scholarly journals Epigenetic Regulation and Environmental Sex Determination in Cichlid Fishes

2021 ◽  
Vol 15 (1-3) ◽  
pp. 93-107
Author(s):  
Suzy C.P. Renn ◽  
Peter L. Hurd
Keyword(s):  
Life History ◽  
Sex Determination ◽  
Female Offspring ◽  
Epigenetic Mechanism ◽  
Life History Strategies ◽  
Comparative Approach ◽  
Environmental Sex Determination ◽  
Reproductive Tactics ◽  
Male And Female ◽  
Underlying Mechanisms

Studying environmental sex determination (ESD) in cichlids provides a phylogenetic and comparative approach to understand the evolution of the underlying mechanisms, their impact on the evolution of the overlying systems, and the neuroethology of life history strategies. Natural selection normally favors parents who invest equally in the development of male and female offspring, but evolution may favor deviations from this 50:50 ratio when environmental conditions produce an advantage for doing so. Many species of cichlids demonstrate ESD in response to water chemistry (temperature, pH, and oxygen concentration). The relative strengths of and the exact interactions between these factors vary between congeners, demonstrating genetic variation in sensitivity. The presence of sizable proportions of the less common sex towards the environmental extremes in most species strongly suggests the presence of some genetic sex-determining loci acting in parallel with the ESD factors. Sex determination and differentiation in these species does not seem to result in the organization of a final and irreversible sexual fate, so much as a life-long ongoing battle between competing male- and female-determining genetic and hormonal networks governed by epigenetic factors. We discuss what is and is not known about the epigenetic mechanism behind the differentiation of both gonads and sex differences in the brain. Beyond the well-studied tilapia species, the 2 best-studied dwarf cichlid systems showing ESD are the South American genus <i>Apistogramma</i> and the West African genus <i>Pelvicachromis</i>. Both species demonstrate male morphs with alternative reproductive tactics. We discuss the further neuroethology opportunities such systems provide to the study of epigenetics of alternative life history strategies and other behavioral variation.

Conservation biology of two endemic Beyeria species (Euphorbiaceae) from southern Western Australia

2015 ◽  
Vol 63 (6) ◽  
pp. 484 ◽  
Author(s):  
Brian J. Vincent ◽  
Sarah Barrett ◽  
Anne Cochrane ◽  
Julie A. Plummer ◽  
Michael Renton
Keyword(s):  
Life History ◽  
Western Australia ◽  
Seed Viability ◽  
Ex Situ ◽  
Life History Strategies ◽  
Reproductive Phenology ◽  
Habitat Specificity ◽  
Male And Female ◽  
Female Flowering ◽  
Threatening Processes

Beyeria cockertonii Halford & R.J.F.Hend. and Beyeria villosa Halford & R.J.F.Hend. (Euphorbiaceae) are two short-range endemic monoecious congeners from southern Western Australia. We sought to determine whether life-history characteristics were responsible for their limited distribution and to identify aspects of their ecology that might render them vulnerable to current threatening processes. We investigated reproductive phenology in relation to climate, pollinator activity and synchronicity of male and female flowering. In addition seed dispersal, regeneration, demography and seed viability were examined and ex situ germination experiments conducted to determine seed-dormancy mechanisms. Flowering in the conservation-listed B. cockertonii was significantly correlated with temperature, whereas fruit set was correlated with pollinator abundance and movement; male and female flowering showed limited synchrony. The presence of soil-stored seeds lacking a caruncle at sites absent of adult plants of either species suggests that seed may be ant-dispersed (myrmecochory). Fresh seeds of B. cockertonii were significantly more viable than those of its more common congener, B. villosa (72 vs 0.5%, P < 0.001). Fresh B. cockertonii seeds would not germinate with an intact caruncle; caruncle removal elicited germination of 64% and 60% (10°C and 15°C, respectively). Aqueous smoke further stimulated germination to 72% and 83% germination (10°C and 15°C, respectively), providing a link between fire and germination. Beyeria villosa was affected by high levels of pre-dispersal predation (up to 70%) and seed abortion (88%) and appeared to have lower reproductive fitness than B. cockertonii. Life-history strategies did not explain the greater abundance and wider distribution of B. villosa than those of the conservation-listed B cockertonii, nor was the greater rarity of B. cockertonii fully explained by habitat specificity, with both species being restricted to ultra-mafic volcanic rock associated with Achaean greenstone. However, an apparent dependence of B. cockertonii on a specific insect pollinator from the family Miridae may render this species vulnerable to threatening processes.

