Sexual System, Sex Ratio, and Group Living in the Shrimp Thor amboinensis (De Man): Relevance to Resource-Monopolization and Sex-Allocation Theories

2010 ◽  
Vol 219 (2) ◽  
pp. 151-165 ◽  
Author(s):  
J. A. Baeza ◽  
C. Piantoni
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
Group Living ◽  
Sexual System ◽  
Resource Monopolization ◽  
De Man

scholarly journals Sex Allocation, Diet, and Small Population Management of African Rhinoceros

2021 ◽  
Author(s):  
◽  
Elizabeth Victoria Berkeley
Keyword(s):  
Sex Ratio ◽  
Population Growth ◽  
Survival Probability ◽  
Sex Allocation ◽  
Sex Ratios ◽  
Small Population ◽  
Ex Situ ◽  
Sex Bias ◽  
Theoretic Approach ◽  
Wet Season

<p>The application of sex allocation theory can provide useful insight into endangered rhinoceros biology to improve in situ and ex situ conservation efforts by understanding the factors that cause a female to produce one sex of calf. By decreasing the birth sex ratio (number of males born per number of females born) in a population it may be possible to increase population growth rates. The first aim was to determine if an environmentally cued sex allocation response occurred in black rhinos. By examining rainfall and calf sex records in a wild black rhino population, I identified that birth sex ratios increase in rainy seasons and rainy years. Mothers were more likely to be observed with male calves if they conceived during the wet season (57.3% male) than during the dry season (42.9% male). Mothers were more likely to raise male calves if they conceived during wet years (60.2% male) than during dry years (46.1% male). Next, I examined whether pulsatile or random variation in sex ratios of different magnitudes, as might occur under changes in climate patterns, would be detrimental to rhinoceros population growth. Results demonstrated that while random increases in the magnitude of birth sex ratio variation, in either direction, increased population survival probability up to 0.907, sequential pulsed years of birth sex ratio bias had the opposite effect on population performance down to a survival probability of 0.619. Furthermore, for both scenarios, populations of less than 50 animals are particularly vulnerable to extinction. Since the sex biases observed in the captive rhinoceros population were attributed to several factors, I used an information theoretic approach to evaluate the relative importance of different hypotheses for birth sex bias for predicting calf sex. The results demonstrated that none of the models tested were greatly predictive of calf sex. Suspecting that the mechanisms that were cueing calf sex occur close to the time of conception and were nutritionally cued, in the final experiment, I measured changes in blood glucose in white rhinos after they ate different meals. At 90 minutes, serum glucose levels in rhinos eating the 10 % lucerne hay diet were significantly lower than the 5% glucose and 10% glucose diets but not the 10% pellet nor 10% grass hay diets. This is the first time such an experiment has been published in a wildlife species and not only demonstrates the feasibility of training rhinos for successive blood draws but also that captive diets are low glycemic for white rhinos. Overall, my research confirmed that an environmentally cued sex allocation response does occur in African rhinos, and changes in the duration and magnitude of sex ratio patterns can decrease population growth and increase potential for extinction. Additionally, none of the previous hypotheses for the suspected male-sex bias in captive born rhinos were influential on calf sex, which shifts the focus of sex allocation research in rhinos to more acute signals around the time of conception, such as changes in diet and body condition.</p>

scholarly journals Patterns of split sex ratio in ants have multiple evolutionary causes based on different within-colony conflicts

2009 ◽  
Vol 5 (5) ◽  
pp. 713-716 ◽  
Author(s):  
Rolf Kümmerli ◽  
Laurent Keller
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
Social Hymenoptera ◽  
Kin Structure ◽  
Widespread Phenomenon ◽  
Queen Production

Split sex ratio—a pattern where colonies within a population specialize in either male or queen production—is a widespread phenomenon in ants and other social Hymenoptera. It has often been attributed to variation in colony kin structure, which affects the degree of queen–worker conflict over optimal sex allocation. However, recent findings suggest that split sex ratio is a more diverse phenomenon, which can evolve for multiple reasons. Here, we provide an overview of the main conditions favouring split sex ratio. We show that each split sex-ratio type arises due to a different combination of factors determining colony kin structure, queen or worker control over sex ratio and the type of conflict between colony members.

