scholarly journals Decoupled Maternal and Zygotic Genetic Effects Shape the Evolution of Development

2017 ◽  
Author(s):  
Christina Zakas ◽  
Jennifer M. Deutscher ◽  
Alex D. Kay ◽  
Matthew V. Rockman
Keyword(s):  
Larval Feeding ◽  
Heritable Variation ◽  
Larval Size ◽  
Adult Form ◽  
Planktonic Food ◽  
Large Numbers ◽  
Indirect Development ◽  
Larval Evolution ◽  
Size And Morphology ◽  
Positive Frequency Dependence

AbstractMany animals develop indirectly via a larval stage that is morphologically and ecologically distinct from its adult form. Hundreds of lineages across animal phylogeny have secondarily lost larval forms, instead producing offspring that directly develop into adult form without a distinct larval ecological niche1–7. Indirect development in the sea is typically planktotrophic: females produce large numbers of small offspring that require exogenous planktonic food to develop before metamorphosing into benthic juveniles. Direct development is typically lecithotrophic: females produce a smaller number of larger eggs, each developing into a juvenile without the need for larval feeding, provisioned by yolk. Evolutionary theory suggests that these alternative developmental strategies represent stable alternative fitness peaks, while intermediate states are disfavored4,8–11. Transitions from planktotrophy to lecithotrophy thus require crossing a fitness valley and represent radical and coordinated transformations of life-history, fecundity, ecology, dispersal, and development7,12–16. Here we dissect this transition in Streblospio benedicti, the sole genetically tractable species that harbors both states as heritable variation17–19. We identify large-effect loci that act maternally to influence larval size and independent, unlinked large-effect loci that act zygotically to affect discrete aspects of larval morphology. Because lecithotrophs and planktotrophs differ in both size and morphology, the genetic basis of larval form exhibits strong maternal-by-zygotic epistasis for fitness20. The fitness of zygotic alleles depends on their maternal background, creating a positive frequency-dependence that may homogenize local populations. Developmental and population genetics interact to shape larval evolution.

scholarly journals Decoupled maternal and zygotic genetic effects shape the evolution of development

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Christina Zakas ◽  
Jennifer M Deutscher ◽  
Alex D Kay ◽  
Matthew V Rockman
Keyword(s):  
Population Genetic ◽  
Genetic Factors ◽  
Forward Genetics ◽  
Larval Size ◽  
Evolutionary Transitions ◽  
Major Transition ◽  
Larval Evolution ◽  
Streblospio Benedicti ◽  
Positive Frequency Dependence ◽  
Positive Frequency

Evolutionary transitions from indirect to direct development involve changes in both maternal and zygotic genetic factors, with distinctive population-genetic implications, but empirical data on the genetics of such transitions are lacking. The polychaete Streblospio benedicti provides an opportunity to dissect a major transition in developmental mode using forward genetics. Females in this species produce either small eggs that develop into planktonic larvae or large eggs that develop into benthic juveniles. We identify large-effect loci that act maternally to influence larval size and independent, unlinked large-effect loci that act zygotically to affect discrete aspects of larval morphology. The likely fitness of zygotic alleles depends on their maternal background, creating a positive frequency-dependence that may homogenize local populations. Developmental and population genetics interact to shape larval evolution.

scholarly journals GENETIC VARIATION IN WEED SEED DORMANCY AND THEIR MANAGEMENT IN CROPS: A REVIEW

2021 ◽  
Vol 21 (no 1) ◽  
Author(s):  
Bhagirath Singh Chauhan ◽  
Michael Thompson ◽  
Romesh Kumar Salgotra
Keyword(s):  
Genetic Variation ◽  
Seed Dormancy ◽  
Environmental Heterogeneity ◽  
Clonal Propagation ◽  
Large Population ◽  
Reproductive Traits ◽  
Weed Species ◽  
Heritable Variation ◽  
Large Numbers ◽  
High Level

