Developmental processes underlying heterochrony as an evolutionary mechanism

1984 ◽  
Vol 62 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Brian K. Hall
Keyword(s):  
Growth Rate ◽  
Morphological Change ◽  
Mitotic Activity ◽  
Skeletal Development ◽  
Relative Time ◽  
Evolutionary Mechanism ◽  
Rate Of Development ◽  
Tissue Interactions ◽  
Lower Jaw ◽  
Developmental Mechanisms

Heterochrony, the change in the relative time of appearance or rate of development of a character during phylogeny, has been an important mechanism for generating morphological change during evolution. Retardation and acceleration are two processes which drive heterochrony. I have considered the developmental mechanisms which govern three parameters of heterochrony (when growth starts, growth rate, when growth stops) during skeletal development and conclude that the number and mitotic activity of the cells in the initial skeletal condensation emerges as a fundamental level of control. A developmental explanation for heterochrony should therefore focus on what controls the size of condensation and where and when they arise. Inductive tissue interactions regulate the formation of the condensations in which skeletal elements form, and the timing of these interactions can be modified genetically. As an example, evidence is presented to show that the timing of the interaction which leads to the formation of Meckel's cartilage in the lower jaw varies from one vertebrate group to another, being earlier in birds and later in mammals than it is in amphibians. Variation in the timing of inductive tissue interactions is identified as one mechanism controlling skeletal condensations, and therefore as one possible basis for heterochrony.

scholarly journals Altering Developmental Trajectories in Mice by Restricted Index Selection

Genetics ◽  
1997 ◽  
Vol 146 (2) ◽  
pp. 629-640
Author(s):  
William R Atchley ◽  
Shizhong Xu ◽  
David E Cowley
Keyword(s):  
Growth Rate ◽  
Body Weight ◽  
Weight Gain ◽  
Complex Traits ◽  
Body Weight Gain ◽  
Developmental Trajectories ◽  
Cell Number ◽  
Index Selection ◽  
Early Postnatal Development ◽  
Rate Of Development

A restricted index selection experiment on mice was carried out for 14 generations on rate of early postnatal development (growth rate from birth to 10 days of age) vs. rate of development much later in ontogeny (growth rate from 28 to 56 days of age). Early rate of development (E) approximates hyperplasia (changes in cell number) and later rate (L) reflects hypertropy (changes in cell size). The selection criteria were as follows: E+L0 was selected to increase early body weight gain while holding late body weight gain constant; E–L0 was selected to decrease early body gain while holding late gain constant; E0L+ was selected to increase late gain holding early gain constant; and E0L– was selected to decrease late gain holding early gain constant. After 14 generations of selection, significant divergence among lines has occurred and the changes in the growth trajectories are very close to expectation. The genetic and developmental bases of complex traits are discussed as well as the concept of developmental homoplasy.

scholarly journals BONE GROWTH AND DISTRIBUTION IN SWINE AS INFLUENCED BY LIVEWEIGHT, BREED, SEX, AND RATION

1972 ◽  
Vol 52 (1) ◽  
pp. 47-56 ◽  
Author(s):  
R. J. RICHMOND ◽  
R. T. BERG
Keyword(s):  
Growth Rate ◽  
Bone Growth ◽  
Skeletal Development ◽  
Lumbar Vertebrae ◽  
High Energy ◽  
Low Energy ◽  
Thoracic Vertebrae ◽  
Yorkshire Pigs ◽  
Tibia Length ◽  
Anterior Posterior

Individual bones of the skeleton, dissected from one-half of the carcass were weighed and expressed as a percentage of total bone for 23 Duroc × Yorkshire, 42 Hampshire × Yorkshire, and 27 Yorkshire × Yorkshire barrows and gilts fed either low energy (LE) (2757 kcal DE/kg and 15.3% protein) or high energy (HE) (3652 kcal DE/kg and 19.9% protein) rations and slaughtered at either 68, 91, or 114 kg liveweight. To determine bone measurements at the start of the experiment bone data were collected from seven barrows and seven gilts of the same breed groups slaughtered at 23 kg liveweight. The scapula, humerus, radius, and ulna, femur, and tibia bones, in addition to being weighed, were measured to determine length and circumference. Increases in bone length were proportionate to liveweight up to 91 kg, after which growth rate decreased for all measured bones except the humerus. Growth in circumference increased rapidly for all measured bones up to 68 kg liveweight, after which increases were of lesser magnitude. Between 23 and 68 kg liveweight, increases in bone circumference were slightly greater than those in length. Weight for each measured bone increased linearily relative to liveweight. Among breed groups Duroc × Yorkshire pigs had the greatest radius and ulna circumference and Hampshire × Yorkshire the smallest tibia weight (P < 0.05). Gilts had a greater scapula length and weight and a greater femur and tibia length than did barrows (P < 0.05). Pigs fed the low energy ration exceeded those fed the high energy ration in scapula length (19.67 vs. 19.08 cm) and weight (171.52 vs. 157.25 g). Sex-liveweight and sex-ration interactions occurred for femur weight and percent scapula, respectively. Percentage bone in the carcass decreased as liveweight increased but percent bone within the hind and front quarters remained relatively constant after 68 kg liveweight. The influence of breed, sex, and ration on percentages of individual bones were observed only for the scapula, radius, and ulna and sternum and rib cartilage. A decrease in percent thoracic vertebrae and increase in percent ribs and lumbar vertebrae indicated an anterior-posterior pattern of skeletal development. Differentiation in bone distribution appeared to be essentially complete at or before 23 kg liveweight.

