Med, Fall 2013). Skeletal changes chronicle at least five attempts by vertebrates to breach land, but molecular ‘fossil’ evidence functionally interconnects skeletal and visceral organ evolution. During the WLT, there were three gene duplications‐ the Parathyroid Hormone‐related Protein Receptor (PTHrPR), the βAdrenergic Receptor (βAR), and the Glucocorticoid Receptor (GR). All three of these gene amplifications were necessary for the evolution of the lung from the swim bladder, functional homologs which exploited lipids for efficient gas exchange. Key to understanding the cellular‐molecular changes that mediated the evolution of the gas‐exchanger is lung surfactant, a mixture of proteins and lipids sythesized and secreted into the alveolar air space, mediated by mesenchymal‐epithelial interactions that accommodated both the phylogenetic and ontogenetic decreases in the alveolar surface area‐to‐blood volume ratio to maximize oxygenation for metabolic drive among land vertebrates. Mechanistically, shearing of microvessel walls, particularly in those tissues necessary for land adaptation, generated Radical Oxygen Species, causing context‐specific, adaptive gene mutations in response to physiologic stress‐ PTHrP is necessary for the formation of alveoli, the βARs allowed for the independent regulation of systemic and alveolar blood pressure, and the GR facilitated βAR expression. Such evolutionary connections between the pulmonary and neuroendocrine systems help solve homeostatic puzzles, and these functional genomic interrelationships provide deep insights to the First Principles of lung Physiology, referring all the way back to cholesterol, the most primitive lung surfactant, in the cell membranes of unicellular eukaryotes.

Towards a whole animal, whole lineage perspective on the evolution of tetrapod locomotion

One of the great mysteries regarding the evolution of animals is how and when tetrapods achieved the ability to stand and move on solid ground. Old perceptions that our fish ancestors gradually evolved limbs with digits on terra firma have been discarded in light of new evidence favouring a wholly aquatic origin. But which pioneering tetrapod species could move on land and how well‾ This question must be resolved in order to piece together how “modern” walking evolved. Our recent work has shown that the morphology of known stem tetrapods could not have supported walking in a typical salamander‐like fashion and that a mudskipper‐like crutching gait was more likely to be employed. Such a hypothesis means we still know very little about the evolution of modern walking behaviours. To further our investigation, we are forging work that links three‐dimensional whole animal morphology, empirically tested biomechanical performance indices, and whole lineage character changes. Our goal is to create validated, dynamic simulations of locomotion in extinct tetrapods bridging the water‐land transition.