Environmental Sex Determination in Southern Brook Lamprey, Ichthyomyzon gagei

1993 ◽  
Vol 50 (6) ◽  
pp. 1299-1307 ◽  
Author(s):  
F. William H. Beamish
Keyword(s):  
United States ◽  
Sex Determination ◽  
Sex Ratios ◽  
Southeastern United States ◽  
Larval Density ◽  
Larval Growth ◽  
Age Groups ◽  
Differential Mortality ◽  
Environmental Sex Determination ◽  
Brook Lamprey

Sex ratios were determined for 20 populations of southern brook lamprey larvae, Ichthyomyzon gagei, collected from throughout much of their range in the southeastern United States. Ratios varied between 9 and 49% males. Differential mortality was an unlikely factor, as sex ratios were similar among age groups within each population. Environmental sex determination is suggested. Sex ratio varied with growth (expressed as length of larvae at specific ages), larval density, pH, and annual mean temperature of the natal stream. Generally, under conditions promoting rapid growth, the percentage of males varied directly with density and inversely with temperature. Where growth was slow, the percentage of males declined as larval density increased, the response being less at low than at high pH. Temperature had little effect when larval growth was slow. The percentage of males declined when growth was rapid under otherwise similar environmental conditions.

Nest site choice compensates for climate effects on sex ratios in a lizard with environmental sex determination

2006 ◽  
Vol 20 (4) ◽  
pp. 307-330 ◽  
Author(s):  
J. Sean Doody ◽  
Enzo Guarino ◽  
Arthur Georges ◽  
Ben Corey ◽  
Glen Murray ◽  
...  
Keyword(s):  
Sex Determination ◽  
Nest Site ◽  
Sex Ratios ◽  
Environmental Sex Determination ◽  
Climate Effects ◽  
Nest Site Choice

Larval density and the Charnov–Bull model of adaptive environmental sex determination in a copepod

2005 ◽  
Vol 83 (7) ◽  
pp. 943-954 ◽  
Author(s):  
Maarten J Voordouw ◽  
H Eve Robinson ◽  
Gabe Stebbins ◽  
Arianne Y.K Albert ◽  
Bradley R Anholt
Keyword(s):  
Body Size ◽  
Sex Determination ◽  
Larval Density ◽  
Specific Pattern ◽  
Male Body ◽  
Weak Effect ◽  
Environmental Sex Determination ◽  
Adult Body Size ◽  
Female Body Size ◽  
Adult Body

Charnov and Bull suggested that environmentally induced variation in adult body size coupled with sex-specific differences in fitness can select for the evolution of adaptive environmental sex determination (ESD). In this study we determine whether larval density affects sex determination in the copepod Tigriopus californicus (Baker, 1912), as predicted by Charnov and Bull. Individuals reared at low densities developed faster and were significantly larger than siblings reared at high densities. For these laboratory-reared individuals, sexual selection on male body size was stronger than fecundity selection on female body size, but this sex-specific pattern of selection was reversed in the field. Differences in food availability (for females) and the mode of competition (for males) may account for the conflicting results between laboratory and field. We found a weak effect of larval density on sex determination in a pilot experiment but no effect in a second, more powerful experiment. While larval density did not affect the sex ratio of T. californicus, our sex-specific estimates of selection on adult body size will inform future models of adaptive ESD in this species and other copepods.

scholarly journals Do Covariances Between Maternal Behavior and Embryonic Physiology Drive Sex-Ratio Evolution Under Environmental Sex Determination?

2019 ◽  
Vol 110 (4) ◽  
pp. 411-421 ◽  
Author(s):  
Fredric J Janzen ◽  
David M Delaney ◽  
Timothy S Mitchell ◽  
Daniel A Warner
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Environmental Conditions ◽  
Oviposition Behavior ◽  
Thermal Sensitivity ◽  
Sex Ratios ◽  
Theoretical Work ◽  
Environmental Sex Determination ◽  
Turtle Species ◽  
Primary Sex Ratio

Abstract Fisherian sex-ratio theory predicts sexual species should have a balanced primary sex ratio. However, organisms with environmental sex determination (ESD) are particularly vulnerable to experiencing skewed sex ratios when environmental conditions vary. Theoretical work has modeled sex-ratio dynamics for animals with ESD with regard to 2 traits predicted to be responsive to sex-ratio selection: 1) maternal oviposition behavior and 2) sensitivity of embryonic sex determination to environmental conditions, and much research has since focused on how these traits influence offspring sex ratios. However, relatively few studies have provided estimates of univariate quantitative genetic parameters for these 2 traits, and the existence of phenotypic or genetic covariances among these traits has not been assessed. Here, we leverage studies on 3 species of reptiles (2 turtle species and a lizard) with temperature-dependent sex determination (TSD) to assess phenotypic covariances between measures of maternal oviposition behavior and thermal sensitivity of the sex-determining pathway. These studies quantified maternal behaviors that relate to nest temperature and sex ratio of offspring incubated under controlled conditions. A positive covariance between these traits would enhance the efficiency of sex-ratio selection when primary sex ratio is unbalanced. However, we detected no such covariance between measures of these categories of traits in the 3 study species. These results suggest that maternal oviposition behavior and thermal sensitivity of sex determination in embryos might evolve independently. Such information is critical to understand how animals with TSD will respond to rapidly changing environments that induce sex-ratio selection.

scholarly journals Field study suggests that sex determination in sea lamprey is directly influenced by larval growth rate

2017 ◽  
Vol 284 (1851) ◽  
pp. 20170262 ◽  
Author(s):  
Nicholas S. Johnson ◽  
William D. Swink ◽  
Travis O. Brenden
Keyword(s):  
Growth Rate ◽  
Sex Determination ◽  
Sex Ratios ◽  
Petromyzon Marinus ◽  
Larval Growth ◽  
Sea Lamprey ◽  
Growth Conditions ◽  
Larval Growth Rate ◽  
Sex Determination Mechanisms ◽  
Insight Into

Sex determination mechanisms in fishes lie along a genetic-environmental continuum and thereby offer opportunities to understand how physiology and environment interact to determine sex. Mechanisms and ecological consequences of sex determination in fishes are primarily garnered from teleosts, with little investigation into basal fishes. We tagged and released larval sea lamprey ( Petromyzon marinus ) into unproductive lake and productive stream environments. Sex ratios produced from these environments were quantified by recapturing tagged individuals as adults. Sex ratios from unproductive and productive environments were initially similar. However, sex ratios soon diverged, with unproductive environments becoming increasingly male-skewed and productive environments becoming less male-skewed with time. We hypothesize that slower growth in unproductive environments contributed to the sex ratio differences by directly influencing sex determination. To the best of our knowledge, this is the first study suggesting that growth rate in a fish species directly influences sex determination; other studies have suggested that the environmental variables to which sex determination is sensitive (e.g. density, temperature) act as cues for favourable or unfavourable growth conditions. Understanding mechanisms of sex determination in lampreys may provide unique insight into the underlying principles of sex determination in other vertebrates and provide innovative approaches for their management where valued and invasive.

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.

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