Evolution in the seed dormancy depends on the presence of heritable variation in weed populations. This genetic variation in weeds arises because of abundant, grow rapidly, and produce large numbers of off springs. Compared with other plant species, populations of weed species frequently show limited genetic variation in seed dormancy due to colonization, extensive clonal propagation, inbreeding, and the relative environmental homogeneity. Nevertheless, populations of weed species contain substantial store of genetic variation and genetic differentiation for seed dormancy and other reproductive traits because of pervasive feature of widely distributed nature of weed species. As a result, high level of genetic diversity among the weeds is fostered by hybridization, habitat longevity, environmental heterogeneity, outcrossing and large population size. The objective of this review is to update the existing literature concerned with genetic variation in seed dormancy and reproductive traits in weeds.

scholarly journals Baby makes three: maternal, paternal, and zygotic genetic effects shape larval phenotypic evolution

2020 ◽  
Author(s):  
Christina Zakas ◽  
Matthew V Rockman
Keyword(s):  
Life History ◽  
Early Life ◽  
Genetic Architecture ◽  
Life History Evolution ◽  
Evolutionary Potential ◽  
Larval Size ◽  
Offspring Genotype ◽  
Size And Morphology ◽  
Genomic Locations ◽  
Larval Traits

The evolutionary potential of a population is shaped by the genetic architecture of its life-history traits. Early-life phenotypes are influenced by both maternal and offspring genotype, and efforts to understand life-history evolution therefore require consideration of the interactions between these separate but correlated genomes. We used a four-generation experimental pedigree to estimate the genetic architecture of early-life phenotypes in a species with dramatic variation in larval size and morphology. In the polychaete annelid Streblospio benedicti, females make either many small eggs that develop into complex larvae that feed in the plankton or few large eggs that develop into benthic juveniles without having to feed as larvae. By isolating the contributions of maternal, paternal, and zygotic genotype to larval traits, we determined that larval anatomical structures are governed by the offspring genotype at a small number of large-effect loci. Larval size is not shaped by the larva's own genotype but instead depends on loci that act in the mother, and at two genomic locations, by loci that act in the father. The overall phenotype of each larva thus depends on three separate genomes, and a population's response to selection on larval traits will reflect the interactions among them.

Some Biological Attributes of Sawflies in the Neodiprion fulviceps Complex in a Brushfield Pine Plantation (Hymenoptera: Diprionidae)

1966 ◽  
Vol 98 (10) ◽  
pp. 1055-1083 ◽  
Author(s):  
Donald L. Dahlsten
Keyword(s):  
Adult Emergence ◽  
Distinct Species ◽  
Mortality Factor ◽  
Differential Mortality ◽  
Larval Feeding ◽  
Larval Size ◽  
Host Trees ◽  
Males And Females ◽  
Morphological Differences ◽  
Biological Differences

AbstractAlthough adults from each of four study areas in California showed no morphological differences and were identified as belonging to the Neodiprion fulviceps complex, a number of biological differences in different stages of development indicate that there are three distinct populations of one species or subspecies of a species in the, N. fulviceps complex in California.The life stages are typical of Neodiprion species. Overwintering as eggs, eclosion commences in the spring. The larvae drop to the ground after four to six feeding instars, spinning their cocoons in the duff beneath the host trees. Pre pupal larvae spend the summer in the cocoon; pupation occurs in the fall and adult emergence follows two to three weeks after.The foliage chosen for oviposition is mainly the current year's growth. Oviposition occurs largely in the upper crown of trees less than 10 feet in height, while in trees larger than 10 feet the lower crown is preferred. The outer two-thirds of the foliage of an individual tip and the lower gravitation edges of needles are favored for oviposition.Some of the differences supporting the belief that there are distinct species or subspecies include number of eggs per female, number of needles in each fascicle used for oviposition, number of eggs inserted in each needle, spacing of egg pockets, egg color, number of feeding instars, date of larval eclosion, larval size, and larval feeding capacity.Males and females emerged in synchrony in the laboratory and the field. Males predominated in cocoon collections but females predominated in rearings of larvae. This discrepancy in sex ratio may be due to a differential mortality factor. (In this study no prepupae were found to go into an extended diapause.)One adult morphological character was found that may be of significance in supporting the contention that distinct populations or subspecies occur. Females in one study area generally had more antennal segments than females in other areas. This character along with the biological differences may prove adequate to describe these populations as subspecies or even species in the future bur it was felt that additional names, at this time, would only add to the confusion in the genus. Such descriptions should wait until the entire N. fulviceps complex can be considered.