scholarly journals Glide analysis and bone strength tests indicate powered flight capabilities in hatchling pterosaurs

2017 ◽  
Author(s):  
Mark P Witton ◽  
Elizabeth Martin-Silverstone ◽  
Darren Naish
Keyword(s):  
Growth Rate ◽  
Body Weight ◽  
Bone Strength ◽  
Bending Strength ◽  
Skeletal Development ◽  
Maximum Size ◽  
Strength Analysis ◽  
Life Stages ◽  
Strength Tests ◽  
Very High

Pterosaur embryos and ‘hatchling’ specimens show a surprising level of skeletal development including well-ossified skeletons and large wings. This has prompted interpretations of pterosaurs as being flight-capable from the earliest ontogenetic stages, contrasting them against the majority of other flying animals, living or extinct. Though popular, this hypothesis is not universally accepted. Some authors propose that pterosaurs only became flight capable once they reached 50% of maximum size, explaining a slowing of growth rate in later ontogeny as metabolic resources were diverted into an energy-demanding form of locomotion. We investigated these hypotheses through glide performance and wing bone strength analysis on hatchling-grade specimens of two pterosaurs, Pterodaustro guinazui and Sinopterus dongi. We found that hatchling pterosaurs were excellent gliders, but with a wing ecomorphology more comparable to powered fliers than obligate gliders. Bone strength analysis shows that hatchling pterosaur wing bones are structurally identical to those of larger pterosaurs and – because of their very low body masses – their bending strength relative to body weight is very high, comparable to or exceeding the greatest values estimated for larger, more mature pterosaurs. Hatchling pterosaurs are thus as mechanically adapted to powered flight stresses as other pterosaurs, if not moreso. Together with our glide tests, this result supports interpretations of hatchling pterosaurs as flight-capable. Size differences between pterosaur hatchlings and larger members of their species dictate differences in wing ecomorphology and flight capabilities at different life stages, which might have bearing on pterosaur ontogenetic niching.

The use of inherited abnormalities in studies on the embryogenesis of Dermestes maculatus (Coleoptera)

Development ◽  
1964 ◽  
Vol 12 (3) ◽  
pp. 539-549
Author(s):  
D. A. Ede ◽  
Anne M. Rogers
Keyword(s):  
Large Range ◽  
Normal Embryo ◽  
Primary Defect ◽  
Insect Embryogenesis ◽  
Dermestes Maculatus ◽  
Tissue Interactions ◽  
Developmental Mechanisms ◽  
Embryological Analysis

The possibility of using inherited abnormalities in place of conventional experimental embryological methods has been explored by several workers in Drosophila, where there is a large range of lethal and female sterile genes readily available (reviewed Waddington, 1956). These genes are usually pleiotropic, i.e. with manifold effects, and tracing these diverse effects back as far as possible to a single primary defect gives information about the corresponding developmental mechanisms in the normal embryo. Two disadvantages have attended these studies: (1) dipteran embryology is extremely specialized and difficult to relate to that of other insects, (2) it is almost entirely mosaic in character, and therefore throws no light on the important subject of tissue interactions. The present study was undertaken in order to extend this method of embryological analysis to an insect with a less specialized embryology, and hence to show its applicability to studies on insect embryogenesis in general.

scholarly journals Rampant tooth loss across 200 million years of frog evolution

2021 ◽  
Author(s):  
Daniel J. Paluh ◽  
Karina Riddell ◽  
Catherine M. Early ◽  
Maggie M. Hantak ◽  
Gregory F.M. Jongsma ◽  
...  
Keyword(s):  
Evolutionary History ◽  
Tooth Loss ◽  
Micro Computed Tomography ◽  
Phenotypic Data ◽  
Invertebrate Prey ◽  
Lower Jaw ◽  
Developmental Mechanisms ◽  
Actinopterygian Fishes ◽  
History Of ◽  
Specialized Diet

