Heterochrony

The experimental approach to the evolution and development of the vertebrate skeleton has to a large extent relied on "direct-developing" amniote model organisms, such as the mouse and the chicken. These organisms can however only be partially informative where it concerns secondarily lost features or anatomical novelties not present in their lineages. The widely used anamniotes Xenopus and zebrafish are "indirect-developing" organisms that proceed through an extended time as free-living larvae, before adopting many aspects of their adult morphology, complicating experiments at these stages, and increasing the risk for lethal pleiotropic effects using genetic strategies. Here, we provide a detailed description of the development of the osteology of the African mouthbrooding cichlid Astatotilapia burtoni, primarily focusing on the trunk (spinal column, ribs and epicentrals) and the appendicular skeleton (pectoral, pelvic, dorsal, anal, caudal fins and scales), and...

HETEROTOPIA AND HETEROCHRONY IN METAVERSE AS
CHANGING PERCEPTION OF SPACE AND TIME
ABSTRACT
Looking at the Metaverse universe or virtual communication environments in which XR technologies are used, it is evident that heterogeneity enriches it, let alone reflecting the reality since a set of positions and even reality itself is played with. In Virtual reality platforms, in Extended, Augmented, or Mixed reality, it is possible to encounter confusing situations regarding reality, space, and time. Where space and time collide, realities can also change in multiple layers. Real life itself takes place in heterogeneous spaces but this heterogeneity is not a space where people and
things can be placed, and most importantly, spaces and lives are designed within a set of relations defined by locations. For Foucault, understanding life and space is partly based on understanding these positions and the ensemble of relationships that surround them. In real life, space is a place full of certain qualities, rather than a homogeneous and empty space, which is given meaning in our minds, dreams, and memories. This study therefore will analyze Foucault’s and other scholars’ ideas on
heterotopia and heterochrony by attaching these concepts to the multiple spaces and universes created in the Metaverse. From a correlated perspective, Ray Oldenburg defines the subject's experience of space as the third place which is somehow the interaction between space, body, and duration. With this conceptualization, the third space is a place realized with the body and time is not an empty time with a definite beginning and end. A beginning and an end of time convey full of vitality about the existence of the body. On the other hand, technological arrangements in which Virtual Reality and Augmented Reality were applied did not only change the visual perception, visual narrative language, and the type of entertainment. The perception of alternative space or the idea that other lives are possible is an intrinsic search for the subject. When looking at Metaverse environments from a Levinasian perspective, virtual reality perhaps appears as a new alternative that provides the opportunity to escape from existence. The idea of creating different spaces and alternative realities by experiencing a different sense of time can be attached to the predictions of Byung Chul Han, who relates today's crisis to time. For Chul Han, time, today no longer has a regulating rhythm.
Keywords: Heterotopia, Heterochrony, Dyssynchrony, Metaverse, XR Technologies, XR, VR, AR, Third Place

Two indicators of a clade's success are its diversity (number of included species) and its disparity (extent of morphospace occupied by its members). Many large genera show high diversity with low disparity, while others such as Euphorbia and Drosophila are highly diverse but also exhibit high disparity. The largest genera are often characterized by key innovations that often, but not necessarily, coincide with their diagnostic apomorphies. In terms of their contribution to speciation, apomorphies are either permissive (e.g. flightlessness) or generative (e.g. nectariferous spurs). Except for Drosophila, virtually no genus among those with the highest diversity or disparity includes species currently studied as model species in developmental genetics or evolutionary developmental biology (evo-devo). An evo-devo approach is, however, potentially important to understand how diversity and disparity could rapidly increase in the largest genera currently accepted by taxonomists. The ...

Habitat is one of the most important factors shaping organismal morphology, but it may vary across life history stages. Ontogenetic shifts in ecology may introduce antagonistic selection that constrains adult phenotype, particularly with ecologically distinct developmental phases such as the free-living, feeding larval stage of many frogs (Lissamphibia: Anura). We test the relative influences of developmental and ecological factors on the diversification of adult skull morphology with a detailed analysis of 15 individual cranial regions across 173 anuran species, representing every extant family. Skull size, adult microhabitat, larval feeding, and ossification timing are all significant factors shaping aspects of cranial evolution in frogs, with late-ossifying elements showing the greatest disparity and fastest evolutionary rates. Size and microhabitat show the strongest effects on cranial shape, and we identify a “large size-wide skull” pattern of anuran, and possibly amphibian, ev...

