Society for Reproductive Biology Founders' Lecture 2006 Life in the pouch: womb with a view

2006 ◽  
Vol 18 (7) ◽  
pp. 721 ◽  
Author(s):  
Marilyn B. Renfree
Keyword(s):  
Sex Determination ◽  
Umbilical Cord ◽  
Sexual Differentiation ◽  
Comparative Genomic ◽  
Embryonic Diapause ◽  
Seasonal Breeding ◽  
Mode Of Reproduction ◽  
Genomic Biology ◽  
Marsupial Species ◽  
Reproductive Events

Marsupials give birth to an undeveloped altricial young after a relatively short gestation period, but have a long and sophisticated lactation with the young usually developing in a pouch. Their viviparous mode of reproduction trades placentation for lactation, exchanging the umbilical cord for the teat. The special adaptations that marsupials have developed provide us with unique insights into the evolution of all mammalian reproduction. Marsupials hold many mammalian reproductive ‘records’, for example they have the shortest known gestation but the longest embryonic diapause, the smallest neonate but the longest sperm. They have contributed to our knowledge of many mammalian reproductive events including embryonic diapause and development, birth behaviour, sex determination, sexual differentiation, lactation and seasonal breeding. Because marsupials have been genetically isolated from eutherian mammals for over 125 million years, sequencing of the genome of two marsupial species has made comparative genomic biology an exciting and important new area of investigation. This review will show how the study of marsupials has widened our understanding of mammalian reproduction and development, highlighting some mechanisms that are so fundamental that they are shared by all today’s marsupial and eutherian mammals.

scholarly journals The Diversity and Evolution of Sex Chromosomes in Frogs

Genes ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 483
Author(s):  
Wen-Juan Ma ◽  
Paris Veltsos
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Comparative Genomic ◽  
Ancestral State ◽  
Heteromorphic Sex Chromosomes ◽  
Genomic Studies ◽  
Evolutionary Trajectories ◽  
Heterogametic Sex

Frogs are ideal organisms for studying sex chromosome evolution because of their diversity in sex chromosome differentiation and sex-determination systems. We review 222 anuran frogs, spanning ~220 Myr of divergence, with characterized sex chromosomes, and discuss their evolution, phylogenetic distribution and transitions between homomorphic and heteromorphic states, as well as between sex-determination systems. Most (~75%) anurans have homomorphic sex chromosomes, with XY systems being three times more common than ZW systems. Most remaining anurans (~25%) have heteromorphic sex chromosomes, with XY and ZW systems almost equally represented. There are Y-autosome fusions in 11 species, and no W-/Z-/X-autosome fusions are known. The phylogeny represents at least 19 transitions between sex-determination systems and at least 16 cases of independent evolution of heteromorphic sex chromosomes from homomorphy, the likely ancestral state. Five lineages mostly have heteromorphic sex chromosomes, which might have evolved due to demographic and sexual selection attributes of those lineages. Males do not recombine over most of their genome, regardless of which is the heterogametic sex. Nevertheless, telomere-restricted recombination between ZW chromosomes has evolved at least once. More comparative genomic studies are needed to understand the evolutionary trajectories of sex chromosomes among frog lineages, especially in the ZW systems.

scholarly journals ZZ/ZW Sex Determination with Multiple Neo-Sex Chromosomes is Common in Madagascan Chameleons of the Genus Furcifer (Reptilia: Chamaeleonidae)

Genes ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 1020 ◽  
Author(s):  
Rovatsos ◽  
Altmanová ◽  
Augstenová ◽  
Mazzoleni ◽  
Velenský ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Comparative Genomic ◽  
Telomeric Sequences ◽  
Female Heterogamety ◽  
Chromosomal Variability ◽  
Determination System ◽  
Hybridization In Situ ◽  
Sex Determination System

Chameleons are well-known, highly distinctive lizards characterized by unique morphological and physiological traits, but their karyotypes and sex determination system have remained poorly studied. We studied karyotypes in six species of Madagascan chameleons of the genus Furcifer by classical (conventional stain, C-banding) and molecular (comparative genomic hybridization, in situ hybridization with rDNA, microsatellite, and telomeric sequences) cytogenetic approaches. In contrast to most sauropsid lineages, the chameleons of the genus Furcifer show chromosomal variability even among closely related species, with diploid chromosome numbers varying from 2n = 22 to 2n = 28. We identified female heterogamety with cytogenetically distinct Z and W sex chromosomes in all studied species. Notably, multiple neo-sex chromosomes in the form Z1Z1Z2Z2/Z1Z2W were uncovered in four species of the genus (F. bifidus, F. verrucosus, F. willsii, and previously studied F. pardalis). Phylogenetic distribution and morphology of sex chromosomes suggest that multiple sex chromosomes, which are generally very rare among vertebrates with female heterogamety, possibly evolved several times within the genus Furcifer. Although acrodontan lizards (chameleons and dragon lizards) demonstrate otherwise notable variability in sex determination, it seems that female heterogamety with differentiated sex chromosomes remained stable in the chameleons of the genus Furcifer for about 30 million years.