AbstractTeeth have been broadly maintained across most clades of vertebrates but have been lost completely at least once in actinopterygian fishes and several times in amniotes. Using phenotypic data collected from over 500 genera via micro-computed tomography, we provide the first rigorous assessment of the evolutionary history of dentition across all major lineages of amphibians. We demonstrate that dentition is invariably present in caecilians and salamanders, but teeth have been lost completely more than 20 times in frogs, a much higher occurrence of edentulism than in any other vertebrate group. The repeated loss of teeth in anurans is associated with a specialized diet of small invertebrate prey as well as shortening of the lower jaw, but it is not correlated with a reduction in body size. Frogs provide an unparalleled opportunity for investigating the molecular and developmental mechanisms of convergent tooth loss on a large phylogenetic scale.

Embryos and Ancestors

2020 ◽  
pp. 92-122
Author(s):  
David F. Bjorklund
Keyword(s):  
Developmental Biology ◽  
Growth Rate ◽  
Cognitive Abilities ◽  
Homo Sapiens ◽  
Great Apes ◽  
Evolutionary Developmental Biology ◽  
Developmental Mechanisms ◽  
The Social ◽  
Group Members ◽  
Evo Devo

Evolutionary developmental biology, or Evo Devo, examines how developmental mechanisms affect evolutionary change. Heterochrony refers to genetic-based differences in developmental timing. One important type of heterochrony for humans is neoteny, which refers to the retention of juvenile traits into later development. Humans are a neotenous species, as seen in infants’ features of “babyness,” which promote attention and caring from adults, extending the primate prenatal brain growth rate well past birth, and a reduction of reactive aggression relative to great apes, which facilitated increased cooperation among group members. Homo sapiens extended the time it takes to reach adulthood by inventing new two life stages—childhood and adolescence. The social and cognitive abilities of Homo sapiens’ youth may be well suited to the childhood and adolescent stages and to the attainment of skills necessary for developing into functional adults.

Anchors and snorkels: heterochrony, development and form in functionally constrained fossil crassatellid bivalves

Paleobiology ◽  
2016 ◽  
Vol 42 (2) ◽  
pp. 305-316 ◽  
Author(s):  
Katie S. Collins ◽  
James S. Crampton ◽  
Helen L. Neil ◽  
Euan G. C. Smith ◽  
Michael F. Gazley ◽  
...  
Keyword(s):  
Growth Rate ◽  
New Zealand ◽  
Morphological Change ◽  
Predator Avoidance ◽  
Morphological Variability ◽  
Developmental Timing ◽  
Environmental Pressure ◽  
Life Habit ◽  
Infaunal Bivalve ◽  
Key Drivers

AbstractNew growth rate estimates for nine species from three genera of New Zealand Crassatellidae (Mollusca: Bivalvia), combined with existing morphometric ontogenetic descriptions, allow identification of heterochronic processes in the evolution of these genera. Both paedomorphosis (progenesis and neoteny) and peramorphosis (hypermorphosis and acceleration) have occurred within the clade. Overall, morphological variability and response to environmental pressure in this nonsiphonate group is restricted by the interplay of anatomical and life habit constraints. Stability in the substrate, predator avoidance, sluggish burrowing speed, and inability to escape by deep burial are suggested as key drivers of, or constraints on, morphological change. Two groups of shell characters are identified: heavy, armored “anchors” and elongate “snorkels,” which combine juvenile and adult traits in shells of different sizes and ages, produced by heterochronic variation in developmental timing. Anchors and snorkels both represent different “solutions” to the problems of life as a nonsiphonate, infaunal bivalve.

ACCELERATION OF DEVELOPMENT OF LARVAE OF THE ONION MAGGOT, HYLEMYA ANTIQUA (MEIG.), BY MICROORGANISMS

1959 ◽  
Vol 37 (5) ◽  
pp. 721-727 ◽  
Author(s):  
W. G. Friend ◽  
E. H. Salkeld ◽  
I. L. Stevenson
Keyword(s):  
Growth Rate ◽  
Bacterial Cells ◽  
Onion Maggot ◽  
Hylemya Antiqua ◽  
Rate Of Development ◽  
Sonic Treatment ◽  
Living Bacteria

On a chemical diet, larvae of H. antiqua developed more rapidly in the presence of various living bacteria, of certain nonviable bacterial cells, or of the dialyzate of these cells. The stimulation by the nonviable cells was not affected when the cells were disrupted by sonic treatment. Additions of ashed cells to the chemical diet had no stimulatory effect. Some stimulation in rate of development was noted on addition of casein to the diets but to a lesser degree than that caused by equivalent concentrations of nonviable cells. The growth rate and the rate of metamorphosis stayed in phase with one another when development was accelerated.

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