Developmental constraints can have significant influence on the magnitude and direction of evolutionary change, and many studies have demonstrated that these effects are manifested on macroevolutionary scales. Phenotypic integration, or the strong interactions among traits, has been similarly invoked as a major influence on morphological variation, and many studies have demonstrated that trait integration changes through ontogeny, in many cases decreasing with age. Here, we unify these perspectives in a case study of the ontogeny of the mammalian cranium, focusing on a comparison between marsupials and placentals. Marsupials are born at an extremely altricial state, requiring, in most cases, the use of the forelimbs to climb to the pouch, and, in all cases, an extended period of continuous suckling, during which most of their development occurs. Previous work has shown that marsupials are less disparate in adult cranial form than are placentals, particularly in the oral apparatus, a...

Heterochronic changes in the rate or timing of development underpin many evolutionary transformations. In particular, the onset and rate of bone development have been the focus of many studies across large clades. In contrast, the termination of bone growth, as estimated by suture closure, has been studied far less frequently, although a few recent studies have shown this to represent a variable, although poorly understood, aspect of developmental evolution. Here, we examine suture closure patterns across 25 species of carnivoran mammals, ranging from social‐insectivores to hypercarnivores, to assess variation in suture closure across taxa, identify heterochronic shifts in a phylogenetic framework and elucidate the relationship between suture closure timing and ecology. Our results show that heterochronic shifts in suture closure are widespread across Carnivora, with several shifts identified for most major clades. Carnivorans differ from patterns identified for other mammalian clad...

Plants develop through at least three distinct phases after germination: a juvenile vegetative phase; an adult vegetative phase; and a reproductive phase. Therefore, there exist two main ontogenetic transitions, the juvenile-adult vegetative transition or vegetative phase change, and the adult vegetative-reproductive phase transition or reproductive phase change. The genetic and physiological control of the transition to flowering has been studied intensively over the past four decades but the other major transition has received much less attention. This study investigates the genetic and physiological regulation of vegetative phase change in the garden pea (Pisum sativum L) using a novel heterochronic mutant, accelerated phase change (apc), which expresses a consistent difference in the rate of vegetative phase change when compared to the wild type plants. Genetic analyses, using morphological and enzyme markers, revealed that the apc locus is on linkage group 131 (between a and aa...

This review explores challenges and opportunities in developmental physiology outlined by a symposium at the 2014 American Physiological Society Intersociety Meeting: Comparative Approaches to Grand Challenges in Physiology. Across animal taxa, adverse embryonic/fetal environmental conditions can alter morphological and physiological phenotypes in juveniles or adults, and capacities for developmental plasticity are common phenomena. Human neonates with body sizes at the extremes of perinatal growth are at an increased risk of adult disease, particularly hypertension and cardiovascular disease. There are many rewarding areas of current and future research in comparative developmental physiology. We present key mechanisms, models, and experimental designs that can be used across taxa to investigate patterns in, and implications of, the development of animal phenotypes. Intraspecific variation in the timing of developmental events can be increased through developmental plasticity (hete...

As shown in a taxonomically broad study, domestication modifies postnatal growth. Skull shape across 1128 individuals was characterized by 14 linear measurements, comparing 13 pairs of wild versus domesticated forms. Among wild forms, the boar, the rabbit and the wolf have the highest proportion of allometric growth, explaining in part the great morphological diversity of the domesticated forms of these species. Wild forms exhibit more isometric growth than their domesticated counterparts. Multivariate comparisons show that dogs and llamas exhibit the greatest amount of differences in trajectories with their wild counterparts. The least amount is recorded in the pig-boar, and camel and horse pairs. Bivariate analyses reveal that most domesticated forms have growth trajectories different from their respective wild counterparts with regard to the slopes. In pigs and camels slopes are shared and intercepts are different. There is a trajectory extension in most domesticated herbivores a...

Phenotypic integration is a pervasive characteristic of organisms. Numerous analyses have demonstrated that patterns of phenotypic integration are conserved across large clades, but that significant variation also exists. For example, heterochronic shifts related to different mammalian reproductive strategies are reflected in postcranial skeletal integration and in coordination of bone ossification. Phenotypic integration and modularity have been hypothesized to shape morphological evolution, and we extended simulations to confirm that trait integration can influence both the trajectory and magnitude of response to selection. We further demonstrate that phenotypic integration can produce both more and less disparate organisms than would be expected under random walk models by repartitioning variance in preferred directions. This effect can also be expected to favour homoplasy and convergent evolution. New empirical analyses of the carnivoran cranium show that rates of evolution, in ...

