Sexual Dimorphism in the Bathypelagic Gulper Eel Eurypharynx pelecanoides (Lyomeri: Eurypharyngidae), with Comments on Reproductive Strategy

Copeia ◽  
1983 ◽  
Vol 1983 (2) ◽  
pp. 560 ◽  
Author(s):  
John V. Gartner
Keyword(s):  
Sexual Dimorphism ◽  
Reproductive Strategy

scholarly journals Reproductive strategy, sexual development and attraction to facial characteristics

2006 ◽  
Vol 361 (1476) ◽  
pp. 2143-2154 ◽  
Author(s):  
R. Elisabeth Cornwell ◽  
Miriam J Law Smith ◽  
Lynda G Boothroyd ◽  
Fhionna R Moore ◽  
Hasker P Davis ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Sexual Maturation ◽  
Sexual Development ◽  
Reproductive Strategy ◽  
Early Life ◽  
Early Age ◽  
Successful Implementation ◽  
Sexually Dimorphic ◽  
First Sex ◽  
Opposite Sex

Sexual reproduction strategies vary both between and within species in the level of investment in offspring. Life-history theories suggest that the rate of sexual maturation is critically linked to reproductive strategy, with high investment being associated with few offspring and delayed maturation. For humans, age of puberty and age of first sex are two developmental milestones that have been associated with reproductive strategies. Stress during early development can retard or accelerate sexual maturation and reproduction. Early age of menarche is associated with absence of younger siblings, absence of a father figure during early life and increased weight. Father absence during early life is also associated with early marriage, pregnancy and divorce. Choice of partner characteristics is critical to successful implementation of sexual strategies. It has been suggested that sexually dimorphic traits (including those evident in the face) signal high-quality immune function and reproductive status. Masculinity in males has also been associated with low investment in mate and offspring. Thus, women's reproductive strategy should be matched to the probability of male investment, hence to male masculinity. Our review leads us to predict associations between the rate of sexual maturation and adult preferences for facial characteristics (enhanced sexual dimorphism and attractiveness). We find for men, engaging in sex at an early age is related to an increased preference for feminized female faces. Similarly, for women, the earlier the age of first sex the greater the preference for masculinity in opposite-sex faces. When we controlled sexual dimorphism in male faces, the speed of sexual development in women was not associated with differences in preference for male facial attractiveness. These developmental influences on partner choice were not mediated by self-rated attractiveness or parental relationships. We conclude that individuals assort in preferences based on the rapidity of their sexual development. Fast developing individuals prefer opposite-sex partners with an increased level of sexually dimorphic facial characteristics.

Sexual dimorphism in sister species ofLeucorajaskate and its relationship to reproductive strategy and life history

2016 ◽  
Vol 18 (2) ◽  
pp. 105-115 ◽  
Author(s):  
Christopher M. Martinez ◽  
F. James Rohlf ◽  
Michael G. Frisk
Keyword(s):  
Life History ◽  
Sexual Dimorphism ◽  
Reproductive Strategy ◽  
Sister Species

Ontogeny and heterochrony in the Middle Carboniferous ammonoidArkanites relictus(Quinn, McCaleb, and Webb) from northern Arkansas

2002 ◽  
Vol 76 (5) ◽  
pp. 810-821 ◽  
Author(s):  
Daniel A. Stephen ◽  
Walter L. Manger ◽  
Cathy Baker
Keyword(s):  
Sexual Dimorphism ◽  
Late Stage ◽  
Reproductive Strategy ◽  
Sexual Maturity ◽  
Mass Mortality ◽  
Ontogenetic Stage ◽  
Age At Death ◽  
Interesting Possibility ◽  
Middle Carboniferous