scholarly journals B Chromosome System in the Korean Field Mouse Apodemus peninsulae Thomas 1907 (Rodentia, Muridae)

Genes ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 472 ◽  
Author(s):  
Yuri Borisov ◽  
Igor Zhigarev
Keyword(s):  
Russian Far East ◽  
Far East ◽  
B Chromosome ◽  
Field Mouse ◽  
Origin And Evolution ◽  
Apodemus Peninsulae ◽  
Large Numbers ◽  
Size And Morphology ◽  
Korean Field Mouse ◽  
The Russian Far East

In this paper, we analyzed B chromosome variation in Korean field mouse Apodemus peninsulae Thomas 1907 (Rodentia, Muridae) based on a 40-year study of karyotypes collected from geographically distant populations in East Siberia, North Mongolia, China, the Russian Far East, and Japan (Hokkaido). We developed the database of individual variants of B chromosome systems in A. peninsulae. In Siberian populations all animals had Bs. The karyotypes of the studied animals contain from 1 to 30 Вs differing in size and morphology. Analysis of B chromosome systems in 598 individuals from different localities of the range shows the presence of 286 variants of Вs combinations in these animals. Unique sets of B morphotypes make up most of these variants (64.7 ± 1.3%), probably suggesting that individual Bs systems normally result from stochastic processes in the populations. The proportion of animals with a large number of Bs gradually decreases, probably due to increased complexities in the inheritance of large numbers of Bs. A. peninsulae is thus proposed as a good model for studying the origin and evolution of extra elements in the karyotype.

Cytoplasmic Granules in Lymphocytes from Rats Dosed with SK&F 14336-D

1971 ◽  
Vol 29 ◽  
pp. 556-557
Author(s):  
T. G. Merrill ◽  
B. J. Payne ◽  
A. J. Tousimis
Keyword(s):  
Lipid Storage ◽  
Pokeweed Mitogen ◽  
Electron Microscopic ◽  
Cytoplasmic Granules ◽  
Storage Diseases ◽  
Tay Sachs Disease ◽  
Large Numbers ◽  
Microscopic Studies ◽  
Neurovisceral Lipidosis

Rats given SK&F 14336-D (9-[3-Dimethylamino propyl]-2-chloroacridane), a tranquilizing drug, developed an increased number of vacuolated lymphocytes as observed by light microscopy. Vacuoles in peripheral blood of rats and humans apparently are rare and are not usually reported in differential counts. Transforming agents such as phytohemagglutinin and pokeweed mitogen induce similar vacuoles in in vitro cultures of lymphocytes. These vacuoles have also been reported in some of the lipid-storage diseases of humans such as amaurotic familial idiocy, familial neurovisceral lipidosis, lipomucopolysaccharidosis and sphingomyelinosis. Electron microscopic studies of Tay-Sachs' disease and of chloroquine treated swine have demonstrated large numbers of “membranous cytoplasmic granules” in the cytoplasm of neurons, in addition to lymphocytes. The present study was undertaken with the purpose of characterizing the membranous inclusions and developing an experimental animal model which may be used for the study of lipid storage diseases.

Prolonged Fixation Studies For Spaceflight

1973 ◽  
Vol 31 ◽  
pp. 332-333
Author(s):  
Robert Corbett ◽  
Delbert E. Philpott ◽  
Sam Black
Keyword(s):  
High Pressure ◽  
Living Systems ◽  
Prolonged Storage ◽  
Time Intervals ◽  
Early Signs ◽  
Large Numbers

Observation of subtle or early signs of change in spaceflight induced alterations on living systems require precise methods of sampling. In-flight analysis would be preferable but constraints of time, equipment, personnel and cost dictate the necessity for prolonged storage before retrieval. Because of this, various tissues have been stored in fixatives and combinations of fixatives and observed at various time intervals. High pressure and the effect of buffer alone have also been tried.Of the various tissues embedded, muscle, cartilage and liver, liver has been the most extensively studied because it contains large numbers of organelles common to all tissues (Fig. 1).