Birds and crocodiles show radically different patterns of brain development, and it is of interest to compare these to determine the pattern of brain growth expected in dinosaurs. Here we provide atlases of 3D brain (endocast) reconstructions for Alligator mississippiensis (alligator) and Struthio camelus (ostrich) through ontogeny, prepared as digital restorations from CT scans of stained head and dry skull specimens. Our morphometric analysis confirms that ostrich brains do not change significantly in shape during postnatal growth, whereas alligator brains unfold from a cramped bird‐like shape in the hatchling to an elongate, straight structure in the adult. We confirm that birds exhibit paedomorphic dinosaur endocranial traits such as retaining an enlarged and compact brain shape in the adult, whereas crocodiles show peramorphic traits where the brain elongates with growth as the skull elongates. These atlases of ontogenetic stages of modern bird and crocodilian endocrania provid...

In this article, it is pointed out that the requirement for organogenetic termination is the new spatial constraint for animal development and heredity, based on that: (a) organogenesis manifests limitation in time and possession of termination, while infinite cell proliferation known as cancer is lethal; (b) the notable indeterminate growth in some fishes and a few outgrowing skin derivatives reversely demonstrates that termination is required for organogenesis inside the animal. In further, it is supplemented this new spatial constraint to Haeckel and von Baer for development and evolution. While not influencing the temporal and spatial reorganization of morphogenesis during evolution, it places restrictions on alteration of organogenetic mechanisms themselves, as that: (a) addition of new induction mechanism or elimination of termination mechanism would usually cause endless organogenesis, liable to become lethal; (b) addition of new termination mechanism or elimination of induction mechanism in evolution not be affected by this spatial constraint. Finally, it is identified this spatial constraint as partial convergence and partial difference with Haeckel's recapitulation, and as restriction onto Baer's tree. It is perspectives to use the method of mathematical probability and statistics to study the spatial constraint of development onto evolution in future.

The p63 gene is integral to the development of many body parts including limb, palate, teeth, and urogenital tract. Loss of p63 expression may alter developmental rate, which is crucial to normal morphogenesis. To validate a novel, unbiased embryo phenotyping software tool, we tested whether delayed development contributes to the pathological phenotype of a p63 mouse mutant (p63 ). We quantified dysmorphology in p63 embryos and tested for universal growth delay relative to wild-type (WT) embryos. Fixed embryos (n = 6; p63 ) aged day (E) 15.5 were micro-CT scanned and quantitatively analyzed using a digital WT atlas that defined volumetric differences between p63 and WT embryos. p63 embryos showed a growth delay of approximately 22 hr (0.9 days). Among the E15.5 mutants, overall size was closest to WT E14.6 mice but shape was closest to WT E14.0. The atlas clearly identified in p63 embryos malformations of epithelial derivatives including limbs, tail, urogenital structures, brain, fa...

The heterochronic genes lin-28, let-7, and lin-41, regulate fundamental developmental transitions in animals, e.g. stemness vs. differentiation and juvenile vs. adult states. We identify a new heterochronic gene, lep-2, in Caenorhabditis elegans. Mutations in lep-2 cause a delay in the juvenile/adult transition, with adult males retaining pointed, juvenile tail tips, and displaying defective sexual behaviors. In both sexes, lep-2 mutants fail to cease molting or produce an adult cuticle. We find that lep-2 post-translationally regulates LIN-28 by promoting LIN-28 protein degradation. lep-2 is the sole C. elegans ortholog of the Makorin (Mkrn) family of proteins. Like lin-28 and other heterochronic pathway members, vertebrate Mkrns are involved in developmental switches, including the timing of pubertal onset in humans. Based on shared roles, conservation, and the interaction between lep-2 and lin-28 shown here, we propose that Mkrns—together with other heterochronic genes—constitute...

Hundreds of specimens of the rhynchonellide brachiopod Clarkeia antisiensis (d'Orbigny) recovered from the stratotype of the Tarabuco Formation of Bolivia form a complete series of growth stages providing a good opportunity for reconstructing its ontogenetic development. The fact that juvenile specimens of C. antisiensis are nearly indistinguishable from adult individuals of Harringtonina australis Boucot strongly suggests that Clarkeia evolved from Harringtonina by the heterochronic process of peramorphosis. On the other hand, adult specimens of both the Brazilian Anabaia paraia Clarke and the Precordilleran specimrens of Anabaia never exceed the youngest ontogenetic stage of Harringtonina australis, to which share small hinge plates supported by a septalium-like structure and absence of cardinal process. The overlap of adult morphology of Anabaia with the juvenile morphology of Harringtonina australis allows interpreting this succession as an evolutionary lineage showing incre...