Sex-lethal, A Link between Sex Determination and Sexual Differentiation in Drosophila melanogaster

1985 ◽  
Vol 50 (0) ◽  
pp. 595-604 ◽  
Author(s):  
E.M. Maine ◽  
H.K. Salz ◽  
P. Schedl ◽  
T.W. Cline
Keyword(s):  
Drosophila Melanogaster ◽  
Sex Determination ◽  
Sexual Differentiation ◽  
Sex Lethal

Sexual differentiation of merozoites of Eimeria tenella

Parasitology ◽  
1972 ◽  
Vol 65 (1) ◽  
pp. 131-136 ◽  
Author(s):  
B. Klimes ◽  
D. G. Rootes ◽  
Zabel Tanielian
Keyword(s):  
Cell Culture ◽  
Sex Determination ◽  
Kidney Cell ◽  
Sexual Differentiation ◽  
Eimeria Tenella ◽  
Kidney Cell Culture ◽  
Pas Staining

In chickens kidney-cell culture gametogony of E. tenella usually occurs in a limited number of selected cells in the form of nests of gametocytes. Some cells contain only macrogametocytes, others only microgametocytes and some cells contain both sexes together. Mixed nests of gametocytes are evidence for genetic sex determination. By using PAS staining the origin of macrogametocytes and microgametocytes can be retraced to the merozoites and schizonts of the last generation, which are differentiated by this technique.

Sexual differentiation in the spiny softshell turtle (Apalone spinifera), a species with genetic sex determination

2001 ◽  
Vol 290 (2) ◽  
pp. 190-200 ◽  
Author(s):  
Eli Greenbaum ◽  
John L. Carr
Keyword(s):  
Sex Determination ◽  
Sexual Differentiation ◽  
Apalone Spinifera ◽  
Softshell Turtle

scholarly journals The iso1 gene of Chlamydomonas is involved in sex determination.

1995 ◽  
Vol 6 (1) ◽  
pp. 87-95 ◽  
Author(s):  
A M Campbell ◽  
H J Rayala ◽  
U W Goodenough
Keyword(s):  
Sex Determination ◽  
Chlamydomonas Reinhardtii ◽  
Mating Type ◽  
Dna Sequences ◽  
Sexual Differentiation ◽  
Type Locus ◽  
Mating Structure ◽  
Mating Type Locus

Sexual differentiation in the heterothallic alga Chlamydomonas reinhardtii is controlled by two mating-type loci, mt+ and mt-, which behave as a pair of alleles but contain different DNA sequences. A mutation in the mt minus-linked imp11 gene has been shown previously to convert a minus gamete into a pseudo-plus gamete that expresses all the plus gametic traits except the few encoded by the mt+ locus. Here we describe the iso1 mutation which is unlinked to the mt- locus but is expressed only in minus gametes (sex-limited expression). A population of minus gametes carrying the iso1 mutation behaves as a mixture of minus and pseudo-plus gametes: the gametes isoagglutinate but they do not fuse to form zygotes. Further analysis reveals that individual gametes express either plus or minus traits: a given cell displays one type of agglutinin (flagellar glycoprotein used for sexual adhesion) and one type of mating structure. The iso1 mutation identifies a gene unlinked to the mating-type locus that is involved in sex determination and the repression of plus-specific genes.

scholarly journals REPRODUÇÃO DE PEIXES DE RIACHO: ESTADO DA ARTE, MÉTODOS E PERSPECTIVAS

2021 ◽  
Vol 25 (02) ◽  
pp. 323-343
Author(s):  
Érica Pellegrini Caramaschi ◽  
◽  
Marcelo Fulgêncio Guedes Brito ◽  
Keyword(s):  
Life History Traits ◽  
Neotropical Region ◽  
Stream Fish ◽  
Natural Environments ◽  
Fish Reproduction ◽  
Mode Of Reproduction ◽  
Sexual Dimorphisms ◽  
Reproductive Life ◽  
Basic Studies ◽  
Reproductive Events