Analysis of the Anterior Secretory Cells of Onchidohs Muricata (Nudibranchia)

1981 ◽  
Vol 39 ◽  
pp. 614-615
Author(s):  
Roy Skidmore
Keyword(s):  
Endoplasmic Reticulum ◽  
Secretory Granules ◽  
Golgi Body ◽  
The Body ◽  
Secretory Cells ◽  
Secretory Vesicles ◽  
High Magnification ◽  
Large Numbers ◽  
Membrane Bound ◽  
Sole Of The Foot

The long-necked secretory cells in Onchidoris muricata are distributed in the anterior sole of the foot. These cells are interspersed among ciliated columnar and conical cells as well as short-necked secretory gland cells. The long-necked cells contribute a significant amount of mucoid materials to the slime on which the nudibranch travels. The body of these cells is found in the subepidermal tissues. A long process extends across the basal lamina and in between cells of the epidermis to the surface of the foot. The secretory granules travel along the process and their contents are expelled by exocytosis at the foot surface.The contents of the cell body include the nucleus, some endoplasmic reticulum, and an extensive Golgi body with large numbers of secretory vesicles (Fig. 1). The secretory vesicles are membrane bound and contain a fibrillar matrix. At high magnification the similarity of the contents in the Golgi saccules and the secretory vesicles becomes apparent (Fig. 2).

Selective Sampling and Orientation of Non-Homogeneous Tissues

1968 ◽  
Vol 26 ◽  
pp. 98-99
Author(s):  
C. C. Clawson ◽  
L. W. Anderson ◽  
R. A. Good
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Random Sampling ◽  
New Method ◽  
Microscope Examination ◽  
Small Areas ◽  
Selective Sampling ◽  
Large Numbers ◽  
Specific Orientation

Investigations which require electron microscope examination of a few specific areas of non-homogeneous tissues make random sampling of small blocks an inefficient and unrewarding procedure. Therefore, several investigators have devised methods which allow obtaining sample blocks for electron microscopy from region of tissue previously identified by light microscopy of present here techniques which make possible: 1) sampling tissue for electron microscopy from selected areas previously identified by light microscopy of relatively large pieces of tissue; 2) dehydration and embedding large numbers of individually identified blocks while keeping each one separate; 3) a new method of maintaining specific orientation of blocks during embedding; 4) special light microscopic staining or fluorescent procedures and electron microscopy on immediately adjacent small areas of tissue.

Microanalysis of precipitates in a ferritic steel

1978 ◽  
Vol 36 (1) ◽  
pp. 618-619
Author(s):  
J.M. Titchmarsh
Keyword(s):  
Ferritic Steel ◽  
Particle Identification ◽  
Energy Dispersive ◽  
Objective Lens ◽  
Ferritic Steels ◽  
Replica Technique ◽  
X Ray ◽  
Large Numbers ◽  
Scanning Transmission ◽  
Made In

The advances in recent years in the microanalytical capabilities of conventional TEM's fitted with probe forming lenses allow much more detailed investigations to be made of the microstructures of complex alloys, such as ferritic steels, than have been possible previously. In particular, the identification of individual precipitate particles with dimensions of a few tens of nanometers in alloys containing high densities of several chemically and crystallographically different precipitate types is feasible. The aim of the investigation described in this paper was to establish a method which allowed individual particle identification to be made in a few seconds so that large numbers of particles could be examined in a few hours.A Philips EM400 microscope, fitted with the scanning transmission (STEM) objective lens pole-pieces and an EDAX energy dispersive X-ray analyser, was used at 120 kV with a thermal W hairpin filament. The precipitates examined were extracted using a standard C replica technique from specimens of a 2¼Cr-lMo ferritic steel in a quenched and tempered condition.

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