The reticuloceratid ammonoidArkanites relictus(Quinn, McCaleb, and Webb, 1962) is represented by hundreds to thousands of individuals from horizons isolated both stratigraphically and geographically in northern Arkansas. These assemblages appear to represent mass mortality events resulting from a semelparous reproductive strategy.Arkanites relictusoccurs as a dimorphic pair (depressed, widely umbilicate, cadiconic conchs and compressed, narrowly umbilicate, pachyconic conchs) thought to reflect sexual dimorphism. Late stage ontogenetic modifications, such as septal crowding and change in aperture profile, are widely cited evidence of sexual maturity in ammonoids. Septal crowding begins at a predictable ontogenetic stage in the compressed forms ofA. relictus,but specimens with cadiconic conchs do not have crowded septa even at the largest diameters available.Depending on the trait examined and the proxy for age of individuals, the dimorphism inArkanites relictus(using the depressed form as the reference morph) is the result of acceleration, neoteny, or hypermorphosis plus neoteny. If size (diameter) is considered a proxy for age, the dimorphs were the same age at death, and the septa in the compressed variants developed via acceleration relative to the depressed variants. Regarding conch shape (width vs. diameter), the compressed morphs developed via neoteny relative to the depressed morphs. If septal count is considered a proxy for age, the dimorphs were not the same age at death, and the compressed forms were produced by a combination of hypermorphosis plus neoteny, i.e., they grew longer yet slower than the depressed forms. InA. relictus,the heterochronic processes of hypermorphosis and neoteny may have been operating simultaneously, which is an interesting possibility because it is an example of a combination of both peramorphic and paedomorphic processes.

scholarly journals Gonadossomatic relation and reproductive strategy of Brycon opalinus (Cuvier, 1819) in the Serra do Mar State Park - Núcleo Santa Virgínia, Atlantic Forest, Brazil

2007 ◽  
Vol 67 (4) ◽  
pp. 727-733 ◽  
Author(s):  
LM Gomiero ◽  
FMS Braga
Keyword(s):  
Sexual Dimorphism ◽  
Sex Ratio ◽  
Sperm Competition ◽  
Atlantic Forest ◽  
Reproductive Strategy ◽  
Reproductive Season ◽  
Serra Do Mar ◽  
Males And Females ◽  
Three Rivers

The objective of this study was to analyze the gonadossomatic relation of males and females of Brycon opalinus (the Pirapitinga do Sul) in the Serra do Mar State Park-Núcleo Santa Virgínia. The study area included three rivers: Paraibuna, Ipiranga, and Grande. From the gonadossomatic relation, it was possible to determine the reproductive season and strategy of this species. The gonadossomatic relation was high throughout the year for both males and females. Sperm competition and dilution of the ejaculate in the spawning locations favored substantial development of the testicles. The sex ratio of Brycon opalinus was always in favor of females. The existence of sexual dimorphism in this species was confirmed from the larger size of the females.

scholarly journals Female reproductive strategy predicts preferences for sexual dimorphism in male faces

2009 ◽  
Vol 7 (3) ◽  
pp. 211-224 ◽  
Author(s):  
Fhionna Moore ◽  
Miriam Law Smith ◽  
Clare Cassidy ◽  
David Perrett
Keyword(s):  
Sexual Dimorphism ◽  
Reproductive Strategy

The Evolution of Behaviors Regulating Density and Age-Specific Sex Ratios in a Primate Population

Behaviour ◽  
1979 ◽  
Vol 69 (3-4) ◽  
pp. 265-301 ◽  
Author(s):  
Wolfgang P.J. Dittus
Keyword(s):  
Sex Differences ◽  
Sexual Dimorphism ◽  
Population Size ◽  
Reproductive Strategy ◽  
Inclusive Fitness ◽  
Sex Ratios ◽  
Male And Female ◽  
Kin Investment ◽  
Limiting Resources ◽  
Age And Sex