scholarly journals The deteriorating soma and the indispensable germline: gamete senescence and offspring fitness

2019 ◽  
Vol 286 (1917) ◽  
pp. 20192187 ◽  
Author(s):  
Pat Monaghan ◽  
Neil B. Metcalfe
Keyword(s):  
Life History ◽  
Mitochondrial Function ◽  
Evolutionary Biology ◽  
Life History Evolution ◽  
Comparative Approach ◽  
Offspring Fitness ◽  
Age Related ◽  
Underlying Mechanisms ◽  
Weismann Barrier

The idea that there is an impenetrable barrier that separates the germline and soma has shaped much thinking in evolutionary biology and in many other disciplines. However, recent research has revealed that the so-called ‘Weismann Barrier’ is leaky, and that information is transferred from soma to germline. Moreover, the germline itself is now known to age, and to be influenced by an age-related deterioration of the soma that houses and protects it. This could reduce the likelihood of successful reproduction by old individuals, but also lead to long-term deleterious consequences for any offspring that they do produce (including a shortened lifespan). Here, we review the evidence from a diverse and multidisciplinary literature for senescence in the germline and its consequences; we also examine the underlying mechanisms responsible, emphasizing changes in mutation rate, telomere loss, and impaired mitochondrial function in gametes. We consider the effect on life-history evolution, particularly reproductive scheduling and mate choice. Throughout, we draw attention to unresolved issues, new questions to consider, and areas where more research is needed. We also highlight the need for a more comparative approach that would reveal the diversity of processes that organisms have evolved to slow or halt age-related germline deterioration.

scholarly journals Time for a change: patterns of sex expression, health and mortality in a sex-changing tree

2019 ◽  
Vol 124 (3) ◽  
pp. 367-377 ◽  
Author(s):  
Jennifer Blake-Mahmud ◽  
Lena Struwe
Keyword(s):  
Life History ◽  
Sex Determination ◽  
Classification Tree ◽  
Sex Ratios ◽  
Sex Expression ◽  
Life History Trait ◽  
Differential Mortality ◽  
Male And Female ◽  
Female Sex ◽  
Theoretical Predictions

Abstract Background and Aims The ability of individuals to change sex during their lifetime is known as environmental sex determination (ESD). This represents a unique life history trait, allowing plants to allocate resources differentially to male and female functions across lifetimes, potentially maximizing fitness in response to changing environmental or internal cues. In this study, Acer pensylvanicum, a species with an unconfirmed sex determination system, was investigated to see what patterns in sex expression existed across multiple years, if there were sex-based differences in growth and mortality, and whether this species conformed to theoretical predictions that females are larger and in better condition. Methods Patterns of sex expression were documented over 4 years in a phenotypically subdioecious A. pensylvanicum population located in New Jersey, USA, and data on size, mortality, health and growth were collected. A machine-learning algorithm known as a boosted classification tree was used to develop a model to predict the sex of a tree based on its condition, size and previous sex. Results In this study, 54 % of the trees switched sex expression during a 4-year period, with 26 % of those trees switching sex at least twice. Consistently monoecious trees could change relative sex expression by as much as 95 %. Both size and condition were influential in predicting sex, with condition exerting three times more relative influence than size on expressed sex. Contrary to theoretical predictions, the model showed that full female sex expression did not increase with size. Healthy trees were more likely to be male; predicted female sex expression increased with deteriorating health. Growth rate negatively correlated with multiple years of female sex expression. Populations maintained similar male-skewed sex ratios across years and locations and may result from differential mortality: 75 % of dead trees flowered female immediately before death. Conclusions This study shows conclusively that A. pensylvanicum exhibits ESD and that femaleness correlates with decreased health, in contrast to prevailing theory. The mortality findings advance our understanding of puzzling non-equilibrium sex ratios and life history trade-offs resulting from male and female sex expression.