Translocation reverses birth sex ratio bias depending on its timing during gestation: evidence for the action of two sex-allocation mechanisms

2007 ◽  
Vol 19 (7) ◽  
pp. 831 ◽  
Author(s):  
W. L. Linklater
Keyword(s):  
Glucose Metabolism ◽  
Sex Ratio ◽  
Sex Allocation ◽  
Preimplantation Embryo ◽  
Sex Ratio Bias ◽  
In Captivity ◽  
Developmental Asynchrony ◽  
Adjustment Mechanisms ◽  
Excess Glucose

Many sex allocation mechanisms are proposed but rarely have researchers considered and tested more than one at a time. Four facultative birth sex ratio (BSR) adjustment mechanisms are considered: (1) hormone-induced conception bias; (2) sex-differential embryo death from excess glucose metabolism; (3) sex-differential embryo death from embryo–uterine developmental asynchrony; and (4) pregnancy hormone suppression and resource deprivation. All mechanisms could be switched on by the corticoadrenal stress response. A total of 104 female rhinoceroses (Rhinocerotidae), translocated from 1961 to 2004 at different stages of gestation or conceived soon after arrival in captivity, were used to test for a reversal in BSR bias as evidence for the action of multiple sex-allocation mechanisms. Translocation induced a statistically significant BSR reversal between early gestation (86% male births from 0 to 0.19 gestation) and mid-gestation (38% male from 0.2 to 0.79 gestation). Captivity also induced a strongly male-biased (67% male) BSR for conceptions after arrival in captivity. The results indicate the action of at least two sex-allocation mechanisms operating in sequence, confirm the important role of sex-differential embryo death around implantation and of stress in sex allocation, and lend support to suggestions that sex-differential glucose metabolism by the preimplantation embryo likely plays a role in facultative BSR adjustment.

scholarly journals Mate limitation and sex ratio evolution

2018 ◽  
Vol 5 (2) ◽  
pp. 171135 ◽  
Author(s):  
Jussi Lehtonen ◽  
Lisa E. Schwanz
Keyword(s):  
Sex Ratio ◽  
Kin Selection ◽  
Sex Allocation ◽  
Evolutionarily Stable Strategy ◽  
Mathematical Relationship ◽  
Stable Strategy ◽  
Local Mate ◽  
Mate Limitation ◽  
Mating Function ◽  
Evolutionarily Stable

Sex ratio evolution has been one of the most successful areas of evolutionary theory. Pioneered by Düsing and Fisher under panmixia, and later extended by Hamilton to cover local mate competition (LMC), these models often assume, either implicitly or explicitly, that all females are fertilized. Here, we examine the effects of relaxing this assumption, under both panmictic and LMC models with diploid genetics. We revisit the question of the mathematical relationship between sex ratio and probability of fertilization, and use these results to model sex ratio evolution under risk of incomplete fertilization. We find that (i) under panmixia, mate limitation has no effect on the evolutionarily stable strategy (ESS) sex allocation; (ii) under LMC, mate limitation can make sex allocation less female-biased than under complete fertilization; (iii) contrary to what is occasionally stated, a significant fraction of daughters can remain unfertilized at the ESS in LMC with mate limitation; (iv) with a commonly used mating function, the fraction of unfertilized daughters can be quite large, and (v) with more realistic fertilization functions, the deviation becomes smaller. The models are presented in three equivalent forms: individual selection, kin selection and group selection. This serves as an example of the equivalence of the methods, while each approach has their own advantages. We discuss possible extensions of the model to haplodiploidy.

scholarly journals Sperm sex ratio adjustment in a mammal: perceived male competition leads to elevated proportions of female-producing sperm

2020 ◽  
Vol 16 (6) ◽  
pp. 20190929
Author(s):  
Renée C. Firman ◽  
Jamie N. Tedeschi ◽  
Francisco Garcia-Gonzalez
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
Sex Ratios ◽  
Female Offspring ◽  
Male Competition ◽  
Offspring Sex ◽  
Sex Ratio Adjustment ◽  
Adaptive Adjustment ◽  
Male House

Mammal sex allocation research has focused almost exclusively on maternal traits, but it is now apparent that fathers can also influence offspring sex ratios. Parents that produce female offspring under conditions of intense male–male competition can benefit with greater assurance of maximized grand-parentage. Adaptive adjustment in the sperm sex ratio, for example with an increase in the production of X-chromosome bearing sperm (CBS), is one potential paternal mechanism for achieving female-biased sex ratios. Here, we tested this mechanistic hypothesis by varying the risk of male–male competition that male house mice perceived during development, and quantifying sperm sex ratios at sexual maturity. Our analyses revealed that males exposed to a competitive ‘risk’ produced lower proportions of Y-CBS compared to males that matured under ‘no risk’ of competition. We also explored whether testosterone production was linked to sperm sex ratio variation, but found no evidence to support this. We discuss our findings in relation to the adaptive value of sperm sex ratio adjustments and the role of steroid hormones in socially induced sex allocation.