AbstractAdult females within a macaque troop are related to one another and to all infants and juveniles. Thus, the evolution of social behaviors that impose mortality differentially by age and sex is interpreted in light of classical and kin selection. Parental and kin investment are defined and measured by the degree to which dominant relatives tolerate (closely associate with but do not exploit) subordinate relatives during foraging; and, by the degree to which subordinate relatives are exploited for resources by their dominant relatives. Sex differences in mortality among juveniles and infants are the outcome of differences in parental and kin investments which are geared to maximize fitness according to sex differences in reproductive strategy. Relative to females, males grow faster during youth, and acquire larger adult size and a greater ability to compete for mates. Males also suffer higher mortality as adults and particularly during adolescence when males emigrate from the maternal troop and when the attributes necessary for male reproductive success develop most. Such differences probably evolved through intrasexual selection. Investment involves offsetting mortality occurring in males after they emigrate from the maternal troop by investing in them heavily prior to their emigration so as to maximize their chances of survival and development to reproductive age and state. This is achieved at the expense of investment in their infant and juvenile female peers, which consequently suffer greater mortality than do infant and juvenile males. Males, however, must emigrate at adolescence to prevent additional investment in them at the further expense of related female peers. By emigrating, adolescent males safeguard the kinship component of their inclusive fitness and gain an opportunity to improve their otherwise jeopardized individual fitness in a new social setting. The relatively low investment in females during the infant and juvenile period is balanced or compensated to equal that in males by continued investment in them through adulthood, as females do not emigrate from their maternal troop. Thus, total investment in the sexes is equal and parents and kin gain equal fitness through male and female progeny and kin. The male and female cohorts utilize contested resources equally. Altruistic and exploitative behavioral relations between related or unrelated males and females are explained on the basis of a balance between cost and benefit in fitness (classical and inclusive) that these behavioral relations confer. Relative to equilibrium conditions (Ro = 1), when food supply decreases (Ro<1), mortality increases among the infants and youngest juveniles, and among female relative to male juveniles; whereas under food surplus (Ro>1) survivorship among these animals improves. Thus, when the availability of limiting resources changes, the effects of parental and kin investments on growth and survivorship, and probably their nature, change as well, so as to maximize fitness under the new conditions. I propose that the regulation of population size and age-sex distribution is an outcome of classical and kin selected (aggressive and affiliative) behaviors that (1) influence growth rates and impose mortality by determining access to vital resources and estrous females differentially by age, sex and the degree of relatedness, r; (2) function to maximize the classical fitness of unrelated animals and the inclusive fitness of related troop members in accordance with reproductive strategy and the availability of limiting resources; and (3) results in bringing the troop size and population size into equilibrium with the availability of food resources and non-socially imposed mortality. Though scant, data from other species are in accord with those from M. sinica, thereby suggesting a broader relevance of the hypotheses and conclusions set forth in this paper. For example, as parental and kin investment are geared to maximize fitness according to the degree of sexual dimorphism, it is reasonable to expect parental and kin investment behaviors, and thence the age-specific sex ratios, to vary according to the magnitude of the difference in sexual dimorphism in size and mating strategy. A monomorphic mating system (as in lemurs and gibbons) predictably would require a minimum of difference in parental and kin investment behaviors by sex, and sex ratios should therefore tend forwards equality at all ages. But, in highly dimorphic species (e.g., patas monkeys and baboons) differences in parental and kin investment in male and female offspring and kin would be accentuated, such that the need to develop large adult male size, for example, might be compensated for by decreasing the number of males among adults. Comparative data support these implications. Other selective pressures, concerning for example, trophic adaptations, might limit the effects of intrasexual selection on the degree of sexual dimorphism, and in this indirect way influence investment behaviors and age-specific sex ratios. Similarly, niche adaptations that are specific to one age or sex only may alter the age and sex ratios in favor of the age-sex class exclusively benefiting from the additionally exploitable resource. Thus, reproductive strategies, trophic and similar life-sustaining adaptations and the availability of limiting resources influence social behaviors which determine the age-specific sex ratios of the population.

Was That Cheating? Perceptions Vary by Type of Behavior and Reproductive Strategy

2010 ◽  
Author(s):  
Daniel J. Kruger ◽  
Maryanne Fisher ◽  
Sarah L. Strout ◽  
Carey Fitzgerald
Keyword(s):  
Reproductive Strategy ◽  
Type Of Behavior
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