Stream fish reproduction is still poorly studied in natural environments, especially in the Neotropical region. In this chapter, we recollect some characteristics of fish reproduction and some questions to guide current research, as: Does sexual dimorphism occur in the species? Which is the mode of reproduction? When and where does the species reproduce? Which environmental factors trigger reproductive events? When does the reproductive life begin? Which is the fecundity? Most of these questions can be answered when we have many specimens available, captured at different periods of the year, measured, weighed and dissected following appropriate protocols. Obtained data represent life history traits that allow to categorize the species in reproductive styles related to parental care and to determine their accordance to models of reproductive strategy associated with the predictability of environmental conditions. We highlight some aspects to be considered in current and future field and lab procedures, such as the recognition of sexual dimorphisms, the importance of naturalistic observation and lab procedures. We draw attention to the advances in studies on reproductive modalities in fish groups well represented in streams, such as inseminating characiforms and viviparous cyprinodontiforms. Finally, we highlight gaps, urgencies, and current perspectives for studies on the reproduction of stream fish, with emphasis on the need for basic studies of species biology, on the importance for building theoretical references and for the conservation of stream habitats in all Brazilian biomes.

scholarly journals A partially sex-reversed giant kelp sheds light into the mechanisms of sexual differentiation in a UV sexual system

2021 ◽  
Author(s):  
Dieter Mueller ◽  
Enora Gachet ◽  
Olivier Godfroy ◽  
Josselin Gueno ◽  
Guillaume Cossard ◽  
...  
Keyword(s):  
Gene Expression ◽  
Sex Determination ◽  
Sexual Differentiation ◽  
Expression Patterns ◽  
Specific Region ◽  
Autosomal Gene ◽  
Giant Kelp ◽  
Developmental Programs ◽  
Male And Female ◽  
Developmental Program

In UV sexual systems, sex is determined during the haploid phase of the life cycle and males have a V chromosome whereas females have a U chromosome. Previous work in the brown algal model Ectocarpus revealed that the V chromosome has a dominant role in male sex determination and suggested that the female developmental program may occur by default, triggered in the absence of the male master sex determination gene(s). Here, we describe the identification of a genetically male giant kelp strain presenting phenotypic features typical of a female, despite lacking the U-specific region. The conversion to the female developmental program is however incomplete, because gametes of this feminised male are unable to produce the sperm-attracting pheromone lamoxirene. We identify the transcriptomic patterns underlying the male and female specific developmental programs, and reveal the faster evolutionary rates of male-biased genes compared to female-biased and unbiased genes. Moreover, we show that the phenotypic feminisation of the variant strain is associated with both feminisation and de-masculinisation of gene expression patterns. Importantly, the feminisation phenotype was associated with the dramatic downregulation of two V-specific genes including a candidate sex-determining gene on the V-specific region. Our results reveal the transcriptional changes associated with sexual differentiation in a UV system with marked sexual dimorphism, and contribute to disentangling the role of sex-linked genes and autosomal gene expression in the initiation of the male and female developmental programs. Overall, the data presented here imply that the U-specific region in the giant kelp is not required to initiate the female developmental program, but is critical to produce fully functional eggs, arguing against the idea that female is the default sex in this species.

Her, a gene required for sexual differentiation in Drosophila, encodes a zinc finger protein with characteristics of ZFY-like proteins and is expressed independently of the sex determination hierarchy

Development ◽  
1998 ◽  
Vol 125 (2) ◽  
pp. 225-235
Author(s):  
H. Li ◽  
B.S. Baker
Keyword(s):  
Sex Determination ◽  
Sexual Differentiation ◽  
Zinc Finger Protein ◽  
Genetic Characterization ◽  
Zinc Fingers ◽  
Molecular Genetic ◽  
Control Female ◽  
Finger Protein ◽  
Molecular Genetic Characterization

The zygotic function of the hermaphrodite (her) gene of Drosophila plays an important role in sexual differentiation. Our molecular genetic characterization of her suggests that her is expressed sex non-specifically and independently of other known sex determination genes and that it acts together with the last genes in the sex determination hierarchy, doublesex and intersex, to control female sexual differentiation. Consistent with such a terminal function in sexual differentiation, her encodes a protein with C2H2-type zinc fingers. The her zinc fingers are atypical and similar to the even-numbered zinc fingers of ZFY and ZFX proteins in humans and other vertebrates.

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