Female-biased sex ratio of immature loggerhead sea turtles inhabiting the Atlantic coastal waters of Florida

1991 ◽  
Vol 69 (12) ◽  
pp. 2973-2977 ◽  
Author(s):  
Thane Wibbels ◽  
R. Erik Martin ◽  
David W. Owens ◽  
Max S. Amoss Jr.
Keyword(s):  
Sex Ratio ◽  
Coastal Waters ◽  
Sex Allocation ◽  
Sea Turtles ◽  
The United States ◽  
Loggerhead Sea Turtles ◽  
Blood Samples ◽  
Sex Allocation Theory ◽  
Biased Sex Ratio ◽  
Atlantic Coastal

The sex ratio of immature loggerhead sea turtles, Caretta caretta, inhabiting the Atlantic coastal waters of Florida was investigated. Blood samples were obtained from 223 turtles that were captured in the intake channel of a power plant on Hutchinson Island. A serum androgen sexing technique was utilized to sex individual turtles. The sex ratio of the turtles (2.1 female: 1.0 male) differed significantly from 1:1 and thus appears to differ from predictions of sex allocation theory. These observations are consistent with those of a previous study, and collectively the results suggest that the sex ratio of immature C. caretta inhabiting the Atlantic coastal waters of the United States is significantly female biased: approximately two females per male.

Altered sex ratio in giant fresh water prawn, Macrobrachium rosenbergii (de Man) using hormone bioencapsulated live Artemia feed

2004 ◽  
Vol 35 (10) ◽  
pp. 943-947 ◽  
Author(s):  
Dharmendra S Baghel ◽  
Wazir S Lakra ◽  
Guttula P Satyanarayana Rao
Keyword(s):  
Sex Ratio ◽  
Fresh Water ◽  
Macrobrachium Rosenbergii ◽  
De Man

Host size-dependent sex allocation behaviour in a parasitoid: implications forCatolaccus grandis(Hymenoptera: Pteromalidae) mass rearing programmes

1998 ◽  
Vol 88 (1) ◽  
pp. 37-45 ◽  
Author(s):  
K.M. Heinz
Keyword(s):  
Biological Control ◽  
Sex Ratio ◽  
Sex Allocation ◽  
Sex Ratios ◽  
Boll Weevil ◽  
Mass Rearing ◽  
Host Size ◽  
Offspring Sex Ratio ◽  
Offspring Sex ◽  
Control Programmes

AbstractAn often encountered problem associated with augmentative and inundative biological control programmes is the high cost of producing sufficient numbers of natural enemies necessary to suppress pest populations within the time constraints imposed by ephemeral agroecosystems. In many arrhenotokous parasitoids, overproduction of males in mass-rearing cultures inflates costs (per female) and thus limits the economic feasibility of these biological control programmes. Within the context of existing production technologies, experiments were conducted to determine if the sex ratio ofCatolaccus grandis(Burks), an ectoparasitoid of the boll weevilAnthonomous grandisBoheman, varied as a function of boll weevil larval size. Results from natural and manipulative experiments demonstrate the following behavioural characteristics associated with C.grandissex allocation behaviour: (i) femaleC. grandisoffspring are produced on large size hosts and male offspring are produced on small hosts; (ii) whether a host is considered large or small depends upon the overall distribution of host sizes encountered by a female parasitoid; and (iii) female parasitoids exhibit a greater rate of increase in body size with host size than do male parasitoids. The observed patterns cannot be explained by sex-specific mortality of immature parasitoids developing on the different host size categories. In subsequent experiments, laboratory cultures ofC. grandisexposed daily to successively larger sizes ofA. grandislarvae produced successively greater female biased offspring sex ratios, cultures exposed daily to successively smaller sizes of host larvae produced successively greater male biased offspring sex ratios, and cultures exposed daily to equivalent host size distributions over time maintained a uniform offspring sex ratio. By increasing the average size ofA. grandislarval hosts exposed toC. grandisby 2.5 mg per day in mass rearing cultures, the percentage of male progeny can be reduced from 33% to 23% over a period of four consecutive exposure days.

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