Mixed life-history strategies in a local population of the ectoparasitic flyCarnus hemapterus

Parasitology ◽  
2012 ◽  
Vol 139 (8) ◽  
pp. 1045-1053 ◽  
Author(s):  
M. AMAT-VALERO ◽  
R. VÁCLAV ◽  
T. MARTÍNEZ ◽  
F. VALERA
Keyword(s):  
Life History ◽  
Local Population ◽  
Population Level ◽  
Life History Strategies ◽  
Coracias Garrulus ◽  
Sturnus Unicolor ◽  
Evolution Of Life ◽  
European Roller ◽  
Underlying Mechanisms ◽  
Host Parasite

SUMMARYA major issue for the proper understanding of the evolution of life-cycle histories is the regulation of voltinism and its variation. Diapause characteristics are known to regulate voltinism, but the underlying mechanisms are poorly understood. This paper studies diapause duration and voltinism variation in a haematophagous diptera parasitizing 2 sympatric hosts with very different breeding phenologies. We hypothesize that bivoltinism will be more frequent in carnid flies parasitizing an early breeding, multi-brooded species than in flies parasitizing a late breeder, single-brooded species. We obtained evidence of the co-occurrence of uni- and bivoltinism in both clutches of the multi-brooded Spotless starling (Sturnus unicolor) as well as in clutches of the single-brooded European roller (Coracias garrulus). Unexpectedly, the proportion of bivoltine flies was similar in both host species. A remarkable degree of host-parasite synchronization at the population level was found for bivoltine flies. Our findings reveal the facultative nature of diapause inCarnus. We discuss the influence of abiotic conditions and host availability on polymorphism in life-history cycles and the consequences both for the parasite and the host.

The Fate of Paternal Mitochondrial DNA in Developing Female Mussels, Mytilus edulis: Implications for the Mechanism of Doubly Uniparental Inheritance of Mitochondrial DNA

Genetics ◽  
1998 ◽  
Vol 148 (1) ◽  
pp. 341-347 ◽  
Author(s):  
Brent Sutherland ◽  
Donald Stewart ◽  
Ellen R Kenchington ◽  
Eleftherios Zouros
Keyword(s):  
Mitochondrial Dna ◽  
Mitochondrial Genome ◽  
Sex Determination ◽  
Female Offspring ◽  
Male Offspring ◽  
Uniparental Inheritance ◽  
Doubly Uniparental Inheritance ◽  
Marine Mussel ◽  
Male And Female ◽  
The Relationship

Abstract Species of the marine mussel family Mytilidae have two types of mitochondrial DNA: one that is transmitted from the mother to both female and male offspring (the F type) and one that is transmitted from the father to sons only (the M type). By using pair matings that produce only female offspring or a mixture of female and male offspring and a pair of oligonucleotide primers that amplify part of the COIII gene of the M but not the F mitochondrial genome, we demonstrate that both male and female embryos receive M mtDNA through the sperm and that within 24 hr after fertilization the M mtDNA is eliminated or is drastically reduced in female embryos but maintained in male embryos. These observations are important for understanding the relationship between mtDNA transmission and sex determination in species with doubly uniparental inheritance of mitochondrial DNA.

scholarly journals Seasonal reproductive tactics: annual timing and the capital-to-income breeder continuum

2017 ◽  
Vol 372 (1734) ◽  
pp. 20160250 ◽  
Author(s):  
Cory T. Williams ◽  
Marcel Klaassen ◽  
Brian M. Barnes ◽  
C. Loren Buck ◽  
Walter Arnold ◽  
...  
Keyword(s):  
Life History ◽  
Resource Use ◽  
Supply And Demand ◽  
Life History Strategies ◽  
Environmental Cues ◽  
Stored Energy ◽  
Reproductive Tactics ◽  
Free Living ◽  
Temporal Synchrony ◽  
Plastic Trait

Tactics of resource use for reproduction are an important feature of life-history strategies. A distinction is made between ‘capital’ breeders, which finance reproduction using stored energy, and ‘income’ breeders, which pay for reproduction using concurrent energy intake. In reality, vertebrates use a continuum of capital-to-income tactics, and, for many species, the allocation of capital towards reproduction is a plastic trait. Here, we review how trophic interactions and the timing of life-history events are influenced by tactics of resource use in birds and mammals. We first examine how plasticity in the allocation of capital towards reproduction is linked to phenological flexibility via interactions between endocrine/neuroendocrine control systems and the sensory circuits that detect changes in endogenous state, and environmental cues. We then describe the ecological drivers of reproductive timing in species that vary in the degree to which they finance reproduction using capital. Capital can be used either as a mechanism to facilitate temporal synchrony between energy supply and demand or as a means of lessening the need for synchrony. Within many species, an individual's ability to cope with environmental change may be more tightly linked to plasticity in resource allocation than to absolute position on the capital-to-income breeder continuum. This article is part of the themed issue ‘Wild clocks: integrating chronobiology and ecology to understand timekeeping in free-living animals’.

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